Minimum Backflow Power and ZVS Efficiency Conditions in Dual Active Bridge DC-DC Converter using Extended-Phase-Shift Control

This paper aims to improve the efficiency of the dual active bridge DC-DC Converter(DAB) by achieving Zero Voltage Switching (ZVS) conditions and minimizing backflow power (MBP) through Extended-Phase-Shift (EPS) control. The conventional EPS control method assumes fixed input and output voltages and determines the optimal two phase shift ratios for these voltages. However, using only two decision variables makes it challenging to fully optimize for loss reduction. Therefore, this paper introduces an approach that incorporates input voltage as an additional decision variable, resulting in a total of three decision variables: input voltage and two phase shift ratios. By including input voltage as a decision variable, it is possible to determine more efficient optimal values for the desired power transfer, while satisfying ZVS conditions and MBP. Experiments on the DAB Converter were conducted using the SPICE model PSIM. Assuming the presence of a pre-converter to adjust the input voltage, the efficiency and response of the DAB Converter were evaluated by optimizing the three decision variables.