This paper proposes a system topology of the distributed wind-photovoltaic-storage system and mainly researches on a distributed wind-photovoltaic-storage system bidirectional DC-DC converter. The bidirectional DC-DC converter connects the DC link and the battery to implement the power exchange between solar panels, wind turbine, grid and the battery, which is the key part of the whole system. We use high step up double active full bridge DC-DC converter as the bidirectional DC-DC converter. It can connect the low voltage battery and the high voltage DC link, further, it can implement the bidirectional power flow and soft switching. A 3kW prototype is built up to test the bidirectional DC-DC converter.