Modeling the effect of dead-time on the soft-switching characteristic of variable-frequency modulated series-resonant DAB converter

Under wide-range variations in output current and voltage, dual-active-bridge (DAB) converter can operate with increased conduction and switching loss. A variable frequency-based power modulation scheme for an LC-type series resonant DAB converter is presented to achieve minimum-tank-current operation along with full-range soft switching. The proposed minimum-tank-current operation establishes an in-phase relationship between tank current and secondary-side voltage (low voltage and high current), which allows the switching devices of DAB converter to operate in soft-switching region. Resonant transitions of parasitic capacitances within the dead-time interval of switching devices are considered to avoid incomplete soft switching. Simulation and experimental results show the effectiveness of the proposed method with a maximum efficiency of 96.8 %.