The Research Of Wind Speed Detection And Variable Pitch Control Strategy Of Wind Turbine

Under the effect of pitch control,the blade pitch angle of large-scale wind turbines can be adjusted appropriately.By changing the angle of attack between the blades and the airflow,the aerodynamic torque captured by the wind wheel is changed,which ensures stable operation of wind turbine system.Variable pitch wind turbine has become one of the main development directions of wind turbines due to its flexible control method and high energy conversion efficiency.However,due to the unpredictability of wind speed and direction change in wind field,which has brought great difficulties to the pitch control of wind turbines.For this reason,this paper makes a study of the wind speed detection technology and the pitch control method of wind turbines.After analyzing and comparing the conventional wind speed detection methods,wind speed is detected by ultrasonic time difference method and the corresponding mathematical model is established.The hardware circuit and software program of the wind speed detector are designed.The hardware circuit includes the design of the control circuit,the ultrasonic receiving and transmitting circuit and the signal processing circuit.The wind speed detector can obtain the wind speed which should be detected after being calculated by the software program which is set.After analyzing the actual test data,it is shown that the wind speed detector can meet the detection accuracy requirements and can be used to detect the wind speed on the wind turbine.When designing the pitch angle controller,the control strategy combining PID pitch control and repetitive control is adopted.Based on the PID control theory,a PID pitch controller is designed to control the blade pitch uniformly to suppress the disturbance caused by the random wind speed change in the wind field.The simulation results show that the wind turbine speed can be stabilized near the rated value under the control by the PID pitch controller,which ensures the output of the wind turbine is stable.However,due to the wind shear effect,when the wind wheel is rotating,the wind speed acting on the blades during the sweep is different,which will result in the occurrence of periodic pulsation of the wind wheel torque.In this regard,based on the repetitive control theory,a pitch angle compensation controller with compensation adjustment for the pitch angle is designed to weaken the periodic pulsation effect of the wind shear effect on the wind wheel torque.The simulation results show that the designed pitch angle controller can ensure the stable operation of the wind turbine system,and also weaken the periodic pulsation of the wind shear effect on the wind wheel torque,and improve the stability of the system output power.