Harmonic Instability Analysis of Wind Farms and Electrified Railways Jointly Connected to the Power Grid

With the continuous growth of China's installed wind power capacity and high-speed railroad mileage, there is a growing risk of harmonic instability in many regions where wind farms and electrified railways jointly connect to the power grid's point of common coupling (PCC). To address this problem, this paper conducts a stability analysis of wind farms and multi-vehicle traction network coupling systems (for the sake of elaboration, the traction network is considered a part of the traction power supply system in this paper). An integrated sequence impedance model for the coupling system of the grid, wind farm, and trains coupling, whose accuracy is verified utilizing the impedance sweeping. Then, the impact of transmission line length on the stability of the integrated coupling system is analyzed. Based on the admittance bode diagrams of wind farms and trains, the mechanism of the interaction between wind farms and trains is revealed, and the ratio of the number of vehicles to the number of direct-drive permanent magnet synchronous generators (PMSGs) when the coupling system is critically stable is provided. Finally, the proposed model's accuracy and the theoretical analysis's correctness are verified through Matlab/Simulink simulation and Starsim/HIL hardware-in-the-loop simulation platform.