Research

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23 pages, 11194 KiB

Open AccessArticle

Characteristic Analysis and Indexing of Multimachine Transient Stabilization Using Virtual Synchronous Generator Control

by Yuko Hirase, Kazusa Uezaki, Dai Orihara, Hiroshi Kikusato and Jun Hashimoto

Energies 2021, 14(2), 366; https://0-doi-org.brum.beds.ac.uk/10.3390/en14020366 - 11 Jan 2021

Cited by 5 | Viewed by 2196

Abstract

As distributed power sources via grid-connected inverters equipped with functions to support system stabilization are being rapidly introduced, individual systems are becoming more complex, making the quantification and evaluation of the stabilizing functions difficult. Therefore, to introduce distributed power sources and achieve stable [...] Read more.

As distributed power sources via grid-connected inverters equipped with functions to support system stabilization are being rapidly introduced, individual systems are becoming more complex, making the quantification and evaluation of the stabilizing functions difficult. Therefore, to introduce distributed power sources and achieve stable system operation, a system should be reduced to a necessary but sufficient size in order to enable the quantification of its behavior supported by transient theory. In this study, a system in which multiple distributed power supplies equipped with virtual synchronous generator control are connected is contracted to a two-machine system: a main power supply and all other power supplies. The mechanical torque of each power supply is mathematically decomposed into inertia, damping, synchronization torques, and the governor effect. The system frequency deviations determined by these elements are quantitatively indexed using MATLAB/Simulink. The quantification index displayed in three-dimensioned graphs illustrates the relationships between the various equipment constants of the main power supply, the control variables of the grid-connected inverter control, and the transient time series. Moreover, a stability analysis is performed in both the time and frequency domains. Full article

(This article belongs to the Special Issue Microgrids 2020)

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23 pages, 3409 KiB

Open AccessArticle

IoVT: Internet of Vulnerable Things? Threat Architecture, Attack Surfaces, and Vulnerabilities in Internet of Things and Its Applications towards Smart Grids

by Pooja Anand, Yashwant Singh, Arvind Selwal, Pradeep Kumar Singh, Raluca Andreea Felseghi and Maria Simona Raboaca

Energies 2020, 13(18), 4813; https://0-doi-org.brum.beds.ac.uk/10.3390/en13184813 - 15 Sep 2020

Cited by 35 | Viewed by 6516

Abstract

In recent years, people have witnessed numerous Internet of Things (IoT)-based attacks with the exponential increase in the number of IoT devices. Alongside this, the means to secure IoT-based applications are maturing slower than our budding dependence on them. Moreover, the vulnerabilities in [...] Read more.

In recent years, people have witnessed numerous Internet of Things (IoT)-based attacks with the exponential increase in the number of IoT devices. Alongside this, the means to secure IoT-based applications are maturing slower than our budding dependence on them. Moreover, the vulnerabilities in an IoT system are exploited in chains to penetrate deep into the network and yield more adverse aftereffects. To mitigate these issues, this paper gives unique insights for handling the growing vulnerabilities in common IoT devices and proposes a threat architecture for IoT, addressing threats in the context of a three-layer IoT reference architecture. Furthermore, the vulnerabilities exploited at the several IoT attack surfaces and the challenges they exert are explored. Thereafter, the challenges in quantifying the IoT vulnerabilities with the existing framework are also analyzed. The study also covers a case study on the Intelligent Transportation System, covering road transport and traffic control specifically in terms of threats and vulnerabilities. Another case study on secure energy management in the Smart Grid is also presented. This case study covers the applications of Internet of Vulnerable Things (IoVT) in Smart energy Grid solutions, as there will be tremendous use of IoT in future Smart Grids to save energy and improve overall distribution. The analysis shows that the integration of the proposed architecture in existing applications alarms the developers about the embedded threats in the system. Full article

(This article belongs to the Special Issue Microgrids 2020)

