Special Issue "Power Quality in Smart Grids"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Power Electronics".

Deadline for manuscript submissions: closed (30 April 2019).

Special Issue Editor

Prof. Dr. Shuhui Li
E-Mail Website
Guest Editor
Department of Center for Advanced Vehicle Technologies, College of Electrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama, USA
Tel. +(205) 348-9085
Interests: smart grid and smart microgrid; renewable energy; systems power; electronics; electric machines and drives; power systems; artificial intelligence and neural networks modeling; analysis and simulation of dynamic systems; massively parallel processing applications software; engineering measurements and instrumentations
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Special Issue Information

Dear Colleagues,

The electric power grid of today is experiencing a significant change because of the rapid development of renewable energy technologies, on the generation side, and electric vehicles and plug-in hybrid electric vehicles, on the energy consumption side. The smart grid is the key to enhance the penetration of renewable energy into electric power systems and EV integration with the grid. However, due to the intermittent and distributed nature of renewable energy sources and electric vehicles as well as special role of power electronic converters for grid interconnection of both, power quality is becoming an increasing important issue for the healthy development and growth of smart grid technology. Power quality issue also is growing on the high voltage transmission side of the smart grid due to the adoption of power electronic based new technologies in the transmission grid, such as HVDC and STATCOM.  This Special Issue focuses on recent advances of new technologies that can improve the power quality (such as voltage stability, frequency stability, and harmonic distortion) of the grid so as to strengthen the growth of smart electric power grid and accommodate interconnection of more renewable energy and EVs into electric utility systems. The Special Issue is interested in, but not limited to, the following issues associated with the power quality in a smart grid:
1) power electronic converter system topologies and circuit designs;
2) converter control technologies;
3) filtering technologies for power electronics based devices;
4) dispatchable generation reserves required to improve smart grid power quality and under what circumstances;
5) impact of increased sustainable energy and EV penetration;
6) how do impacts vary with renewable and EV penetration?
7) how will sustainable energy generation and EV interconnection affect system operating strategies? Energy storage, demand response, microgrids, etc. 

Dr. Shuhui Li
Guest Editor

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Keywords

  • grid reliability and stability
  • voltage regulation
  • frequency regulation
  • harmonic distortion
  • power electronics
  • control of power electronic converter system
  • passive and active filtering
  • solar photovoltaics
  • wind power
  • electric vehicles
  • distributed generation
  • FACTs devices
  • microgrid
  • power generation control
  • energy storage
  • automatic generation control
  • grid operators
  • demand response
  • grid monitoring and measurement

Published Papers (13 papers)

