Research On Perturbation Suppression Method Of Pitch Control For Large Wind Turbine

After years of development,wind power generation technology in China and the world has made great progress.With the application of hydraulic technology in the wind turbine industry,hydraulic pitch control is gradually adopted in large wind turbine.However,the fore-aft vibration of tower in the process of hydraulic pitch control can affect the stability of the output power of the wind turbine to a certain extent,so that the incoming flow velocity received by the wind turbine is not consistent with the wind speed at the actual wind wheel,resulting in the deviation of the actual o utput power.At the same time,unknown delay will occur during the operation of the h ydraulic pitch control system,this delay may cause perturbation to the system,make the wind turbine tower fore-aft vibration signals has a certain delay relative to the signal of the pitch,make wind turbine transient load increases,the stability of the output power down.This thesis takes a certain type of 3MW wind turbine in China as the research object,the fore-aft vibration and delay perturbation of the tower caused by hydraulic pitch are studied.The main research contents are as follows:Firstly,the basic principle of wind turbine was analyzed,and based on this theory,the wind turbine model composed of wind speed model,generator model,wind wheel model and pitch control perturbation model were built on the MATLAB/Simulink simulation platform,which laid a theoretical foundation for the follow-up research.Secondly,the modeling of the pitch angle and the fore-aft vibration of the tower was studied.The transfer function between the change in pitch angle and the fore-aft vibration displacement of the tower was derived and calculated,then a collective pitch controller and independent pitch controller joint control was designed.The final pitch signal was input into the transfer function to obtain the fore-aft vibration displacement of the tower in the ideal no-delay model,so as to calculate the fore-aft vibration velocity of the tower.The fore-aft vibration velocity of the tower and the wind speed at the wind wheel were treated as the true inflow velocity of the wind wheel to improve the wind wheel model,and then input the wind turbine parameters of the whole wind turbine model into MATLAB/Simulink to simulate the wind turbine model before and after the improvement.Compare the output power and output torque before and after the improvement,the results show that the improved wind wheel model is effective for the stable output of wind turbine.Finally,according to the actual operation of the hydraulic pitch control in the wind turbine,a delay model was added to the original ideal no-delay model to simulate the delay in the process of hydraulic pitch control.The delay model was expanded to transform the delay into the disturbance of the system.And then the delay estimation compensator was designed,the initial state value was determined,and the delay of the system was estimated and compensated.The simulation results show that the delay estimation compensator can accurately estimate the delay caused by the system,the estimation error converges and fluctuates within the allowable range,and the output power and output torque of the wind turbine are consistent with the ideal model without delay.The system simulation and the experiment by changing the arbitrary delay or wind model prove that the delay estimation and compensation system can also estimate the delay of the compensation system well,which indicates that the system had good robustness.