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23 pages, 8767 KiB

Open AccessArticle

Research on Synchronverter-Based Regenerative Braking Energy Feedback System of Urban Rail Transit

by Shuting Li, Songrong Wu, Shiqiang Xiang, Yabo Zhang, Josep M. Guerrero and Juan C. Vasquez

Energies 2020, 13(17), 4418; https://0-doi-org.brum.beds.ac.uk/10.3390/en13174418 - 26 Aug 2020

Cited by 8 | Viewed by 2720

Abstract

Generally running with frequent braking over short distances, the urban rail transit train generates great quantities of regenerative braking energy (RBE). The RBE feedback system can effectively recycle RBE and give it back to the AC grid. However, the lack of damp and [...] Read more.

Generally running with frequent braking over short distances, the urban rail transit train generates great quantities of regenerative braking energy (RBE). The RBE feedback system can effectively recycle RBE and give it back to the AC grid. However, the lack of damp and inertia of generators makes conventional PWM RBE feedback system more sensitive to power fluctuations. To address this issue, a synchronverter-based RBE feedback system of urban rail transit is designed in this paper. First, the structure of the feedback system is presented. Then, the synchronverter-based control strategy with greater flexibility and higher stability is fully discussed. Furthermore, the parameter design of the system is analyzed in detail. Finally, simulation results and experimental results are provided to show the good dynamic performance of the system. Using this synchronverter-based approach, the system supplies traction power to the traction network when the train accelerates and gives the RBE back to the AC grid when the train brakes, in light of the variation of the DC bus voltage. Moreover, the system can be self-synchronized with the AC grid and make corresponding power management on the basis of changes in the voltage amplitude as well as the frequency of the grid. In this sense, the RBE feedback system becomes more flexible, effective and robust. Full article

(This article belongs to the Special Issue Microgrids 2020)

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17 pages, 9899 KiB

Open AccessArticle

Design and Implementation of a Dual-Input Single-Output Photovoltaic Converter

by Ersan Kabalci, Yasin Kabalci and Josep M. Guerrero

Energies 2020, 13(14), 3679; https://0-doi-org.brum.beds.ac.uk/10.3390/en13143679 - 16 Jul 2020

Cited by 1 | Viewed by 3686

Abstract

In many solar inverters, a dc/dc converter is mainly located between the solar arrays and the inverter. This study presents an enhanced maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems that drives solar array voltages to track a reference value and [...] Read more.

In many solar inverters, a dc/dc converter is mainly located between the solar arrays and the inverter. This study presents an enhanced maximum power point tracking (MPPT) algorithm for photovoltaic (PV) systems that drives solar array voltages to track a reference value and decreases fluctuations and oscillations in PV voltage. Different from the previously presented methods, a novel MPPT method is proposed that ensures tracking accuracy by considering output voltage in addition to input voltage and currents. The proposed method detects

d I / d V

variations, compares the output voltage with the desired reference to shift operation mode and refreshes step size. The digital filtering, enhanced PI, and perturb-and-observe (P&O) tracking features of the proposed MPPT method make it robust to mitigate source fluctuations and sensitivity to partial shading based oscillations. In order to validate the success of the proposed method, a test rig has been installed with dual boost converters. The performance improvements have been verified by both simulation and experimental results that are compared to InCon and P&O MPPT methods. It is also confirmed by experimental results that the proposed MPPT method provides robust control capability in terms of tracking the reference voltage and rejecting the effects of various shading situations on solar arrays. Full article

(This article belongs to the Special Issue Microgrids 2020)

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18 pages, 13503 KiB

Open AccessArticle

Enhanced Intelligent Energy Management System for a Renewable Energy-Based AC Microgrid

by Mehdi Dhifli, Abderezak Lashab, Josep M. Guerrero, Abdullah Abusorrah, Yusuf A. Al-Turki and Adnane Cherif

Energies 2020, 13(12), 3268; https://0-doi-org.brum.beds.ac.uk/10.3390/en13123268 - 24 Jun 2020

Cited by 10 | Viewed by 2958

Abstract

This paper proposes an enhanced energy management system (EEMS) for a residential AC microgrid. The renewable energy-based AC microgrid with hybrid energy storage is broken down into three distinct parts: a photovoltaic (PV) array as a green energy source, a battery (BT) and [...] Read more.

