Digital switching scheme for cascaded multilevel inverters

Abstract

In this paper, a new digital switching technique for cascaded H bridge multilevel inverter (CMLI) for the purpose of power quality improvement is proposed in order to ensure an efficient voltage utilization and better harmonic spectrum. The method presented shows a topology to control cascaded multilevel inverter that is implemented with multiple DC sources to get 2n+1−1 levels. Whereas a standard cascade multilevel inverter requires n DC sources or n number of transformers for 2n+1 levels at the output, where n is the number of inverter stages. Moreover, the experimental results are carried out on a scaled down prototype to prove the effectiveness of the proposed topology. This topology of firing can be implemented without using PWM technique which considerably reduces the switching losses and also brings down the Total Harmonic Distortion (THD). Simulation and experimental results show the superiority of this technique over the conventional methods.