Dynamic Modeling and Stability Analysis for Repeated LVRT Process of Wind Turbine Based on Switched System Theory

Abstract

The significant electrical distance between wind power collection points and the main grid poses challenges for weak grid-connected wind power systems. A new type of voltage oscillation phenomenon induced by repeated low voltage ride-through (LVRT) of the wind turbine has been observed, threatening the safe and stable operation of such power systems. Therefore, exploring dynamic evolution mechanisms and developing stability analysis approaches for this phenomenon have become pressing imperatives. This paper introduces switched system theory for dynamic modeling, mechanism elucidation, and stability analysis of the repeated LVRT process. Firstly, considering the external connection impedance and internal control dynamics, a novel wind turbine grid-side converter (WT-GSC) switched system model is established to quantitatively characterize the evolution dynamic and mechanism of the voltage oscillation. Subsequently, a sufficient stability criterion, as well as stability index, grounded in the common Lyapunov function is proposed for stability analysis and assessment of the WT-GSC switched system. Moreover, to enhance the system stability, the Sobol' global sensitivity analysis method is adopted to identify dominant parameters, which can be further optimized via the particle swarm optimization (PSO) algorithm. Finally, simulations conducted on a modified IEEE 39-bus test system verify the effectiveness of the proposed dynamic modeling and stability analysis methods.