This paper proposes an enhanced energy management system (EEMS) for a residential AC microgrid. The renewable energy-based AC microgrid with hybrid energy storage is broken down into three distinct parts: a photovoltaic (PV) array as a green energy source, a battery (BT) and a supercapacitor (SC) as a hybrid energy storage system (HESS), and apartments and electric vehicles, given that the system is for residential areas. The developed EEMS ensures the optimal use of the PV arrays’ production, aiming to decrease electricity bills while reducing fast power changes in the battery, which increases the reliability of the system, since the battery undergoes fewer charging/discharging cycles. The proposed EEMS is a hybrid control strategy, which is composed of two stages: a state machine (SM) control to ensure the optimal operation of the battery, and an operating mode (OM) for the best operation of the SC. The obtained results show that the EEMS successfully involves SC during fast load and PV generation changes by decreasing the number of BT charging/discharging cycles, which significantly increases the system’s life span. Moreover, power loss is decreased during passing clouds phases by decreasing the power error between the extracted power by the sources and the required equivalent; the improvement in efficiency reaches 9.5%. Full article

(This article belongs to the Special Issue Microgrids 2020)

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29 pages, 6902 KiB

Open AccessArticle

Comparative Study of Control Strategies for Stabilization and Performance Improvement of DC Microgrids with a CPL Connected

by Isaías V. de Bessa, Renan L. P. de Medeiros, Iury Bessa, Florindo A. C. Ayres Junior, Alessandra R. de Menezes, Gustavo M. Torres and João Edgar Chaves Filho

Energies 2020, 13(10), 2663; https://0-doi-org.brum.beds.ac.uk/10.3390/en13102663 - 25 May 2020

Cited by 3 | Viewed by 2618

Abstract

The DC microgrid system is composed by converters that operate like feeders and loads. Among these loads, we highlight the constant power loads (CPLs) that may cause instability in the microgrid, observed in the form of undesired oscillations due to its negative impedance [...] Read more.

The DC microgrid system is composed by converters that operate like feeders and loads. Among these loads, we highlight the constant power loads (CPLs) that may cause instability in the microgrid, observed in the form of undesired oscillations due to its negative impedance behavior. Therefore, this work proposes to use performance indices and stability margins to evaluate state and output feedback control strategies for stabilization of DC microgrids. In particular, it is proposed to evaluate the stability margin of the proposed methodologies by means of the impedance relations in the microgrid based on the Middlebrook criterion. Our simulations and tests showed the relation between the performance and stability degradation and the microgrid impedances variation. Full article

(This article belongs to the Special Issue Microgrids 2020)

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Review

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37 pages, 1180 KiB

Open AccessFeature PaperReview

The Spectrum of Proactive, Resilient Multi-Microgrid Scheduling: A Systematic Literature Review

by Michael H. Spiegel, Eric M. S. P. Veith and Thomas I. Strasser

Energies 2020, 13(17), 4543; https://0-doi-org.brum.beds.ac.uk/10.3390/en13174543 - 02 Sep 2020

Cited by 14 | Viewed by 3217

Abstract

Multi-microgrids address the need for a resilient, sustainable, and cost-effective electricity supply by providing a coordinated operation of individual networks. Due to local generation, dynamic network topologies, and islanding capabilities of hosted microgrids or groups thereof, various new fault mitigation and optimization options [...] Read more.

