Soft-Switching Flying-Capacitor-Type 3L/2L Hybrid Buck–Boost Converter With Minimized Inductor Current Ripple

The bidirectional dc-dc converter plays an indispensable role in interfacing the energy storage unit (ESU) to the renewable energy generation system. Compared to the conventional four-switch buck-boost (FSBB) converter, the flying-capacitor-type three-level/two-level hybrid buck-boost (FC-3L/2L-BB) converter offers the advantages of lower voltage stress, lower switching loss, and higher control flexibility, which makes it promising for interfacing the high-voltage ESU with wide voltage range. In this paper, soft-switching modulation is proposed for the FC-3L/2L-BB, achieving zero-voltage-switching (ZVS) for all switching devices throughout the whole input voltage and output load. For saving the conduction loss of all the switching devices and copper/core loss of the filter inductor, the minimized inductor current ripple control is further proposed, resulting in higher conversion efficiency. Finally, a 6.6kW full SiC FC-3L/2L-BB prototype, with 500V–1500V input, is built and tested in the lab, achieving an overall efficiency higher than 98.5% throughout the entire input voltage range with the peak efficiency at 99.6%.