Elimination of Lower Order Harmonics in Multilevel Cascaded Inverters with Equal DC Sources Using PSO

Abstract

This paper presents elimination of lower order harmonics in multilevel inverters with equal DC sources using PSO. To eliminate the selected lower order harmonics from the output voltage or current waveform of a cascaded multilevel inverter, appropriate switching angles were calculated and the power switching devices were switched accordingly. The switching angles were calculated from the non-linear equations derived from the Fourier series expansion of the output voltage of the inverter. A PSO algorithm was developed to solve the nonlinear equations. With the proposed approach, the required switching angles are efficiently computed using PSO to eliminate the lower order harmonics from the inverter voltage waveform for different modulation indices (ma).The PSO algorithm was developed in the Matlab environment, and the three phase multilevel cascaded inverter systems have been simulated using the PSIM software. The performance of the proposed method for a nine-level cascaded H-bridge inverter was evaluated based on simulation and experimental studies. Lower order harmonic up to the 11th order are eliminated.