Multi-microgrids address the need for a resilient, sustainable, and cost-effective electricity supply by providing a coordinated operation of individual networks. Due to local generation, dynamic network topologies, and islanding capabilities of hosted microgrids or groups thereof, various new fault mitigation and optimization options emerge. However, with the great flexibility, new challenges such as complex failure modes that need to be considered for a resilient operation, appear. This work systematically reviews scheduling approaches which significantly influence the feasibility of mitigation options before a failure is encountered. An in-depth analysis of identified key contributions covers aspects such as the mathematical apparatus, failure models and validation to highlight the current methodical spectrum and to identify future perspectives. Despite the common optimization-based framework, a broad variety of scheduling approaches is revealed. However, none of the key contributions provides practical insights beyond lab validation and considerable effort is required until the approaches can show their full potential in practical implementations. It is expected that the great level of detail guides further research in improving and validating existing scheduling concepts as well as it, in the long run, aids engineers to choose the most suitable options regarding increasingly resilient power systems. Full article

(This article belongs to the Special Issue Microgrids 2020)

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22 pages, 6241 KiB

Open AccessReview

Review of Dynamic Positioning Control in Maritime Microgrid Systems

by Mojtaba Mehrzadi, Yacine Terriche, Chun-Lien Su, Muzaidi Bin Othman, Juan C. Vasquez and Josep M. Guerrero

Energies 2020, 13(12), 3188; https://0-doi-org.brum.beds.ac.uk/10.3390/en13123188 - 19 Jun 2020

Cited by 21 | Viewed by 12434

Abstract

For many offshore activities, including offshore oil and gas exploration and offshore wind farm construction, it is essential to keep the position and heading of the vessel stable. The dynamic positioning system is a progressive technology, which is extensively used in shipping and [...] Read more.

For many offshore activities, including offshore oil and gas exploration and offshore wind farm construction, it is essential to keep the position and heading of the vessel stable. The dynamic positioning system is a progressive technology, which is extensively used in shipping and other maritime structures. To maintain the vessels or platforms from displacement, its thrusters are used automatically to control and stabilize the position and heading of vessels in sea state disturbances. The theory of dynamic positioning has been studied and developed in terms of control techniques to achieve greater accuracy and reduce ship movement caused by environmental disturbance for more than 30 years. This paper reviews the control strategies and architecture of the DPS in marine vessels. In addition, it suggests possible control principles and makes a comparison between the advantages and disadvantages of existing literature. Some details for future research on DP control challenges are discussed in this paper. Full article

(This article belongs to the Special Issue Microgrids 2020)

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31 pages, 2468 KiB

Open AccessReview

Recent Developments and Challenges on AC Microgrids Fault Detection and Protection Systems–A Review

by Noor Hussain, Mashood Nasir, Juan Carlos Vasquez and Josep M. Guerrero

Energies 2020, 13(9), 2149; https://0-doi-org.brum.beds.ac.uk/10.3390/en13092149 - 01 May 2020

Cited by 53 | Viewed by 5328

Abstract

The protection of AC microgrids (MGs) is an issue of paramount importance to ensure their reliable and safe operation. Designing reliable protection mechanism, however, is not a trivial task, as many practical issues need to be considered. The operation mode of MGs, which [...] Read more.

The protection of AC microgrids (MGs) is an issue of paramount importance to ensure their reliable and safe operation. Designing reliable protection mechanism, however, is not a trivial task, as many practical issues need to be considered. The operation mode of MGs, which can be grid-connected or islanded, employed control strategy and practical limitations of the power electronic converters that are utilized to interface renewable energy sources and the grid, are some of the practical constraints that make fault detection, classification, and coordination in MGs different from legacy grid protection. This article aims to present the state-of-the-art of the latest research and developments, including the challenges and issues in the field of AC MG protection. A broad overview of the available fault detection, fault classification, and fault location techniques for AC MG protection and coordination are presented. Moreover, the available methods are classified, and their advantages and disadvantages are discussed. Full article

(This article belongs to the Special Issue Microgrids 2020)

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