Evolutionary algorithm based selective harmonic elimination for three-phase cascaded H-bridge multilevel inverters with
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ORIGINAL ARTICLE
Evolutionary algorithm based selective harmonic elimination for three‑phase cascaded H‑bridge multilevel inverters with optimized input sources S. Sankara Kumar1 · M. Willjuice Iruthayarajan1 · T. Sivakumar1 Received: 9 January 2020 / Revised: 8 June 2020 / Accepted: 10 June 2020 © The Korean Institute of Power Electronics 2020
Abstract Multilevel inverters are finding wide application in electric drives, traction, flexible AC transmission systems (FACTS) and renewable energy systems. A cascaded H-bridge type multilevel inverter (CHBMLI) produces a near sinusoidal output voltage with lower switching stress and a higher conversion efficiency than the other types of MLIs. The Selective Harmonic Elimination (SHE) strategy is used to eliminate lower-order harmonic profiles and to regulate the fundamental component in the output voltage. SHE has the advantages of low switching frequency, low switching losses and low stress. In this paper, the modulation index and input voltage values are also considered as optimization variables along with the conventional switching angles to analyze the performance improvement in selective harmonic elimination. Heterogeneous Comprehensive Learning Particle Swarm Optimization (HCLPSO) and Gravitational Search Algorithm (GSA) algorithms are used to find the optimal switching angles, modulation index and input voltage source values for minimizing the lower-order harmonics present in the output voltage of seven-level and eleven-level CHBMLIs, while maintaining the fundamental component of the output voltage. The results obtained from MATLAB simulations and an experimental setup clearly indicate that the proposed HCLPSO-based multilevel inverter provides better performance when compared with GSA, firefly and Differential Search Algorithm (DSA)-based MLIs. Keywords Cascaded H-bridge multilevel inverters · Selective harmonic elimination · Evolutionary algorithm · Harmonics · THD
1 Introduction In recent years, power electronics-based multilevel voltage source inverters have become more popular in high-voltage and high-power applications. Diode-clamped, flying capacitor and cascaded H-bridge are the major types of inverter design [1]. Multilevel inverters provide a near sine wave output with low THD values, minimum voltage stress on the switches, reduced electromagnetic interference, and reduced common mode voltage and switching frequency [2]. Harmonic distortion in the output voltage can be minimized by progressive increment in the number of levels [3]. However, an increase in the number of levels results in the increased * S. Sankara Kumar [email protected] 1
Department of Electrical and Electronics Engineering, National Engineering College, Kovilpatti, India
complexity of the control circuit and the number of isolated DC sources required. The SHE strategy helps to further reduce the harmonic in the output voltage. The switching instances of various unequal DC sources are obtained by solving transcendental equations for the SHE to eliminate chosen harmonics a
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