基于变-定频混合优化调制策略的单级双有源桥型AC-DC变换器OA

To address the issues of large turn-off current and high switching frequency in single-stage dual active bridge(DAB)AC-DC converters,a modulation strategy based on variable-fixed frequency hybrid optimization is proposed in this paper.First,the turn-off current and soft-switching implementation conditions under variable-frequency single phase-shift modulation are analyzed,and the expression of switching frequency is derived.The analysis shows that re⁃ducing the turn-off current will lead to a significant increase in switching frequency under light-load conditions.There⁃fore,a maximum switching frequency threshold is preset,and a hybrid optimization modulation strategy based on vari⁃able-frequency single phase-shift and fixed-frequency extended phase-shift is put forward.Second,to optimize the fixed-frequency mode,the implementation conditions of full-range soft switching and power factor correction in this mode are analyzed,and the expression of phase shift ratio is also derived.This modulation strategy can effectively reduce the turn-off current of switches,limit the excessively high switching frequency and achieve zero-voltage switching across the en⁃tire operating range.Finally,the feasibility and effectiveness of the proposed modulation strategy were verified through simulations and experiments.