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19 pages, 1229 KiB

Open AccessArticle

Distributed Power Quality Conditioning System for Three-Phase Four-Wire Low Voltage Networks

by Valery Dovgun, Sergei Temerbaev, Maxim Chernyshov, Viktor Novikov, Natalia Boyarskaya and Elena Gracheva

Energies 2020, 13(18), 4915; https://0-doi-org.brum.beds.ac.uk/10.3390/en13184915 - 19 Sep 2020

Cited by 24 | Viewed by 1788

Abstract

This paper presents distributed power quality conditioning system to compensate current and voltage distortions in three-phase four-wire networks caused by unbalanced non-linear single-phase loads. The proposed conditioning system consists of several hybrid filter units installed in various nodes for compensation of excessive neutral [...] Read more.

This paper presents distributed power quality conditioning system to compensate current and voltage distortions in three-phase four-wire networks caused by unbalanced non-linear single-phase loads. The proposed conditioning system consists of several hybrid filter units installed in various nodes for compensation of excessive neutral currents and voltage distortions in a selected area of the distribution network. The system is open and it can be easily modified by installation of new filter units. A novel hybrid filter design procedure based on filter frequency characteristics optimization in the parameters of passive and active parts is presented. A digital system of control signal computation for active filters based on the use of modern methods of spectral analysis is considered. The proposed digital control system enables selective compensation of fundamental and harmonic components. The mathematical model of the proposed power quality conditioning system is developed in the MatLab software. The simulated results show that the presented conditioning system reduces the level of neutral conductor currents and the voltage unbalance as well ensures harmonic compensation in three-phase four-wire networks. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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20 pages, 8578 KiB

Open AccessArticle

Impact of Nonlinear Lighting Loads on the Neutral Conductor Current of Low Voltage Residential Grids

by Jairo Hernández, Andrés A. Romero, Jan Meyer and Ana María Blanco

Energies 2020, 13(18), 4851; https://0-doi-org.brum.beds.ac.uk/10.3390/en13184851 - 16 Sep 2020

Cited by 2 | Viewed by 2679

Abstract

In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have [...] Read more.

In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have a substantial impact on harmonic currents and, consequently, on the current flowing in the neutral conductor. This paper analyzes the impact of modern energy-efficient lighting technologies on the neutral conductor current by using a synthetic Low Voltage residential grid. Different load scenarios reflecting the transition from incandescent lamps, via CFL, to LED lamps are compared concerning the neutral conductor current at different points in the network. The inherent randomness related to the use of lighting devices by each residential customer is considered employing a Monte Carlo simulation. Obtained results show that the use of CFL has a greater impact on the neutral conductor current of Low Voltage (LV) residential grids and that, with increasing use of LED lamps, a decreasing impact can be expected in the future. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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24 pages, 13179 KiB

Open AccessArticle

Thermal Analysis of Dry-Type Air-Core Coils for the Optimization of Passive Filtering Systems

by Josué Rodríguez D., G. Alonso Orcajo, José M. Cano, Joaquín G. Norniella and Asier Vicente

Energies 2020, 13(17), 4540; https://0-doi-org.brum.beds.ac.uk/10.3390/en13174540 - 2 Sep 2020

Cited by 8 | Viewed by 2887

Abstract

The analysis of harmonic currents in distribution networks of industrial facilities and the associated filtering stages is essential to optimize the production of these installations. Dry-type air-core reactors are one of the main elements of harmonic filter banks. A thermal analysis of these [...] Read more.

The analysis of harmonic currents in distribution networks of industrial facilities and the associated filtering stages is essential to optimize the production of these installations. Dry-type air-core reactors are one of the main elements of harmonic filter banks. A thermal analysis of these reactors in conventional steel plants and an evaluation of the criteria used to adjust the corresponding thermal protections are proposed in this paper. Accordingly, harmonic currents through the different filter branches are assessed. The proposed methodology builds a thermal magnetic model using the finite element method (FEM) whereby electromagnetic fields, currents and losses are emulated, to allow for recreating the actual coil temperature. The study aims at increasing the reliability of filtering systems by lowering the number of unscheduled shutdowns due to conservative adjustments of thermal protections. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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18 pages, 1370 KiB

