Analysis of asymmetrical and symmetrical three phase cascaded multilevel inverter using multicarrier SPWM techniques

This work proposes a comparison study of cascaded H-bridge multilevel inverter (CHBMLI) in which symmetrical and asymmetrical arrangement of five level and seven level H-bridge inverters are compared in order to find an optimized output voltage quality with lower harmonic distortion. Several studies have been conducted on the three phase cascaded symmetrical multilevel inverter (MLI). However, there are few studies that actually discuss or evaluate the performance of three phase H-bridge asymmetrical MLI. Here, three multicarrier pulse width modulation (PWM) techniques such as constant switching frequency, variable switching frequency and phase shifted PWM are proposed. MATLAB/SIMULINK software is used for simulation. The carried out simulation studies shows that an asymmetrical configuration provides high output voltage with very low total harmonic distortion (THD) using less switching devices.