Improvement of Switching Characteristics for an Active Buffer Dual-Active-Bridge AC-DC Converter

抄録

In this paper, a control method to realize zero-voltage turn on in the discharging circuit is proposed of a single-phase converter based on a dual-active-bridge (DAB) dc-dc converter with an active energy buffer. The discharging circuit is composed of a buffer capacitor connected in series with a MOSFET switch. The main source of losses in the discharging switch is revealed theoretically through an analysis on the threshold level of the gate signal voltages and their switching timing. A modified gate signal with delay time for the discharging switch is proposed to prevent the parasitic output capacitor from short circuit of MOSFET and flowing inrush current to the DAB converter. Experimental results under 5.4kW power condition verifies the theoretical assumptions in terms of power losses on each switching devices. As a results, power conversion efficiency with the proposed control method has been improved to 93.5% from the results without the proposed one of 92.9%.