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Research

Open AccessArticle
Control of Internal Dynamics of Grid-Connected Modular Multilevel Converter Using an Integral Backstepping Controller
Electronics 2019, 8(4), 456; https://doi.org/10.3390/electronics8040456 - 24 Apr 2019
Abstract
The modular multilevel converter (MMC) has significant applications in power systems due to its promising features, such as modularity, reliability, scalability, and low harmonic distortion. One of the challenges in the operation of MMC is to regulate the circulating current in its phase [...] Read more.
The modular multilevel converter (MMC) has significant applications in power systems due to its promising features, such as modularity, reliability, scalability, and low harmonic distortion. One of the challenges in the operation of MMC is to regulate the circulating current in its phase leg and sub module (SM) capacitor voltage. This paper presents the control of internal dynamics, i.e., circulating current and submodule capacitor voltage, of the MMC using an integral backstepping algorithm. The design of the controller is based on Lyapunov stability function. The backstepping control ensures the convergence of the error signal to zero. Additionally, the integral action in the control law increases the robustness and reliability of the system against the external disturbances and model uncertainties. Moreover, the integral term in the controller eliminates the residual steady-state error. The Lyapunov function-based design of the backstepping controller guarantees the convergence of circulating current as well as submodule capacitor voltage for any possible initial condition. Moreover, the performance of the proposed integral backstepping controller is compared with the proportional resonant (PR) controller. The proposed backstepping control scheme for three-phase MMC has been implemented in MATLAB/Simulink. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Multi-Objective Service Restoration of Radial Distribution System in the Presence of Non-Linear Loads
Electronics 2019, 8(3), 369; https://doi.org/10.3390/electronics8030369 - 26 Mar 2019
Abstract
Most of the power electronic components act as non-linear loads because they draw non- sinusoidal current from the power supply. Due to these non-linear loads, current harmonics are injected in the power network. For normal operation, any power network is equipped with provisions [...] Read more.
Most of the power electronic components act as non-linear loads because they draw non- sinusoidal current from the power supply. Due to these non-linear loads, current harmonics are injected in the power network. For normal operation, any power network is equipped with provisions to keep the harmonics level to a minimum value. Whenever a fault occurs in the distribution system, the primary goal is to re-energize the healthy part of the network which got interrupted. It can be done by changing the topology of the network. This method is called as Service Restoration (SR). In this paper, a service restoration strategy is proposed when non-linear loads are present in the radial distribution system. Service restoration problem is formulated as a multi-objective, constrained optimization problem. Three new objectives are included to address the problem of harmonics injection by non-linear loads. Multi-Objective Particle Swarm Optimization (MOPSO) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) are used to find the optimal switching sequence for restoration. To test the effectiveness of the proposed methodology, IEEE 33 bus and IEEE 69 bus test systems are taken. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Power Balance Method using Coupled Shunt Inductor and Multiple-Input Transformer for ISOP LLC Converter
Electronics 2019, 8(3), 352; https://doi.org/10.3390/electronics8030352 - 22 Mar 2019
Abstract
High-capacity power-supply systems using a large input voltage typically improve efficiency and can be miniaturized by dividing the input voltage into multiple small voltages, thereby minimizing the stress on the switching element and thus materializing a fast switching function. When a large input [...] Read more.
High-capacity power-supply systems using a large input voltage typically improve efficiency and can be miniaturized by dividing the input voltage into multiple small voltages, thereby minimizing the stress on the switching element and thus materializing a fast switching function. When a large input voltage is divided into small voltages in series through a DC link capacitor, power is supplied to each converter and the power of each LLC (Inductor-Inductor-Capacitor) converter can be divided and converted. However, such LLC converters, which are configured by the division of the input voltage, have power imbalance due to the parameter variation between active and passive elements of the power board, which results in an increase in the stress and heat of a particular element. As this problem of power balance necessitates a design for securing a power margin and as the heated element increases its volume, the efficiency and reliability of the LLC converter are degenerated. Accordingly, this study attempted to solve the problem of the power imbalance of LLC converters at each level using a coupled shunt inductor and multiple-input transformers sharing magnetic coupling. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Strategies Comparison for Voltage Unbalance Mitigation in LV Distribution Networks Using EV Chargers
Electronics 2019, 8(3), 289; https://doi.org/10.3390/electronics8030289 - 05 Mar 2019
Abstract
The increasing penetration of Electric Vehicles (EVs) in LV distribution networks can potentially cause voltage quality issues such as voltage unbalance and under-voltage conditions. According to the EV charger characteristics, some strategies can be adopted to mitigate the aforementioned effects. Smart decentralized charging [...] Read more.
