A Comprehensive Steady-State Performance Optimization Method of Dual Active Bridge DC-DC Converters Based onWith Triple-Phase-Shift Modulation

The dual active bridge (DAB) DC-DC converter has been widely adopted in microgrid, power conversion applications. However, the power backflow is the critical factor to lower the efficiency of DAB converters with the phase shift modulation. In addition, when the input voltage of the transformer is mismatched with the output voltage, the current stress is great and leads to the efficiency reduction. To achieve ZVS, backflow power reduction and current stress optimization, a comprehensive optimization with triple-phase-shift (TPS) is proposed. Firstly, based on the backflow power optimization, the minimum current stress optimization, and the limitation of ZVS, the relationship between the voltage conversion ratio and the phase shift ratios is described. However, the phase shift ratios are only related to the voltage conversion ratio, the power transmission is limited. Thus, the switching frequency is used to regulate the transmit power. Then, to simplify computational complexity, the switching frequency is defined as the output of the PI controller, of which the input is the deviation of desired and actual output voltage. The proposed comprehensive optimization can reduce the current stress and improve the efficiency of the DAB converter. Finally, an experiment phototype of the DAB converter is developed, and comparison experiments with the PI control method and the practical fundamental-optimal (PFO) strategy are carried out to proof the effectiveness of the proposed method.