Wind Turbine Pitch Control Based On Direct Model Reference Adaptive Control

With the capacity of wind turbine increasing,the diameter of the rotor is also increasing.The nonlinearity of large rotor poses more severe challenges to pitch controller of wind turbines.In order to achieve stable power control and torsional vibration suppression of drive train above rated wind speed,the dynamic model of doubly-fed wind turbine is established,the characteristics of rotor and drive train are analyzed,a direct model reference adaptive pitch controller and a torsional vibration controller of drive train are designed.By Matlab/Simulink simulation and GH Bladed simulation,the effect of direct model reference adaptive control(DMRAC)and gain-scheduling PI pitch controller are compared.The main research contents are as follows.(1)The LPV model of wind turbines is established.It is found that the aerodynamic torque of wind turbines has a strong nonlinear relationship with the rotor speed,pitch angle and wind speed.The nonlinearity of aerodynamic torque makes the coefficients of the transfer function change,which poses a severe challenge to the gain-scheduling PI controller.(2)A new structure of direct model reference adaptive controller for wind turbine pitch control is proposed in view of the change of transfer function coefficients and the existence of output disturbance.Matlab/Simulink simulation and GH Bladed simulation show that DMRAC has better ability to stabilize wind turbine power than gain-scheduling PI controller,and the power standard deviation decreases by about 40%.(3)The feasibility of suppressing torsional vibration of drive train by additional ripple torque is verified by establishing the dynamic model of drive train of wind turbine.(4)According to the dynamic model,a Kalman filter is designed.The GH Bladed simulation results show that the Kalman filter can effectively reduce the torsional vibration of drive train natural frequency,and the auto-spectra density decreases to about 4.47%of that without torsional vibration control.Compared to band-pass filter,Kalman filter control can reduce the vibration of other frequencies.The additional torque ripple of Kalman filter controller makes the power fluctuation of the generator larger,but the average power of the generator was affected slightly thus the energy yield was hardly reduced.