Performance analysis of three-phase five-level NPC inverter by using triangular and trapezoidal triangular carrier-based modulation techniques

Abstract

In this paper, the performance of three-phase five-level neutral-point-clamped inverter using different carrier waves namely trapezoidal (T) and trapezoidal triangular (TT) with different modulation techniques applying three different modulating signals is studied. In this study, three basic level-shifted multicarrier PWM strategies namely, alternative phase opposition disposition (APOD), phase opposition disposition (PD) and phase disposition (POD) are implemented using those two carrier waves. The total harmonics distortion (THD) and RMS values of line voltage for a five level NPC inverter employing the TT carrier wave for different modulation indices are acquired and the results are compared with that of the conventional triangular (T) carrier wave. It is observed that the TT carrier approach reduces the total harmonic distortion and also enhances the DC utilization of the output line voltage in higher modulation index region with an expense of introducing some lower harmonics in the output voltages.