Anewbuck-boost integrated multilevel inverter with reduced capacitors and capacitor size for low-frequency AC applications

Abstract

This paper proposes a new buck-boost integrated multilevel inverter with reduced capacitors and capacitor size. The proposed multilevel inverter consists of a 5-level basic unit formed by two interleaved buck-boost converters, whose outputs are cascaded with the source to achieve a voltage gain of five. The capacitors pre sent in the buck-boost converters are charged at the high switching frequency; therefore, the proposed multilevel inverter utilizes small capacitors compared to the existing switched capacitor multilevel inverter (SCMLI) topologies. Moreover, capacitors presented in the conventional SCMLI are limited to fixed voltage charg ing, whereas the capacitors of the proposed inverter can be charged to desired voltages by adjusting respective buck-boost converter duty cycles. Hence, the pro posed inverter requires a relatively less number of compact capacitors to produce the higher number of voltage levels. In this paper, the design and operation of the proposed 11-level inverter are presented. A 500 W proof-of-concept is developed and the experimental results are presented for linear and nonlinear loads under static and dynamic load conditions. In addition, a comprehensive comparative study of the proposed inverter and the recent SCMLIs is presented.