Improved SHEPWM Strategy By The Robustness Optimization Algorithm In Multilevel Inverters With Equal DC Sources

Abstract

A multilevel Inverters have many advantages such as reduced Harmonics, no need for a transformer, cost and loss reduction. In this paper the multilevel inverter with equal DC sources is used for THD optimization. Different modulation methods have been proposed to control the multilevel inverters. This paper focuses on the Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) technique in multilevel inverter with equal DC sources. In the SHEPWM technique for multilevel inverters, in order to eliminate N-1 non-triplen odd harmonics of the AC-side voltage and to regulate the output line voltage amplitude, N switching angles need to be determined. Therefore a set of N non-linear transcendental equations must be solved to find the desired switching angles for any value of the modulation index. In this paper a new robustness optimization algorithm is presented to elimination of selective low order harmonics (LOH) in the output line voltage of the multilevel inverter based on the Multi Population Particle Swarm Optimization (MPPSO) algorithm. The switching angles are computed by a MPPSO algorithm to eliminate of LOH with high accuracy and determine the fundamental component to the desired value simultaneously. The proposed algorithm can generate stepped voltage waveforms with a wide range of modulation indices. The performance of the proposed algorithm for a seven-level cascaded H-bridge converter, based on simulation studies, is evaluated. MATLAB software is used for programming and simulation.