Revelation of Soft-Switching Operation for Isolated DC to Single-phase AC Converter with Power Decoupling

This paper discuses soft-switching range in an isolated single-phase matrix converter with a center-tapped transformer for HVDC (high voltage direct current) power feeding systems. The proposed converter consist of a full bridge inverter, a high frequency transformer and a matrix converter which it does not require a bulky electrolytic capacitor. The power decoupling operation is accomplished by the center-tapped transformer and a small LC buffer. In comparison with a conventional DC to single-phase AC converter without power decoupling operation, the proposed circuit partly achieve the Zero Voltage Switching (ZVS) operation of the full bridge inverter on the primary side of the transformer. In this paper, a principle of ZVS using the LC buffer circuit is described. From a simulation result, the soft-switching operation is confirmed at low load current region by using the LC buffer. Meanwhile it is experimentally confirmed that the proposed power decoupling method reduces the DC bus current ripple by 85.1%. In addition, the ZVS operation on the primary side of the proposed DC to single-phase AC converter is confirmed in experiment.