Design Optimization of Dual Active Bridge Converter for Supercapacitor Application

Supercapacitor (SC) is an energy storage suitable for meeting short-term requirements in power conversion systems. However, the low and variable terminal voltage of SC-based energy storage poses challenges to the design of its power electronic interface (PEI) to achieve a high round-trip efficiency and a rapid response of the energy storage system. The PEI design methodologies existing in the literature do not clearly tackle the mitigation of switching and conduction losses over the entire operating range of the SC. This article proposes a design strategy for an SC-interface dual active bridge (DAB) converter. The terminal characteristics of the SC are incorporated into an analytical design formulation aiming to maximize the DAB efficiency over the SC discharging cycle. The resulting optimization problem, addressing both conduction and switching losses, is solved numerically to obtain the optimal circuit parameters. The realization of the design objectives and the obtained efficiency is validated in circuit simulation and experiments on a 250 W laboratory prototype with a 125 V dc bus and a nominal SC voltage of 37.5 V, illustrating the improvement achieved over the conventional design approach.