With the rapid development of intelligent electric vehicles, the number of electrical equipment increases, and the interconnection and energy transmission between onboard dc buses has become urgent. This article proposes a partial isolated bidirectional converter based on dual active bridge (DAB) 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 pulsewidth 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. Under wide gain and different power distribution conditions, multiobjective optimization is realized. Finally, the correctness of theoretical analysis is verified by experiments.