Research On Pitch Control System And Dynamic Characteristics Of Horizontal Axis Wind Turbines

With the rapid development of society and science and technology,the demand for energy in countries around the world is increasing,and a large amount of fossil energy is extracted,which leads to the depletion of fossil energy and the destruction of the ecological environment.In order to cope with this worldwide problem,countries around the world have begun to increase investment in new energy research and develop clean and environmentally friendly renewable energy.As an important part of renewable energy,wind energy has the characteristics of no pollution,clean,sustainable,wide distribution and large storage.Countries around the world have regarded the development of wind energy as one of the important strategies for sustainable development.The general utilization form of wind energy is wind power generation.With the increase of the capacity and volume of the wind turbine,the wind power system has large inertia,large delay and overshoot,which increases the complexity of the wind power control system.Therefore,the thesis designs variable pitch control strategies for wind turbines when the external wind speed is higher than the rated wind speed of wind turbines.By designing variable pitch control strategies and algorithms,the output power of the wind turbine is maintained near the rated power value,and the load of the main components of the wind turbine is reduced,and the stability of the wind power system is enhanced.Aiming at the problems of unmodeled parts and internal and external disturbances in wind power systems,an Active Disturbance Rejection Control(ADRC)for wind turbines is proposed.The expansion state observer is used to estimate the state of the wind power system,and the unmodeled part of the wind power system and the internal and external disturbances are defined as the "expansion state" to compensate the system.In addition,a nonlinear function is designed in the controller to counteract the nonlinearity and overshoot of the wind power system.The nonlinear state error feedback control rate is used to combine the system deviation signals to obtain a variable pitch control law.Finally,comparing the simulation experiment of the auto-disturbance variable pitch controller with the conventional PID pitch controller,it is found that the auto-disturbance variable pitch control greatly improves the control performance of the wind power system compared to the conventional PID pitch control.In view of the difficulty in determining the exact mathematical model of wind power systems,a BP neural network PID(BP-PID)feedback variable pitch controller is proposed.The BP-PID variable pitch controller does not depend on the precise mathematical model of the wind power system.It only needs to know the expected and actual values of the rotor speed.The BP-PID controller is used to adjust the deviation between the expected and actual values of the rotor speed.The neural network adjusts the PID parameters online to achieve the optimal combination of PID parameters,thereby performing pitch control.Simulation experiments show that,compared with conventional PID pitch control,BP-PID pitch control can effectively adjust the output power and component load of wind turbine.Aiming at the problems of large inertia and delay in wind power systems,a Kalman wind speed prediction feedforward variable pitch controller is proposed.BP-PID is a feedback controller.It needs to detect the feedback signal of the system to control the system.There is a certain delay.Therefore,a Kalman wind speed prediction feedforward controller is designed to compensate the BP-PID feedback controller.A Kalman filter is used to predict the wind speed signal in advance,and a correlation function between the wind speed and the pitch angle is constructed.The wind speed is used as the input and the pitch angle is used as the output,so that a pitch for compensating the feedback link is obtained according to the predicted wind speed.Angle compensation amount.Simulation experiments show that the proposed Kalman wind speed prediction controller can better compensate the feedback link and improve the delay effect of the wind power system.Aiming at the problem of many control objectives in wind power systems,a pitch controller based on Multi-objective Optimization Problem(MOP)is proposed.Taking output power,blade root load and generator torque as control objectives,by designing multi-objective optimization strategies and multi-objective optimization functions,the corresponding optimal solutions are solved,so that the single-target control of the wind power system is converted into Multi-objective control to further optimize the output of the wind power system.Finally,based on FAST and MATLAB/Simulink platform simulation experiments,it is found that the proposed multi-objective optimized pitch control strategy is feasible,effectively controlling the overshoot of the wind power system,reducing the load of the unit,and enhancing the safety of the wind power system and stability.