Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.2	5.5	2008	16.1 Days	CHF 2600
Electronics electronics	2.9	4.7	2012	15.6 Days	CHF 2400
Batteries batteries	4.0	5.4	2015	17.7 Days	CHF 2700
Electricity electricity	-	-	2020	20.3 Days	CHF 1000

22 pages, 2671 KiB

Open AccessArticle

Optimal Reactive Power Dispatch under Transmission and Distribution Coordination Based on an Accelerated Augmented Lagrangian Algorithm

by Bin Zhou, Xiaodong Shen, Caimei Pan, Yuanbao Bai and Tian Wu

Energies 2022, 15(11), 3867; https://0-doi-org.brum.beds.ac.uk/10.3390/en15113867 - 24 May 2022

Cited by 3 | Viewed by 1306

Abstract

As many distributed power sources flood into the distribution network, the relationship between transmission and distribution grids in reactive power and voltage is becoming closer and closer. The traditional way of independent reactive power optimization in transmission and distribution grids is no longer [...] Read more.

As many distributed power sources flood into the distribution network, the relationship between transmission and distribution grids in reactive power and voltage is becoming closer and closer. The traditional way of independent reactive power optimization in transmission and distribution grids is no longer appropriate. In this study, a collaborative and distributed reactive power optimization method for transmission and distribution grids based on the accelerated augmented Lagrangian (AAL) algorithm is proposed to adapt to the independence of the transmission and distribution grids in operation and management. The global reactive power optimization problem is decomposed into the transmission network subproblem and several distribution network subproblems. According to AAL, subproblems are solved in a distributed manner until the optimal global solution is finally reached after several iterations, and coordination between transmission and distribution grids is achieved only through the interaction of information on coordinating variables. For better convergence, a linearized and convergence-guaranteed optimal power flow model (OPF) with reactive power and voltage magnitude was applied to model the transmission grid optimization subproblem, while the second-order cone programming (SOCP) technique is used in the distribution network subproblems. The simulation results confirm that the method in this paper can effectively reduce network losses and achieve better economic performance, and converges better when compared to other algorithms. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 4459 KiB

Open AccessArticle

Hardware Implementation of Novel Shade Dispersion PV Reconfiguration Technique to Enhance Maximum Power under Partial Shading Conditions

by Vinaya Chandrakant Chavan, Suresh Mikkili and Tomonobu Senjyu

Energies 2022, 15(10), 3515; https://0-doi-org.brum.beds.ac.uk/10.3390/en15103515 - 11 May 2022

Cited by 13 | Viewed by 1723

Abstract

Partial shade condition is a significant factor contributing to the PV panel performance in mismatch losses and power generation. The technique suggested in this study allows the physical rearrangement of the PV panel to distribute the shade on the entire PV array. MPPT, [...] Read more.

Partial shade condition is a significant factor contributing to the PV panel performance in mismatch losses and power generation. The technique suggested in this study allows the physical rearrangement of the PV panel to distribute the shade on the entire PV array. MPPT, selecting suitable inverter topology, or PV panel reconfiguration enhances the performance of the PV panel. This study proposes a new shade dispersing method, novel shade dispersion (NSD). It compares the performance of the NSD method with conventional configurations (CCs). This research article models and simulates 6 × 6 PV array configurations such as Series-Parallel (SP), Total-Cross-Tide (TCT), Bridge-Linked (BL), Honey-Comb (HC), and the newly proposed NSD method under non-shading and nine different partial shading cases. The performance indices used for comparative analysis are global maximum power points, efficiency, power enhancement, open circuit voltage, short circuit current, and number of crests. The Soltech 1 STH-215-P PV module was selected in the MATLAB/Simulink environment to simulate PV array arrangements. Hardware experiments validate the performance of the NSD method. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 11406 KiB

Open AccessArticle

Indonesia’s Vast Off-River Pumped Hydro Energy Storage Potential

by David Firnando Silalahi, Andrew Blakers, Bin Lu and Cheng Cheng

Energies 2022, 15(9), 3457; https://0-doi-org.brum.beds.ac.uk/10.3390/en15093457 - 09 May 2022

Cited by 4 | Viewed by 6425

Abstract

Indonesia has vast solar energy potential, far more than needed to meet all its energy requirements without the use of fossil fuels. This remains true after per capita energy consumption rises to match developed countries, and most energy functions are electrified to minimize [...] Read more.

Indonesia has vast solar energy potential, far more than needed to meet all its energy requirements without the use of fossil fuels. This remains true after per capita energy consumption rises to match developed countries, and most energy functions are electrified to minimize the use of fossil fuels. Because Indonesia has relatively small energy potential from hydro, wind, biomass, geothermal and ocean energy, it will rely mostly on solar for its sustainable energy needs. Thus, Indonesia will require large amounts of storage for overnight and longer periods. Pumped hydro comprises 99% of global energy storage for the electricity industry. In this paper, we demonstrate that Indonesia has vast practical potential for low-cost off-river pumped hydro energy storage with low environmental and social impact; far more than it needs to balance a solar-dominated energy system. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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17 pages, 10926 KiB

Open AccessArticle

An Integrated Elitist Approach to the Design of Axial Flux Permanent Magnet Synchronous Wind Generators (AFPMWG)

by Omid Shariati, Ali Behnamfar and Ben Potter

Energies 2022, 15(9), 3262; https://0-doi-org.brum.beds.ac.uk/10.3390/en15093262 - 29 Apr 2022

Cited by 3 | Viewed by 2055

Abstract

This paper addresses an integrated and developed approach to the design of an Axial Flux Permanent Magnet Wind Generator (AFPMWG). The proposed analytical method of design employs the size equations and precise inductance calculations simultaneously, as well as considering the mechanical constraints of [...] Read more.

This paper addresses an integrated and developed approach to the design of an Axial Flux Permanent Magnet Wind Generator (AFPMWG). The proposed analytical method of design employs the size equations and precise inductance calculations simultaneously, as well as considering the mechanical constraints of the back-iron disc of the rotor. An Elitist Genetic Algorithm (EGA), such as a high capability optimization method, has been used to solve the equations and design of a wind generator with predefined rating power. The objectives of the coreless AFPMWG design process are minimizing the magnet consumption, maximizing machine efficiency, and achieving maximum sinusoidal induction voltage, considering the wind properties of the geographical area of utilization. The optimal calculation of the permanent magnet thickness is also taken into consideration in this work. The flux density distribution in all parts of the machine has been investigated for the magnetic saturation phenomenon. In this regard, special attention is paid to rotor back discs, which are made from nonlinear material with an optimum thickness. The inductance of the leakage flux of the coreless machine has been considered by parallel computation via the Finite Element Method (FEM) and analytical equations. Finally, three-dimensional and two-dimensional finite element analyses are used to validate the performance of the machine design according to the characteristics of Iran wind resources. The results show the high ability of the proposed approach in AFPMWG design and in considering the objectives and constraints carefully. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 4430 KiB

Open AccessArticle

Consensus-Based Distributed Secondary Frequency Control Method for AC Microgrid Using ADRC Technique

by Wenguo Li, Mingmin Zhang and Yaqi Deng

Energies 2022, 15(9), 3184; https://0-doi-org.brum.beds.ac.uk/10.3390/en15093184 - 27 Apr 2022

Cited by 7 | Viewed by 1444

Abstract

To ensure safe and reliable operation, the ability to ride through various disturbances is vital for a microgrid with multi-inverters. As the voltage and frequency support comes from the power-electronic-based inverters, it is necessary to find a proper control strategy to improve the [...] Read more.

To ensure safe and reliable operation, the ability to ride through various disturbances is vital for a microgrid with multi-inverters. As the voltage and frequency support comes from the power-electronic-based inverters, it is necessary to find a proper control strategy to improve the rejection ability of the DG inverter against disturbances. In this regard, this paper proposes a new distributed secondary frequency control approach for islanded microgrids, in which the main purpose is to remove the frequency deviation under droop control method with better disturbance rejection performance. Unlike many traditional approaches which rely on a detailed control model, the proposed one needs little model information thanks to the model-independent characteristic of active disturbance rejection control (ADRC) technique. A linear extended state observer is introduced to estimate the useless model dynamics (including unknown disturbances, unmodeled dynamics and nonlinear dynamics) which are then compensated in the control input. After the active compensation procedure, the nonlinear frequency control model can be converted into a quasi-linear model, based on which a proportional distributed control algorithm is established to restore the frequency and equalize the active power among the DGs. Simulation results based on a four-inverter-based microgrid show that the proposed approach achieves frequency restoration, active power sharing, as well as satisfactory disturbance rejection performance. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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1 pages, 457 KiB

Open AccessCorrection

Correction: Frick et al. Voltage Flip Efficiency Enhancement for Piezo Energy Harvesting. Electronics 2021, 10, 2400

by Vincent Frick, Liana Wassouf and Ehsan Jamshidpour

Electronics 2022, 11(9), 1312; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11091312 - 21 Apr 2022

Viewed by 911

Abstract

In the original publication [...] Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 2190 KiB

Open AccessArticle

Multiobjective Load Dispatch for Coal-Fired Power Plants under Renewable-Energy Accommodation Based on a Nondominated-Sorting Grey Wolf Optimizer Algorithm

by Yue Cao, Tao Li, Tianyu He, Yuwei Wei, Ming Li and Fengqi Si

Energies 2022, 15(8), 2915; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082915 - 15 Apr 2022

Cited by 6 | Viewed by 1401

Abstract

Coal-fired power plants are widely used to achieve a power balance in grids with renewable energy, which leads to new requirements for speediness in load dispatch. This paper presents a nondominated-sorting grey wolf optimizer algorithm (NSGWO) for the multiobjective load dispatch of coal-fired [...] Read more.

Coal-fired power plants are widely used to achieve a power balance in grids with renewable energy, which leads to new requirements for speediness in load dispatch. This paper presents a nondominated-sorting grey wolf optimizer algorithm (NSGWO) for the multiobjective load dispatch of coal-fired power plants that employed efficient nondominated sorting, a reference-point selection strategy, and a simulated binary crossover operator. The optimization results of the benchmark functions indicated that the NSGWO algorithm had a better accuracy and a better distribution than the traditional multiobjective grey wolf optimizer algorithm. Regarding the load dispatch of economy, environmental protection, and speediness strategies, the NSGWO had the best performance of all the simulated algorithms. The optimal-compromise solutions of the economy and speediness strategies of the NSGWO algorithm had a good distribution, which elucidated that this novel algorithm was favorable to allowing coal-fired power plants to accommodate renewable energy. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 1539 KiB

Open AccessArticle

Research on an Optimization Method for Injection-Production Parameters Based on an Improved Particle Swarm Optimization Algorithm

by Yukun Dong, Yu Zhang, Fubin Liu and Zhengjun Zhu

Energies 2022, 15(8), 2889; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082889 - 14 Apr 2022

Cited by 3 | Viewed by 1411

Abstract

The optimization of injection–production parameters is an important step in the design of gas injection development schemes, but there are many influencing factors and they are difficult to determine. To solve this problem, this paper optimizes injection-production parameters by combining an improved particle [...] Read more.

The optimization of injection–production parameters is an important step in the design of gas injection development schemes, but there are many influencing factors and they are difficult to determine. To solve this problem, this paper optimizes injection-production parameters by combining an improved particle swarm optimization algorithm to study the relationship between injection-production parameters and the net present value. In the process of injection-production parameter optimization, the particle swarm optimization algorithm has shortcomings, such as being prone to fall into local extreme points and slow in convergence speed. Curve adaptive and simulated annealing particle swarm optimization algorithms are proposed to further improve the optimization ability of the particle swarm optimization algorithm. Taking the Tarim oil field as an example, in different stages, the production time, injection volume and flowing bottom hole pressure were used as input variables, and the optimal net present value was taken as the goal. The injection-production parameters were optimized by improving the particle swarm optimization algorithm. Compared with the particle swarm algorithm, the net present value of the improved scheme was increased by about 3.3%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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15 pages, 8311 KiB

Open AccessArticle

A Novel Step Current Excitation Control Method to Reduce the Torque Ripple of Outer-Rotor Switched Reluctance Motors

by Jieyun Wang, Wei Jiang, Shuren Wang, Jingying Lu, Barry W. Williams and Qianlong Wang

Energies 2022, 15(8), 2852; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082852 - 13 Apr 2022

Cited by 4 | Viewed by 1542

Abstract

Featured in low-speed and high-torque operation, outer-rotor switched reluctance motors (OSRMs) have the potential to be widely deployed in low-speed commuter and logistics vehicle applications. In this paper, a five-phase OSRM and the control method featuring torque ripple reduction has been proposed, which [...] Read more.

Featured in low-speed and high-torque operation, outer-rotor switched reluctance motors (OSRMs) have the potential to be widely deployed in low-speed commuter and logistics vehicle applications. In this paper, a five-phase OSRM and the control method featuring torque ripple reduction has been proposed, which can be applied as the wheel hub motor in the electric vehicles. The simulation was carried out to analyze the OSRM operation. The electromagnetic characteristics of single-phase and two-phase hybrid excitation mode, as well as step current excitation mode, were compared and analyzed. To solve the problem of the large torque ripple of OSRMs under traditional excitation modes, the torque ripple suppression method based on step current excitation was also studied. The experiment design, including motor start-up control, speed control, and torque ripple reduction, are presented to verify the system torque ripple mitigation method. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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20 pages, 3106 KiB

Open AccessArticle

Home Energy Management Considering Renewable Resources, Energy Storage, and an Electric Vehicle as a Backup

by Oussama Ouramdane, Elhoussin Elbouchikhi, Yassine Amirat, Franck Le Gall and Ehsan Sedgh Gooya

Energies 2022, 15(8), 2830; https://0-doi-org.brum.beds.ac.uk/10.3390/en15082830 - 13 Apr 2022

Cited by 27 | Viewed by 2683

Abstract

The vehicle-to-grid concept emerged very quickly after the integration of renewable energy resources because of their intermittency and to support the grid during on-peak periods, consequently preventing congestion and any subsequent grid instability. Renewable energies offer a large source of clean energy, but [...] Read more.

The vehicle-to-grid concept emerged very quickly after the integration of renewable energy resources because of their intermittency and to support the grid during on-peak periods, consequently preventing congestion and any subsequent grid instability. Renewable energies offer a large source of clean energy, but they are not controllable, as they depend on weather conditions. This problem is solved by adding energy storage elements, implementing a demand response through shiftable loads, and the vehicle-to-grid/vehicle-to-home technologies. Indeed, an electric vehicle is equipped with a high-capacity battery, which can be used to store a certain amount of energy and give it back again later when required to fulfill the electricity demand and prevent an energy shortage when the main-grid power is limited for security reasons. In this context, this paper presents a comparative study between two home microgrids, in one of which the concept of vehicle-to-home is integrated to provide a case study to demonstrate the interest of this technology at the home level. The considered microgrid is composed of renewable energy resources, battery energy storage, and is connected to the main grid. As the vehicle is not available all day, in order to have consistent results, its intervention is considered in the evening, night, and early morning hours. Two case studies are carried out. In the first one, the vehicle-to-home concept is not taken into account. In this case, the system depends only on renewable resources and the energy storage system. Subsequently, the electric vehicle is considered as an additional energy storage device over a few hours. Electric vehicle integration brings an economic contribution by reducing the cost, supporting the other MG components, and relieving the main grid. Simulation results using real weather data for two cities in France, namely Brest and Toulon, show the effectiveness of the vehicle-to-home concept in terms of cost, energy self-sufficiency, and continuity of electrical service. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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23 pages, 5745 KiB

Open AccessArticle

Reserve-Constrained Unit Commitment Considering Adjustable-Speed Pumped-Storage Hydropower and Its Economic Effect in Korean Power System

by Woo-Jung Kim, Yu-Seok Lee, Yeong-Han Chun and Hae-Seong Jeong

Energies 2022, 15(7), 2386; https://0-doi-org.brum.beds.ac.uk/10.3390/en15072386 - 24 Mar 2022

Cited by 8 | Viewed by 2239

Abstract

The Korean government has declared the goal of net-zero-carbon emissions with a focus on renewable energy expansion. However, a high proportion of baseload generators and an increasing proportion of variable renewable energy (VRE) may cause problems in the power system operation owing to [...] Read more.