Open AccessArticle

A Proposed Harmonic Monitoring System for Large Power Users Considering Harmonic Limits

by Rosalia Sinvula, Khaled Mohamed Abo-Al-Ez and Mohamed Tariq Kahn

Energies 2020, 13(17), 4507; https://0-doi-org.brum.beds.ac.uk/10.3390/en13174507 - 1 Sep 2020

Cited by 7 | Viewed by 2836

Abstract

Most power utilities within Southern Africa are faced with the challenges of harmonic distortion due to the high penetration of renewable energy sources (RES) and the use of electronic devices. There is an excessive total harmonic distortion (THD) measured at the point of [...] Read more.

Most power utilities within Southern Africa are faced with the challenges of harmonic distortion due to the high penetration of renewable energy sources (RES) and the use of electronic devices. There is an excessive total harmonic distortion (THD) measured at the point of common coupling (PCC). In this paper, a proposed harmonic monitoring system for large power users (LPUs) is developed. This proposed system considers harmonic limits of the individual and THD of the customers allowed injecting into the network, which should be part of the contractual electricity supply agreement (ESA). Hence, it will enable the monitoring of harmonic distortion to be smooth by determining whether the customer has passed or failed compliance for individual harmonic order and the THD of the voltage. The measurements of harmonic distortion are done using the Unipower power quality (PQ) analyzers that are connected at different points within the industrial network. Measurements of harmonic distortion of an industrial site are compared to the simulation results performed by DIgSILENT software to validate the proposed harmonic monitoring system. Based on the validation results, it is recommended that the ESA between the power utilities and the customers should consist of the harmonic limits. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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16 pages, 3415 KiB

Open AccessArticle

Measurement-Based Distribution Grid Harmonic Impedance Models and Their Uncertainties

by Ravi Shankar Singh, Vladimir Ćuk and Sjef Cobben

Energies 2020, 13(16), 4259; https://0-doi-org.brum.beds.ac.uk/10.3390/en13164259 - 17 Aug 2020

Cited by 7 | Viewed by 2387

Abstract

Aggregated Norton’s equivalent models, with parallel impedance and current injection at different harmonic frequencies are used to model the distribution grid in harmonic studies. These models are derived based on measurements and/or prior knowledge about the grid. The measurement-based distribution (sub-)grid impedance estimation [...] Read more.

Aggregated Norton’s equivalent models, with parallel impedance and current injection at different harmonic frequencies are used to model the distribution grid in harmonic studies. These models are derived based on measurements and/or prior knowledge about the grid. The measurement-based distribution (sub-)grid impedance estimation method uses harmonic phasors of 3-phase current and voltage measurements to capture the response of the distribution (sub-)grid before and after an event in the utility side of the grid. However, due to increasing non-linear components in the grid, knowledge about uncertainty in parameters of such equivalent models which intrinsically describe a linear grid becomes important. The aim of this paper is to present two novel methods to calculate the uncertainty of the measurement-based Norton’s equivalent harmonic model of the distribution (sub-)grids as seen from the utility side at the Point of Common Coupling (PCC). The impedance and the uncertainty calculations are demonstrated on a simulated network. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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17 pages, 3695 KiB

Open AccessArticle

Assessing and Mitigating Impacts of Electric Vehicle Harmonic Currents on Distribution Systems

by Dima Alame, Maher Azzouz and Narayan Kar

Energies 2020, 13(12), 3257; https://0-doi-org.brum.beds.ac.uk/10.3390/en13123257 - 23 Jun 2020

Cited by 25 | Viewed by 2824

Abstract

Harmonic currents of electric vehicle (EV) chargers could jeopardize the power quality of distribution systems and add to the transformer’s losses, thus degrading its lifetime. This paper assesses and mitigates the impacts of different EV chargers on distribution transformers and the voltage quality [...] Read more.

