A novel three-phase bidirectional dc-dc converter is proposed in this paper to interface with low ultracapacitor(UC). The new topology has the advantage of simple circuit topology,soft-switching implementation without additonal device and high efficiency. These advantage make the new converter promising for medium and high power application especially for anxiliary power upply in fuel cell vehicle and power generation where the high power density, low cost, lightweight and high reliability power converter are required.Major features of the converter include: 1) draws and injects smooth current from UC; 2) increase input current rating by interleaving three phases, not by paralleling componets; 3) reduce core number and current ripple with improved efficiency by integrating three input inductors into a single core with coupling; 4) achieve zero-voltage-switching (ZVS) over a wide range by hybrid pulse-width-modulation (PWM) and phase-shift-modulation (PSM) control. The operation principle, the development of the switching power supply, the research method includes the theory analysis, integrated magnetic design the simulation and the practical experiments are presented in the paper.Firstly, this paper describes the working principle and the control mode of the three-phase bidirectional dc-dc converter. This paper presents the detailed analysis of the soft Switching full-bridge topology, the principle and mode. Then ,the design and consideration of the main circuit, control circuit and protect circuit are presented. Phase shift modulation plus PWM control are applied to bidirectonal TPDAB converter to achieve the converter optimized including the minimization of current stress and maintaining soft switching conditions regardless the wide variation of dc operating voltage of UC. Finally, the design of the intergrated three-phase coupling inductors and high frequency transformer was proposed, also the simulation results and experiments results was provided to verify the theoretical analysis.
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