A Novel Power Decoupling Technique for Single-Phase Photovoltaic Grid-Connected Inverter

In the single-phase grid-connected PV system, considering unity power factor operation, the instantaneous output power consists of a pulsating power with twice the frequency oscillation. PV modules give constant power under MPPT control method when the temperature and sunshine intensity is stable. The instantaneous power imbalance between them is usually solved by a large electrolytic capacitor. However, the electrolytic capacitor typically has a limited lifetime. In this paper the principle of power decoupling and the work of a multi-stage single-phase PV grid-connected inverter are analyzed. A novel DC link power decoupling circuit is presented. Simulation results show that the presented decoupling circuit effectively reduces the capacitor value on the DC link, which improves the reliability of inverter and extends its lifetime.