Analysis of Direct-drive Turbine Shaft Torsional Vibration under Inertia Control Strategy

In the study of inertia control strategies for wind turbines, the flexibility of the shaft system is often neglected. However, inertia control can affect the oscillation of the turbine shaft system to some extent, which may impact the stability of the wind power system. Therefore, it is necessary to conduct an in-depth analysis of the impact of inertia control on the torsional vibration of the wind turbine shaft system. Currently, the commonly used inertia control strategies in wind power systems are virtual inertia control and virtual synchronous generator (VSG) control. This paper analyzes the effects of virtual inertia control and VSG control, along with their important parameters, on the torsional vibration of the shaft system in permanent magnet synchronous wind turbines. The study indicates that both inertia control strategies can induce torsional vibrations in the turbine shaft system, and the control parameters significantly influence the intensity of these free torsional vibrations. Additionally, under both inertia control strategies, the stronger the inertia response capability of the wind turbine, the greater the excitation of the shaft system torsional vibrations. Under the condition of having the same inertia response capability, VSG control results in a lesser degree of excitation to the wind turbine shaft system torsional vibrations.