Self-balanced switched-capacitor multilevel inverter with asymmetric double-wing structure

Abstract

In order to solve the problems of complex structure, high power losses and voltage stress of switches of existing 13-level inverters, this paper presents a new multilevel inverter (MLI) to convert a single DC source’s voltage to an AC voltage with 13 levels. It consists of a switched-capacitor (SC) unit, a T-type unit and an inverting half-bridge. The SC unit can be placed either on the right side of the DC source to halve the input voltage and supply it to the end-side T-type unit, or on the left side of the DC source to double the input voltage and supply it to the end-side inverting half-bridge. Of course, multiple SC units with the same circuit configuration can be placed on both right and left sides of the DC source, simultaneously, to generate more output levels. In addition to flexible structure, the proposed MLI has the advantages of low standing voltage of switches, high boosting capability and power conversion efficiency as well as self-balanced capacitor voltages, which is very suitable for renewable energy sources applications such as photovoltaic and fuel cells. The circuit configuration, working principle, performance analysis under the nearest level modulation and comparative study are presented in detail. And experimental results are provided to evaluate steady state and dynamic characteristics of the proposed MLI.