Optimized current stress strategy for dual-phase-shift modulated dual active bridge converters to ensure full-load-range ZVS

Dual active bridge (DAB) converters have two control variables when they work with dual phase shift (DPS) modulation. These control variables are the inner phase-shift ratio and the outer phase-shift ratio. They can be optimized to achieve minimum current stress during the operation of DAB converters. Conventional optimization methods cannot ensure soft-switching of the power semiconductor devices, which limits the efficiency and reliability of DAB converters. To balance the current stress and switching loss of DAB converters with DPS modulation, a novel optimal DPS strategy is proposed for DAB converters. The proposed strategy can ensure ZVS and avoid voltage spikes of the power semiconductor devices in DAB converters over the full load range. Meanwhile, it can achieve the minimum current stress under heavy loads and near-minimum current stress under middle and light loads for the components in DAB converters. The experimental results reveal that the proposed strategy achieves higher efficiency than conventional optimization methods under heavy and light loads. For middle loads, it is predicted that the proposed strategy can achieve higher efficiency when the switching loss is dominant. Moreover, the experimental results show that the voltage spikes of the MOSFETs are eliminated by the proposed strategy, which indicates a higher reliability than conventional strategies.