Analysis and Design of a Bidirectional Step-Up/Down Partial Power Converter for Battery Energy Storage System

The increasing power of battery energy storage systems (BESS) poses challenges to DC-DC converters in terms of efficiency, power density, and cost. To tackle these challenges and meet the requirements of voltage step-up/down between the DC bus and BESS in practical applications, a bidirectional (BD) step-up/down (SUD) series-connected partial power converter based on a full-bridge push-pull circuit is designed. After analyzing the particular characteristics of the BDSUD four-quadrant operations, solutions are proposed for the problems of differential port voltage over-zero, boundary condition, and control strategy. System simulation is performed to implement four-quadrant automatic operation with accurate tracking to charging and discharging strategy, and verify the switching effect between quadrants. Efficiency is analyzed in conjunction with BESS full-range operation, achieving 99.3% at peak.