PLL-Based Stability Enhancement of Single-Phase Grid- Connected Inverters Under Grid-Impedance Uncertainty

This paper investigates current instability and low-order harmonic distortion in single-phase grid-connected inverters under grid-impedance uncertainty using an impedance-based stability framework. The effects of phase-locked loop (PLL) dynamics on inverter output impedance are analyzed by comparing Notch-PLL and SOGI-PLL structures. In addition, a Harmonic Resonant Controller (HRC) is employed to suppress the ۳rd, ۵th, and ۷th harmonics. Simulation results in MATLAB/Simulink demonstrate that the proposed approach improves current stability and significantly reduces low-order harmonic distortion under uncertain grid conditions.

کلیدواژه ها:

Grid impedance uncertainty ، Harmonic Resonant Controller (HRC) ، Impedance-based stability ، Low-order harmonics ، Phase-Locked Loop (PLL)