A FDPS-MQPR Control Strategy with PGVF for Weak-Grid Stability Enhancement

With the increasing penetration of renewable energy sources, variations in grid impedance and background voltage harmonics have become major challenges to the operational stability and power quality of grid-connected inverters. Although conventional grid-voltage proportional feedforward (GVPF) effectively suppresses grid-voltage disturbances, its frequency-domain phase characteristics are highly sensitive to grid impedance variations, leading to reduced stability margins and even system instability under weak-grid conditions. To address this issue, this paper proposes a Frequency-Domain Phase-Shaping-Based Multi-Quasi-Proportional Resonant (FDPS-MQPR-PGVF) Control Strategy. Based on the established system impedance model, the phase characteristics at critical harmonic frequencies are systematically reshaped according to the impedance-based stability criterion (IBSC), enabling a systematic controller parameter design that simultaneously enhances weak-grid stability and background harmonic suppression. Simulation and experimental results demonstrate that the proposed strategy maintains stable operation under weak-grid conditions while significantly improving harmonic suppression performance. The proposed method provides an effective frequency-domain phase-shaping framework for enhancing the stability and harmonic performance of grid-connected inverters operating in weak grids.