Aeroelastic model of flexible blades of wind turbines under complex wind speed profiles

With the increasing size of wind turbines, the inflow conditions are also becoming more and more complex, and the rotor speed and blade-pitch angle are unknown under complex inflow conditions, so in order to avoid establishing an equivalent wind speed model, the control system was coupled to the blade element momentum theory (BEMT) to establish an aerodynamic model. In addition, due to the increasing flexibility of blades, a structural model of blades that can solve any section shape and any material properties was established based on the geometrically exact beam theory. Finally, the aerodynamic model and the structural model were coupled to establish the aeroelastic model and implemented by C++. The model was applied to engineering calculations, and the aerodynamic characteristics of wind rotors and the dynamic response of blades under different low-level jets (LLJ) were calculated and analyzed. The results show that when the control system is coupled to the BEMT, part of the power error is transferred to the rotor speed for below-rated wind speeds, and all the power error is transferred to blade-pitch angle for the above-rated wind speeds. The structural model can accurately calculate the static, dynamic displacement and natural frequency of the blades. When the LLJ height is different, the control system weakens the influence of strong shear wind on the average aerodynamic force on the sweeping surface of the wind rotor, but the amplitude of aerodynamic force is still greatly affected by the LLJ height. When the aerodynamic force on the blade is similar, the law of structure dynamic response is the same, which is mainly affected by the natural frequency of the blade. Our work has important reference significance for calculating the aerodynamic characteristics of wind rotors and the dynamic response of blades.