A variable switching frequency hybrid control for ZVS dual active bridge converters to achieve high efficiency in wide load range

The Dual Active Bridge (DAB) converter with the Conventional Phase-shift Modulation (CPM) and Triangular Current Modulation (TCM) are compared in terms of the power transfer and total loss. It is noted that there exists an optimal design trade off among the switching loss, conduction loss and drive loss according to different load current and switching frequency. Therefore, the optimal switching frequency design would be beneficial to minimize the total loss and improve the performance of the DAB converter. A hybrid modulation strategy with variable switching frequency is proposed to reduce the dominant loss and improve the efficiency in wide load range. A 500 W prototype was built to verity the benefits of the proposed control method.