V2G bi-directional battery charger with flexible AC/DC converter

This paper proposes a novel bi-directional battery charger structure for V2G applications. The proposed structure consists of a flexible AC/DC converter and a series resonant converter (SRC). The flexible AC/DC converter changes the DC bus voltage according to the power flow direction of the charger. In this way, SRC which basically only works in buck mode is able to operate in both directions, and keeps the advantages of SRC. The operation stages of the proposed charger are analyzed. Hybrid IGBT modules are used in both the primary and secondary H-bridges of the SRC. The SRC then operates in capacitive region so that zero-current-turn-off is realized for the switches in the SRC. Furthermore, burst mode control is used to regulate the output power in forward mode under light load condition. Finally, experimental results and the control scheme are demonstrated on a 3.3kW prototype with the SRC operating in capacitive region.