Abstract: Grid-connected only distributed generation cannot satisfy the users requirements of electricity costs saving. Multi-source converter （MSC）, which can help manage the energy utilization in demand, is accepted by users. Bi-directional converter for battery, which is characterized in wide range input voltage, high rise ratio, electrical isolation and high conversion efficiency, is the core component of MSC and one of the difficult points in MSC design. This paper designs the bi-directional converter for battery based on the cascaded scheme of buck/boost bi-directional circuit and bi-directional LLC circuit. Firstly, we analyze the topology, the operation principle and its characteristics, and deduce the small signal model for the bi-directional LLC circuit with resonant frequency. Then, combining the voltage, efficiency and other indicators, we optimally design the intermediate voltage of converter, LLC resonance circuit and other parameters. Finally, we adopt experiments to verify the effectiveness and and feasibility of the design of the proposed cascaded bi-directional converter.

Key words: cascaded bi-directional converter, multi-source converter, bi-directional LLC resonance circuit