A novel wavelet transform based voltage sag/swell detection algorithm

This paper proposes a novel sag/swell detection algorithm based on wavelet transform (WT) operating even in the presence of flicker and harmonics in source voltage. The developed algorithm is the hybrid of Daubechies wavelets of order 2 (db2) and order 8 (db8) to detect voltage sag/swell with and without positive/negative phase jumps. The hybrid detection algorithm can detect the start and end times of voltage sag/swell with and without phase jumps within 0.5 ms and 1.15 ms, respectively. The performance of the proposed voltage sag/swell detection method is compared with the results of dq-transformation, Fast Fourier Transform (FFT) and Enhanced Phase Locked Loop (EPLL) based voltage sag/swell detection methods. The good robustness and faster processing time to detect balanced and unbalanced voltage sag/swell are provided using proposed method. With the proposed hybrid detection algorithm consisting of db2 and db8 wavelet functions, a robust sag/swell detection is achieved which can give precise and quick response. The performance of proposed hybrid algorithm is validated and confirmed through simulation studies using the PSCAD/EMTDC analysis program. ©2015 Elsevier Ltd. All rights reserved

Review of multifunctional inverter topologies and control schemes used in distributed generation systems

Recent developments in power electronics technology have spurred interest in the use of renewable energy sources as distributed generation (DG) generators. The key component in DG generators is a grid-connected inverter that serves as an effective interface between the renewable energy source and the utility grid. The multifunctional inverter (MFI) is special type of grid-connected inverter that has elicited much attention in recent years. MFIs not only generate power for DGs but also provide increased functionality through improved power quality and voltage and reactive power support; thus, the capability of the auxiliary service for the utility grid is improved. This paper presents a comprehensive review of the various MFI system configurations for single-phase (two-wire) and three-phase (three- or four-wire) systems and control strategies for the compensation of different power quality problems. The advances in practical applications and recent research on MFIs are presented through a review of nearly 200 papers

Multi-functional static synchronous compensator for distribution systems [Dagitim sistemleri için çok fonksiyonlu statik senkron kompanzatör]

Power quality problems cause the damage and inefficient operation of the electronic devices and sensitive loads, and lead to substantial economic losses. In order to eliminate these problems, Distribution Static Synchronous Compensator (D-STATCOM) is widely used due to the fast response to the changes in the system dynamics and the capability of controlling the power system parameters. In this research study, D-STATCOM, having a control method based on General Wavelet Transform, is firstly introduced and the balanced/unbalanced voltage fluctuations, current/voltage harmonics and reactive power that are most common types of power quality problems in the distribution systems are simultaneously compensated. With this study, it is the first time to formulate the general wavelet algorithm as mathematically in the literature. The performance of the proposed method is tested with several case studies by using PSCAD/EMTDC program

Mitigation of power quality problems using distribution static synchronous compensator: A comprehensive review

Electric power quality (PQ) in distribution system has become increasingly significant subject both for end users and power suppliers with the deregulation of the electric power market. The inadequate performance of conventional compensation devices to mitigate PQ problems has revealed the use of advanced power electronics based compensation devices. Distribution static synchronous compensator (DSTATCOM) is one of the shunt connected custom power devices used to improve PQ, voltage and reactive power support and to increase the capability of the auxiliary service for utility grid. This study presents a comprehensive review of the various DSTATCOM configurations for single-phase (two-wire) and three-phase (three or four-wire) systems and control strategies for the compensation of different PQ problems in distribution systems. In addition, comprehensive explanation, comparison and discussion on DSTATCOM technology are performed. Furthermore, latest trends, practical consideration and some future research fields on DSTATCOMs are discussed in detail. This is intended to present a broad perspective on the status of DSTATCOM technology to researchers dealing with compensation of PQ problems in distribution systems. © The Institution of Engineering and Technology 2015

A novel adaptive switching method to reduce DC-Link capacitor ripple in PV based grid-connected inverter

In this paper, the developed switching method has been developed to generate trigger signals for the voltage source inverter (VSI) to reduce the current harmonics on the DC-link capacitor. In the novel switching method, at the durations where the DC link capacitor current is greatest, the waveform of the input current of the inverter and the waveform of the output current of the DC side are approximated. The main contribution is to provide a low harmonic content capacitor current with the same capacitor size, thereby increasing the power delivered to the grid. In order to examine the performance of the developed switching method, the spectrum of DC link current obtained by Fast Fourier Transform (FFT) in MATLAB/Simulink. Simulation results have been evaluated according to the value of the harmonic amplitude at the switching frequency. It shows novel switching strategy is more effective in reducing current ripples than the carrier-based Sinusoidal Pulse Width Modulation (SPWM) method which is used as a reference strategy. © 2018 Elsevier Lt