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Three-phase LCL-type grid-connected inverter is an important interface element of centralized photovoltaic (PV) gridconnected system. However, the inherent resonance in the LCL filter may lead to system instability. This research suggests an improved capacitor current feedback active damping (CCFAD) approach to address this issue. Firstly, the sequence impedance model of the PV grid-connected inverter is established using harmonic linearization method, and the resonant characteristics of the PV grid-connected system is revealed based on stability criterion. Subsequently, based on the proportional CCFAD strategy, an improved CCFAD strategy with delay compensation is proposed, which not only widens the positive damping zone of the traditional CCFAD, but also effectively improves the phase margin of the output impedance of the PV grid-connected inverter. Finally, the effectiveness of the proposed active damping control strategy is verified by simulation results.
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