Simultaneous PWM control to operate the three-phase dual active bridge converter under soft switching in the whole load range

The three-phase dual active bridge (3p-DAB) topology has been widely applied in high power dc-dc conversion, which has advantages of bidirectional power transfer, inherent soft switching capability and small filter size. The phase shift control is the conventional modulation strategy for three-phase DAB. However, the conventional control strategy can´t operate the converter under soft switching at low loads, especially when the voltage conversion ratio is far from the unit ratio. The aim of this paper is to propose a novel simultaneous pulse-widthmodulation (PWM) control strategy for the three-phase DAB to realize zero-voltage-switching (ZVS) in the whole load range. Seven switching modes are confirmed based on relative relationships of control parameters. The transmission power is calculated and soft switching operation is analyzed in each switching mode. Comparative analysis of ZVS operation with the conventional phase shift control and the proposed control strategy is then presented. A three-phase DAB converter is modeled in Saber and improvements by applying the proposed control strategy are verified by the simulation results.