A Novel Interleaved Nonisolated Bidirectional DC-DC Converter With High Voltage-Gain and Full-Range ZVS

A nonisolated soft-switching bidirectional dc-dc converter (BDC) with interleaved technique and built-in transformer (BT) is proposed for the interface between the energy storage system and dc microgrid bus in this article. A T-type neutral-point-clamped circuit is integrated into an interleaved conventional buck-boost BDC to obtain a high voltage-gain ratio and decrease voltage stresses of power switches effectively. Compared with the couple-inductor, BT allows for a small magnetic core size, owing to its inherent saturation avoidance. The interleaved structure is employed to reduce the current ripple in the low-voltage side and helps to achieve voltage matching on both sides of the BT under pulsewidth modulation control. Thus, the circulating current can be lowered to improve efficiency. Phase-shift control is adopted to regulate the power flows of the proposed BT-BDC. Moreover, the optimal design is given for the component parameters to accomplish zero-voltage switching in a wide voltage range, which can reduce the switching losses. The operational principles and characteristics of the proposed BT-BDC are presented in detail. The analysis and performance have been fully validated experimentally on a 4060 V/400 V 1-kW prototype. The accordance between the analysis and the experimental results further testifies the advantages.