The Korean government has declared the goal of net-zero-carbon emissions with a focus on renewable energy expansion. However, a high proportion of baseload generators and an increasing proportion of variable renewable energy (VRE) may cause problems in the power system operation owing to the low cycling capability of baseload generators and variability of VRE. To maintain system reliability, the government is planning to construct pumped-storage hydropower (PSH) plants, which can provide flexibility to the system. This study evaluated the operating cost savings obtained by different types of PSH: the adjustable-speed PSH (AS-PSH) and fixed-speed PSH (FS-PSH), based on the duck-curve phenomenon and the increase in spinning reserve requirement. In this study, the reserve-constrained unit commitment was formulated using a mixed-integer-programming considering the operational characteristics of AS-PSH and conventional generators. To consider the duck-shaped net-load environment, the projected VRE output data were calculated through physical models of wind turbines and photovoltaic modules. The operating costs for the non-PSH, FS-PSH, and AS-PSH construction scenarios were KRW 43,129.38, 40,038.44, and 34,030.46, respectively. The main factor that derived this difference was determined to be the primary reserve of AS-PSH’s pumping mode. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 3941 KiB

Open AccessArticle

On the Road to Sustainable Energy Storage Technologies: Synthesis of Anodes for Na-Ion Batteries from Biowaste

by Nekane Nieto, Olatz Noya, Amaia Iturrondobeitia, Paula Sanchez-Fontecoba, Usue Pérez-López, Verónica Palomares, Alexander Lopez-Urionabarrenechea and Teófilo Rojo

Batteries 2022, 8(4), 28; https://0-doi-org.brum.beds.ac.uk/10.3390/batteries8040028 - 22 Mar 2022

Cited by 9 | Viewed by 3500

Abstract

Hard carbon is one of the most promising anode materials for sodium-ion batteries. In this work, new types of biomass-derived hard carbons were obtained through pyrolysis of different kinds of agro-industrial biowaste (corncob, apple pomace, olive mill solid waste, defatted grape seed and [...] Read more.

Hard carbon is one of the most promising anode materials for sodium-ion batteries. In this work, new types of biomass-derived hard carbons were obtained through pyrolysis of different kinds of agro-industrial biowaste (corncob, apple pomace, olive mill solid waste, defatted grape seed and dried grape skin). Furthermore, the influence of pretreating the biowaste samples by hydrothermal carbonization and acid hydrolysis was also studied. Except for the olive mill solid waste, discharge capacities typical of biowaste-derived hard carbons were obtained in every case (≈300 mAh·g⁻¹ at C/15). Furthermore, it seems that hydrothermal carbonization could improve the discharge capacity of biowaste samples derived from different nature at high cycling rates, which are the closest conditions to real applications. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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14 pages, 4851 KiB

Open AccessArticle

A Method for Detecting the Existence of an Over-Discharged Cell in a Lithium-Ion Battery Pack via Measuring Total Harmonic Distortion

by Jonghyeon Kim and Julia Kowal

Batteries 2022, 8(3), 26; https://0-doi-org.brum.beds.ac.uk/10.3390/batteries8030026 - 21 Mar 2022

Cited by 3 | Viewed by 3121

Abstract

This paper deals with a method to detect the existence of an over-discharged cell in a lithium-ion battery (LIB) pack by measuring the total harmonic distortion (THD) rate in the voltage response. Over-discharge of the LIB cell reduces the available capacity by irreversible [...] Read more.

This paper deals with a method to detect the existence of an over-discharged cell in a lithium-ion battery (LIB) pack by measuring the total harmonic distortion (THD) rate in the voltage response. Over-discharge of the LIB cell reduces the available capacity by irreversible chemical reactions, resulting in serious safety risks such as explosions. Even if only one over-discharged cell exists in the battery pack, it accelerates the decomposition of other cells. In general, the measurement of each cell voltage in a battery pack is required to detect one over-discharged cell. This is because if only the voltage of the battery pack is measured, it cannot be distinguished whether the voltage of each cell is uniformly low or one specific weak cell is over-discharged. The proposed method measures the frequency response through the voltage at only two terminals of the battery pack to detect the presence of one over-discharged cell. When the battery cell is discharged beyond a certain level, the system nonlinearity of the battery pack increases, and it can be detected from the increased THD rate of the battery pack. The proposed method is verified by simulation and measurement. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 5145 KiB

Open AccessArticle

Multi-Objective Optimal Integration of Solar Heating and Heat Storage into Existing Fossil Fuel-Based Heat and Power Production Systems

by Guangxuan Wang and Julien Blondeau

Energies 2022, 15(5), 1942; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051942 - 07 Mar 2022

Cited by 1 | Viewed by 1980

Abstract

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO₂ emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems [...] Read more.

Increasing the share of Renewable energy sources in District Heating (DH) systems is of great importance to mitigate their CO₂ emissions. The combined integration of Solar Thermal Collectors (STC) and Thermal Energy Storage (TES) into existing Combined Heat and Power (CHP) systems can be a very cost-effective way to do so. This paper aims at finding the optimal design of STC and TES systems integrated in existing CHP’s considering two distinct objectives: economic profitability and environmental impact. To do so, we developed a three-stage framework based on Pareto-optimal solutions generated by multi-objective optimization, a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)-entropy method to select the optimal solution, followed by the definition of final Operation strategy. We proposed relevant improvement of the state-of-the-art models used in similar analysis. We also applied the proposed methodology to the case of a representative, 12 MW_th CHP plant. Our results show that, while the addition of TES or STC alone results in limited performances and/or higher costs, both the cost and the CO₂ emissions can be reduced by integrating the optimal combination of STC and TES. For the selected, optimal solution, carbon emissions are reduced by 10%, while the Annual Total Cost (ATC) is reduced by 3%. It also improves the operational flexibility and the efficiency by peak load shaving, load valley filling and thus by decreasing the peak load boiler operation. Compared to the addition of STC alone, the use of TES results in an increased efficiency, from 88% to 92%. The optimal share of STC is then increased from 7% to 10%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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17 pages, 5054 KiB

Open AccessArticle

Distributed Generation Based Virtual STATCOM Configuration and Control Method

by Su-Han Pyo, Tae-Hun Kim, Byeong-Hyeon An, Jae-Deok Park, Jang-Hyun Park, Myoung-Jin Lee and Tae-Sik Park

Energies 2022, 15(5), 1762; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051762 - 26 Feb 2022

Cited by 2 | Viewed by 1921

Abstract

Recently, because of the increase in the number of connections to Distributed Generation (DG), the problem of lowering voltage stability in the distribution system has become an issue. Reactive power compensators, such as Static Synchronous Compensators (STATCOM), may be used to solve the [...] Read more.

Recently, because of the increase in the number of connections to Distributed Generation (DG), the problem of lowering voltage stability in the distribution system has become an issue. Reactive power compensators, such as Static Synchronous Compensators (STATCOM), may be used to solve the problem of voltage stability degradation. However, because of the complexity of the distribution system, it is very difficult to select the installation location for STATCOM. Furthermore, when installed in the wrong location, economical efficiency and availability problems may occur. This paper proposes a Virtual STATCOM Configuration and Control method that would operate like a single STATCOM based on multiple DGs connected to the system. The proposed Virtual STATCOM has the merit of being economical by using existing facilities without adding new power facilities, and it solves the problem of the difficulty of selecting the installation location because of the complexity of the distribution system. In addition, while the conventional STATCOM uses an independent control method in consideration of the power quality of the access point, the Virtual STATCOM performs the Point of Common Coupling (PCC) power quality compensation using the integrated control of multiple DGs connected to the system. In the proposed method, the Virtual STATCOM integrated control algorithm is configured by adopting linear programming, and the compensation is performed while considering the distance between DG and PCC, the inverter’s rated capacity, and the power generation. The performance of the Virtual STATCOM power quality compensation was verified using MATLAB/SIMULINK and Real Time Simulator (OPAL-RT). Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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13 pages, 7208 KiB

Open AccessArticle

Displacement Estimation of Six-Pole Hybrid Magnetic Bearing Using Modified Particle Swarm Optimization Support Vector Machine

by Gai Liu and Huangqiu Zhu

Energies 2022, 15(5), 1610; https://0-doi-org.brum.beds.ac.uk/10.3390/en15051610 - 22 Feb 2022

Cited by 8 | Viewed by 1397

Abstract

In order to solve the problems of the large volume and high cost of a six-pole hybrid magnetic bearing (SHMB) with displacement sensors, a displacement estimation method using a modified particle swarm optimization (MPSO) least-squares support vector machine (LS-SVM) is proposed. Firstly, the [...] Read more.

In order to solve the problems of the large volume and high cost of a six-pole hybrid magnetic bearing (SHMB) with displacement sensors, a displacement estimation method using a modified particle swarm optimization (MPSO) least-squares support vector machine (LS-SVM) is proposed. Firstly, the inertial weight of the MPSO is changed to achieve faster iterations, and the prediction model of an LS-SVM-based MPSO is built. Secondly, the prediction model is simulated and verified according to the parameters optimized by the MPSO, and the predicted values of MPSO and PSO are compared. Finally, static and dynamic suspension experiments and a disturbance experiment are carried out, which verify the robustness and stability of the displacement estimation method. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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20 pages, 10168 KiB

Open AccessArticle

High Frequency Resonance Suppression Strategy of Three-Phase Four-Wire Split Capacitor Inverter Connected to Parallel Compensation Grid

by Guoli Feng, Zhihao Ye, Yihui Xia, Heng Nian, Liming Huang and Zerun Wang

Energies 2022, 15(4), 1486; https://0-doi-org.brum.beds.ac.uk/10.3390/en15041486 - 17 Feb 2022

Cited by 3 | Viewed by 1423

Abstract

With the continuous penetration and development of renewable energy power generation, the distributed grid and the microgrid are becoming increasingly important in modern power systems. In distribution networks and the microgrid, the grid impedance is comparatively large and cannot be ignored. Usually, the [...] Read more.

With the continuous penetration and development of renewable energy power generation, the distributed grid and the microgrid are becoming increasingly important in modern power systems. In distribution networks and the microgrid, the grid impedance is comparatively large and cannot be ignored. Usually, the parallel compensation is used to improve the grid quality. In the grid with parallel compensation, the large phase angle difference between the impedance of the grid-connected inverter and the impedance of the grid at amplitude intersection will result in high frequency resonance (HFR). Because the inverter shows filter characteristics due to limited bandwidth of the controller, the parallel compensation grid, respectively, performs as the capacitance characteristic and inductance characteristic in different high frequency range. Compared with the three-phase, three-wire system, an additional zero-sequence path exists in the three-phase four-wire split capacitor inverter (TFSCI) system, so that the existing high frequency resonance suppression methods will be not effective. Since the zero-sequence component is neglected, HFR will also occur, in addition to the positive-sequence component and the negative-sequence component. Therefore, in order to suppress the high frequency resonance caused by positive-sequence, negative-sequence and zero-sequence components, an impedance reshaping strategy based on current feedback is proposed in this paper. This proposed method can reshape the amplitude and phase of the inverter impedance in a high frequency range without affecting the performance of the fundamental frequency control and ensure that the inverter contains a sufficient phase margin. Additionally, the proposed method can reshape the impedance of TFSCI within a wide frequency range, which makes it able to cope with the challenge of the parallel compensation degree change. Theoretical analysis and experiments verify the availability of the proposed control strategy. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 5733 KiB

Open AccessArticle

An Online Data-Driven LPV Modeling Method for Turbo-Shaft Engines

by Ziyu Gu, Shuwei Pang, Wenxiang Zhou, Yuchen Li and Qiuhong Li

Energies 2022, 15(4), 1255; https://0-doi-org.brum.beds.ac.uk/10.3390/en15041255 - 09 Feb 2022

Cited by 7 | Viewed by 1950

Abstract

The linear parameter-varying (LPV) model is widely used in aero engine control system design. The conventional local modeling method is inaccurate and inefficient in the full flying envelope. Hence, a novel online data-driven LPV modeling method based on the online sequential extreme learning [...] Read more.

The linear parameter-varying (LPV) model is widely used in aero engine control system design. The conventional local modeling method is inaccurate and inefficient in the full flying envelope. Hence, a novel online data-driven LPV modeling method based on the online sequential extreme learning machine (OS-ELM) with an additional multiplying layer (MLOS-ELM) was proposed. An extra multiplying layer was inserted between the hidden layer and the output layer, where the hidden layer outputs were multiplied by the input variables and state variables of the LPV model. Additionally, the input layer was set to the LPV model’s scheduling parameter. With the multiplying layer added, the state space equation matrices of the LPV model could be easily calculated using online gathered data. Simulation results showed that the outputs of the MLOS-ELM matched that of the component level model of a turbo-shaft engine precisely. The maximum approximation error was less than 0.18%. The predictive outputs of the proposed online data-driven LPV model after five samples also matched that of the component level model well, and the maximum predictive error within a large flight envelope was less than 1.1% with measurement noise considered. Thus, the efficiency and accuracy of the proposed method were validated. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 3468 KiB

Open AccessArticle

Optimal Power Sharing in Microgrids Using the Artificial Bee Colony Algorithm

by Kalim Ullah, Quanyuan Jiang, Guangchao Geng, Sahar Rahim and Rehan Ali Khan

Energies 2022, 15(3), 1067; https://0-doi-org.brum.beds.ac.uk/10.3390/en15031067 - 31 Jan 2022

Cited by 17 | Viewed by 3627

Abstract

In smart grids, a hybrid renewable energy system that combines multiple renewable energy sources (RESs) with storage and backup systems can provide the most cost-effective and stable energy supply. However, one of the most pressing issues addressed by recent research is how best [...] Read more.

In smart grids, a hybrid renewable energy system that combines multiple renewable energy sources (RESs) with storage and backup systems can provide the most cost-effective and stable energy supply. However, one of the most pressing issues addressed by recent research is how best to design the components of hybrid renewable energy systems to meet all load requirements at the lowest possible cost and with the best level of reliability. Due to the difficulty of optimizing hybrid renewable energy systems, it is critical to find an efficient optimization method that provides a reliable solution. Therefore, in this study, power transmission between microgrids is optimized to minimize the cost for the overall system and for each microgrid. For this purpose, artificial bee colony (ABC) is used as an optimization algorithm that aims to minimize the cost and power transmission from outside the microgrid. The ABC algorithm outperforms other population-based algorithms, with the added advantage of requiring fewer control parameters. The ABC algorithm also features good resilience, fast convergence, and great versatility. In this study, several experiments were conducted to show the productivity of the proposed ABC-based approach. The simulation results show that the proposed method is an effective optimization approach because it can achieve the global optimum in a very simple and computationally efficient way. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 14828 KiB

Open AccessArticle

Nonlinear Dynamic Characteristics of Rod Fastening Rotor with Preload Relaxation

by Li Zhao, Haosui Zhang, Peng Shen and Yibing Liu

Energies 2022, 15(3), 1052; https://0-doi-org.brum.beds.ac.uk/10.3390/en15031052 - 30 Jan 2022

Cited by 3 | Viewed by 2050

Abstract

Compared to ordinary rotor, rod fastening rotor has the advantages of lighter weight, higher strength and easier installation, so it is widely used in gas turbine. However, in the process of a long-term operation, the rod may be deformed due to the influence [...] Read more.

Compared to ordinary rotor, rod fastening rotor has the advantages of lighter weight, higher strength and easier installation, so it is widely used in gas turbine. However, in the process of a long-term operation, the rod may be deformed due to the influence of alternating load, high temperature and other uncertain factors. In serious cases, it can even lead to a major accident. The discontinuous characteristic of rod fastening rotor leads to great differences in dynamic characteristics compared to ordinary rotor. Based on the Herz contact theory and GW contact model, the contact effect between two discs was studied, and the relationship among the contact load, the distance between two disks and the equivalent bending stiffness was obtained. Findings show the bending stiffness to decrease nonlinearly with the decrease in contact load. The lumped mass method was used to establish the rotor model. The contact effect was considered and the Runge–Kutta method was used to solve the model. Combined with the bifurcation diagram, time domain diagram and spectrum diagram, the influence of contact stiffness on rotor dynamic characteristics was analyzed. The results show that the dynamic characteristics of the rod fastening rotor are rich due to the influence of nonlinear factors. In the case of uniform relaxation, the contact stiffness has different effects on the response state and frequency doubling amplitude of the system at different speeds, which is mainly related to the motion state of the system. In the case of non-uniform relaxation, the degree of relaxation does not affect the motion state of the system, but only changes the amplitude of vibration. The results provide theoretical support for condition monitoring and fault diagnosis of rod fastening rotor. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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17 pages, 1108 KiB

Open AccessArticle

A High-Gain Non-Isolated Three-Port Converter for Building-Integrated PV Systems

by Abdelsalam Elmakawi and Kamil Bayındır

Electronics 2022, 11(3), 387; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11030387 - 27 Jan 2022

Cited by 6 | Viewed by 2355

Abstract

Using a hybrid renewable energy source with an energy storage system, this paper proposed a novel multi-stage non-isolated three-port converter with a 5H inverter to feed a residential load varying from 50 Watts to 3500 Watts. The proposed three-port converter operates in grid-tied [...] Read more.