The increasing penetration of Electric Vehicles (EVs) in LV distribution networks can potentially cause voltage quality issues such as voltage unbalance and under-voltage conditions. According to the EV charger characteristics, some strategies can be adopted to mitigate the aforementioned effects. Smart decentralized charging controls seem to be a more practical solution than centralized controls, since there is no need for communication because they rely only on local measurements. The four most relevant decentralized charging strategies, two for single-phase and two for three-phase EV chargers, have been implemented in a typical three-phase four-wire European LV distribution network. Simulations have been carried out for scenarios with single-phase EV chargers, three-phase EV chargers, and a combination of both. Single-phase controls are aimed at under-voltage regulation, while three-phase controls are focused on mitigating voltage unbalance. Results show that the implementation of a decentralized EV charging control is an adequate solution for Distribution System Operators (DSOs) since it improves the reliability and security of the network. Moreover, even though decentralized charging control does not use any communication, the combination of three-phase and single-phase controls is able to mitigate voltage unbalance while preventing the under-voltage condition. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Structural Improvements in Consensus-Based Cooperative Control of DC Microgrids
Electronics 2019, 8(2), 187; https://doi.org/10.3390/electronics8020187 - 06 Feb 2019
Abstract
This study is dedicated to establishing a comparative analysis of the performance of different local controllers on the cooperative control of DC microgrids. One of the elementary and challenging issues in DC microgrids is the assurance of fairness in proportional current sharing while [...] Read more.
This study is dedicated to establishing a comparative analysis of the performance of different local controllers on the cooperative control of DC microgrids. One of the elementary and challenging issues in DC microgrids is the assurance of fairness in proportional current sharing while accomplishing voltage regulation in parallelly connected distributed energy sources. In this work, structural improvements are proposed to enhance the system stability and control performance. A finite-gain controller was employed in the outer voltage control loop with a simple proportional (P) controller in the inner current control loop of a converter. Due to the finite-gain controller, droop-like power sharing was achieved without droop coefficient. In order to further enhance the power-sharing accuracy and DC voltage regulation, a different method was adopted in consensus-based cooperative control to estimate the average current and average voltage difference. Moreover, small signal analysis was used to scrutinize the stability and control performance of the local controller, while different communication delays and current disturbances were applied to examine the performance of the controller. Finally, a four-node-based DC microgrid setup was developed in MATLAB/Simulink environment, and simulation results of the proposed and existing techniques were scrutinized. The simulations results demonstrated the effectiveness of the proposed controller. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Harmonic PMU Algorithm Based on Complex Filters and Instantaneous Single-Sideband Modulation
Electronics 2019, 8(2), 135; https://doi.org/10.3390/electronics8020135 - 29 Jan 2019
Abstract
Phasor measurement units (PMUs) have become powerful monitoring tools for many applications in smart grids. In order to address the different issues related to harmonics in power systems, the fundamental phasor estimator in a PMU has been extended to the harmonic phasor estimator [...] Read more.
Phasor measurement units (PMUs) have become powerful monitoring tools for many applications in smart grids. In order to address the different issues related to harmonics in power systems, the fundamental phasor estimator in a PMU has been extended to the harmonic phasor estimator by several researchers around the world. Yet, the development of harmonic phasor estimators is a challenge because they have to consider time-varying frequencies since the frequency deviation in the harmonic components is proportional to the harmonic order in a dynamic way. In this work, a new algorithm for harmonic phasor estimation using an instantaneous single-sideband (SSB) modulation is presented. Unlike other SSB-based approaches, its implementation in this work is based on concepts of instantaneous phase and instantaneous frequency. In general, the proposed algorithm is divided into two stages. Firstly, the estimation of the fundamental phasor is carried out by means of a complex finite impulse response (FIR) filter which provides the analytic signal used to compute the instantaneous magnitude, phase, and frequency. Secondly, a complex FIR filter bank is proposed for the estimation of the harmonic components, where the instantaneous SSB modulation technique is applied in order to center the harmonic components into specific narrow bands for each complex filter when an off-nominal frequency occurs. The validation of the proposed algorithm is carried out by means of the current standards of phasor measurement units, i.e., Std. C37.118.1-2011 and C37.118.1a-2014, which involve steady-state, dynamic, and time performance tests. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Optimal Power Flow Controller for Grid-Connected Microgrids using Grasshopper Optimization Algorithm
Electronics 2019, 8(1), 111; https://doi.org/10.3390/electronics8010111 - 19 Jan 2019
Cited by 1
Abstract
Despite the vast benefits of integrating renewable energy sources (RES) with the utility grid, they pose stability and power quality problems when interconnected with the existing power system. This is due to the production of high voltages and current overshoots/undershoots during their injection [...] Read more.
