Study of stability after low voltage ride-through caused by phase-locked loop of grid-side converter

In a power system with a high percentage of converter coupled generation, dynamic characteristics of the converter affects the stability of the whole power system. The interaction of the various control loops of the grid-side converter, e.g., the phase-locked loop and the DC link voltage control loop, dominates the various dynamic characteristics of the grid-side converter, including its low voltage ride-through ability. In this paper, the phase-locked loop is modeled and analyzed and a stability criterion for the converter, depending on the grid impedance, is obtained. According to this criterion, a common low voltage ride-through test device based on the shunt impedance voltage sag generator is analyzed. The results show that, and explain why, the test device cannot reproduce the characteristics of the practical grid, which is also verified by experiments using a controller-Hardware-in-the-loop system.