Using a hybrid renewable energy source with an energy storage system, this paper proposed a novel multi-stage non-isolated three-port converter with a 5H inverter to feed a residential load varying from 50 Watts to 3500 Watts. The proposed three-port converter operates in grid-tied and standalone power modes. A novel demand-side management algorithm, which covers eight operation modes, is described. Additionally, a complete control system is discussed. The proposed control system controls the PV maximum power point and battery charging/discharging, and regulates the 400 V DC bus voltage, the load voltage in standalone mode, and the grid-tied injected current. The proposed converter and the control system are validated through simulation for all power modes. The simulation results reveal that the proposed system is viable for Building-Integrated PV Systems. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 2054 KiB

Open AccessReview

Energy Management Strategy for Plug-In Hybrid Electric Vehicles Based on Driving Condition Recognition: A Review

by Chunna Liu and Yan Liu

Electronics 2022, 11(3), 342; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11030342 - 23 Jan 2022

Cited by 16 | Viewed by 4023

Abstract

Appropriate energy management strategies (EMSs) have been selected for plug-in hybrid electric vehicles (PHEVs) based on driving-condition recognition (DCR) according to the acquired driving information, so as to minimize the target parameters. With online control and offline optimization, the strategy is suitable for [...] Read more.

Appropriate energy management strategies (EMSs) have been selected for plug-in hybrid electric vehicles (PHEVs) based on driving-condition recognition (DCR) according to the acquired driving information, so as to minimize the target parameters. With online control and offline optimization, the strategy is suitable for real-time applications and is of great significance to repetitive routes, owing to its simplicity and ease of implementation. This paper aims to identity the DCR-based EMSs, develop efficient EMSs, and invite researchers involved in this field to discover new solutions. This paper presents a comprehensive analysis of EMSs based on DCR in terms of principles, the scope of application as well as their advantages and disadvantages, and provides a thorough survey of the latest progress in EMSs. We concluded that DCR-based EMSs show an improvement in energy saving and the pollutant-discharging effect. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 3846 KiB

Open AccessArticle

VMD-WSLSTM Load Prediction Model Based on Shapley Values

by Bilin Shao, Yichuan Yan and Huibin Zeng

Energies 2022, 15(2), 487; https://0-doi-org.brum.beds.ac.uk/10.3390/en15020487 - 11 Jan 2022

Cited by 1 | Viewed by 1659

Abstract

Accurate short-term load forecasting can ensure the safe operation of the grid. Decomposing load data into smooth components by decomposition algorithms is a common approach to address data volatility. However, each component of the decomposition must be modeled separately for prediction, which leads [...] Read more.

Accurate short-term load forecasting can ensure the safe operation of the grid. Decomposing load data into smooth components by decomposition algorithms is a common approach to address data volatility. However, each component of the decomposition must be modeled separately for prediction, which leads to overly complex models. To solve this problem, a VMD-WSLSTM load prediction model based on Shapley values is proposed in this paper. First, the Shapley value is used to select the optimal set of special features, and then the VMD decomposition method is used to decompose the original load into several smooth components. Finally, WSLSTM is used to predict each component. Unlike the traditional LSTM model, WSLSTM can simplify the prediction model and extract common features among the components by sharing the parameters among the components. In order to verify the effectiveness of the proposed model, several control groups were used for experiments. The results show that the proposed method has higher prediction accuracy and training speed compared with traditional prediction methods. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 7295 KiB

Open AccessArticle

Techno-Economic Evaluation of Hybrid Energy Systems Using Artificial Ecosystem-Based Optimization with Demand Side Management

by Hammed Olabisi Omotoso, Abdullah M. Al-Shaalan, Hassan M. H. Farh and Abdullrahman A. Al-Shamma’a

Electronics 2022, 11(2), 204; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11020204 - 10 Jan 2022

Cited by 18 | Viewed by 2922

Abstract

Electrification of remote rural areas by adopting renewable energy technologies through the advancement of smart micro-grids is indispensable for the achievement of continuous development goals. Satisfying the electricity demand of consumers while adhering to reliability constraints with docile computation analysis is challenging for [...] Read more.

Electrification of remote rural areas by adopting renewable energy technologies through the advancement of smart micro-grids is indispensable for the achievement of continuous development goals. Satisfying the electricity demand of consumers while adhering to reliability constraints with docile computation analysis is challenging for the optimal sizing of a Hybrid Energy System (HES). This study proposes the new application of an Artificial Ecosystem-based Optimization (AEO) algorithm for the optimal sizing of a HES while satisfying Loss of Power Supply Probability (LPSP) and Renewable Energy Fraction (REF) reliability indices. Furthermore, reduction of surplus energy is achieved by adopting Demand Side Management (DSM), which increases the utilization of renewable energy. By adopting DSM, 28.38%, 43.05%, and 65.37% were achieved for the Cost of Energy (COE) saving at 40%, 60%, and 80% REF, respectively. The simulation and optimization results demonstrate the most cost-competitive system configuration that is viable for remote-area utilization. The proposed AEO algorithm is further compared to Harris Hawk Optimization (HHO) and the Future Search Algorithm (FSA) for validation purpose. The obtained results demonstrate the efficacy of AEO to achieve the optimal sizing of HES with the lowest COE, the highest consistent level, and minimal standard deviation compared with HHO and FSA. The proposed model was developed and simulated using the MATLAB/code environment. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 8226 KiB

Open AccessArticle

Energy Management and Voltage Control in Microgrids Using Artificial Neural Networks, PID, and Fuzzy Logic Controllers

by Khaizaran Abdulhussein Al Sumarmad, Nasri Sulaiman, Noor Izzri Abdul Wahab and Hashim Hizam

Energies 2022, 15(1), 303; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010303 - 03 Jan 2022

Cited by 45 | Viewed by 4988

Abstract

Microgrids, comprising distributed generation, energy storage systems, and loads, have recently piqued users’ interest as a potentially viable renewable energy solution for combating climate change. According to the upstream electricity grid conditions, microgrid can operate in grid-connected and islanded modes. Energy storage systems [...] Read more.

Microgrids, comprising distributed generation, energy storage systems, and loads, have recently piqued users’ interest as a potentially viable renewable energy solution for combating climate change. According to the upstream electricity grid conditions, microgrid can operate in grid-connected and islanded modes. Energy storage systems play a critical role in maintaining the frequency and voltage stability of an islanded microgrid. As a result, several energy management systems techniques have been proposed. This paper introduces a microgrid system, an overview of local control in a microgrid, and an efficient EMS for effective microgrid operations using three smart controllers for optimal microgrid stability. We designed a microgrid consisting of renewable sources, Li-ion batteries, the main grid as a backup system, and AC/DC loads. The proposed system control was based on supplying loads as efficiently as possible using renewable energy sources and monitoring the battery’s state of charge. The simulation results using MATLAB Simulink demonstrate the performance of the three proposed microgrid stability strategies (PID, artificial neural network, and fuzzy logic). The comparison results confirmed the viability and effectiveness of the proposed technique for energy management in a microgrid which is based on fuzzy logic controllers. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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12 pages, 2328 KiB

Open AccessArticle

FPGA in the Loop Implementation for Observer Sliding Mode Control of DFIG-Generators for Wind Turbines

by Houda El Alami, Badre Bossoufi, Saad Motahhir, Eman H. Alkhammash, Mehedi Masud, Mohammed Karim, Mohammed Taoussi, Manale Bouderbala, Mouna Lamnadi and Mohammed El Mahfoud

Electronics 2022, 11(1), 116; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11010116 - 30 Dec 2021

Cited by 23 | Viewed by 2637

Abstract

This paper presents a new contribution of the nonlinear control technique of electrical energy in a wind energy system. The nonlinear sliding mode technique used to control the powers of the DFIG-Generator is connected to the power grid by two converters (grid side [...] Read more.

This paper presents a new contribution of the nonlinear control technique of electrical energy in a wind energy system. The nonlinear sliding mode technique used to control the powers of the DFIG-Generator is connected to the power grid by two converters (grid side and machine side). The proposed model is validated using tracking and robustness tests with a real wind speed. The control was developed under Matlab/Simulink, and the FPGA in the Loop technique was used to design the DFIG model. By employing a co-simulation, the purpose is to test the controller for the FPGA simulated model or system in its entirety. The results obtained by the cο-simulation show the efficiency of the proposed model in terms of speed and robustness with a rate THD = 0.95, and the proposed model of the sliding mode controller shows a significant improvement in the quality of energy produced by the wind system. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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12 pages, 4369 KiB

Open AccessArticle

Investigation of Partial Shading Scenarios on a Photovoltaic Array’s Characteristics

by Abdelilah Chalh, Aboubakr El Hammoumi, Saad Motahhir, Abdelaziz El Ghzizal, Aziz Derouich, Mehedi Masud and Mohammed A. AlZain

Electronics 2022, 11(1), 96; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11010096 - 29 Dec 2021

Cited by 11 | Viewed by 2120

Abstract

The purpose of this study is to investigate the impact of different partial shading scenarios on a PV array’s characteristics in order to develop a simple and easy-to-implement GMPP controller that tracks the PV array’s global maximum power point (GMPP). The P-V characteristic [...] Read more.

The purpose of this study is to investigate the impact of different partial shading scenarios on a PV array’s characteristics in order to develop a simple and easy-to-implement GMPP controller that tracks the PV array’s global maximum power point (GMPP). The P-V characteristic of the PV array becomes more complicated under partial shading, owing to the presence of many power peaks, as opposed to uniform irradiance conditions, when there is only one peak called the maximum power point. In fact, and according to an experiment conducted in this study, when a PV array is partially shaded, the P-V characteristic mostly presents two peaks, given the existence of only two levels of irradiance, one of which is called the global peak (i.e., the GMPP). Furthermore, the first peak is located at Vmpp1 (the PV array’s voltage corresponds to this peak), whereas the second is at Vmpp2. The proposed approach works by estimating the values of Vmpp1 and Vmpp2 using two equations in order to control the DC/DC converter of the PV system. The first equation is used when the GMPP is at the first peak, while the other is used when the GMPP is at the second peak. Several scenarios are simulated and presented in this paper to verify the accuracy of these equations. In addition, some conclusions are drawn to suggest a simple method for tracking the GMPP. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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14 pages, 9492 KiB

Open AccessArticle

Optimal Power Dispatch in Energy Systems Considering Grid Constraints

by Alejandro Rubio, Frank Schuldt, Peter Klement and Karsten von Maydell

Energies 2022, 15(1), 192; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010192 - 28 Dec 2021

Cited by 2 | Viewed by 2107

Abstract

As a consequence of the increasing share of renewable energies and sector coupling technologies, new approaches are needed for the study, planning, and control of modern energy systems. Such new structures may add extra stress to the electric grid, as is the case [...] Read more.

As a consequence of the increasing share of renewable energies and sector coupling technologies, new approaches are needed for the study, planning, and control of modern energy systems. Such new structures may add extra stress to the electric grid, as is the case with heat pumps and electrical vehicles. Therefore, the optimal performance of the system must be estimated considering the constraints imposed by the different sectors. In this research, an energy system dispatch optimization model is employed. It includes an iterative approach for generating grid constraints, which is decoupled from the linear unit commitment problem. The dispatch of all energy carriers in the system is optimized while considering the physical electrical grid limits. From the considered scenarios, it was found that in a typical German neighborhood with 150 households, a PV penetration of ∼5 kW_p per household can lead to curtailment of ∼60 MWh per year due to line loading. Furthermore, the proposed method eliminates grid violations due to the addition of new sectors and reduces the energy curtailment up to

45 %

. With the optimization of the heat pump operation, an increase of

7 %

of the self-consumption was achieved with similar results for the combination of battery systems and electrical vehicles. In conclusion, a safe and optimal operation of a complex energy system is fulfilled. Efficient control strategies and more accurate plant sizing could be derived from this work. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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15 pages, 8889 KiB

Open AccessArticle

Research on Voltage Stabilizing Control Strategy of Critical Load in Unplanned Island Based on Electric Spring

by Hongjun Wang, Chunchao Song, Youjun Yue and Hui Zhao

Electronics 2022, 11(1), 80; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11010080 - 27 Dec 2021

Cited by 6 | Viewed by 2177

Abstract

Aiming to solve the problem of voltage fluctuation of critical load caused by lack of control when an unplanned island occurs in a microgrid, a voltage stabilizing control strategy of critical load based on electric spring is proposed in this paper. When unplanned [...] Read more.

Aiming to solve the problem of voltage fluctuation of critical load caused by lack of control when an unplanned island occurs in a microgrid, a voltage stabilizing control strategy of critical load based on electric spring is proposed in this paper. When unplanned islanding occurs in a microgrid system, the system bus voltage fluctuates dramatically due to instantaneous power imbalance, compromising the power supply safety of important loads on the bus. In this paper, the electric spring control mode is integrated into the voltage stabilizing control strategy of critical loads in an unplanned island for the first time to realize the protection of critical loads. First of all, a model of an optical storage AC/DC hybrid microgrid is built, the overall system architecture is determined, and the microgrid is divided into four working states. Second, the working principle of electric spring is introduced, and a decoupling control strategy based on double closed loop is proposed. Finally, the experimental simulation of the proposed control strategy is experimentally simulated in Matlab/Simulink environment. The simulation findings show that when the bus voltage and current of microgrid change due to an unplanned island, the proposed control strategy based on electric spring may achieve the stability of voltage and current on critical loads. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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17 pages, 7657 KiB

Open AccessArticle

Design Optimization of a Dual-Bleeding Recirculation Channel to Enhance Operating Stability of a Transonic Axial Compressor

by Tien-Dung Vuong and Kwang-Yong Kim

Energies 2022, 15(1), 159; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010159 - 27 Dec 2021

Cited by 3 | Viewed by 2696

Abstract

The present work performed a comprehensive investigation to find the effects of a dual-bleeding port recirculation channel on the aerodynamic performance of a single-stage transonic axial compressor, NASA Stage 37, and optimized the channel’s configuration to enhance the operating stability of the compressor. [...] Read more.

The present work performed a comprehensive investigation to find the effects of a dual-bleeding port recirculation channel on the aerodynamic performance of a single-stage transonic axial compressor, NASA Stage 37, and optimized the channel’s configuration to enhance the operating stability of the compressor. The compressor’s performance was examined using three parameters: The stall margin, adiabatic efficiency, and pressure ratio. Steady-state three-dimensional Reynolds-averaged Navier–Stokes analyses were performed to find the flow field and aerodynamic performance. The results showed that the addition of a bleeding channel increased the recirculation channel’s stabilizing effect compared to the single-bleeding channel. Three design variables were selected for optimization through a parametric study, which was carried out to examine the influences of six geometric parameters on the channel’s effectiveness. Surrogate-based design optimization was performed using the particle swarm optimization algorithm coupled with a surrogate model based on the radial basis neural network. The optimal design was found to increase the stall margin by 51.36% compared to the case without the recirculation channel with only 0.55% and 0.28% reductions in the peak adiabatic efficiency and maximum pressure ratio, respectively. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 5614 KiB

Open AccessArticle

Parameter Estimation of Photovoltaic Cell/Modules Using Bonobo Optimizer

by Abdullrahman A. Al-Shamma’a, Hammed O. Omotoso, Fahd A. Alturki, Hassan. M. H. Farh, Abdulaziz Alkuhayli, Khalil Alsharabi and Abdullah M. Noman

Energies 2022, 15(1), 140; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010140 - 26 Dec 2021

Cited by 16 | Viewed by 3733

Abstract

In this paper, a new application of Bonobo (BO) metaheuristic optimizer is presented for PV parameter extraction. Its processes depict a reproductive approach and the social conduct of Bonobos. The BO algorithm is employed to extract the parameters of both the single diode [...] Read more.

In this paper, a new application of Bonobo (BO) metaheuristic optimizer is presented for PV parameter extraction. Its processes depict a reproductive approach and the social conduct of Bonobos. The BO algorithm is employed to extract the parameters of both the single diode and double diode model. The good performance of the BO is experimentally investigated on three commercial PV modules (STM6-40 and STP6-120/36) and an R.T.C. France silicon solar cell under various operating circumstances. The algorithm is easy to implement with less computational time. BO is extensively compared to other state of the art algorithms, manta ray foraging optimization (MRFO), artificial bee colony (ABO), particle swarm optimization (PSO), flower pollination algorithm (FPA), and supply-demand-based optimization (SDO) algorithms. Throughout the 50 runs, the BO algorithm has the best performance in terms of minimal simulation time for the R.T.C. France silicon, STM6-40/36 and STP6-120/36 modules. The fitness results obtained through root mean square (RMSE), standard deviation (SD), and consistency of solution demonstrate the robustness of BO. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 2112 KiB

Open AccessArticle

Fusion of Improved Sparrow Search Algorithm and Long Short-Term Memory Neural Network Application in Load Forecasting

by Gwo-Ching Liao

Energies 2022, 15(1), 130; https://0-doi-org.brum.beds.ac.uk/10.3390/en15010130 - 24 Dec 2021

Cited by 11 | Viewed by 2911

Abstract

Load forecasting (LF) is essential in enabling modern power systems’ safety and economical transportation and energy management systems. The dynamic balance between power generation and load in the optimization of power systems is receiving increasing attention. The intellectual development of information in the [...] Read more.

