Stability Analysis of the PLL for the Control of Solar-PV System Interfaced with Low Voltage Weak Grid

This paper investigates the influence of adverse increases in grid impedance on the stability of phase-locked Loop (PLL) in grid-connected PhotoVoltaic (PV) systems. A weak grid is characterized by limited short-circuit capacity, leading to voltage instability and sensitivity to fluctuations in power generation. Understanding PLL dynamics amidst these conditions is critical for ensuring the reliability and resilience of grid-connected PV systems. The mathematical modeling evaluates how control loop interaction disturbs PLL stability during a weak grid. The small signal stability analysis helps reveal the stability of PLL. The outcomes contribute to the scholarly discourse on weak grid conditions in renewable energy systems, aiding in developing strategies to fortify system stability and grid integration. The simulation studies show the stability analysis of the PLL during a weak grid condition from 0.4s to 0.6s using MATLAB®/SIMULINK. The results are as per the standards of IEEE 519-2022. Further, the simulated results are verified using the Hardware in Loop(HIL) results.