Analysis, design and implementation of isolated bidirectional converter with winding-cross-coupled inductors for high step-up and high step-down conversion system

In this study, a zero voltage switching (ZVS) isolated bidirectional DC/DC converter is proposed for high step-up and high step-down conversion systems. In the low voltage side, an interleaved Buck and Boost converter is employed to reduce the current ripple and improve the power level. In the high voltage side, a modified three-level structure is adopted to bring each power switch sustain half of the high bus voltage, which makes the low voltage rated MOSFETs available for the performance improvement. Two coupled inductors are interleaved in the low voltage side and in series in the high voltage side, which can not only serve as the filter inductors for the current ripple cancellation, but also as the transformer for isolation, which is named as winding-cross-coupled inductors. As a result, the magnetic size can be reduced to enhance the power density. ZVS operation is ensured from light load to full load conditions by the advanced pulse width modulation plus phase shift control strategy. The voltage regulation and transferred power are decoupled for easy design and implementation. Finally, a 1.5 kW 48 V/800 V prototype is built to verify the effectiveness of the proposed converter.