Load forecasting (LF) is essential in enabling modern power systems’ safety and economical transportation and energy management systems. The dynamic balance between power generation and load in the optimization of power systems is receiving increasing attention. The intellectual development of information in the power industry and the data acquisition system of the smart grid provides a vast data source for pessimistic load forecasting, and it is of great significance in mining the information behind power data. An accurate short-term load forecasting can guarantee a system’s safe and reliable operation, improve the utilization rate of power generation, and avoid the waste of power resources. In this paper, the load forecasting model by applying a fusion of Improved Sparrow Search Algorithm and Long Short-Term Memory Neural Network (ILSTM-NN), and then establish short-term load forecasting using this novel model. Sparrow Search Algorithm is a novel swarm intelligence optimization algorithm that simulates sparrow foraging predatory behavior. It is used to optimize the parameters (such as weight, bias, etc.) of the ILSTM-NN. The results of the actual examples are used to prove the accuracy of load forecasting. It can improve (decrease) the MAPE by about 20% to 50% and RMSE by about 44.1% to 52.1%. Its ability to improve load forecasting error values is tremendous, so it is very suitable for promoting a domestic power system. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 2965 KiB

Open AccessArticle

Distributed Economic Control for AC/DC Hybrid Microgrid

by Hongjun Wang, Wanfeng Li, Youjun Yue and Hui Zhao

Electronics 2022, 11(1), 13; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics11010013 - 22 Dec 2021

Cited by 9 | Viewed by 2687

Abstract

In this paper, a new double-layer droop control mode for island AC/DC microgrids is proposed to realize autonomous and cost-effective operation. The optimal power reference iterative algorithm is used to realize the internal active power distribution in the subnet. On this basis, secondary [...] Read more.

In this paper, a new double-layer droop control mode for island AC/DC microgrids is proposed to realize autonomous and cost-effective operation. The optimal power reference iterative algorithm is used to realize the internal active power distribution in the subnet. On this basis, secondary frequency and voltage adjustments are introduced to realize the economic operation, autonomy and stability of the subnet. At the microgrid level, the local control strategy of cost micro increment deviation is designed to optimize the exchange power between subnets. The cooperation of the two can realize the global economic operation of the microgrid, as well as voltage following and frequency regulation in the subnet. Based on the hybrid AC/DC microgrid simulation model, the effectiveness of the proposed method is verified. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 1845 KiB

Open AccessArticle

A Novel Mean Field Game-Based Strategy for Charging Electric Vehicles in Solar Powered Parking Lots

by Samuel M. Muhindo, Roland P. Malhamé and Geza Joos

Energies 2021, 14(24), 8517; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248517 - 17 Dec 2021

Cited by 3 | Viewed by 3562

Abstract

We develop a strategy, with concepts from Mean Field Games (MFG), to coordinate the charging of a large population of battery electric vehicles (BEVs) in a parking lot powered by solar energy and managed by an aggregator. A yearly parking fee is charged [...] Read more.

We develop a strategy, with concepts from Mean Field Games (MFG), to coordinate the charging of a large population of battery electric vehicles (BEVs) in a parking lot powered by solar energy and managed by an aggregator. A yearly parking fee is charged for each BEV irrespective of the amount of energy extracted. The goal is to share the energy available so as to minimize the standard deviation (STD) of the state of charge (SOC) of batteries when the BEVs are leaving the parking lot, while maintaining some fairness and decentralization criteria. The MFG charging laws correspond to the Nash equilibrium induced by quadratic cost functions based on an inverse Nash equilibrium concept and designed to favor the batteries with the lower SOCs upon arrival. While the MFG charging laws are strictly decentralized, they guarantee that a mean of instantaneous charging powers to the BEVs follows a trajectory based on the solar energy forecast for the day. That day ahead forecast is broadcasted to the BEVs which then gauge the necessary SOC upon leaving their home. We illustrate the advantages of the MFG strategy for the case of a typical sunny day and a typical cloudy day when compared to more straightforward strategies: first come first full/serve and equal sharing. The behavior of the charging strategies is contrasted under conditions of random arrivals and random departures of the BEVs in the parking lot. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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13 pages, 2343 KiB

Open AccessArticle

Implementation and Validation of Hybrid Control for a DFIG Wind Turbine Using an FPGA Controller Board

by Mohammed Taoussi, Badre Bossoufi, Manale Bouderbala, Saad Motahhir, Eman H. Alkhammash, Mehedi Masud, Nada Zinelaabidine and Mohammed Karim

Electronics 2021, 10(24), 3154; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10243154 - 17 Dec 2021

Cited by 14 | Viewed by 2505

Abstract

In this study, a novel control approach for a doubly-fed induction generator (DFIG) is developed and applied to improve the system’s dynamic response and performance for providing high energy quality while avoiding harmonic accumulations. Because of its ease of implementation, field-oriented control (FOC) [...] Read more.

In this study, a novel control approach for a doubly-fed induction generator (DFIG) is developed and applied to improve the system’s dynamic response and performance for providing high energy quality while avoiding harmonic accumulations. Because of its ease of implementation, field-oriented control (FOC) is frequently used. This control has great sensitivity to the machine’s parametric variations. For this reason, adaptive Backstepping control (ABC) is capable of preserving almost all of the performance and robustness properties. However, its analytical formulation has a problem. To overcome these disadvantages, the hybrid control (HC) is developed and verified to enable rapid response, complete reference tracking, and appropriate dynamic behavior with a low ripple level. This control is a combination of FOC’s and ABC’s control laws. The prepared control is explored by simulation testing using Matlab/Simulink and practical implementation using an FPGA board with actual turbine settings and a real wind profile of Dakhla City, Morocco. The results of hardware simulation show the efficacy of the HC in terms of speed and robustness, with a total harmonic distortion THD = 0.95, a value of THD that reveals the quality of the energy injected into the grid. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 1070 KiB

Open AccessArticle

Optimized Cooling Power of a Vuilleumier Refrigerator with Limited Regeneration

by Abdellah Khodja, Raphael Paul, Andreas Fischer and Karl Heinz Hoffmann

Energies 2021, 14(24), 8376; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248376 - 12 Dec 2021

Cited by 9 | Viewed by 1944

Abstract

Vuilleumier refrigerators provide cooling power by utilizing a heat source at temperatures above the ambient. This is particularly helpful in situations where waste heat is available and other power sources are limited. Vuilleumier refrigerators come in different technical configurations; here we analyze the [...] Read more.

Vuilleumier refrigerators provide cooling power by utilizing a heat source at temperatures above the ambient. This is particularly helpful in situations where waste heat is available and other power sources are limited. Vuilleumier refrigerators come in different technical configurations; here we analyze the thermodynamic performance of a configuration utilizing two displacer pistons with integrated regenerators. More specifically, we optimize the cooling power by optimizing the piston movement for a range of operation speeds. The optimization is based on the AS motion class for cyclic dynamics and uses an endoreversible model for the refrigerator. Our focus is on the influence of the regeneration extent present, and we find performance gains of about 17% for high regeneration extent and of about 28% for lower regeneration extent. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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17 pages, 705 KiB

Open AccessArticle

Co-Optimizing Battery Storage for Energy Arbitrage and Frequency Regulation in Real-Time Markets Using Deep Reinforcement Learning

by Yushen Miao, Tianyi Chen, Shengrong Bu, Hao Liang and Zhu Han

Energies 2021, 14(24), 8365; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248365 - 11 Dec 2021

Cited by 7 | Viewed by 3506

Abstract

Battery energy storage systems (BESSs) play a critical role in eliminating uncertainties associated with renewable energy generation, to maintain stability and improve flexibility of power networks. In this paper, a BESS is used to provide energy arbitrage (EA) and frequency regulation (FR) services [...] Read more.

Battery energy storage systems (BESSs) play a critical role in eliminating uncertainties associated with renewable energy generation, to maintain stability and improve flexibility of power networks. In this paper, a BESS is used to provide energy arbitrage (EA) and frequency regulation (FR) services simultaneously to maximize its total revenue within the physical constraints. The EA and FR actions are taken at different timescales. The multitimescale problem is formulated as two nested Markov decision process (MDP) submodels. The problem is a complex decision-making problem with enormous high-dimensional data and uncertainty (e.g., the price of the electricity). Therefore, a novel co-optimization scheme is proposed to handle the multitimescale problem, and also coordinate EA and FR services. A triplet deep deterministic policy gradient with exploration noise decay (TDD–ND) approach is used to obtain the optimal policy at each timescale. Simulations are conducted with real-time electricity prices and regulation signals data from the American PJM regulation market. The simulation results show that the proposed approach performs better than other studied policies in literature. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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24 pages, 10015 KiB

Open AccessArticle

Design of Hybrid (PV-Diesel) System for Tourist Island in Karimunjawa Indonesia

by Nurul Hiron, Nundang Busaeri, Sutisna Sutisna, Nurmela Nurmela and Aceng Sambas

Energies 2021, 14(24), 8311; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248311 - 09 Dec 2021

Cited by 17 | Viewed by 2512

Abstract

The main problem with electricity supply on densely populated islands is reliable, low-carbon, and sustainable electricity. The availability of potential energy needs in-depth observation to ensure that the system can be built sustainably. This paper examines the integration of PV systems and diesel [...] Read more.

The main problem with electricity supply on densely populated islands is reliable, low-carbon, and sustainable electricity. The availability of potential energy needs in-depth observation to ensure that the system can be built sustainably. This paper examines the integration of PV systems and diesel power systems on Karimunjawa Island to meet the need for reliable systems from economic, ecological, and technological aspects. Using the DigSilent Power Factory program to obtain the system response interference and penetration of the Photovoltaic (PV) system. Furthermore, this paper also tests short circuit analysis and economic feasibility analysis while validating the Levelized Cost of Electricity (LCOE) and Electric Production Cost (EPC) approaches. The results show that the availability of irradiation can handle the electricity needs on Karimunjawa Island. In addition, it proposes the designed requirements for an integrated PV power system and Diesel Power Plant (DPP) system. The research has also captured the synergistic profile of PV and DPP working coordination within 24 h. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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13 pages, 4907 KiB

Open AccessFeature PaperArticle

Optimization for a Photovoltaic Pumping System Using Indirect Field Oriented Control of Induction Motor

by Ikram Saady, Mohammed Karim, Badre Bossoufi, Saad Motahhir, Mohamed said Adouairi, Btissam Majout, Mouna Lamnadi, Mehedi Masud and Jehad F. Al-Amri

Electronics 2021, 10(24), 3076; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10243076 - 09 Dec 2021

Cited by 11 | Viewed by 2928

Abstract

Due to the increase in electricity and diesel costs, solar photovoltaic pumping systems have become a good solution, especially in rural areas. This work presents a standalone photovoltaic (PV) water pumping system (PVWPS) driven by an induction motor without energy storage to improve [...] Read more.

Due to the increase in electricity and diesel costs, solar photovoltaic pumping systems have become a good solution, especially in rural areas. This work presents a standalone photovoltaic (PV) water pumping system (PVWPS) driven by an induction motor without energy storage to improve the pumping system’s performance. First, a comparison is made between two types: perturb and observe (P&O) method and incremental conductance (INC) MPPT method with a variable step size that is automatically adjusted. Studying these two techniques helps to understand which one can result in a system with less oscillation and greater efficiency when tracking the maximum power point from the PV panel under sudden irradiation conditions. This MPPT works on the operating duty cycle of the boost converter. Then, that converter combines with a voltage source inverter (VSI) to convert DC power to AC power. Second, we use indirect field-oriented control (IRFOC), which drives the three-phase of an induction motor in turn to run the centrifugal pump. The simulation results of this work were obtained using the MATLAB Simulink platform. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 8817 KiB

Open AccessArticle

An Online Parameter Estimation Using Current Injection with Intelligent Current-Loop Control for IPMSM Drives

by Faa-Jeng Lin, Syuan-Yi Chen, Wei-Ting Lin and Chih-Wei Liu

Energies 2021, 14(23), 8138; https://0-doi-org.brum.beds.ac.uk/10.3390/en14238138 - 04 Dec 2021

Cited by 6 | Viewed by 2050

Abstract

An online parameter estimation methodology using the d-axis current injection, which can estimate the distorted voltage of the current-controlled voltage source inverter (CCVSI), the varying dq-axis inductances, and the rotor flux, is proposed in this study for interior permanent magnet synchronous [...] Read more.

An online parameter estimation methodology using the d-axis current injection, which can estimate the distorted voltage of the current-controlled voltage source inverter (CCVSI), the varying dq-axis inductances, and the rotor flux, is proposed in this study for interior permanent magnet synchronous motor (IPMSM) drives in the constant torque region. First, a d-axis current injection-based parameter estimation methodology considering the nonlinearity of a CCVSI is proposed. Then, during current injection, a simple linear model is developed to model the cross- and self-saturation of the dq-axis inductances. Since the d-axis unsaturated inductance is difficult to obtain by merely using the recursive least square (RLS) method, a novel tuning method for the d-axis unsaturated inductance is proposed by using the theory of the maximum torque per ampere (MTPA) with the combination of the RLS method. Moreover, to improve the bandwidth of the current loop, an intelligent proportional-integral-derivative (PID) neural network controller with improved online learning algorithm is adopted to replace the traditional PI controller. The estimated the dq-axis inductances and the rotor flux are adopted in the decoupled control of the current loops. Finally, the experimental results at various operating conditions of the IPMSM in the constant torque region are given. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 5049 KiB

Open AccessArticle

Analysis of Intrinsic Mechanistic of Stability-Tracking Control for Distributed Drive Autonomous Electric Vehicle

by Xuequan Tang, Yunbing Yan, Baohua Wang, Xiaowei Xu and Lin Zhang

Electronics 2021, 10(23), 3010; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10233010 - 02 Dec 2021

Cited by 3 | Viewed by 1780

Abstract

For distributed drive autonomous vehicles, adding lateral stability control (LSC) to the trajectory tracking control (TTC) can optimize the distribution of the driving torque of each wheel, so that the vehicle can track the planned trajectory while maintaining stable lateral motion. However, the [...] Read more.

For distributed drive autonomous vehicles, adding lateral stability control (LSC) to the trajectory tracking control (TTC) can optimize the distribution of the driving torque of each wheel, so that the vehicle can track the planned trajectory while maintaining stable lateral motion. However, the influence of adding LSC on the TTC system is still unclear. Firstly, a stability-track hierarchical control structure composed of LSC and TTC was established, and the interaction between the two layers was identified as the key of this paper. Then, the Intrinsic Mechanistic framework of the stability-tracking control (STC) was proposed by establishing and analyzing the vehicle dynamic model and control process of two layers. Finally, through simulation experiments, it was found that the change in the curvature of the target trajectory will make the tracking target trajectory and maintaining the lateral stability of the vehicle appear to conflict; in addition, in the LSC layer, the steering characteristics and delay characteristics of different reference models have a greater impact on the lateral stability and trajectory tracking performance; moreover, adjusting the preview time has a more obvious effect on trajectory tracking and lateral stability than the stability correction intensity coefficient. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 5244 KiB

Open AccessArticle

Implementation and Control of Six-Phase Induction Motor Driven by a Three-Phase Supply

by Mohamed I. Abdelwanis, Essam M. Rashad, Ibrahim B. M. Taha and Fathalla F. Selim

Energies 2021, 14(22), 7798; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227798 - 22 Nov 2021

Cited by 6 | Viewed by 3967

Abstract

This paper is interested in implementing and controlling a modified six-phase induction motor (MSPIM) when fed from a three-phase supply either via an inverter or with a direct grid connection loaded by a centrifugal pump. The main aims of using the MSPIM are [...] Read more.

