Individual pitch control strategy of wind turbine to reduce load fluctuations and torque ripples
Wind velocity distribution differences in wind wheel rotation plane caused by wind shear and tower shadow, not only causes load fluctuations of wind turbine blades, but also leads to pulsations of wind turbine aerodynamic torque and output power. In order to reduce the influence of wind shear and tower shadow on the fluctuations of three-bladed wind turbine, an individual pitch control strategy based on the pitch angle signal adjusted jointly by wind turbine output power and rotor azimuth angle is proposed. A band-pass filter is designed to filter out the three times pulsating component of the wind turbine output power, and a PID controller is used to obtain regulatory signal of pitch angle, which is then converted to tiny variable of each blade combining with the azimuth angle signal and superimposed to the reference pitch angle of the collective pitch control. Simulation results on GH Bladed platform show that the proposed individual pitch control strategy is effective to smooth blade load fluctuation, diminish aerodynamic torque ripple, reduce rotor fatigue damage, and prolong life time of wind turbine.