Coupling Mechanism Of Dual-excitation Fatigue Loading System Of Wind Turbine Blades

The fatigue test on the blade is applied to determine the fatigue weak parts and fatigue performance of wind turbine blade in the design stage. In the current fatigue loading test of wind turbine blade, the main test method at home and abroad is single-excitation fatigue loading. But this method has the problem of distortion of the testing results and lacking of driving force. Therefore, in this paper a new dual-excitation fatigue loading mode was put forward to improve the testing accuracy. Based on the dual-excitation loading mode, a set of dual-excitation fatigue loading test system of wind turbine blade was built. The main research contents are as follows:Firstly, electromechanical coupling mathematical model of the dual-excitation fatigue loading vibration system of wind turbine blade was built. Based on the analysis about the relationship among the asynchronous motor windings, the mathematical model of the three-phase asynchronous motor was simplified by coordinate transformation and the simplified mathematical model under two-phase rotating coordinate system was built; Then the differential equations of the vibrating mechanical system were built applying the Lagrange equation method; The two above equations constituted the electromechanical coupling mathematical model of the dual-excitation fatigue loading vibration system of wind turbine blade. From the electromechanical coupling mathematical model, it could be seen that the initial phase, the mounting positions of the two fatigue loading system, the eccentricity of the eccentric mass, the motor speed, the blade’s stiffness and damping and the mechanical properties of the motor influenced the coupling properties of the vibration system.Secondly, according to the electromechanical coupling mathematical model, the dynamic simulation model in the simulation software MATLAB/Simulink was built. Under the influencing parameters of different initial phase, different motor speed, different installation position, etc., the vibration coupling process of the dual-excitation fatigue loading vibration system of wind turbine blade was simulated and the vibration coupling properties were obtained and analyzed.At last, a set of dual-excitation fatigue loading test system of wind turbine blade was built and a small blade was used as experimental project. Through the on-site test, it was found that the test results were consistent with the numerical simulation results, which verified the accuracy of the simulation model and electromechanical coupling mathematical model of dual-excitation fatigue loading vibration system of wind turbine blade. The electromechanical coupling mathematical model built in this paper could not only express the coupling nature between vibrating mechanical systems and exciting motor system but also express the coupling nature between the two fatigue loading systems based on flexible connection of blade.