Vibration Attenuation Technology Of Wind Turbine Based On Individual Pitch Cntrol

Wind energy is one of the effective choices to solve the energy problem. The capacity of horizontal axis wind turbine continuously increases which is obviously reflected on the longer blade and the bigger rotor. Under normal operation, the blades of wind turbine rotationally sample the wind field, so the asymmetric load of the rotor caused by wind shear is prominent, as well as the vibration of the blades and tower excited by the load. The periodic flapwise aerodynamic load on the blades seriously affects the reliability and the life of wind turbine, and individual pitch control is one of the key technologies to solve these problems. The controller cooperatively regulates the pitch angle of each blade to change the aerodynamic load of wind turbine according to the sensor signal. Eventually, the asymmetric load of the rotor is eliminated and the vibration of the blade is also attenuated.Considering the flapwise periodic aerodynamic load and the vibration of wind turbine, the relevant theory of individual pitch control was studied and the controllers were designed. Firstly, the modeling principle of wind turbine controlling was summarized from the point of aerodynamics and structural dynamics, and the modeling and simulation software FAST which used in analysis and design process was introduced. Then the power regulation of wind turbine was studied from the point of systematic operation, including modeling, designing and simulation. The generator torque controller was based on lookup table while the collective pitch controller used the variable gain, and the power regulation of wind turbine was guaranteed at the whole operating region. The spectrum analysis was conducted for the bending moment and the vibration signal of the power-regulated wind turbine, and the main frequency of the signal in blade was found mainly the multiples of rotational frequency while wind shear changed the amplitude of the periodic signal. Finally, the individual pitch control of wind turbine was analyzed and studied from the point of reducing the flapwise periodic load and attenuating the flapwise forced vibration. Multi-blade coordinate transformation was introduced because of the inherent periodicity and the coupling vibration of wind turbine, and the asymmetry of load was found while wind shear exacerbated this asymmetry. The blade-tower coupled vibration model of wind turbine was established and decoupled by multi-blade coordinate transformation. Two individual pitch control schemes were analyzed and designed based on blade flapwise load output feedback.The result of load reduction and vibration attenuation was compared for the collective and two different individual pitch control schemes through interactive simulation between MATLAB and FAST. When feedback regulation was performed under steady wind speed,the simplification of controller designing and the better control result was showed because the flapwise periodic load is decomposed into more basement, even valuable result was showed under dynamic wind speed.