Despite the vast benefits of integrating renewable energy sources (RES) with the utility grid, they pose stability and power quality problems when interconnected with the existing power system. This is due to the production of high voltages and current overshoots/undershoots during their injection or disconnection into/from the power system. In addition, the high harmonic distortion in the output voltage and current waveforms may also be observed due to the excessive inverter switching frequencies used for controlling distributed generator’s (DG) power output. Hence, the development of a robust and intelligent controller for the grid-connected microgrid (MG) is the need of the hour. As such, this paper aims to develop a robust and intelligent optimal power flow controller using a grasshopper optimization algorithm (GOA) to optimize the dynamic response and power quality of the grid-connected MG while sharing the desired amount of power with the grid. To validate the effectiveness of proposed GOA-based controller, its performance in achieving the desired power sharing ratio with optimal dynamic response and power quality is compared with that of its precedent particle swarm optimization (PSO)-based controller under MG injection and abrupt load change conditions. The proposed controller provides tremendous system’s dynamic response with minimum current harmonic distortion even at higher DG penetration levels. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Homogeneity-PMU-Based Method for Detection and Classification of Power Quality Disturbances
Electronics 2018, 7(12), 433; https://doi.org/10.3390/electronics7120433 - 12 Dec 2018
Cited by 1
Abstract
Over the past few years, power quality (PQ) monitoring has become of paramount importance for utilities and users since poor PQ generates negative consequences. In monitoring, fast detection and accurate classification of PQ disturbances (PQDs) are desirable features. In this work, a new [...] Read more.
Over the past few years, power quality (PQ) monitoring has become of paramount importance for utilities and users since poor PQ generates negative consequences. In monitoring, fast detection and accurate classification of PQ disturbances (PQDs) are desirable features. In this work, a new method to detect and classify PQDs is proposed. The proposal takes advantage of the low computational resources of both a phasor measurement unit (PMU)-based signal processing scheme and the homogeneity approach. To classify the PQDs, if–then–else rules are used. To validate and test the proposal, synthetic and real signals of sags, swells, interruptions, notching, spikes, harmonics, and oscillatory transients are considered. For the generation of real signals, a PQD generator based on a power inverter is used. In the proposed method, the PMU information is directly used to classify sags, swells, and interruptions, whereas the homogeneity index is used to distinguish among the remaining PQDs. Results show that the proposal is an effective and suitable tool for PQ monitoring. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
A Hierarchical Control Methodology for Renewable DC Microgrids Supporting a Variable Communication Network Health
Electronics 2018, 7(12), 418; https://doi.org/10.3390/electronics7120418 - 10 Dec 2018
Cited by 2
Abstract
The monitoring and control of renewable energy sources (RESs) based on DC (Direct Current) microgrids (DC MG) are gaining much consideration at this time. In comparison with the isolated individual control of converters in a microgrid, DC microgrids provide better voltage regulation and [...] Read more.
The monitoring and control of renewable energy sources (RESs) based on DC (Direct Current) microgrids (DC MG) are gaining much consideration at this time. In comparison with the isolated individual control of converters in a microgrid, DC microgrids provide better voltage regulation and harmonized energy generation/consumption. To address the inherent vulnerability of communication links, robust methods have been proposed that improve the resilience of communication-based control. However, the failure of the communication links in microgrid control layers remains a considerable issue that may lead to one or more nodes being disconnected and operating as a communication island. Such types of communication islanding may cause the unpredictable behavior of the system and further destabilization may lead to a cascaded failure. This paper proposes a fast algorithm to detect and evaluate network connectivity based on the information stored at every node in the form of a look-up table. The control structure has been modified under communication islanding, and a communication connectivity observer is used at every node to detect and address power flow issues under communication islanding. The proposed method has been verified through mathematical analysis, simulation, and experimental results. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
Proposed Scheme of Pliable Gas Insulated Transmission Line and Its Comparative Appraisal Regarding Electrostatic and Dielectric Aspects
Electronics 2018, 7(11), 328; https://doi.org/10.3390/electronics7110328 - 16 Nov 2018
Cited by 3
Abstract
Gas insulated transmission lines (GILs) are being used in electrical systems regarding power transmission and substation interconnection. However, operational complexities of conventional schemes, such as structural rigidity, corrosion protection, gas leakage in case of seismic vibrations, larger bending radius and jointing complexities which [...] Read more.
Gas insulated transmission lines (GILs) are being used in electrical systems regarding power transmission and substation interconnection. However, operational complexities of conventional schemes, such as structural rigidity, corrosion protection, gas leakage in case of seismic vibrations, larger bending radius and jointing complexities which restrain their application perspectives, could be curtailed by developing a flexible GIL. In this research paper, a new pliable scheme of gas insulated transmission line is proposed. Further, COMSOL Multiphysics® (version 5.1, COMSOL Inc., Stockholm, Sweden) based electrostatic assay and practically performed high voltage tests-based dielectric analysis is performed for the proposed scheme. Electrostatic appraisal is comprised of field utilization based electrostatic stress analysis. In addition, dimensional optimization of pliable GIL regarding enclosure and pitch sizes in relation to electrostatic stresses and field utilization is also performed. Regarding dielectric perusal, experimental setup has been developed for standard lightning impulse and disruptive discharge tests in order to investigate the synergistic dielectric characteristics of proposed flexible post insulators for pliable GIL. Experimental and simulation appraisal unveil that the proposed scheme exhibits almost analogous electrostatic and dielectric behavior in comparison to the conventional GIL scheme and could simplify the operational intricacies associated with conventional scheme. The proposed modifications could eliminate the requirement of trench development, corrosion protection and acceleration dampers, along with a significant reduction in required land area at bends, due to a smaller bending radius which will ultimately result in substantial cost reduction. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