This paper is interested in implementing and controlling a modified six-phase induction motor (MSPIM) when fed from a three-phase supply either via an inverter or with a direct grid connection loaded by a centrifugal pump. The main aims of using the MSPIM are to enhance motor reliability and reduce torque pulsation. A three-to-six phase transformer has been designed, implemented, and employed to enable the SPIM to be driven from a three-phase supply. It is preferable to use the three-to-six phase transformers integrated with three-phase inverter on using the six-phase inverter to generate lower values of harmonics and lower steady-state error of speed and reduce the starting current and because also it isolates the primary circuit from the secondary, and the cost will be lower compared to the design of a special six-phase inverter. Dynamic models of SPIM, three-to-six phase transformer, and three-phase variable speed drive are derived. Then, a scalar (V/F) closed-loop control of SPIM is employed, and the results are discussed. Fine-tuning of PID controllers is used to keep the motor speed tracking the reference value. A low pass filter is connected to reduce the ripple of voltage and current waveforms. An experimental setup has been built and implemented to check the possibility of controlling SPIM by a variable speed drive system fed from a three-to-six phase transformer. It is found that the proposed method can be effectively used to drive the SPIM from a three-phase supply. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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20 pages, 693 KiB

Open AccessArticle

Multi-Objective Immune-Commensal-Evolutionary Programming for Total Production Cost and Total System Loss Minimization via Integrated Economic Dispatch and Distributed Generation Installation

by Mohd Helmi Mansor, Ismail Musirin and Muhammad Murtadha Othman

Energies 2021, 14(22), 7733; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227733 - 18 Nov 2021

Cited by 1 | Viewed by 1369

Abstract

Economic Dispatch (ED) problems have been solved using single-objective optimization for so long, as Grid System Operators (GSOs) previously only focused on minimizing the total production cost. In modern power systems, GSOs require not only optimizing the total production cost but also, at [...] Read more.

Economic Dispatch (ED) problems have been solved using single-objective optimization for so long, as Grid System Operators (GSOs) previously only focused on minimizing the total production cost. In modern power systems, GSOs require not only optimizing the total production cost but also, at the same time, optimizing other important objectives, such as the total emissions of the greenhouse gasses, total system loss and voltage stability. This requires a suitable multi-objective optimization approach in ensuring the ED solution produced is satisfying all the objectives. This paper presents a new multi-objective optimization technique termed Multi-Objective Immune-Commensal-Evolutionary Programming (MOICEP) for minimizing the total production cost and total system loss via integrated Economic Dispatch and Distributed Generation installation (ED-DG). This involved the application of a weighted-sum multi-objective approach that combined with an optimization technique called Immune-Commensal-Evolutionary Programming (ICEP). The proposed MOICEP has been compared with other multi-objective techniques, which are Multi-Objective-Evolutionary Programming (MOEP) and Multi-Objective-Artificial Immune System (MOAIS). It was found that MOICEP performs very well in producing better optimization results for all the three types of Economic Dispatch (ED) problems compared to MOEP and MOAIS in terms of cheap total production costs and low total system loss. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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32 pages, 10053 KiB

Open AccessArticle

Voltage Rise Regulation with a Grid Connected Solar Photovoltaic System

by Akinyemi Ayodeji Stephen, Kabeya Musasa and Innocent Ewean Davidson

Energies 2021, 14(22), 7510; https://0-doi-org.brum.beds.ac.uk/10.3390/en14227510 - 10 Nov 2021

Cited by 6 | Viewed by 2403

Abstract

Renewable Distributed Generation (RDG), when connected to a Distribution Network (DN), suffers from power quality issues because of the distorted currents drawn from the loads connected to the network over generation of active power injection at the Point of Common Coupling (PCC). This [...] Read more.

Renewable Distributed Generation (RDG), when connected to a Distribution Network (DN), suffers from power quality issues because of the distorted currents drawn from the loads connected to the network over generation of active power injection at the Point of Common Coupling (PCC). This research paper presents the voltage rise regulation strategy at the PCC to enhance power quality and continuous operation of RDG, such as Photovoltaic Arrays (PVAs) connected to a DN. If the PCC voltage is not regulated, the penetration levels of the renewable energy integration to a DN will be limited or may be ultimately disconnected in the case of a voltage rise issue. The network is maintained in both unity power factor and voltage regulation mode, depending on the condition of the voltage fluctuation occurrences at the PCC. The research investigation shows that variation in the consumer’s loads (reduction) causes an increase in the power generated from the PVA, resulting in an increase in the grid current amplitude, reduction in the voltage of the feeder impedance and an increase in the phase voltage amplitude at the PCC. When the system is undergoing unity power factor mode, PCC voltage amplitude tends to rises with the loads. Its phase voltage amplitude rises above an acceptable range with no-loads which are not in agreement, as specified in the IEEE-1547 and Southern Africa grid code prerequisite. Incremental Conduction with Integral Regulator bases (IC + PI) are employed to access and regulate PVA generation, while the unwanted grid current distortions are attenuated from the network using an in-loop second order integral filtering circuit algorithm. Hence, the voltage rise at the PCC is mitigated through the generation of positive reactive power to the grid from the Distribution Static Compensator (DSTATCOM), thereby regulating the phase voltage. The simulation study is carried out in a MATLAB/Simulink environment for PVA performance. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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32 pages, 9288 KiB

Open AccessArticle

Balancing Energy Trilemma Using Hybrid Distributed Rooftop Solar PV (DRSP)/Battery/Diesel Microgrid: A Case Study in Gilutongan Island, Cordova, Cebu, Philippines

by Jaybee Lacea, Edward Querikiol and Evelyn Taboada

Energies 2021, 14(21), 7358; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217358 - 05 Nov 2021

Cited by 6 | Viewed by 4054

Abstract

Design strategies for achieving reliable, affordable, and clean electricity are crucial for energy sustainability. Attaining it requires managing the three core factors (TCF) of the energy trilemma (ET) to increase reliability (energy equity), minimize the levelized cost of electricity (LCOE) (energy equity), and [...] Read more.

Design strategies for achieving reliable, affordable, and clean electricity are crucial for energy sustainability. Attaining it requires managing the three core factors (TCF) of the energy trilemma (ET) to increase reliability (energy equity), minimize the levelized cost of electricity (LCOE) (energy equity), and avoid potential CO₂ emission (environmental sustainability) simultaneously. This paper aims to present a design strategy for the hybrid energy system microgrid (HESM) model, consisting of a distributed rooftop solar PV (DRSP), battery, and diesel-generator to meet the increasing demand while balancing the TCF of the ET. The design strategy was applied in a cluster of 11 households in Gilutongan Island, Cebu, Philippines, where there is no open land space for a solar PV microgrid system. This study used PVSyst and HOMER Pro software to perform the techno-enviro-economic (TEE) analysis to select all feasible system configurations (FSCs). To identify the optimal FSC, a scoring mechanism that considers the LCOE based on the 5% household electricity expense limit, the 5% unmet load fraction, and the renewable penetration fraction was used. Results show that the optimal system requires an average of 32.2% excess energy from DRSP to balance the TCF of the ET based on the energy demand considered. Thus, planning when energy demand increases is vital to map the next appropriate steps toward sustainable energy transition. Overall, the obtained results can support project developers and policymakers to make informed decisions in balancing the ET from various trade-offs of energy systems. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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24 pages, 6581 KiB

Open AccessArticle

Modified Beetle Annealing Search (BAS) Optimization Strategy for Maxing Wind Farm Power through an Adaptive Wake Digraph Clustering Approach

by Yanfang Chen, Young-Hoon Joo and Dongran Song

Energies 2021, 14(21), 7326; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217326 - 04 Nov 2021

Cited by 6 | Viewed by 1548

Abstract

Owing to scale-up and complex wake effects, the centralized control that processes the command from turbines may be unsuitable, as it incurs high communication overhead and computational complexity for a large offshore wind farm (OWF). This paper proposes a novel decentralized non-convex optimization [...] Read more.

Owing to scale-up and complex wake effects, the centralized control that processes the command from turbines may be unsuitable, as it incurs high communication overhead and computational complexity for a large offshore wind farm (OWF). This paper proposes a novel decentralized non-convex optimization strategy for maxing power conversion of a large OWF based on a modified beetle antennae search (BAS) algorithm. First, an adaptive threshold algorithm which to establish a pruned wake direction graph while preserving the most critical wake propagation relationship among wind turbines are presented. The adaptive graph constraints were used to create wake sub-digraphs that split the wind farm into nearly uncoupled clustering communication subsets. On this basis, a Monte Carlo-based beetle annealing search (MC-BAS) nonlinear optimization strategy was secondly designed to adjust the yaw angles and axial factors for the maximum power conversion of each turbine subgroup. Finally, the simulation results demonstrated that a similar gain could be achieved as a centralized control method at power conversion and reduces the computational cost, allowing it to solve the nonlinear problem and real-time operations of the OWF. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 11534 KiB

Open AccessArticle

Vibration Characteristics of a Hydroelectric Generating System with Different Hydraulic-Mechanical-Electric Parameters in a Sudden Load Increasing Process

by Yixuan Guo, Xiao Liang, Ziyu Niu, Zezhou Cao, Liuwei Lei, Hualin Xiong and Diyi Chen

Energies 2021, 14(21), 7319; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217319 - 04 Nov 2021

Cited by 3 | Viewed by 1831

Abstract

In a sudden load increasing process (SLIP), the hydroelectric generating system (HGS) experiences a severe vibration response due to the sudden change of the hydraulic-mechanical-electric parameters (HMEPs). The instability of HGS limits the ability of sudden load increase, and its flexibility and reliability [...] Read more.

In a sudden load increasing process (SLIP), the hydroelectric generating system (HGS) experiences a severe vibration response due to the sudden change of the hydraulic-mechanical-electric parameters (HMEPs). The instability of HGS limits the ability of sudden load increase, and its flexibility and reliability are reduced. Thus, in this study, a new transient nonlinear coupling model of HGS is proposed, which couples the hydro-turbine governing system (HTGS) and the hydro-turbine generator shafting system (HGSS) with the hydraulic-mechanical-electric coupling force, rotating speed, flow rate, hydro-turbine torque, electromagnetic torque, and guide vane opening. By using numerical simulation, the influences of different HMEPs on the vibration characteristics of HGS in SLIP are analyzed. The result shows that, compared with stable operating conditions, the vibration amplitude of HGS increases sharply in SLIP. The increase of the sudden load increasing amount, blade exit flow angle, mass eccentricity and excitation current, and the decrease in guide bearing stiffness and average air gap between the stator and rotor cause abnormal vibration of different degrees in the HGS. Hydraulic factors have the greatest influence on the nonlinear dynamic behavior of HGS. The maximum vibration amplitude of HGS in SLIP is increased by 70.46%, compared with that under stable operating conditions. This study provides reasonable reference for the analysis of the nonlinear dynamic behavior of HGS in SLIP under the multiple vibration sources. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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13 pages, 501 KiB

Open AccessArticle

Deduction of Optimal Control Strategies for a Sector-Coupled District Energy System

by Adrian Grimm, Patrik Schönfeldt, Herena Torio, Peter Klement, Benedikt Hanke, Karsten von Maydell and Carsten Agert

Energies 2021, 14(21), 7257; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217257 - 03 Nov 2021

Cited by 1 | Viewed by 1736

Abstract

We present a method to turn the results of model-based optimisations into resilient and comprehensible control strategies. Our approach is to define priority lists for all available technologies in a district energy system. Using linear discriminant analysis and the results of the optimisations, [...] Read more.

We present a method to turn the results of model-based optimisations into resilient and comprehensible control strategies. Our approach is to define priority lists for all available technologies in a district energy system. Using linear discriminant analysis and the results of the optimisations, these are then assigned to discrete time steps using a set of possible steering parameters. In contrast to the model-based optimisations, the deduced control strategies do not need predictions or even perfect foresight but solely rely on data about the present. The case study using priority lists presents results in terms of emissions and prices that are only about 5% off the linear optimum. Considering that the priority lists only need information about the present, the results of the control strategies obtained using the proposed method can be considered competitive. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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15 pages, 3799 KiB

Open AccessArticle

Experimental Validation of Predictive Current Control for DFIG: FPGA Implementation

by Manale Bouderbala, Badre Bossoufi, Olivier Deblecker, Hala Alami Aroussi, Mohammed Taoussi, Ahmed Lagrioui, Saad Motahhir, Mehedi Masud and Fahad A. Alraddady

Electronics 2021, 10(21), 2670; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10212670 - 31 Oct 2021

Cited by 19 | Viewed by 2650

Abstract

The purpose of this study is to design a real-time current predictive control for a wind energy conversion system (WECS) using a doubly-fed induction generator (DFIG). A wind emulator and a test bench for assessing control strategies were conceptualized. The DSPACE DS1104 board [...] Read more.

The purpose of this study is to design a real-time current predictive control for a wind energy conversion system (WECS) using a doubly-fed induction generator (DFIG). A wind emulator and a test bench for assessing control strategies were conceptualized. The DSPACE DS1104 board served as the foundation for the design of a wind emulation system. While power is indirectly regulated via currents, the latter is controlled directly by current predictive control. Using discrete time, the control suggests the appropriate voltages to the converter for each sample period to attain the specified set points and control the power. The field-oriented control is employed to ensure that the two components, axes d and q, are decoupled. The present predictive control was established to regulate a DFIG’s active and reactive capabilities. To begin, a thorough examination of the WECS is discussed. Following that, a comprehensive description of predictive control laws based on reference frame orientation is offered. As a result, a simulation was done using Matlab/Simulink environments to assess the performance and resilience of the proposed control model. The predictive current control was then experimentally validated on a test bench to demonstrate its efficacy. The observed results reveal an astonishing correlation between simulations and experiments. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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25 pages, 2870 KiB

Open AccessArticle

Piezoelectric Power Generation from the Vortex-Induced Vibrations of a Semi-Cylinder Exposed to Water Flow

by Christina Hamdan, John Allport and Azadeh Sajedin

Energies 2021, 14(21), 6964; https://0-doi-org.brum.beds.ac.uk/10.3390/en14216964 - 23 Oct 2021

Cited by 9 | Viewed by 2181

Abstract

The aim of this work is to design a piezoelectric power generation system that extracts power from the vibration of a cantilever beam. A semi-cylinder placed in a water stream and attached to the beam is excited into vortex-induced vibrations (VIV), which triggers [...] Read more.

The aim of this work is to design a piezoelectric power generation system that extracts power from the vibration of a cantilever beam. A semi-cylinder placed in a water stream and attached to the beam is excited into vortex-induced vibrations (VIV), which triggers the piezoelectric deformation. The mechanical system is modelled using parametric equations based on Hamilton’s extended principle for the cantilever beam and the modified Van der Pol model for the bluff body (the semi-cylinder). These equations are simulated using the MATLAB software. The dimensions of the model, the flow velocity and the resistance are treated as design parameters and an optimization study is conducted using MATLAB to determine the combination of optimal values at which maximum power is extracted. The key findings of this research lie in the identification of the effect of changing the design parameters on output power. In addition to the numerical simulation, a finite element analysis is carried out on the bluff body and the hydrodynamic forces and velocity profiles are observed. It is determined that the vibration amplitudes increase with increasing diameter of the bluff body, length of the bluff body and water velocity. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 3123 KiB

Open AccessArticle

Modeling and Control of a Phase-Shifted Full-Bridge Converter for a LiFePO₄ Battery Charger

by Ivan A. Mendoza-Varela, Alfredo Alvarez-Diazcomas, Juvenal Rodriguez-Resendiz and Miguel Angel Martinez-Prado

Electronics 2021, 10(21), 2568; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10212568 - 21 Oct 2021

Cited by 9 | Viewed by 3479

Abstract

A proper charge in an electric vehicle (EV) battery allows it to have a longer useful life and lower maintenance costs. For this purpose, the voltage and current supplied to the battery must be precisely regulated. In this article, the model of a [...] Read more.

A proper charge in an electric vehicle (EV) battery allows it to have a longer useful life and lower maintenance costs. For this purpose, the voltage and current supplied to the battery must be precisely regulated. In this article, the model of a phase-shifted full-bridge (PSFB) converter is obtained. Moreover, a dual control loop was designed to regulate the state of charge of a lithium ferrofosfate (LiFePO

_{4}

) battery. The autoregressive exogenous (ARX) model is used to model the system. Once the plant model is obtained, it is controlled using a classical controller. A couple of cases are evaluated where the control parameters are modified, and the best approach is selected. From the obtained model, the controller is designed for the proposed cases. The theoretical controller response is compared with the experimental response. The results show a 94% accuracy of the model. In the same way, the result obtained from the controller is accurate in a 96% by comparing it with a simulation. Both the modeling and the control obtained experimentally resemble the results obtained theoretically. The controller manages to respond as expected in all proposed cases. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 2940 KiB

Open AccessArticle

Design of Nonlinear Backstepping Double-Integral Sliding Mode Controllers to Stabilize the DC-Bus Voltage for DC–DC Converters Feeding CPLs

by Subarto Kumar Ghosh, Tushar Kanti Roy, Md. Abu Hanif Pramanik and Md. Apel Mahmud

Energies 2021, 14(20), 6753; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206753 - 17 Oct 2021

Cited by 16 | Viewed by 2195

Abstract

This paper proposes a composite nonlinear controller combining backstepping and double-integral sliding mode controllers for DC–DC boost converter (DDBC) feeding by constant power loads (CPLs) to improve the DC-bus voltage stability under large disturbances in DC distribution systems. In this regard, an exact [...] Read more.

