Active battery/ultracapacitor hybrid energy storage system based on soft-switching bidirectional converter

Because the complementary characteristics of ultracapacitor and battery, the hybrid energy storage system with these two components will be provided with better performances, such as not only power density but also energy density will be upgraded, life time of the system will be prolonged. This paper proposes a active hybrid energy storage system of battery/ultracapacitor based on bidirectional converter, in which synchronous rectification and soft-switching techniques are adopted to reduce power conversion loss. Mathematical model and operation principle of the converter are presented respectively. Simulation results verified the theoretical analysis and the proposed scheme can make most use of the advantages of ultracapacitor, optimize the operation process and prolong the lifetime of battery.