VSG Stability and Coordination Enhancement under Emergency Condition
Electronics 2018, 7(9), 202; https://doi.org/10.3390/electronics7090202 - 17 Sep 2018
Cited by 2
Abstract
Renewable energy sources are integrated into a grid via inverters. Due to the absence of an inherent droop in an inverter, an artificial droop and inertia control is designed to let the grid-connected inverters mimic the operation of synchronous generators and such inverters [...] Read more.
Renewable energy sources are integrated into a grid via inverters. Due to the absence of an inherent droop in an inverter, an artificial droop and inertia control is designed to let the grid-connected inverters mimic the operation of synchronous generators and such inverters are called virtual synchronous generators (VSG). Sudden addition, removal of load or faults in the grid causes power and frequency oscillations in the grid. The steady state droop control of VSG is not effective in dampening such oscillations. Therefore, a new control scheme, namely bouncy control, has been introduced. This control uses a variable emergency gain, to enhance or reduce the power contribution of individual VSGs during a disturbance. The maximum power contribution of an individual VSG is limited by its power rating. It has been observed that this control, successfully minimized the oscillation of electric parameters and the power system approached steady state quickly. Therefore, by implementing bouncy control, VSGs can work in coordination to make the grid more robust. The proposed controller is verified through Lyapunov stability analysis. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessFeature PaperArticle
Novel Neural Control of Single-Phase Grid-Tied Multilevel Inverters for Better Harmonics Reduction
Electronics 2018, 7(7), 111; https://doi.org/10.3390/electronics7070111 - 12 Jul 2018
Cited by 3
Abstract
A single-phase Cascaded H-Bridge (CHB) grid-tied multilevel inverter is introduced with a detailed discussion of the proposed novel neural controller for better efficiency and power quality in the integration of renewable sources. An LCL (inductor-capacitor-inductor) filter is used in the multilevel inverter system [...] Read more.
A single-phase Cascaded H-Bridge (CHB) grid-tied multilevel inverter is introduced with a detailed discussion of the proposed novel neural controller for better efficiency and power quality in the integration of renewable sources. An LCL (inductor-capacitor-inductor) filter is used in the multilevel inverter system to achieve better harmonic attenuation. The proposed Neural Network (NN) controller performs the inner current control and tracks the references generated from the outer loop to satisfy the requirements of voltage or power control. Two multicarrier-based Pulse Width Modulation (PWM) techniques (phase-shifted modulation and level-shifted modulation) are adopted in the development of the simulation model to drive the multilevel inverter system for the evaluation of the neural control technique. Simulations are carried out to demonstrate the effectiveness and efficient outcomes of the proposed neural network controller for grid-tied multilevel inverters. The advantages of the proposed neural control include a faster response speed and fewer oscillations compared with the conventional Proportional Integral (PI) controller based vector control strategy. In particular, the neural network control technique provides better harmonics reduction ability. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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Open AccessArticle
A New Flicker Detection Method for New Generation Lamps Both Robust to Fundamental Frequency Deviation and Based on the Whole Voltage Frequency Spectrum
Electronics 2018, 7(6), 99; https://doi.org/10.3390/electronics7060099 - 19 Jun 2018
Cited by 1
Abstract
A simplified Voltage Peak Detection (VPD)-based flickermeter based on spectral decomposition is proposed in this paper to detect flicker caused by high-frequency interharmonic components which effect the illumination of next-generation lamps, such as LEDs and compact fluorescent lamps. The proposed VPD-based flickermeter is [...] Read more.
A simplified Voltage Peak Detection (VPD)-based flickermeter based on spectral decomposition is proposed in this paper to detect flicker caused by high-frequency interharmonic components which effect the illumination of next-generation lamps, such as LEDs and compact fluorescent lamps. The proposed VPD-based flickermeter is specially designed to be robust to fundamental frequency deviations, which is a reality of all power systems. The proposed flickermeter is developed using a sinusoidal voltage model and it is analytically shown that flicker depends on the additive effect of the amplitudes of all the interharmonic components. Flicker results obtained by the proposed VPD-based flickermeter, IEC 61000-4-15 flickermeter, and another spectral analysis based IEC flickermeter are all compared with both synthetic voltage waveforms and field data collected from parts of the electricity transmission system with intermittent loads such as electric arc furnaces. It has been shown that only the proposed VPD-based flickermeter is sensitive to the high-frequency interharmonic components in the voltage spectrum and they are not detected by the other flickermeters. In the literature, there is no flickermeter that considers the flicker effect of the high-frequency interharmonic components and gives accurate results in cases of fundamental frequency deviations at the same time. Full article
(This article belongs to the Special Issue Power Quality in Smart Grids)
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