Dynamic Analysis Of Rigid-Flexible Coupling Structure For Large Horizontal Axis Wind Turbines

Since the 21 st century,the rapid consumption of fossil energy has intensified the pollution of the earth’s environment,and clean and pollution-free renewable energy has been paid attention to.In renewable energy,wind energy,which has great development advantages and utilization value,has become a hot target pursued by all countries.In order to improve the power generation capacity and efficiency,horizontal axis wind turbines begin to develop towards large scale and lightweight.Under the action of unsteady aerodynamic load,speed control and power control,the influence of blade flexibility on structural dynamics is becoming more and more significant.It is very important to accurately analyze the stress,strain and deformation of wind turbines.Therefore,in this paper,unsteady leaf element momentum method,multi-body dynamics method and PID control method are combined to analyze the structural dynamics characteristics of rigid-flexible coupling system of LEA-15 MW large-scale horizontal axis wind turbine.The operating principle,structure composition and load characteristics of horizontal axis wind turbine are given.Based on the blade element momentum theory,the unsteady aerodynamic load calculation model of large horizontal axis wind turbine is established by combining the dynamic wake model and dynamic stall model.According to the slender structure characteristics of blades and towers,the rigid-flexible coupling model of large scale wind turbine system is simplified,and the structural dynamics calculation model of the rigidflexible coupling system of large scale horizontal axis wind turbine is established based on the multi-body dynamics theory.The geometric model of LEA-15 MW large-scale horizontal axis wind turbine system was established by using Solid Works software.Based on the dynamic model of unsteady aerodynamic loads,a numerical simulation model of unsteady aerodynamic loads for large horizontal axis wind turbines is developed by autonomous programming algorithm,and its effectiveness is verified by comparison.Based on the finite element modal analysis method,the modal characteristics of wind turbine blade and tower are analyzed.Combined with virtual simulation technology,a numerical calculation model of rigid-flexible coupling system of largescale horizontal axis wind turbine is established.Combined with the aerodynamic simulation method and the structural dynamic simulation method,the fluid structure coupling dynamic simulation model of large-scale horizontal axis wind turbine was established on the visualization platform.The rigid-flexible coupling model was co-simulated,the dynamic parameters of the flexible blade and the rigid blade were calculated,the torque,binding force,centroid velocity and acceleration amplitude of the flexible blade and the rigid blade in the X,Y and Z directions were selected,and the time history curves of the blade deformation,stress and strain in the rigid-flexible coupling model were analyzed and summarized.The damping characteristics of rigid and flexible coupling joints are studied.Four sets of different damping parameters are set to analyze the time history curve of blade deformation,centroid velocity and acceleration,tower top displacement and tower top and tower bottom binding force change with damping.It is found that damping can reduce blade deformation,centroid velocity,acceleration,tower top displacement and tower bottom binding force amplitude.Through rigid-flexible coupling model and digital simulation,the effects of changes in wind speed,speed and blade pitch Angle on the system dynamics were investigated,and the effects of changes in blade binding force,blade deformation,torque,centroid velocity and acceleration over time were analyzed.It is found that the variable speed control has obvious optimization effect on the size and period of the centroid velocity and centroid displacement of the flexible blade,and can reduce the amplitude of fixed binding force and the size and period of the deformation between tip blades,and improve the dynamic response time of the flexible blade.