An MPC-based two-stage primary frequency regulation strategy for grid integrated wind farms

With the large-scale integration of offshore wind farms into power grids, the frequency stability of power systems faces significant hurdles because wind turbines (WTs) usually operate in the maximum power point tracking mode. This paper proposes an improved two-stage model predictive control method aimed at providing optimal control throughout the primary frequency regulation process of the wind farm. By considering local wind speed conditions, this method enhances resistance to wind speed disturbances. Given the discrepancies between linearized prediction models and actual models, a model feedback correction scheme is employed to ensure the feasibility and practicality of the proposed method. The method is designed to effectively track the frequency support requirements of grid operators while reducing frequency regulation costs, enabling mode switching without compromising the frequency support performance of WTs and avoiding secondary frequency drop (SFD) while rapidly restoring rotor speed. Finally, simulations on an equivalent power system with a real offshore wind farm containing 40 permanent magnet synchronous generator (PMSG)-based WTs are conducted to validate the effectiveness of the proposed method. The results show that the proposed method could effectively increase the lowest frequency nadir and mitigate SFD, even during periods with variations in wind speed.