A Novel Switching Algorithm to improve Efficiency at light load conditions for Three-Phase DAB Converter in LVDC Application

Abstract

In this paper, a novel switching algorithm for a three-phase dual active bridge (3P-DAB) converter in LVDC applications is proposed to improve the efficiency at light load conditions. The 3P-DAB converter is one of popular topologies in high-power applications due to small filtering size, the lower conduction losses with interleaved construction, the lower switching losses with inherent soft switching capability and seamless control in bi-directional power flow. However, the conventional power control method in 3P-DAB, single phase shift (SPS), does not effective due to possibility of ZVS failure in the light load conditions. In this paper, a novel control strategy for 3DAB converter to realize ZVS in the light load by using asymmetrical pulse width modulation (APWM) cascaded with SPS control algorithm. The transferred powers are calculated in both APWM and SPS mode, respectively. Also, the soft switching range also is also defined in proposed control strategy. A 3-kW prototype is implemented and tested to demonstrate the effectiveness of the proposed methods.