A Balancing Converter with Series Connected MOSFETs for ±700V Bipolar DC Grids

Abstract:
This paper introduces a balancing converter designed for use in ±700 V bipolar DC grids. Integrating a buck-boost topology with triangular current modulation (TCM), the converter achieves zero-voltage switching (ZVS) turn-on across all switches, thereby enhancing efficiency and reducing other issues such as EMI emissions. Additionally, the utilization of series-connected MOSFETs allows for higher blocking voltages, broadening the converter’s applicability. The study also explores how the switching frequency and duty cycle influence power flow, providing valuable insights for optimal operation. A prototype of the converter has been designed and tested, demonstrating a peak efficiency of 97.9% at load power of up to 5 kW. The findings showcase the converter’s practical viability and mark a significant advancement in the design of balancing converters for bipolar DC grids.