A Voltage Stability Research of Connecting Wind Farms to the Receive-side Grid Based on Torque Slip Curves

Under Chinese ''carbon peaking and carbon neutrality goals", the installed capacity of wind turbines in China has increased. The large amount of wind power connected to the grid has an essential impact on the voltage stability of the receive-side grid. This paper analyses the impact of wind turbines on the operating state of induction motors and thus on the transient voltage stability based on the torque slip curve for a simplified system model of wind turbines connected to the receiver grid. Firstly, the load model of the receive-side grid is equated to a two-node system with a virtual induction motor, and the mechanism of voltage stability is analysed in detail. The induction motor's torque slip curve gives an analytical method to determine the voltage stability and calculate the critical clearing slip and critical clearing time after a short-circuit fault. Use this indicator to measure grid strength and analyse the impact of the wind power connected grid. The results show that the participation of wind power improves the stability of the transient slip of the induction motor and extends the critical clearing time, thus improving the transient voltage stability and increasing the load capacity at the receive-side gird. The simulation results show that the load-carrying capacity of the receive-side is increased due to the wind turbine's output support. However, the proportion of external power received by the whole receive-side is reduced, and this conclusion is verified in the actual grid.