Rotor Thrust Control for Large-Scale Wind Turbine in Near-Rated Wind Speed Region

To limit the maximum rotor thrust in the near-rated wind speed region, this paper proposes a novel rotor thrust control scheme for large-scale wind turbines operating. It contains a rotor thrust identificator, a rotor thrust control loop, and a feedforward blade pitch controller. A simplified blade model is first proposed to achieve rotor thrust identification. Based on blade element momentum theory, the rotor thrust can be identified by the blade root out-of-plane bending moments. The rotor thrust control loop is then designed with the identified rotor thrust. Then, a feedforward blade pitch saturator is designed, called Nonlinear Dynamic Inversion based minimum Pitch Saturator (NDI-PS). It is realized by nonlinear dynamic inversion of the thrust coefficient curve. The simulation results exhibit outstanding performance of the proposed control scheme. Compared with existing controllers of NREL and Goldwind, power output is increased by 1% to 1.5%, while blade root and tower bottom loads are mitigated by about 4%.