A new nonisolated three-port DC-DC converter with high step-up/down ratio

A new nonisolated three-port dc-dc converter integrating PV and battery power is proposed in this paper. The topology includes two coupled inductors and two active-clamp circuits. The coupled inductors are used to achieve high step up/down gain and to reduce the voltage stress on both primary and auxiliary switches. Two sets of active-clamp circuits in the proposed converter are used to recycle the energy stored in the leakage inductors. Therefore, the system efficiency can be improved. Charging/discharging transition of the battery is autonomous while tracking the maximum power of PV source and regulating the output voltage simultaneously. When the charging voltage is too high, the control loop of PV port will be switched from maximum power point tracking (MPPT) to battery voltage regulation. Experimental results of a 200W laboratory prototype are presented to verify the performance of the proposed three-port converter.