Aeroelastic Analysis Of Horizontal Axis Wind Turbine Based On The Multibody Model

The aeroelastic coupling and stability analysis are always important research subjects and hot topics in the basic research field of wind turbine. With wind turbine becoming larger and more flexible, the feedback effect of aerodynamic load made by flexible deformation of component and the effects on the wind turbine performance made by the coupling between the flexible deformation and aerodynamic load cause domestic and foreign researchers’attention. In this study, the nolinear elastic deformation of flexible component was described with fewer degrees of freedom. The dynamic model of wind turbine was established and the dynamic characteristics was analyzed and the aeroelsatic coupling of flexible blade was realized based on the modern computational dynamics of multibody system combining with aerodynamic load model and efficient numerical method. The research contents and results have important significance in theory and practical application.The U.S. National Renewable Energy Laboratory(NREL)5MW horizontal axis wind turbine system was divided into two subsystems:flexible body subsystem, including flexible blade, tower and low speed shaft, and rigid body subsystem, including nacelle and hub. Superelement which can describe elastic deformation was used to scatter the flexible component into a series of rigid body connected by springs and dampers, and these spring stiff coefficients were calculated according to the bending and torsion theory of elastic beam.The wind turbine dynamic equations were obtained by the modeling method for hybrid multibody system based on the theory of computational dynamics of multibody system. The analysis of dynamic characteristics of the system were realized by effective numerical integration and Fourier spectrum analysis method. The aeroelastic coupling simulation of blade was realized by combining the dynamic model with aerodynamic model.A general simulation program which can automatically establish and solve the dynamic equations was designed based on MATLAB. The natural frequencies of blade, tower and wind turbine were analyzed by the program and ADAMS/Vibration respectively. The effectiveness of the program and the correctness of the modeling method were verified by comparing the results with those of NREL.The effect of blade rotation on the structure characteristics, especially on the dynamic characteristics, a so-called dynamic stiffening effect, was also studied in this dissertation. The aeroelastic response of blade under rated rotating speed and wind speed was calculated.The results show that superelement modeling method can accurately describe the coupling among the elastic deformation of flexible body and dynamic loads and its displacement well. The modeling approach of hybrid multi-body system is suitable to build the dynamic model of wind turbine system and the program is a feasible analysis platform for the aeroelastic coupling and stability analysis and the design of the control system of wind turbine.