D2.3 A wind farm ancillary service algorithm with optimal fatigue distribution

Ancillary services like inertial response and frequency support are crucial for power systems because they keep the power system stable, reliable, and resilient, especially as more renewable energy (like wind energy) replaces traditional power plants. However, when the wind turbine generators are equipped with the ancillary service function, they need to rapidly change the output power to support the grid frequency variation. As a result, the mechanical torque of the turbine side is changed dynamically. When a larger torque is added to the turbine’s shaft, it might increase the mechanical stress and fatigue of the turbine, which eventually might reduce its lifetime. In order to analyse the impact of the grid-side ancillary service on the mechanical fatigue of the turbine, a full wind turbine generator model, including the aerodynamic wind turbine model, the drive train model, the permanent magnet synchronous generator (PMSG) model, and the back-to-back converter model, is built initially in this task. Then, the two general types of converter control schemes (i.e., machine-side DC voltage control and grid-side DC voltage control) are applied to the developed full wind turbine model. Based on the simulation studies, test results demonstrate that the mechanical stresses by using both control methods are generally identical, but the machine-side DC voltage control leads to a slightly higher mechanical stress compared with the grid-side DC voltage control scheme. According to the above studies, the grid-side DC voltage control scheme with ancillary service is used to minimize fatigue. Besides, a wind farm ancillary service control algorithm based on high-speed side or low-speed side energy reservation is also developed. Finally, the developed wind farm ancillary service control algorithm is applied to a multiple-wind turbine system to show the effectiveness of the ancillary service function and fatigue optimization.