Dual‐Active‐Bridge LC Resonant DC–DC Converter With an Auxiliary Boost Arm for Battery Energy Storage Systems

This study presents a dual‐active‐bridge (DAB) LC resonant DC–DC converter for battery energy storage systems. The proposed converter adds an auxiliary bridge arm to the traditional full‐bridge (FB) LC resonant converter as a boost arm. It features two efficient operating modes: a charging low‐gain (CLG) mode and a discharging high‐gain (DHG) mode. In CLG mode, the converter operates as an FB resonant PWM converter to achieve step‐down functionality. In DHG mode, the boost arm is used for energy storage to increase the voltage gain. Both modes enable soft‐switching operation across the entire load range. Additionally, the converter operates at a fixed switching frequency, simplifying the design of magnetic components. The converter has little magnetizing current and circulating current to increase the efficiency. The resonant capacitor in the converter has lower voltage stress and the transformer without air gap has lower leakage magnetic field, contributing to high power density. A prototype was developed, with batteries voltage of 40–60 V and high voltage DC bus of 360 V. Experimental results validate the feasibility of the proposed converter.