Modified multi-carrier based Pulse Width Modulation technique to obtain optimal switching and even power distribution for multilevel inverter

Abstract

Phase Shifted Pulse Width Modulation(PS-PWM) and Level Shifted Pulse Width Modulation(LS-PWM) are two well known techniques for switching multilevel converters. PS-PWM is generally preferred for cascaded multilevel inverters as it ensures equal power distribution and equal switching frequency on all the switches within a given module. This technique however suffers from lack of optimal switching. On the other hand, LS-PWM technique ensures optimal switching sequences but lacks the even distribution of power between the switches in the modules. This paper compares SVPWM, LS-PWM and PS-PWM in terms of switching sequences and power distribution among modules. A modified carrier based PWM technique is proposed in this paper that combines the characteristics of even power distribution and equal switch utilization along with the optimal switching sequences. The line voltage and switching sequence analysis has been carried out all the three techniques to bridge the gap between them and showcase that all three modulation techniques are the same. The proposed method is supported by simulation results.