Abstract: In order to reduce the backflow power in the dual active bridge DAB converter and realize soft switching, the power model of DAB and the realization conditions of soft switching are derived in this paper. The paper analyzes the working principle of DAB under the two working conditions of voltage conversion ratio greater than 1 and less than 1, and derives the optimal phase shift angle of DAB at different transmission powers under the two working conditions. An improved synchronous triple-phase-shifting control strategy for reducing the backflow power under all operating conditions is proposed. The simulation is carried out on the MATLAB/SIMULINK platform. The simulation experiment results show that this control strategy can significantly reduce the backflow power within a certain transmission power range and it can achieve soft switching and improve conversion efficiency.