This paper proposes a composite nonlinear controller combining backstepping and double-integral sliding mode controllers for DC–DC boost converter (DDBC) feeding by constant power loads (CPLs) to improve the DC-bus voltage stability under large disturbances in DC distribution systems. In this regard, an exact feedback linearization approach is first used to transform the nonlinear dynamical model into a simplified linear system with canonical form so that it becomes suitable for designing the proposed controller. Another important feature of applying the exact feedback linearization approach in this work is to utilize its capability to cancel nonlinearities appearing due to the incremental negative-impedance of CPLs and the non-minimum phase problem related to the DDBC. Second, the proposed backstepping double integral-sliding mode controller (BDI-SMC) is employed on the feedback linearized system to determine the control law. Afterwards, the Lyapunov stability theory is used to analyze the closed-loop stability of the overall system. Finally, a simulation study is conducted under various operating conditions of the system to validate the theoretical analysis of the proposed controller. The simulation results are also compared with existing sliding mode controller (ESMC) and proportional-integral (PI) control schemes to demonstrate the superiority of the proposed BDI-SMC. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 3561 KiB

Open AccessArticle

The Optimal Pumping Power under Different Ice Slurry Concentrations Using Evolutionary Strategy Algorithms

by Shuai Hao, Wenjie Zhou, Junliang Lu and Jiajun Wang

Energies 2021, 14(20), 6738; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206738 - 16 Oct 2021

Cited by 1 | Viewed by 1653

Abstract

A suitable ice slurry fluid with a suitable ice concentration ratio can save operational costs. The design of the optimal ice slurry concentration focuses on finding an evolution strategy, which can further minimize the power consumption of the pump. A theoretical model was [...] Read more.

A suitable ice slurry fluid with a suitable ice concentration ratio can save operational costs. The design of the optimal ice slurry concentration focuses on finding an evolution strategy, which can further minimize the power consumption of the pump. A theoretical model was established to simulate the effect of different ice concentrations and flow rates on the performance of the pump. The data obtained were fitted by curve-fitting function. The process was modeled in the MATLAB evolutionary strategy algorithm to obtain the configuration scheme of the ice concentration and flow under different refrigeration capacities. The simulation results showed that when the required cooling capacity was 13.889 kWh, ice concentration was set to 19.68%, and flow rate was set to 2.1075 × 10⁻⁴ m³/s, the power consumption could be reduced by 23%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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12 pages, 1943 KiB

Open AccessArticle

Performance Analysis of PI and DMRAC Algorithm in Buck–Boost Converter for Voltage Tracking in Electric Vehicle Using Simulation

by Maidul Islam, Alia Farhana Abdul Ghaffar, Erwin Sulaeman, Md Manjurul Ahsan, Abbas Z. Kouzani and M. A. Parvez Mahmud

Electronics 2021, 10(20), 2516; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10202516 - 15 Oct 2021

Cited by 2 | Viewed by 1698

Abstract

This study introduces a Direct Model Reference Adaptive Control (DMRAC) algorithm in a buck–boost converter in the power distribution of an electric vehicle. In this study, DMRAC was used in order to overcome the system nonlinearity due to load demand variation, in case [...] Read more.

This study introduces a Direct Model Reference Adaptive Control (DMRAC) algorithm in a buck–boost converter in the power distribution of an electric vehicle. In this study, DMRAC was used in order to overcome the system nonlinearity due to load demand variation, in case of different driving modes (such as acceleration, stable and regenerative braking system mode), and the presence of disturbances in the system. DMRAC receives popularity because of its robustness in the presence of nonlinearity and ensuring system stability. To evaluate the efficacy of DMRAC in the current system, its performance was compared with a PI controller in the MATLAB/Simulink environment. The simulation results show the superiority of DMRAC over a conventional PI control approach, in both variable load demand and disturbed system cases that were measured by tracking error. The improvement was seen in the DMRAC response, with smaller tracking error and faster transient and disturbance rejection. The main contribution of this work is in introducing DMRAC, particularly in a buck–boost converter, and its efficacy with a DC–DC converter for an electric vehicle, which has not been studied before. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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21 pages, 4191 KiB

Open AccessArticle

Development and Performance Study of Temperature and Humidity Regulator in Baby Incubator Using Fuzzy-PID Hybrid Controller

by Alimuddin Alimuddin, Ria Arafiyah, Irma Saraswati, Rocky Alfanz, Partogi Hasudungan and Taufik Taufik

Energies 2021, 14(20), 6505; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206505 - 11 Oct 2021

Cited by 8 | Viewed by 3673

Abstract

Technological developments in the health sector for the safety of neonates are essential. Such efforts are needed to curb the increase in premature infant mortality cases caused by bacteria, asphyxia, infections, and poor management of facility equipment. Furthermore, preterm and other at-risk babies [...] Read more.

Technological developments in the health sector for the safety of neonates are essential. Such efforts are needed to curb the increase in premature infant mortality cases caused by bacteria, asphyxia, infections, and poor management of facility equipment. Furthermore, preterm and other at-risk babies have low ability to regulate temperature and produce body heat as characterized by their dry skin conditions; hence, the need for baby incubators. For their operation, these baby incubators provide strict regulated energy change that is influenced by heat transfer caused by the surrounding atmospheric temperature and humidity. This paper presents the design, construction, and performance study of a proposed Fuzzy-PID hybrid control system for regulating temperature and humidity in a baby incubator. To accomplish its goal, the proposed controller must be able to distribute heat and maintain humidity in the incubator under fluctuating atmospheric conditions to keep the baby’s body warm. Performance tests of the proposed hybrid controller were conducted by comparing temperature and humidity outputs in the baby incubator against predetermined expected values. Results show that the proposed controller is able to successfully achieve and maintain the temperature and humidity set points. Further examination also suggests that the proposed Fuzzy-PID hybrid control offers an improved overall system response performance compared to the PID controller. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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23 pages, 1382 KiB

Open AccessArticle

Design of a Neural Super-Twisting Controller to Emulate a Flywheel Energy Storage System

by Daniel A. Magallón, Carlos E. Castañeda, Francisco Jurado and Onofre A. Morfin

Energies 2021, 14(19), 6416; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196416 - 07 Oct 2021

Cited by 4 | Viewed by 2211

Abstract

In this work, a neural super-twisting algorithm is applied to the design of a controller for a flywheel energy storage system (FESS) emulator. Emulation of the FESS is achieved through driving a Permanent Magnet Synchronous Machine (PMSM) coupled to a shaft to shaft [...] Read more.

In this work, a neural super-twisting algorithm is applied to the design of a controller for a flywheel energy storage system (FESS) emulator. Emulation of the FESS is achieved through driving a Permanent Magnet Synchronous Machine (PMSM) coupled to a shaft to shaft DC-motor. The emulation of the FESS is carried out by controlling the velocity of the PMSM in the energy storage stag and then by controlling the DC-motor velocity in the energy feedback stage, where the plant’s states of both electrical machines are identified via a neural network. For the neural identification, a Recurrent Wavelet First-Order Neural Network (RWFONN) is proposed. For the design of the velocity controller, a super-twisting algorithm is applied by using a sliding surface as the argument; the latter is designed based on the states of the RWFONN, in combination with the block control linearization technique to the control of the angular velocity from both machines in their respective operation stage. The RWFONN is trained online using the filtered error algorithm. Closed-loop stability analysis is included when assuming boundedness of the synaptic weights. The results obtained from Matlab/Simulink validate the performance of the proposal in the control of an FESS. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 7432 KiB

Open AccessArticle

DSO Strategies Proposal for the LV Grid of the Future

by Bartłomiej Mroczek and Paweł Pijarski

Energies 2021, 14(19), 6327; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196327 - 03 Oct 2021

Cited by 6 | Viewed by 2303

Abstract

A significant challenge for the DSO (Distribution System Operator) will be to choose the optimum strategy for flexibility service in the LV area with high RES (renewable energy sources) penetration. To this end, a representative LV grid operated in Poland was selected for [...] Read more.

A significant challenge for the DSO (Distribution System Operator) will be to choose the optimum strategy for flexibility service in the LV area with high RES (renewable energy sources) penetration. To this end, a representative LV grid operated in Poland was selected for analysis. Three research scenarios with RES generation were presented in the range of 1–8 kW for the power factor from 0.9 to 1. The grid PV capacity was determined for four load profiles. Based on this factor, optimum RES volume management service types were determined. Under the flexibility service, the proposed power conversion services and active RES operations for DSO were proposed. The research was conducted using the Matlab and PowerWorld Simulator environment. Optimum active power values were obtained for the RES generation function for single and dual operation systems of the power conversion system. In future, the knowledge in the field of grid capacity will enable the DSO to increase the operating efficiency of the LV grid. It will enable the optimum use of the RES generation maximisation function and proper strategy selection. It will improve the energy efficiency of the power input through the MV/LV node. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 6524 KiB

Open AccessArticle

Robust Temperature Control of a Variable-Speed Refrigeration System Based on Sliding Mode Control with Optimal Parameters Derived Using the Genetic Algorithm

by Jieun Lee and Seokkwon Jeong

Energies 2021, 14(19), 6321; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196321 - 03 Oct 2021

Cited by 2 | Viewed by 1953

Abstract

A sliding mode control (SMC) technique based on a state observer with a Kalman filter and feedforward controller was established for a variable-speed refrigeration system (VSRS) to ensure robust control against model uncertainties and disturbances, including noise. The SMC was designed using a [...] Read more.

A sliding mode control (SMC) technique based on a state observer with a Kalman filter and feedforward controller was established for a variable-speed refrigeration system (VSRS) to ensure robust control against model uncertainties and disturbances, including noise. The SMC was designed using a state-space model transformed from a practical transfer function model, which was derived by conducting dynamic characteristic experiments. Fewer parameters affecting the model uncertainty were required to be identified, which facilitated modeling. The state observer for estimating the state variables was designed using a Kalman filter to ensure robustness against noise. A feedforward controller was added to the control system to compensate for the deterioration in the transient characteristics due to the saturation function used to avoid chattering. A genetic algorithm was used to alleviate the trial and error involved in determining the design parameters of the saturation function and select optimal values. Simulations and experiments were conducted to verify the control performance of the proposed SMC. The results show that the proposed controller can realize robust temperature control for a VSRS despite stepwise changes in the reference and external heat load, and avoid the trial and error process to design parameters for the saturation function. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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23 pages, 5657 KiB

Open AccessArticle

Research on the State of Charge of Lithium-Ion Battery Based on the Fractional Order Model

by Lin Su, Guangxu Zhou, Dairong Hu, Yuan Liu and Yunhai Zhu

Energies 2021, 14(19), 6307; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196307 - 02 Oct 2021

Cited by 8 | Viewed by 2005

Abstract

Accurate estimation of the state of charge (SOC) of lithium batteries is paramount to ensuring consistent battery pack operation. To improve SOC estimation accuracy and suppress colored noise in the system, a fractional order model based on an unscented Kalman filter and an [...] Read more.

Accurate estimation of the state of charge (SOC) of lithium batteries is paramount to ensuring consistent battery pack operation. To improve SOC estimation accuracy and suppress colored noise in the system, a fractional order model based on an unscented Kalman filter and an H-infinity filter (FOUHIF) estimation algorithm was proposed. Firstly, the discrete state equation of a lithium battery was derived, as per the theory of fractional calculus. Then, the HPPC experiment and the PSO algorithm were used to identify the internal parameters of the second order RC and fractional order models, respectively. As discovered during working tests, the parameters identified via the fractional order model proved to be more accurate. Furthermore, the feasibility of using the FOUHIF algorithm was evaluated under the conditions of NEDC and UDDS, with obvious colored noise. Compared with the fractional order unscented Kalman filter (FOUKF) and integer order unscented Kalman filter (UKF) algorithms, the FOUHIF algorithm showed significant improvement in both the accuracy and robustness of the estimation, with maximum errors of 1.86% and 1.61% under the two working conditions, and a terminal voltage prediction error of no more than 5.29 mV. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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24 pages, 3427 KiB

Open AccessArticle

Control-Oriented Modeling for Nonlinear MIMO Turbofan Engine Based on Equilibrium Manifold Expansion Model

by Chengkun Lv, Ziao Wang, Lei Dai, Hao Liu, Juntao Chang and Daren Yu

Energies 2021, 14(19), 6277; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196277 - 02 Oct 2021

Cited by 5 | Viewed by 1803

Abstract

This paper investigates the control-oriented modeling for turbofan engines. The nonlinear equilibrium manifold expansion (EME) model of the multiple input multiple output (MIMO) turbofan engine is established, which can simulate the variation of high-pressure rotor speed, low-pressure rotor speed and pressure ratio of [...] Read more.

This paper investigates the control-oriented modeling for turbofan engines. The nonlinear equilibrium manifold expansion (EME) model of the multiple input multiple output (MIMO) turbofan engine is established, which can simulate the variation of high-pressure rotor speed, low-pressure rotor speed and pressure ratio of compressor with fuel flow and throat area of the nozzle. Firstly, the definitions and properties of the equilibrium manifold method are presented. Secondly, the steady-state and dynamic two-step identification method of the MIMO EME model is given, and the effects of scheduling variables and input noise on model accuracy are discussed. By selecting specific path, a small amount of dynamic data is used to identify a complete EME model. Thirdly, modeling and simulation at dynamic off-design conditions show that the EME model has model accuracy close to the nonlinear component-level (NCL) model, but the model structure is simpler and the calculation is faster than that. Finally, the linearization results are obtained based on the properties of the EME model, and the stability of the model is proved through the analysis of the eigenvalues, which all have negative real parts. The EME model constructed in this paper can meet the requirements of real-time simulation and control system design. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 1754 KiB

Open AccessReview

Review of Potential Energy Storage in Abandoned Mines in Poland

by Candra Saigustia and Sylwester Robak

Energies 2021, 14(19), 6272; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196272 - 01 Oct 2021

Cited by 8 | Viewed by 3541

Abstract

Poland has had a total of 70 mines, but now more than half of them is out of operation. This mining closure raises with respect to the environment and unemployment. Innovative technology is needed to overcome the problems that arise and could simultaneously [...] Read more.

Poland has had a total of 70 mines, but now more than half of them is out of operation. This mining closure raises with respect to the environment and unemployment. Innovative technology is needed to overcome the problems that arise and could simultaneously make use of abandoned mine infrastructure. The increased electricity generation coming from renewable energy, which produces fluctuating and intermittent energy for the electric power system, causes frequency problems such that energy storage technologies are needed. Abandoned mines can be used for the implementation of energy storage plants. This paper explores the possibility of using abandoned mines in Poland for electrical energy storage. Closed mines can be used to store clean and flexible energy. This idea has the potential to support sustainable economic development within the community following mine closure in Poland. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 2393 KiB

Open AccessArticle

Voltage Flip Efficiency Enhancement for Piezo Energy Harvesting

by Vincent Frick, Liana Wassouf and Ehsan Jamshidpour

Electronics 2021, 10(19), 2400; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10192400 - 01 Oct 2021

Cited by 1 | Viewed by 1751 | Correction

Abstract

In this paper, we analyze the effect of an enhanced voltage flip technique on the power performance of a piezoelectric energy harvester. The enhanced voltage flip principle is based on a synchronized-switch-based architecture, and is referred to as FAR (Full Active Rectifier). It [...] Read more.

In this paper, we analyze the effect of an enhanced voltage flip technique on the power performance of a piezoelectric energy harvester. The enhanced voltage flip principle is based on a synchronized-switch-based architecture, and is referred to as FAR (Full Active Rectifier). It uses a tiny amount of the stored charge to boost the voltage flip. This work aims to demonstrate that, beside the enhanced flip efficiency, the FAR also contributes to improve the power efficiency of the harvester, especially under changing load constraint. Therefore, the paper proposes a thorough comparison between the FAR and its conventional counterpart, the Switch-only technique. The FAR is easy to implement and does not require any external inductor or capacitor. It only needs a reduced set of switches, an active diode and a simple control sequence, and can thus be implemented on a fully integrated circuit. The FAR can be used as a standalone voltage flip solution or in addition to further boost the flip efficiency in a state-of-the-art architecture such as SSHC for example. Tests were performed on a 0.35-µm process CMOS prototype IC. Experimental results revealed that the FAR extracts

19.1 μ W

from an off-the-shelf piezoelectric transducer when the output voltage is regulated at

1

V with

1

V open-circuit voltage and delivers up to 20% more power than the conventional Switch-only technique under load constraint. It also shows over

11 \times

power efficiency improvement compared to a conventional diode-based full bridge rectifier. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 2484 KiB

Open AccessArticle

Optimal Maintenance Policy for Offshore Wind Systems

by Vincent F. Yu, Thi Huynh Anh Le, Tai-Sheng Su and Shih-Wei Lin

Energies 2021, 14(19), 6082; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196082 - 24 Sep 2021

Cited by 2 | Viewed by 1911

Abstract

Employing maintenance threshold plays a critical step in determining an optimal maintenance policy for an offshore wind system to reduce maintenance costs while increasing system reliability. Considering the limited works on this topic, we propose a two-stage procedure to determine the optimal maintenance [...] Read more.

