Power quality enhancement in asymmetrical cascaded multilevel inverter using modified carrier level shifted pulse width modulation approach

Abstract

New modified carrier-based level shifted pulse width modulation approaches for single-phase trinary dc source fed cascaded H-bridge inverters are proposed in this article. In order to suppress the lower order harmonics, the carrier frequency is often tuned higher. However, switching and electromagnetic interference (EMI) problems have a significant influence on the functioning and controlling of the inverter at higher carrier frequency ranges. A new carrier is designed to address the aforementioned issues. To prove the effectiveness of the proposed carrier, this paper provides comparison results of conventional triangular carrier and a new developed carrier. Furthermore, utilizing the most popular phase disposition (PD) level shifted pulse width modulation approach with a new carrier with the similar modulation indices and switching frequency, to improve the fundamental voltage magnitude and shift the dominant harmonics into three times that of the existing traditional carrier-based level shifted pulse width modulation approaches. The effectiveness and feasibility of the proposed new modified carrier-based level shifted pulse width modulation approach have been proven by using MATLAB simulation and prototype results.