A new switched-capacitor inverter for electric vehicles

Abstract

This paper presents a new switched-capacitor inverter circuit based on partial charging. A number of switched-capacitor inverter circuits have been developed, but most of them are based on switching of fully charged capacitors in specific sequence to generate staircase ac voltage. In order to reduce the output distortion, the numbers of capacitors and switches should be increased. However, complexity of the circuits will also be increased dramatically. Moreover, the number of capacitors of conventional switched-capacitor inverters should be limited, otherwise, the peak output voltage could exceed stipulated limit. The new switched-capacitor circuit operates in such a manner that the capacitors will be switched to generate an ac output while they are partially charged. Each capacitor can provide multilevel voltages because the state of charge is varied. Theoretically, ac voltage with unlimited steps can be created with a few of capacitors. Experiments and simulations of a thirteen-level inverter that consists of only two capacitors are included in this paper.