A Novel Three-port Photovoltaic Micro-inverter with Active Power Decoupling Method

Conventional photovoltaic micro-inverters use large electrolytic capacitors to balance the power pulsation with twice of the grid frequency, which will affect the lifetime of the inverter. This paper proposes a novel three-port micro-inverter with active power decoupling circuit and its control strategy. The proposed inverter reduces the sizes of the DC input capacitor and decoupling capacitor, and the small film capacitor is applied to decouple the power pulsation instead of the electrolytic capacitor. In addition, flyback transformer isolates decoupling circuit and PV module. After establishing the equivalent circuit model of the proposed micro-inverter, the circuit parameters are designed. The simulation results show that the proposed circuit effectively buffer the power pulsations with only 30 mu F capacitance, and the output grid-connected current total harmonic distortion is 3.03%. The input DC capacitor is reduced to 20 mu F, which would greatly improve the stability and lifetime of inverters.