ZVS and Inrush Charging Current Suppression Design for Switched-Capacitor Multilevel Inverters

Abstract

Switched-capacitor (SC) based multilevel inverter (MLI) technique has been developed rapidly in recent years. However, the majority SC-MLIs operate with hard-switching and suffer from the inrush charging current problem of capacitors. This seriously restricts performance improvement and application. To overcome this issue, this letter introduces zero-voltage switching (ZVS) technique into SC-MLIs by developing the basic SC unit into resonant SC unit. Different from resonant dc/dc converters of which the duty ratio is usually constant, the ZVS design of SC-MLIs is full of challenges as the duty ratio varies in a wide range. Faced with it, ZVS operation and the corresponding parameter design are analyzed in detail. The feasibility of the ZVS design is effectively verified by a simulation model of a five-level SC inverter. Moreover, experimental results of both five- and seven-level SC inverters are provided to demonstrate the effectiveness of the ZVS design.