The Coupling Dynamics Analysis Of Rotor And Tower Of Horizontal Axis Wind Turbine

Wind turbine is a dynamic system that bears complex random load. The problem about aeroelasticity is related to the interaction of stochastic dynamic aerodynamic and structure dynamic response. And it is a multidisciplinary issue about atmospheric boundary layer turbulent wind field, rotor dynamic aerodynamics and blade and unit structural dynamics. In this paper, aimed at the configuration, operation characteristic and international standard of the modern large scale horizontal axis wind turbine, using the method which combines modern modal analysis theory and finite element numerical analysis, targeting a 1.5MW horizontal axis wind turbine, the analysis method of the large scale wind turbine dynamic response caused by the aerodynamic load and mechanical load is investigated based on the NSFC project"Research on the aeroelasticity problem of wind turbine considering the flexible deformation of the blade".Using blade element momentum theory to calculate aerodynamic load and establishing the structural dynamics model, the structure dynamic response and aeroelasticity load under random aerodynamic load are analysed. At the same time, it should be considered that tower structure deformation has a dynamic feedback to the blade. With the modal synthesis method, the coupling of rotor and tower is achieved. Finally, the security fatigue life of wind turbine based on the Palmgren Miner linear fatigue damage accumulation rule is estimated.The main content of this paper includes the following respects:(1) The basic aerodynamic characteristics of the wind turbine are analysed. According to revised blade element momentum theory, the aerodynamics load on the blade is estimated.(2) The rotor and tower are considered as a cross-section cantilever and appied two-node beam element to the finite element modeling. Multi-DOF Lagrange equations based on the generalized coordinate system is used to build the motion equation. And the modal analysis is used to get natural frequencies and mode shapes. The frequency of the rotating rotor is given and the resonance should be avoided that is caused by the overlap in natural frequency and excited frequency.(3) Mode-superposition method and Newmark method are used to compute the motion equation and determine the dynamic response of the blade and tower under loads. In addition, the numerical programs are developed. (4) Considering that the tower deformation affects the dynamic aerodynamic characteristics of the rotor, the coupling method of the rotor and tower is studied. Low-level lead modes are calculated and the relation between the rotor and tower is established by modal synthesis method. Considering the impact of the aeroelasticity, overlying the timing changes and applying iterative algorithm the response results of lead modes are obtained.(5) The stochastic load spectrum is counted by the rain flow count method. And the fatigue life of the blade is estimated by the Palmgren Miner linear fatigue damage accumulation rule.