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In this paper, a new bidirectional three-phase dc-dc converter and three-phase PWM strategies have been proposed for battery application. The proposed converter acts as an three-phase isolated buck converter when battery is charged from dc link (buck mode) and an three-phase isolated boost converter when battery discharges energy (boost mode). In the buck mode, three-phase hybridge rectifier is employed to improve efficiency and an interleaved operation of three-phase buck converter reduces overall charging current ripple, which is imposed into battery. The interleaved operation increases effective operating frequency and thus, leads to a realization of smaller sized filter components. In addition, the proposed three-phase PWM strategy transfers energy through three-phase paths with zero voltage switching (ZVS) capability. In the boost mode, an interleaved operation of three-phase boost converter induces the same properties as in the three-phase buck converter. In addition, three-phase active clamp branch mitigates not only switching losses by zero voltage switching but also electromagnetic noises caused by hard-switched voltage spikes. These characteristics of the proposed converter reduce operating losses significantly and result in the whole converter efficiency above 95%. The proposed converter and three-phase PWM strategies are analyzed, simulated and implemented in hardware. Experimental results are obtained on a 500 W prototype unit, with all of the design verified and analyzed.
Date of Conference: 15-19 Feb. 2009