Efficiency Enhancement of a Dual Active Bridge Converter with a Variable Inductor for Battery Charging Applications

This paper presents the integration of a variable inductor into a dual-active-bridge (DAB) converter for battery charging applications, emphasizing efficiency improvements. The variable inductor introduces an additional degree of freedom to conventional single-phase-shift modulation. By adjusting the inductance, the converter achieves optimal soft switching and minimizes current circulation, surpassing the performance of the traditional phase-shift method with a fixed inductor, specially under extreme output power conditions. To validate this approach, a 600 W prototype converter was developed to charge a lead-acid battery-bank. The efficiency of the DAB with the variable inductor was measured and compared to that of the DAB with fixed inductor across the full range of the battery voltage and power. Experimental results demonstrate that the DAB converter with variable inductor achieves superior performance for battery charging compared to the traditional DAB with fixed inductor under both low and high-load conditions.