To address the phase lag issue of output impedance in single-phase grid-connected inverters caused by grid voltage feedforward, this paper proposes an output impedance phase frequency-segmented compensation method based on a single-phase LCL-type grid-connected inverter. The method improves the magnitude-frequency and phase-frequency characteristics of the grid-connected inverter’s output impedance by cascading a first-order high-pass filter (HPF) and a first-order low-pass filter (LPF) in the grid voltage feedforward path. Specifically, by reducing the delay coefficient in the low-frequency band, the gain and phase margin of the inverter’s output impedance in the mid-low frequency range are enhanced. Simultaneously, the delay coefficient in the high-frequency band is increased to strengthen the passivity of the output impedance in the high-frequency band range. Simulation and experimental results demonstrate that the proposed method effectively improves the phase margin of the output impedance in photovoltaic grid-connected systems, thereby ensuring the stable operation of the grid-connected system.
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