Study On Yaw System Error And Control Strategy Of The Wind Turbine

The modern large-scale wind turbines are located in the three-dimensional wind field where exist the wind shear and tower shadow effect,the aerodynamic loads and power captured by the rotor are therefore included fluctuating components,which resulting in vibration,power fluctuation and other problems.Meanwhile,natural wind is stochastic,being characterized by its speed and direction which change randomly and frequently.Wind turbines cannot be accurately aligned toward the wind direction because of the yaw body itself and the certain lag in control systems,so yaw error can not be eliminated very well,and the wind turbine is in yaw condition in most cases.Based on the problems mentioned above,a large-scale wind turbine was chosen as the research object in this thesis.Firstly,the equivalent wind speed model based on the wind shear and tower shadow effect was built and its spatial distribution in the rotor disk area was delineate.Then,based on the equivalent wind speed model and the yaw error model,the influence of yaw error on the running characteristics of wind turbine was further studied.Finally,based on the phase difference of the yaw error to the running characteristics of the wind turbine,an improved method of the yaw control strategy optimization was proposed.In this thesis,the MATLAB simulation analysis and wind turbine SCADA actual operation data are compared and analyzed.The main research work and achievements are as follows:With the rapid development of large-scale wind turbines,the effects of wind shear and the tower shadow on the wind turbine have increased significantly,and the wind speeds are different across the rotor disk area and vary tremendously with changes in the rotor diameter,tower dimensions or other geometric parameters due to the effects of wind shear and the tower shadow.Aiming at this problem,a more universal applicability and comprehensive equivalent wind speed model that includes the wind shear and tower shadow effects has been developed for n-bladed wind turbine.Formulas for the relevant disturbance components Wws,Wts,W+ and the equivalent wind speed conversion factor W_eq were derived.The spatial distributions of equivalent wind speed for 2-bladed,3-bladed and 4-bladed rotor were simulated by MATLAB,and their equivalent wind speed spatial distribution characteristics were also analyzed.The 3-bladed wind turbine was taken as an example to study the effects of the correlation parameters（R,H,A,x,α and n）on the equivalent wind speed conversion factor W_eq.The results showed that the equivalent wind speed is closely related to the wind turbine correlation parameters R,H,A,x,α and n,but these parameters have different effects on W_eq.By solving the equivalent wind speed model for the whole rotor disk area of 3-bladed wind turbine,combined with the wind turbine model and the yaw error model,the effects of yaw error on wind turbine running characteristics at different wind speeds and control stages were studied.The mathematical model of the rotor torque coefficient Tc,the rotor speed coefficient Sc and the wind turbine power coefficient Pc were derived.Simulation was carried out in the MATLAB software,and the simulation results were compared with the actual running data of the wind turbine.The results indicate that the effects of the aerodynamic torque,rotor speed and power output due to yaw error at different running stages are different and that the effect rules for each coefficient are not identical when the yaw error varies.Taking some 2MW wind turbines in a wind farm as the research and test objects,Firstly,the SCADA running data of the target wind turbines were described and analyzed,the performance of the yaw system including the yaw process,the distribution characteristics of the yaw error and the stochastic characteristics of the yaw motion were also analyzed,deficiencies in the current yaw control strategy were shown.Then,according to the effects of running characteristics of the wind turbine due to yaw error at different wind speeds and different running stages are different,and take into account the probability distribution of yaw error and its relation with wind speed,new yaw control idea and method of subsection optimization strategy was proposed,and the control procedures was given out.At last,the yaw control parameters are optimized and tested in the target wind turbines,and the effectiveness of the proposed method is verified by the comparison of the SCADA data.The obtained results of this thesis contribute to a better understanding of the effects of the wind turbine correlation parameters on the spatial distribution of equivalent wind speed across the rotor disk area,and it could be conducted to provide a reference for further studying the running characteristics of wind turbine under yaw error.Meanwhile,these results may provide theoretical support for optimizing the yaw control strategies for each stage to increase the running stability of wind turbines and the utilization rate of wind energy.