Two-Stage Power Decoupling for a Single-Phase Photovoltaic Inverter by Controlling the DC-Link Voltage Ripple in the DQ Frame

A two-stage power decoupling for a single-phase photovoltaic (PV) inverter is proposed in this paper. By controlling the DC link voltage ripple, the amount of decoupling power can be controlled on both DC and AC sides. The inverter is first modelled with differential and common signals in the dq frame. Then conventional PI controllers are designed to control the grid current, DC link voltage, and its voltage ripple, respectively. The experimental results show that the amount of decoupling power on the DC sides is controllable by regulating its voltage ripple. The power decoupling on the AC side drastically reduces the DC-link capacitance, i.e., from 900 uF to 68 uF, which makes it possible to replace the electrolytic capacitor by the film capacitor with high reliability.