Uncertainty prediction on the angle of attack of wind turbine blades based on the field measurements

Angle of attack is the most important parameter to determine the aerodynamic behaviors of wind turbine blades. It is difficult to be measured in the field and also ever-changing due to the unsteady inflow condition and dynamic control responses. In this work, a prediction method on the uncertainty of angle of attack was proposed only with the conventional wind turbine SCADA data and validated by the careful measurements in the field with leading-edge probes. As a result, in standstill case, the angle of attack fluctuates quasi-periodically and the amplitude is determined by yawing angle. In normal operating case, The standard deviation of angle of attack decreases from root to tip as the quintic polynomial law. The blade can be divided into three regions based on the contributions of three variables. The dominant variable from root to tip is yawing angle, tip-speed ratio and pitching angle, respectively. With the prediction method, the fluctuations of angle of attack along the blade span can be evaluated quickly for the wind turbine in the services. Also, in the design phase of a new wind turbine, the operation range of angle of attack can be pre-evaluated based on the wind speed, direction and control algorithm.