Employing maintenance threshold plays a critical step in determining an optimal maintenance policy for an offshore wind system to reduce maintenance costs while increasing system reliability. Considering the limited works on this topic, we propose a two-stage procedure to determine the optimal maintenance thresholds for multiple components of an offshore wind power system in order to minimize maintenance costs while achieving the highest possible system reliability. First, using genetic algorithms, a dynamic strategy is developed to determine the maintenance thresholds of individual components where the cost of maintenance and the rate of failure are critical. Then, fuzzy multi-objective programming is applied to find the system’s optimal maintenance threshold considering all components. A variety of factors including weather conditions, system reliability, power generation losses, and electricity market price are carefully considered to enhance the system’s reliability and reduce the costs of maintenance. When maintenance threshold results are compared, component-wise versus system-wise, an average system savings of 1.19% for maintenance cost is obtained while the system reliability is increased by 1.62% on average. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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36 pages, 10463 KiB

Open AccessReview

Review of Technologies and Recent Advances in Low-Temperature Sorption Thermal Storage Systems

by Hamza Ayaz, Veerakumar Chinnasamy, Junhyeok Yong and Honghyun Cho

Energies 2021, 14(19), 6052; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196052 - 23 Sep 2021

Cited by 15 | Viewed by 3127

Abstract

Sorption thermochemical storage systems can store thermal energy for the long-term with minimum amount of losses. Their flexibility in working with sustainable energy sources further increases their importance vis-à-vis high levels of pollution from carbon-based energy forms. These storage systems can be utilized [...] Read more.

Sorption thermochemical storage systems can store thermal energy for the long-term with minimum amount of losses. Their flexibility in working with sustainable energy sources further increases their importance vis-à-vis high levels of pollution from carbon-based energy forms. These storage systems can be utilized for cooling and heating purposes or shifting the peak load. This review provides a basic understanding of the technologies and critical factors involved in the performance of thermal energy storage (TES) systems. It is divided into four sections, namely materials for different sorption storage systems, recent advances in the absorption cycle, system configuration, and some prototypes and systems developed for sorption heat storage systems. Energy storage materials play a vital role in the system design, owing to their thermal and chemical properties. Materials for sorption storage systems are discussed in detail, with a new class of absorption materials, namely ionic liquids. It can be a potential candidate for thermal energy storage due to its substantial thermophysical properties which have not been utilized much. Recent developments in the absorption cycle and integration of the same within the storage systems are summarized. In addition, open and closed systems are discussed in the context of recent reactor designs and their critical issues. Finally, the last section summarizes some prototypes developed for sorption heat storage systems. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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15 pages, 2644 KiB

Open AccessArticle

An Optimized Framework for Energy Management of Multi-Microgrid Systems

by Komal Naz, Fasiha Zainab, Khawaja Khalid Mehmood, Syed Basit Ali Bukhari, Hassan Abdullah Khalid and Chul-Hwan Kim

Energies 2021, 14(19), 6012; https://0-doi-org.brum.beds.ac.uk/10.3390/en14196012 - 22 Sep 2021

Cited by 7 | Viewed by 2731

Abstract

Regarding different challenges, such as integration of green energy and autonomy of microgrid (MG) in the multi-microgrid (MMG) system, this paper presents an optimized and coordinated strategy for energy management of MMG systems that consider multiple scenarios of MGs. The proposed strategy operates [...] Read more.

Regarding different challenges, such as integration of green energy and autonomy of microgrid (MG) in the multi-microgrid (MMG) system, this paper presents an optimized and coordinated strategy for energy management of MMG systems that consider multiple scenarios of MGs. The proposed strategy operates at two optimization levels: local and global. At an MG level, each energy management system satisfies its local demand by utilizing all available resources via local optimization, and only sends surplus/deficit energy data signals to MMG level, which enhances customer privacy. Thereafter, at an MMG level, a central energy management system performs global optimization and selects optimized options from the available resources, which include charging/discharging energy to/from the community battery energy storage system, selling/buying power to/from other MGs, and trading with the grid. Two types of loads are considered in this model: sensitive and non-sensitive. The algorithm tries to make the system reliable by avoiding utmost load curtailment and prefers to shed non-sensitive loads over sensitive loads in the case of load shedding. To verify the robustness of the proposed scheme, several test cases are generated by Monte Carlo Simulations and simulated on the IEEE 33-bus distribution system. The results show the effectiveness of the proposed model. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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27 pages, 5434 KiB

Open AccessArticle

Selection of Output Voltage Compensators Gains in Two Cascaded Boost Converters with Input Filters by Means of the \({\mathfrak{D}}\)-Decomposition Technique

by Karol Najdek, Radosław Nalepa and Robert Lis

Energies 2021, 14(18), 5883; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185883 - 17 Sep 2021

Viewed by 1696

Abstract

In this paper, the

D

-decomposition technique is investigated as an intuitive method for finding the non-linear trajectories of PI-compensator gains. The trajectories reflect the desired dynamic properties at a system level specified by the gain and the phase margin (GMPM) in the [...] Read more.

In this paper, the

D

-decomposition technique is investigated as an intuitive method for finding the non-linear trajectories of PI-compensator gains. The trajectories reflect the desired dynamic properties at a system level specified by the gain and the phase margin (GMPM) in the frequency domain. They are presented as parametric curves in the proportional and the integral gains coordinates in form of

K_{I} = f (K_{P})

functions. The curves are inscribed into global stability boundaries (GSB). The corresponding Nyquist plots are included for comparison. The analysis is based on a system consisting of two serial-connected boost converters. Each converter has its input filter. The major parasitic components of the system are taken into account during the mathematical and simulation modelling. The control circuit time delays and non-linear semiconductors characteristics are also included. A complete set of practically useful system-level transfer functions in form of mathematical formulas is included. Selected aspects, such as the control-to-output voltage and the control-to-input current of one sub-system of the simulation model, have been verified experimentally. The presented results clearly indicate the need for interactions between the sub-systems of a system to be taken into account during controller gains selection. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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19 pages, 4858 KiB

Open AccessArticle

Air-Gap Flux Oriented Vector Control Based on Reduced-Order Flux Observer for EESM

by Feng Cai, Ke Li, Xiaodong Sun and Minkai Wu

Energies 2021, 14(18), 5874; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185874 - 16 Sep 2021

Cited by 2 | Viewed by 1937

Abstract

Electrically excited synchronous motor (EESM) has the characteristics of high order, nonlinear and strong coupling, so it is difficult to be controlled. However, it has the advantages of adjustable power factor, high efficiency, and high precision torque control, so it is widely used [...] Read more.

Electrically excited synchronous motor (EESM) has the characteristics of high order, nonlinear and strong coupling, so it is difficult to be controlled. However, it has the advantages of adjustable power factor, high efficiency, and high precision torque control, so it is widely used in high-power applications. The accuracy of a flux observer influences the speed control system of EESM. Based on state observer in modern control theory and electrical excitation synchronous machine state equation, a reduced-order flux observer is designed. Using the first-order difference method and forward bilinear transformation method, the reduced-order flux observer is discrete, and the stability of the motor system is analyzed. The analysis shows that the stability of the system using the bilinear transformation method is better than that using the first order forward difference method. In motor operation, motor parameters will be affected by the factors of temperature, magnetic saturation, and motor frequency. In this paper, the influence of parameter variation on the motor system is studied by using the variation of the pole distribution. Finally, the speed regulation system using the reduced-order observer is simulated, which verifies the accuracy of the reduced-order flux observer observation. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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25 pages, 3904 KiB

Open AccessArticle

The Potential of Variable Renewable Energy Sources in Mexico: A Temporally Evaluated and Geospatially Constrained Techno-Economical Assessment

by Edgar Ubaldo Peña Sánchez, Severin David Ryberg, Heidi Ursula Heinrichs, Detlef Stolten and Martin Robinius

Energies 2021, 14(18), 5779; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185779 - 14 Sep 2021

Cited by 7 | Viewed by 2835

Abstract

Due to the increasing global importance of decarbonizing human activities, especially the production of electricity, the optimal deployment of renewable energy technologies will play a crucial role in future energy systems. To accomplish this, particular attention must be accorded to the geospatial and [...] Read more.

Due to the increasing global importance of decarbonizing human activities, especially the production of electricity, the optimal deployment of renewable energy technologies will play a crucial role in future energy systems. To accomplish this, particular attention must be accorded to the geospatial and temporal distribution of variable renewable energy sources (VRES), such as wind and solar radiation, in order to match electricity supply and demand. This study presents a techno-economical assessment of four energy technologies in the hypothetical context of Mexico in 2050, namely: onshore and offshore wind turbines and open-field and rooftop photovoltaics. A land eligibility analysis incorporating physical, environmental, and sociopolitical eligibility constraints and individual turbine and photovoltaic park simulations, drawing on 39 years of climate data, is performed for individual sites across the country in an effort to determine the installable potential and the associated levelized costs of electricity. The results reveal that up to 54 PWh of renewable electricity can be produced at a levelized cost of electricity of less than 70 EUR·MWh⁻¹. Around 91% (49 PWh) of this electricity would originate from 23 TW of open-field photovoltaic parks that could occupy up to 578,000 km² of eligible land across the country. The remaining 9% (4.8 PWh) could be produced by 1.9 TW of onshore wind installations allocated to approximately 68,500 km² of eligible land that is almost fully adjacent to three mountainous zones. The combination of rooftop photovoltaic and offshore wind turbines accounts for a very small share of less than 0.03% of the overall techno-economical potential. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 4050 KiB

Open AccessEditor’s ChoiceArticle

Reinforcement Learning for Energy-Storage Systems in Grid-Connected Microgrids: An Investigation of Online vs. Offline Implementation

by Khawaja Haider Ali, Marvin Sigalo, Saptarshi Das, Enrico Anderlini, Asif Ali Tahir and Mohammad Abusara

Energies 2021, 14(18), 5688; https://0-doi-org.brum.beds.ac.uk/10.3390/en14185688 - 09 Sep 2021

Cited by 9 | Viewed by 3174

Abstract

Grid-connected microgrids consisting of renewable energy sources, battery storage, and load require an appropriate energy management system that controls the battery operation. Traditionally, the operation of the battery is optimised using 24 h of forecasted data of load demand and renewable energy sources [...] Read more.

Grid-connected microgrids consisting of renewable energy sources, battery storage, and load require an appropriate energy management system that controls the battery operation. Traditionally, the operation of the battery is optimised using 24 h of forecasted data of load demand and renewable energy sources (RES) generation using offline optimisation techniques, where the battery actions (charge/discharge/idle) are determined before the start of the day. Reinforcement Learning (RL) has recently been suggested as an alternative to these traditional techniques due to its ability to learn optimal policy online using real data. Two approaches of RL have been suggested in the literature viz. offline and online. In offline RL, the agent learns the optimum policy using predicted generation and load data. Once convergence is achieved, battery commands are dispatched in real time. This method is similar to traditional methods because it relies on forecasted data. In online RL, on the other hand, the agent learns the optimum policy by interacting with the system in real time using real data. This paper investigates the effectiveness of both the approaches. White Gaussian noise with different standard deviations was added to real data to create synthetic predicted data to validate the method. In the first approach, the predicted data were used by an offline RL algorithm. In the second approach, the online RL algorithm interacted with real streaming data in real time, and the agent was trained using real data. When the energy costs of the two approaches were compared, it was found that the online RL provides better results than the offline approach if the difference between real and predicted data is greater than 1.6%. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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24 pages, 86834 KiB

Open AccessArticle

Indonesia’s Vast Solar Energy Potential

by David Firnando Silalahi, Andrew Blakers, Matthew Stocks, Bin Lu, Cheng Cheng and Liam Hayes

Energies 2021, 14(17), 5424; https://0-doi-org.brum.beds.ac.uk/10.3390/en14175424 - 31 Aug 2021

Cited by 31 | Viewed by 15234

Abstract

In this paper, we conclude that Indonesia has vast potential for generating and balancing solar photovoltaic (PV) energy to meet future energy needs at a competitive cost. We systematically analyse renewable energy potential in Indonesia. Solar PV is identified to be an energy [...] Read more.

In this paper, we conclude that Indonesia has vast potential for generating and balancing solar photovoltaic (PV) energy to meet future energy needs at a competitive cost. We systematically analyse renewable energy potential in Indonesia. Solar PV is identified to be an energy source whose technical, environmental and economic potential far exceeds Indonesia’s present and future energy requirements and is far larger than all other renewable energy resources combined. We estimate that electricity consumption in Indonesia could reach 9000 terawatt-hours per year by 2050, which is 30 times larger than at present. Indonesia has abundant space to deploy enough solar to meet this requirement, including on rooftops, inland reservoirs, mining wasteland, and in combination with agriculture. Importantly, Indonesia has a vast maritime area that almost never experiences strong winds or large waves that could host floating solar capable of generating >200,000 terawatt-hours per year. Indonesia also has far more off-river pumped hydro energy storage potential than required for balancing solar generation. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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12 pages, 11032 KiB

Open AccessArticle

VxG Pattern-Based Analysis and Battery Deterioration Diagnosis

by Jungho Lim, Sung-Eun Lee, Kwang-Yong Park, Hee-Soo Kim and Jin-Hyeok Choi

Energies 2021, 14(17), 5422; https://0-doi-org.brum.beds.ac.uk/10.3390/en14175422 - 31 Aug 2021

Viewed by 2217

Abstract

This paper presents the results of an analysis using the direct current internal resistance (DCIR) method on a nickel-cobalt-manganese oxide (NCM)-based battery with a nominal capacity of 55.6 Ah. The accelerated degradation test was performed on V0G, V1G, and V2G patterns, representing existing [...] Read more.

This paper presents the results of an analysis using the direct current internal resistance (DCIR) method on a nickel-cobalt-manganese oxide (NCM)-based battery with a nominal capacity of 55.6 Ah. The accelerated degradation test was performed on V0G, V1G, and V2G patterns, representing existing simple power supply, smart charging control, and bi-directional charge/discharge control, respectively. We assumed V0G, V1G, and V2G patterns and conducted charging and discharging experiments according to the set conditions. According to the pattern repetition, changes in the internal resistance of DCIR and AC-impedance were analyzed and battery deterioration was diagnosed. By comparing DCIR and AC-impedance, we confirmed that the changes in internal resistance has a similar trend. In particular, we propose a new DCIR analysis method in the “stop-operation” part rather than the traditional DCIR method. In the case of traditional DCIR method, time is required for the battery to stabilize. However, the newly proposed DCIR analysis method has the advantage of diagnosing the deterioration of the battery during system operation by analyzing the internal resistance without the stabilization time of the battery. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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18 pages, 4775 KiB

Open AccessArticle

Operation Method of a Load Test Device Using an Energy Storage System for Site Acceptance Test of a Fire-Fighting Emergency Generator

by Juan Jin and Seung-Kyou Choi

Energies 2021, 14(17), 5395; https://0-doi-org.brum.beds.ac.uk/10.3390/en14175395 - 30 Aug 2021

Cited by 1 | Viewed by 2184

Abstract

Emergency generators are important facilities that supply emergency power to fire-fighting facilities in the event of a power outage. Accordingly, a load test of the emergency generator should be performed by cutting off the power source of the fire-fighting target in order to [...] Read more.

Emergency generators are important facilities that supply emergency power to fire-fighting facilities in the event of a power outage. Accordingly, a load test of the emergency generator should be performed by cutting off the power source of the fire-fighting target in order to accurately confirm the performance and condition of the emergency generator in normal circumstances. However, the test has usually been carried out without loads due to serious problems, which are caused by a shutdown of the power source for the load test of emergency generators, such as the shutdown of emergency load, etc. In order to overcome these problems, this paper proposes an operation method and algorithm of a load test device using ESS, which can conform to characteristics of emergency loads installed in fire-fighting targets by interconnecting it with the emergency generator. In addition, this paper performs a modeling of an emergency power system using PSCAD/EMTDC, and then this paper confirms the usefulness of the proposed method and operation algorithm of the load test device using ESS. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 6576 KiB

Open AccessReview

Lithium-Ion Battery Operation, Degradation, and Aging Mechanism in Electric Vehicles: An Overview

by Jia Guo, Yaqi Li, Kjeld Pedersen and Daniel-Ioan Stroe

Energies 2021, 14(17), 5220; https://0-doi-org.brum.beds.ac.uk/10.3390/en14175220 - 24 Aug 2021

Cited by 36 | Viewed by 9436

Abstract

Understanding the aging mechanism for lithium-ion batteries (LiBs) is crucial for optimizing the battery operation in real-life applications. This article gives a systematic description of the LiBs aging in real-life electric vehicle (EV) applications. First, the characteristics of the common EVs and the [...] Read more.