Harmonic currents of electric vehicle (EV) chargers could jeopardize the power quality of distribution systems and add to the transformer’s losses, thus degrading its lifetime. This paper assesses and mitigates the impacts of different EV chargers on distribution transformers and the voltage quality of distribution systems. The effect of state-of-charge (SOC) of the EV battery is considered through applying weighted arithmetic mean to accurately assess the impacts of EV harmonic currents on aging and losses of the EV interfacing transformer. The voltage quality of the IEEE 33-bus distribution system, supplying several EV parking lots, is also assessed at different charging levels using a fast-decoupled harmonic power flow. A new optimal harmonic power flow algorithm—that incorporates photovoltaic-based distribution generation units (DGs)—is developed to enhance the voltage quality of distribution systems, and elongate the lifetime of the substation transformer. The effectiveness of the proposed mitigation method is confirmed using the IEEE 33-bus distribution system, hosting several EV charging stations and photovoltaic-based DGs. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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19 pages, 4652 KiB

Open AccessArticle

Selection of C-Type Filters for Reactive Power Compensation and Filtration of Higher Harmonics Injected into the Transmission System by Arc Furnaces

by Andrzej Grzegorz Lange and Grzegorz Redlarski

Energies 2020, 13(9), 2330; https://0-doi-org.brum.beds.ac.uk/10.3390/en13092330 - 7 May 2020

Cited by 19 | Viewed by 3139

Abstract

This article presents a method for selecting the elements of a C-type filter working with a conventional LC-type filter for compensating reactive power and filtering out higher harmonics generated by arc furnaces and ladle furnaces. The study was conducted in a steel mill [...] Read more.

This article presents a method for selecting the elements of a C-type filter working with a conventional LC-type filter for compensating reactive power and filtering out higher harmonics generated by arc furnaces and ladle furnaces. The study was conducted in a steel mill supplied by a 110 kV transmission system, where higher harmonic currents and nonlinear loads were measured. A series of computer simulations were performed under various operating conditions, and an algorithm for selecting the parameters of a third-order C-type filter (for suppressing the second harmonic) and two second-order LC-type filters (for suppressing the third harmonic) was proposed. The filtering system was tested in an arc furnace with the highest rated power, and harmonics in the current spectrum were evaluated. The results of the measurements were used to analyze the effectiveness of the compensation system comprising two passive C-type and LC-type filters at different system configurations. C-type filters significantly influenced current harmonics. The influence of the changes in the number of arc furnace transformers on the true Root Mean Square (RMS) of the currents injected into the 110 kV transmission system and on the voltages of the 110 kV busbars was discussed. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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22 pages, 5935 KiB

Open AccessArticle

The Performance of the BTB-VSC for Active Power Balancing, Reactive Power Compensation and Current Harmonic Filtering in the Interconnected Systems

by Janeth Alcalá, Víctor Cárdenas, Alejandro Aganza, Jorge Gudiño-Lau and Saida Charre

Energies 2020, 13(4), 831; https://0-doi-org.brum.beds.ac.uk/10.3390/en13040831 - 14 Feb 2020

Cited by 10 | Viewed by 2402

Abstract

Nowadays, the use of power converters to control active and reactive power in AC–AC grid-connected systems has increased. With respect to indirect AC–AC converters, the tendency is to enable the back-to-back (BTB) voltage source converter (VSC) as an active power filter (APF) to [...] Read more.

Nowadays, the use of power converters to control active and reactive power in AC–AC grid-connected systems has increased. With respect to indirect AC–AC converters, the tendency is to enable the back-to-back (BTB) voltage source converter (VSC) as an active power filter (APF) to compensate current harmonics. Most of the reported works use the BTB-VSC as an auxiliary topology that, combined with other topologies, is capable of active power regulation, reactive power compensation and current harmonic filtering. With the analysis presented in this work, the framework of the dynamics associated with the control loops is established and it is demonstrated that BTB-VSC can perform the three tasks for which, in the reviewed literature, at least two different topologies are reported. The proposed analysis works to support the performance criteria of the BTB-VSC when it executes the three control actions simultaneously and the total current harmonic distortion is reduced from 27.21% to 6.16% with the selected control strategy. Full article

(This article belongs to the Special Issue Harmonics and Quality of Power)

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