JDP_V1_N1_RP2 S. Sumathi D. Meena C.R. Balamurugan S.P. Natarajan Journal on Digital Signal Processing 2322–0368 1 1 8 17 THD, DCMLI, COPWM-A, VACOPWM-A, COPWM-B, VACOPWM-B, COPWM-C This paper presents the comparison of Variable Amplitude Pulse Width Modulation COPWM techniques for the three phase Diode Clamped Multi Level Inverter (DCMLI). A three phase DCMLI is controlled in this paper with Triangular PWM (TPWM) reference for Carrier Overlapping (CO) techniques. The variation of Total Harmonic Distortion (THD) in the inverter output voltage is observed for various modulation indices. Simulation is performed using MATLAB-SIMULINK. By comparing the various carriers overlapping technique such as COPWM-A, COPWM-B, COPWM-C and COPWM-D, it is observed that COPWM-C provide an output with relatively low distortion and COPWM-A and COPWM-D provides relatively higher fundamental RMS output voltage. By comparing the various variable amplitude carriers overlapping technique such as VACOPWM-A, VACOPWM-B, VACOPWM-C and VACOPWM-D, it is observed that VACOPWM-C provide a output with relatively low distortion and VACOPWM-D provides relatively higher fundamental RMS output voltage. Finally by comparison between the various COPWM and variable amplitude carrier overlapping technique, it is observed that VACOPWM-C provide an output with relatively low distortion and VACOPWM-D provides relatively higher fundamental RMS output voltage. January - March 2013 Copyright © 2013 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=2199