Abstract

The prevalent power quality problems in smart microgrids and power distribution systems are voltage sag, voltage swell, and harmonic distortion. The achievement of pure sinusoidal waveform with proper magnitude and phase is currently a great research and development concern. The aim of this paper is to evaluate and mitigate the smart microgrid harmonics, voltage sag, and voltage swell throughout a 24-h cycle, taking into consideration the variation in solar power generation due to changes in irradiation received by photovoltaic cells, the variation in wind power generation due to changes in wind speed, and the variation of linear and nonlinear load profiles during the day’s cycle. The mitigation of the power quality issues manifested in current harmonics, voltage sag, and voltage swell is achieved through the implementation of a new fully fuzzy controlled unified power quality conditioner (UPQC). It is controlled by an energy management system (EMS). This paper introduces a new control system for the UPQC using full fuzzy logic control. Moreover, fuzzy control is used in current control instead of proportional integral controllers so that it has acceptable performance over a wide range of operating points. The novel approach of an EMS-connected UPQC activates the UPQC at the required time only into the grid. This approach has many benefits by increasing the UPQC lifetime. The effect of the proposed system on the aforementioned issues has been validated through simulation by MATLAB/Simulink. The results are compared with those obtained by conventional methods. The results verify the superior performance of the proposed UPQC to mitigate the problems of current total harmonic distortions, voltage sag, and voltage swell under different operating conditions during the monitoring period.

Highlights

  • The smart grid is a concept and vision that captures a range of advanced information, sensing, communication, control, and energy technology [1]

  • This paper illustrates a new method for a unified power quality conditioner (UPQC) control system based on fuzzy logic control, which is simple and robust

  • Analyzing the simulation results for the proposed smart microgrid system shows that after activating the proposed UPQC the percentage total harmonic distortions (THDs) values are reduced below 5% to become well within the acceptable range with a maximum value of 4.9% at the fifth hour

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Summary

Introduction

The smart grid is a concept and vision that captures a range of advanced information, sensing, communication, control, and energy technology [1]. The power quality challenges in smart microgrids are mainly described by the current harmonic limits set by IEEE 519. The percentage of total harmonic distortions (THDs) at the end-user should not exceed 5% [2]. Voltage sag is defined by IEEE 1159 as the decrease in the RMS voltage level to 10%–90% of the nominal value of the power frequency for a duration of half cycle to one minute [3]. Voltage swell is defined by IEEE 1159 as the increase in the RMS voltage level to 110%-180% of nominal at the power frequency for a duration of a half cycle to 1 min [3]. As per IEEE 1547, when the distributed resources are serving balanced linear loads, the percentage THD must not exceed the limit of 5% harmonic current [4].

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