Performance evaluation of unipolar PWM strategies for three phase five level diode clamped inverter

This paper presents the comparison of unipolar Pulse Width Modulation techniques for a Diode Clamped Multi Level Inverter (DCMLI). In this paper, the DCMLI is controlled with Sinusoidal PWM (SPWM) reference and Third Harmonic Injection (THI) PWM reference with Sub Harmonic PWM (SHPWM), Carrier Overlapping (CO) PWM, Phase Shift (PS) PWM, Variable Frequency (VF) PWM and the variation of Total Harmonic Distortion (THD) in their outputs is observed for various modulation indices. Simulation is performed using MATLAB-SIMULINK. It is observed that SHPWM strategy provides output with relatively low distortion. It is also noticed that COPWM strategy is found to perform better since it provides relatively higher fundamental RMS output voltage.