Multi-modular multi-level pulse width modulated inverters

Abstract

This paper presents the analysis and simulation of single phase multi-level and multi-modular PWM inverters and three phase multi-level inverters using the Power System Computer Aided Design (PSCAD) software. Multi-level voltage source inverters offer several advantages compared to their conventional ones. This technology is based on the synthesis of the AC voltage from several different voltage levels on the DC bus. As the number of voltage levels on the DC side increase, the synthesised output adds more steps, producing staircase wave which approaches the sinusoidal wave with the minimum harmonic distortion. To achieve this, one of the switching techniques called pulse-width modulation (PWM) is applied. In this technique, the comparison of carrier frequency and fundamental frequency is performed to produce modulated frequency. As the carrier frequency increases, the width of the modulated signal become narrower and hence it leads to smoother output waveforms. The effect on total harmonic distortion (THD) is investigated on both proposed multi-level and multi-module designs.