Analysis and Design of UCVB soft-switching buck-boost Converter for energy storage system

A new unbalanced capacitor voltage bidirectional (UCVB) soft-switching buck-boost converter is proposed in this paper. The proposed topology ensures soft-switching operations for all switches and eliminates turn-on and reverse recovery losses from the converter. Compared with traditional soft-switching buck-boost converters, the proposed topology is superior due to its simpler structure, better controllability, and wider soft switching ranges. The topology ensures improved efficiency at low power load and better reliability compared to the traditional buck-boost converter. The topology has been simulated in PLECS from 1 kW to 6 kW with 100 kHz switching frequency. The maximum efficiencies are 93.5% at 200 V input and 80 V output voltages and 96% at 200 V input and 300 V output voltages. These correspond to an efficiency improvement of 4% and 8%, respectively, when compared with a similarly rated traditional buck-boost converter. Finally, the soft-switching operation of the topology has been validated by an experimental prototype that uses SiC MOSFETs as switches.