Research On Influence Of Strong Turbulent Coherent Structure On Load Of Horizontal-axis Wind Turbine

Wind turbines are often subjected to strong turbulent coherent structures and have a significant impact on their loads.The dynamic load characteristics experienced by wind turbines during operation are key factors that affect the service life and safe operation of wind turbines.In order to improve the service life of the wind turbine and reduce the fatigue load during operation,it is necessary to study the dynamic load changes of the wind turbine under various working conditions.This paper uses the NWTCUP(The NREL National Wind Technology Center Model)wind spectrum model coupled with KHB(Kelvin-Helmholtz Billow)flow to construct a strong turbulent coherent structure wind condition,which is calculated using the FAST(Fatigue,Aerodynamics,Structures,and Turbulence)program In this wind condition,the load of WindPACT 1.5MW wind turbine was analyzed.The influence of the turbulent coherent structure of different scales and positions on the wind turbine load,and the change of the wind turbine loaded with the yaw angle in the yaw state is analyzed.Furthermore,it is considered that the strong turbulent coherent structure makes the pitch angle need to be adjusted continuously,which is likely to cause unsynchronized pitch failure,resulting in uneven force on the wind turbine.In the case of uniform flow,the variation law of the deviation angle and load during the failure is analyzed,and the allowable deviation angle range is obtained.(1)By studying the influence of the changes in the scale and position of the turbulent coherent structure on the wind turbine blade root edgewise load,flapwise load,low-speed shaft torque,pitch moment and rotor thrust,it is found that the change of the scale and position of the turbulent coherent structure makes the average value of each load change small,the change range do not exceed 3.5%,and the energy in the frequency domain is mainly concentrated between 0.195 Hz and 1.562 Hz.The changes of KHB scale and position have little effect on the measures of dispersion and frequency energy of edgewise moment and low-speed shaft torque,but there are periodic fluctuations.When the center of the turbulent coherent structure is located in the center of the hub and covers the entire plane of the rotor,the low-speed shaft torque is strongly periodic,and there is a significant change in energy around the pass frequency of the rotor of 1.02 Hz.There is no obvious periodicity of the flapwise moment,pitch moment and rotor thrust at different scales and positions.When the center of the turbulent coherent structure is located in the center of the hub and covers the entire rotor plane,the energy in the frequency domain is the strongest and has a clear response to the large-scale low-frequency turbulence in the incoming flow.(2)By studying the influence of the turbulent coherent structure on the various loads of the yaw wind turbine,it is found that the addition of the turbulent coherent structure and the increase of the yaw angle have little effect on the edgewise moment and low-speed shaft torque,and are related to the Reynolds stress component u ’w’ and v’w ’have obvious cross-correlation.The addition of turbulent coherent structure will cause the fluctuation of Reynolds stress component to increase,which will make the flapwise moment and yaw moment dispersion degree,the frequency domain energy increases obviously.The correlation between the flapwise moment and Reynolds stress component u ’w’ is obvious,and the cross-correlation between yaw moment and v’w’ is obvious.With the increase of the yaw angle,the degree of dispersion of the flapwise and yaw moments increases significantly,and the frequency domain energy increases significantly,And the cross-correlation with u’w’ and v’w’ decreases.(3)By studying the effect of uniformly flowing down the pitch angle asynchronism fault on the wind turbine output power and various loads,it is found that the increase of the positive asynchronization angle will gradually reduce the output power to.When the deviation angle is +5 °,it can be reduced to 1.3MW,and the volatility increases,The blade root load will have a mean value decline and a phase lag phenomenon,which has a significant effect on the mean value of the flapwise moment,with an average decrease rate of 12.77%.The increase of the reverse asynchronous angle will increase the ability of the rotor to capture wind energy and increase the output power.When the deviation angle is-5 °,it can be increased to 1.74 MW,and the volatility stable.The average root load appears the phenomenon of rising and phase advance,and has obvious influence on the mean value and dispersion degree of edgewise and flapwise moment,the average increase rate is 3.06% and 7.79%,10.79% and 13.55% respectively.The failure of the pitch angle asynchrony has little effect on the mean of rotor thrust and pitch moment,but has a greater impact on the degree of dispersion of the latter.The standard deviation is 106.88 at a deviation angle of-1 ° and 99.11 at + 1 °,which is relatively small,so the recommended deviation angle range can be taken as-1 ° ~ + 1 °.