Experimental Verification for Dual Active Bridge Converter by Switching Equivalent-Magnetizing-Current Method

Abstract

This paper proposes a novel dual active bridge (DAB) converter that has an auxiliary inductor and a bi-directional switch connected in parallel to a transformer to achieve zero voltage switching (ZVS) and reduce the inductor current over a wide load range and wide battery voltage variation. In the proposed converter, the equivalent magnetizing inductance is changed by switching the auxiliary inductance depending on the output power. To achieve ZVS at a light load, the equivalent magnetizing current is increased by connecting the auxiliary inductance in parallel. In addition, the inductor current of the low voltage (LV) side is also reduced irrespective of a leakage inductance of a high frequency transformer. At a heavy load, the equivalent magnetizing current is reduced without connecting the auxiliary inductance because ZVS is achieved without any increment of the equivalent magnetizing current. In addition, the auxiliary inductance is switched without the occurrence of DC-offset of the auxiliary-inductor current and the surge voltage of a bi-directional switch. In the experimental results, the ZVS range is extended by up to 49%. In addition, the converter loss at a light load is reduced by up to 36.1%. A high efficiency in the wide load is achieved by the switched auxiliary inductance.