School of Automation and Information Engineering, Xi’an University of Technology, Xi’an 710048, China

In view of the problem that the fatigue loads of doubly-fed wind turbines will significantly increase when participating in power system frequency regulation, an adaptive linear quadratic Gaussian (LQG) primary frequency regulation control strategy for doubly-fed wind turbines considering fatigue loads is proposed. Two linearized doubly-fed wind turbine frequency regulation models are constructed using the small-signal method, one below the rated wind speed and the other above the rated wind speed. The expected output power of the wind turbines is determined by the inertial response and static droop characteristics of the equivalent synchronous generator. A performance index function with the goal of minimizing the difference between the expected output power and the actual output power of the wind turbine, as well as the fatigue load, is constructed. The optimal frequency regulation power of the wind turbine is obtained in real-time by quickly solving the Riccati equation of the performance index function, thereby achieving primary frequency regulation control while reducing the fatigue load of the wind turbine. Furthermore, a method of adaptively adjusting the weight of the performance index function according to the remaining rotor kinetic energy and frequency deviation of the wind turbine is proposed to further optimize the frequency regulation capability of the unit. The simulation results show that the proposed strategy can effectively improve the frequency regulation capability of wind turbines while reducing the fatigue load of the units.