Improved Selective Harmonics Elimination Strategy for Multilevel Inverters with Optimal DC Values

Abstract

This paper examines the computation of optimal DC values and switching angles for eliminating higher order harmonics in Cascaded Multi-Level Inverters (CMLI) output voltage using Nelder Mead (NM) Simplex Algorithm. The goal is to solve the set of non-linear Selective Harmonic Elimination (SHE) equations in order to obtain the required fundamental component as well as eliminate the higher order harmonics. 2- and 3-stage CMLI for single and three phase output is investigated with equal and unequal DC sources and harmonics efficient suppression is reported. Superiority of NM method over Genetic Algorithm and Generalized Search Pattern with respect to convergence and computational time to reach the global minimum is discerned and demonstrated through MATLAB simulations. Results manifest that NM convergence rate and computational time is faster than GPS and GA for identical population of test points. For validation of results, 2- and 3-stage inverter is simulated in MATLAB Simulink for FFT analysis.