Individual Pitch Control For Large Scale Wind Turbines

Wind turbine design objectives have changed a lot in the past 10 years. Modern wind turbines have become larger and they have moved from being fixed-speed, Stall-controlled and with rudimentary control systems to variable-speed, pitchcontrolled, drive-train with or without gearboxes and highly controllable. Thus, they have moved from being convention-driven to being optimization-driven.With great development of wind power technology and increase of wind turbine unit capacity, rotor diameter, nacelle weight and tower height of wind turbine increase rapidly. Dynamic load caused by wind turbulence, tower shadow, and rotor unbalance affects large scale wind turbine more and more distinctly.These additional loads will speed up the wind turbine fatigue, impact of wind turbine life. To reduce these additional loads, the way of individual pitch control is more effective and feasible. Individual pitch control is to overlay an individual pitch signal to the synchronous pitch signal for each blade and make the three blades have different aerodynamic properties to compensate for the additional load caused by the uneven wind.The first and second chapters of this paper introduce the basic principles of wind turbines and the pitch actuator, including the characteristics of wind energy, components of wind turbines, aerodynamics for wind turbines, power train, power generation systems, control objectives execuators for individual pitch control and fiber Bragg grating sensor; In the third chapter, a mathematical model for individual pitch control is established; In the fouth chapter, individual pitch control based on load feedback is simulated; In the fifth chapter, individual pitch control based on load feedback and wind speed feedforward is simulated, simulation results show that:compared with the synchronous pitch technology, individual pitch control based on load feedback significantly reduces the tilt load and yaw load, but the corresponding rate is slowe; individual pitch control based on wind speed feedforward control can significantly reduce the tilt load and yaw load too, and the response is faster, but the feedforward control can not be used alone. Individual pitch control based on load feedback and wind speed feedforward can reduce the tilt load and yaw load both, and achieve the desired effect.