Understanding the aging mechanism for lithium-ion batteries (LiBs) is crucial for optimizing the battery operation in real-life applications. This article gives a systematic description of the LiBs aging in real-life electric vehicle (EV) applications. First, the characteristics of the common EVs and the lithium-ion chemistries used in these applications are described. The battery operation in EVs is then classified into three modes: charging, standby, and driving, which are subsequently described. Finally, the aging behavior of LiBs in the actual charging, standby, and driving modes are reviewed, and the influence of different working conditions are considered. The degradation mechanisms of cathode, electrolyte, and anode during those processes are also discussed. Thus, a systematic analysis of the aging mechanisms of LiBs in real-life EV applications is achieved, providing practical guidance, methods to prolong the battery life for users, battery designers, vehicle manufacturers, and material recovery companies. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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26 pages, 4683 KiB

Open AccessArticle

Solar-Based DG Allocation Using Harris Hawks Optimization While Considering Practical Aspects

by Suprava Chakraborty, Sumit Verma, Aprajita Salgotra, Rajvikram Madurai Elavarasan, Devaraj Elangovan and Lucian Mihet-Popa

Energies 2021, 14(16), 5206; https://0-doi-org.brum.beds.ac.uk/10.3390/en14165206 - 23 Aug 2021

Cited by 15 | Viewed by 2679

Abstract

The restructuring of power systems and the ever-increasing demand for electricity have given rise to congestion in power networks. The use of distributed generators (DGs) may play a significant role in tackling such issues. DGs may be integrated with electrical power networks to [...] Read more.

The restructuring of power systems and the ever-increasing demand for electricity have given rise to congestion in power networks. The use of distributed generators (DGs) may play a significant role in tackling such issues. DGs may be integrated with electrical power networks to regulate the drift of power in the transmission lines, thereby increasing the power transfer capabilities of lines and improving the overall performance of electrical networks. In this article, an effective method based on the Harris hawks optimization (HHO) algorithm is used to select the optimum capacity, number, and site of solar-based DGs to reduce real power losses and voltage deviation. The proposed HHO has been tested with a complex benchmark function then applied to the IEEE 33 and IEEE 69 bus radial distribution systems. The single and multiple solar-based DGs are optimized for the optimum size and site with a unity power factor. It is observed that the overall performance of the systems is enhanced when additional DGs are installed. Moreover, considering the stochastic and sporadic nature of solar irradiance, the practical size of DG has been suggested based on analysis that may be adopted while designing the actual photovoltaic (PV) plant for usage. The obtained simulation outcomes are compared with the latest state-of-the-art literature and suggest that the proposed HHO is capable of processing complex high dimensional benchmark functions and has capability to handle problems pertaining to electrical distribution in an effective manner. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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22 pages, 6262 KiB

Open AccessArticle

Comprehensive Modeling and Control of Grid-Connected Hybrid Energy Sources Using MPPT Controller

by Shazly A. Mohamed, Mohamed A. Tolba, Ayman A. Eisa and Ali M. El-Rifaie

Energies 2021, 14(16), 5142; https://0-doi-org.brum.beds.ac.uk/10.3390/en14165142 - 20 Aug 2021

Cited by 18 | Viewed by 2448

Abstract

Nuclear and renewables energies are the two variants for low-carbon energy and the evolving grid suggests possible synergies between them. Nuclear energy introduces supple operations based on power demand, while renewables such as PV and wind hybrid systems depend on the presence and [...] Read more.

Nuclear and renewables energies are the two variants for low-carbon energy and the evolving grid suggests possible synergies between them. Nuclear energy introduces supple operations based on power demand, while renewables such as PV and wind hybrid systems depend on the presence and strength of sunlight or wind. For grid stability, there is need to improve their performance in order to overcome the impact of this disadvantage. The paper is a step in this direction as it addresses a detailed comprehensive dynamic modeling and an efficient control of grid-connected energy sources such as PV or wind system to increase system reliability and to ensure the power quality and safe operation of critical demands. The behavior of the suggested hybrid system is tested at different climate circumstances such as variation of sun radiation and wind speed. The PV is equipped with a boost converter and a three-phase pulse width modulation (PWM) inverter. The wind energy comprises a doubly fed generator (DFIG) based on a variable-speed wind turbine. The two controllers’ rotor-side and grid-side converters of DFIG have the ability to generate and observe reactive power, to keep constant speed of the rotor and control the DC-link voltage. The proposed scheme was investigated using MATLAB software. The maximum power point tracking (MPPT) was used for two systems, PV and wind, in varying weather conditions. The simulation results prove that the voltage at the point of common coupling was constant. Furthermore, the injected current of the grid side was in sinusoidal form and was synchronized with grid side voltage. In addition, the injected power-to-utility grid was around power delivered by the hybrid PV and wind system. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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15 pages, 5801 KiB

Open AccessArticle

Heat and Mass Transfer Analysis in Chemically Reacting Flow of Non-Newtonian Liquid with Local Thermal Non-Equilibrium Conditions: A Comparative Study

by A. Alhadhrami, B. M. Prasanna, Rajendra Prasad K. C., K. Sarada and Hassan A. H. Alzahrani

Energies 2021, 14(16), 5019; https://0-doi-org.brum.beds.ac.uk/10.3390/en14165019 - 16 Aug 2021

Cited by 4 | Viewed by 1919

Abstract

In the current paper, we endeavour to execute a numerical analysis in connection with the boundary layer flow induced in a non-Newtonian liquid by a stretching sheet with heat and mass transfer. The effects of chemical reactions and local thermal non-equilibrium (LTNE) conditions [...] Read more.

In the current paper, we endeavour to execute a numerical analysis in connection with the boundary layer flow induced in a non-Newtonian liquid by a stretching sheet with heat and mass transfer. The effects of chemical reactions and local thermal non-equilibrium (LTNE) conditions are considered in the modelling. The LTNE model is based on energy equations, and provides unique heat transfer for both liquid phases. As a result, different temperature profiles for both the fluid and solid phases are used in this work. The model equation system is reduced by means of appropriate similarity transformations, which are then numerically solved by employing the classical Runge–Kutta (RK) scheme along with the shooting method. The resultant findings are graphed to show the effects of various physical factors on the involved distributions. Outcomes reveal that Jeffrey fluid shows improved velocity for lower values of porosity when compared to Oldroyd-B fluid. However, for higher values of porosity, the velocity of the Jeffery fluid declines faster than that of the Oldroyd-B fluid. Jeffery liquid shows improved fluid phase mass transfer, and decays more slowly than Oldroyd-B liquid for higher values of chemical reaction rate parameter. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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10 pages, 3369 KiB

Open AccessArticle

Design of Dual Ultra–Wideband Band–Pass Filter Using Stepped Impedance Resonator λg/4 Short Stubs and T–Shaped Band-Stop Filter

by Kicheol Yoon and Kwanggi Kim

Electronics 2021, 10(16), 1951; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10161951 - 13 Aug 2021

Cited by 6 | Viewed by 2513

Abstract

Portable wireless communication systems are increasingly in demand in small sizes for human convenience. In wireless communication systems, the performance, size, and unit cost are very important. A band−pass filter is important to sharp cut–off frequency characteristics, size, and frequency selectivity in wireless [...] Read more.

Portable wireless communication systems are increasingly in demand in small sizes for human convenience. In wireless communication systems, the performance, size, and unit cost are very important. A band−pass filter is important to sharp cut–off frequency characteristics, size, and frequency selectivity in wireless communication systems. The band−pass filter has three types of techniques in the transmission−zero method, stub−loaded resonator, and stepped impedance resonator for the sharp cut−off frequency characteristic, adjustable bandwidth, and excellent frequency response characteristics. To obtain these characteristics, the impedance ratio and length of a stub are mainly adjusted. It also utilizes a multi–mode technique to increase bandwidth. However, it is analyzed that the problem of reducing the size of the device still remains. To solve these problems, the paper is applied to a stub−loaded resonator and a stepped impedance resonator to control the impedance ratio and the length of the stub to obtain the results of the transmission−zero method, bandwidth control, and size reduction through the folded structure. Dual−band bandwidth was secured by integrating a T−shaped band−stop filter. The designed band–pass filter has center frequencies of 243 GHz and 7.49 GHz, and the insertion loss of a proposed band−pass filter is 0.102 dB and 0.103 dB. Additionally, the return loss of a proposed band−pass filter is 19.13 dB and 19.96 dB, respectively. The bandwidth of a filter is 120% and 105%, respectively. The size of the filter is 0.0708 λg × 0.0533 λg. The designed filter has a good skirt phenomenon, small size, low insertion loss, and dual−band characteristics. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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26 pages, 12910 KiB

Open AccessArticle

Complementary Optimization of Hydropower with Pumped Hydro Storage–Photovoltaic Plant for All-Day Peak Electricity Demand in Malawi

by Evance Chaima, Jijian Lian, Chao Ma, Yusheng Zhang and Sheila Kavwenje

Energies 2021, 14(16), 4948; https://0-doi-org.brum.beds.ac.uk/10.3390/en14164948 - 12 Aug 2021

Cited by 7 | Viewed by 2592

Abstract

Solar energy is currently dispatched ahead of other renewable energy sources. For the first time, this study presents a concept of exploiting temporary–periodical runoff discharge in the Shire River. Pumped hydro storage–photovoltaic plant (PHS–PV) was optimized to satisfy the all-day peak electricity demand [...] Read more.

Solar energy is currently dispatched ahead of other renewable energy sources. For the first time, this study presents a concept of exploiting temporary–periodical runoff discharge in the Shire River. Pumped hydro storage–photovoltaic plant (PHS–PV) was optimized to satisfy the all-day peak electricity demand in Malawi. The effect of varying the net head on the PHS system in both the generation and pumping operation modes was investigated. The bi-objective optimization evaluated the system reliability for day-time and night-time operation together with implied costs of investment for the whole system. The optimized system generated above 53% of added power as contrasted to single-source power generation from the existing hydropower plants. The estimated optimal capacities were 182 MWp (solar PV) and 86 MW (PHS plant). These additional optimal capacities achieved a 99.8% maximum system reliability (Loss of Power Supply Probability—LPSP—of 0.2%) and Levelized Cost of Energy—LCOE—of 0.13 USD/kWh. The overall investment cost of the PHS–PV system was estimated at 671.23 USD for an LPSP of 0.20%. The net head varies from 15.5 to 17.8 m with an impact on electricity generation of the PHS–PV system. More notably, the PHS–PV production matches with daily day-time and night-time peak loads and functions as a peaking plant. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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24 pages, 9777 KiB

Open AccessArticle

Energy Management of Hybrid UAV Based on Reinforcement Learning

by Huan Shen, Yao Zhang, Jianguo Mao, Zhiwei Yan and Linwei Wu

Electronics 2021, 10(16), 1929; https://0-doi-org.brum.beds.ac.uk/10.3390/electronics10161929 - 11 Aug 2021

Cited by 5 | Viewed by 2593

Abstract

In order to solve the flight time problem of Unmanned Aerial Vehicles (UAV), this paper proposes a set of energy management strategies based on reinforcement learning for hybrid agricultural UAV. The battery is used to optimize the working point of internal combustion engines [...] Read more.

In order to solve the flight time problem of Unmanned Aerial Vehicles (UAV), this paper proposes a set of energy management strategies based on reinforcement learning for hybrid agricultural UAV. The battery is used to optimize the working point of internal combustion engines to the greatest extent while solving the high power demand issues of UAV and the response problem of internal combustion engines. Firstly, the decision-making oriented hybrid model and UAV dynamic model are established. Owing to the characteristics of the energy management strategy (EMS) based on reinforcement learning (RL), which is an intelligent optimization algorithm that has emerged in recent years, the complex theoretical formula derivation is avoided in the modeling process. In terms of the EMS, a double Q learning algorithm with strong convergence is adopted. The algorithm separates the state action value function database used in derivation decisions and the state action value function-updated database brought by the decision, so as to avoid delay and shock within the convergence process caused by maximum deviation. After the improvement, the off-line training is carried out with a large number of flight data generated in the past. The simulation results demonstrate that the improved algorithm can show better performance with less learning cost than before by virtue of the search function strategy proposed in this paper. In the state space, time-based and residual fuel-based selection are carried out successively, and the convergence rate and application effect are compared and analyzed. The results show that the learning algorithm has stronger robustness and convergence speed due to the appropriate selection of state space under different types of operating cycles. After 120,000 cycles of training, the fuel economy of the improved algorithm in this paper can reach more than 90% of that of the optimal solution, and can perform stably in actual flight. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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16 pages, 3182 KiB

Open AccessArticle

Dissociation and Combustion of a Layer of Methane Hydrate Powder: Ways to Increase the Efficiency of Combustion and Degassing

by Sergey Y. Misyura and Igor G. Donskoy

Energies 2021, 14(16), 4855; https://0-doi-org.brum.beds.ac.uk/10.3390/en14164855 - 09 Aug 2021

Cited by 12 | Viewed by 1917

Abstract

The interest in natural gas hydrates is due both to huge natural reserves and to the strengthened role of environmentally friendly energy sources conditioned by the deterioration of the global environmental situation. The combustion efficiency increase is associated with the development of understanding [...] Read more.

The interest in natural gas hydrates is due both to huge natural reserves and to the strengthened role of environmentally friendly energy sources conditioned by the deterioration of the global environmental situation. The combustion efficiency increase is associated with the development of understanding of both the processes of dissociation and combustion of gas hydrates. To date, the problems of dissociation and combustion have, as a rule, been considered separately, despite their close interrelation. Usually, during combustion, there is a predetermined methane flow from the powder surface. In the present paper, the combustion of methane hydrate is simulated taking into account the non-stationary dissociation process in the powder layer. Experimental studies on the methane hydrate dissociation at negative temperatures have been carried out. It is shown that due to the increase in the layer temperature and changes in the porosity of the layer over time, i.e., coalescence of particles, the thermal conductivity of the layer can change significantly, which affects the heat flux and the dissociation rate. The flame front velocity was measured at different external air velocities. The air velocity and the vapor concentration in the combustion zone are shown to strongly affect the combustion temperature, flame stability and the flame front velocity. The obtained results may be applied to increase the efficiency of burning of a layer of methane hydrate powder, as well as for technologies of degassing the combustible gases and their application in the energy sector. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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28 pages, 1656 KiB

Open AccessArticle

The Network Topology Metrics Contributing to Local-Area Frequency Stability in Power System Networks

by Warren J. Farmer and Arnold J. Rix

Energies 2021, 14(15), 4643; https://0-doi-org.brum.beds.ac.uk/10.3390/en14154643 - 30 Jul 2021

Cited by 5 | Viewed by 2019

Abstract

The power system network topology influences the system frequency response to power imbalance disturbances. Here, the objective is to find the network metric(s) contributing to frequency transient stability. The graph Laplacians of six 4-node network topologies are analysed using Spectral Graph Theory. For [...] Read more.

The power system network topology influences the system frequency response to power imbalance disturbances. Here, the objective is to find the network metric(s) contributing to frequency transient stability. The graph Laplacians of six 4-node network topologies are analysed using Spectral Graph Theory. For homogeneous network connections, we show that the node degree measure indicates node robustness. Based on these analytical results, the investigation expands to a 10-node network topology consisting of two clusters, which provide further insight into the spectral results. The research then involves a simulation of a power imbalance disturbance on three 20-node networks with different topologies based on node degree, where we link the node degree measure to imbalance disturbance propagation through Wave Theory. The results provide an intuitive understanding of the impact of network topology on power system frequency stability. The analytical and simulation results indicate that a node’s sensitivity to disturbances is partially due to its node degree, reactance from disturbance location, and the link it has to other higher degree nodes (hierarchical position in network topology). Testing of the analytical and simulation results takes place on the nonhomogeneous IEEE-14 bus and IEEE-39 bus networks. These results provide insights into optimal inertia placement to improve the frequency robustness of low-inertia power systems. The network topology, considering node degrees, influences the speed at which the disturbance impact propagates from the disturbance location and how fast-standing waves form. The topology thus contributes to how fast the energy in a disturbance dissipates to zero. Full article

(This article belongs to the Topic Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems)

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