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In order to solve the problem of high voltage conversion ratio between DC bus and energy storage unit, a novel bi-directional three-phase DC/DC converter applicable to high power condition is proposed in this paper. With the new PWM strategy and inherent ability of increasing voltage conversion ratio of Y-Δ connected transformer, the voltage conversion ratio is doubled. With the new PWM strategy, the effective duty cycle range of three-phase DC/DC converter is expanded, which results in halved filter inductance. Three-phase full-bridge structure is connected to the DC bus, while current-tripler unit is connected to the battery. As three-phase interleaved structure is adopted, not only current stress of switches decreases, but also the frequency of input and output current ripple increases to three times of switching frequency, which leads to smaller filters and extended lives cycle of batteries. The operating principle and characteristics of the converter are analyzed in detail. A prototype with the 360V DC bus converted to 48V/42A batteries was built and the results are given based on the experiments. Index Terms-high voltage conversion ratio, three-phase DC/DC converter, bi-directional DC/DC converter, Y-Δ connected transformer, interleaved Ke Jin (S'04-M'09) was born in Nanjing, China, in 1978. He received the B.S., M.S., and Ph.D. degrees in electrical engineering from the Nanjing University of