Staircase multicarrier SPWM technique for nine level cascaded inverter

In this paper, novel pulse width modulation technique which use staircase carrier waveform is proposed for nine level cascaded inverter. In staircase carrier waveform, different techniques such as phase disposition (PD), inverted phase disposition (IPD), phase opposition disposition (POD) and alternative phase opposition disposition (APOD) are implemented. The fundamental output voltage and harmonics obtained in each method are compared with the output waveform obtained with the triangular carrier waveform. The proposed switching technique enhances the fundamental component of the output voltage and improves total harmonic distortion. The different PWM methodologies adopting the constant switching frequency multicarrier are simulated for a 1KW, 3φ inverter using MATLAB/SIMULINK. The effect of switching frequency on the fundamental output voltage and harmonics are also analyzed.