With the rapid development of intelligent electric vehicles, the number of electrical equipment increases, and the interconnection and energy transmission between on-board DC buses has become urgent. This paper proposes a partial isolated bidirectional converter based on dual active bridge converter. By partial switch sharing, the converter has a simplified structure and can supply energy to DC loads of different voltage levels. The system adopts a hybrid control strategy of pulse width modulation and triple phase shift modulation, and introduces a fundamental phase shift to reduce coupling between variables. The operation process is analyzed, and the models of transmitted power, current stress and soft-switching range under two typical operation modes, corresponding to the full load and light load, are established respectively. Under wide gain and different power distribution conditions, the multi-objective optimization is realized. Finally, the correctness of theoretical analysis is verified by experiments.