An Investigation of Grid Stability and a New Design of Adaptive Phase-Locked Loop for Wind-Integrated Weak Power Grid

This work investigates the impact of phase-locked loop (PLL) parameters on the stability of a wind-integrated weak power grid. The analysis is based on a weak grid model that integrates a Type-4 wind turbine generator with the grid represented by a lumped group model of a thermal power station with a steam governor and exciter system through a variable impedance network. This model is classically used for a weak grid study representing a real-life system. First, the impact of proportional and integral gain constants of the PLL on stability and oscillation characteristics is discussed in detail. Based on the analysis, an adaptive gain scheduling PI-based PLL architecture is proposed. The advantages of the proposed architecture are studied based on rigorous changes in the grid impedances and the wind dynamics. The results show that the proposed architecture significantly improves grid stability and damping when compared with conventional PLL designs.