Photovoltaic Energy Conditioning System Using Hybrid Active Damping Procedure for Stable and High-quality Operation in Harmonically Distorted Networks

The increasing penetration of grid-connected photovoltaic (PV) systems has intensified the stability challenges associated with LCL-filtered inverters, particularly under weak and harmonically distorted grid conditions. Although capacitor-current feedback (CCF) and point of common coupling (PCC) voltage feedforward are widely used active-damping techniques, each method has a limited effective damping range and may introduce negative damping due to digital control delays and variations in grid impedance. To address these limitations, this paper proposes a unified hybrid active-damping strategy that combines CCF and PCC-voltage feedforward to maximize the positive-damping region over the entire critical frequency range. A comprehensive frequency-domain analysis is carried out to characterize the equivalent virtual impedance of the hybrid structure and to derive explicit conditions for stable operation and gain selection under varying grid inductance. In addition, an integrated control framework is developed for a grid-connected PV power-conditioning system, incorporating coordinated DC-link voltage regulation and AC-side current control to ensure robust power injection under fluctuating irradiance conditions. The proposed design guarantees minimum-phase behavior and enhanced robustness against parameter uncertainties and weak-grid effects. Extensive simulation results demonstrate effective resonance suppression, high-quality current injection with low harmonic distortion, and reliable operation under both weak and harmonically polluted grid scenarios.

کلیدواژه ها:

active damping ، Capacitor-current feedback ، Grid-connected photovoltaic systems ، harmonic distortion ، voltage feedforward ، Weak grid