| The dynamic of a modern wind turbine is governed by the complex interaction of its subsystem and its design requires the skills of a multidisciplinary knowledge with expertise in diverse area: atmospheric wind flow, rotor aerodynamics, control, mechanical systems, electrical systems and civil engineering. The design problem is particularly complicated since wind turbines have little respect for engineering conventions: first, the wind turbine is required to operate in stall; second, it is subject to highly irregular inputs and finally it is required to work over 20 years with unattended operation. Based on the listed wind turbine's unique natural, the followed areas are put special interest:(1) The dynamical behavior of blade. The mathematical modeling of the wind turbine's blade is established based on the theory of thin-wall beam and finite element theory, and it is applied to investigate the natural frequencies and corresponding mode shape, analyze the stress distribution on the skin of the blade and rudimentarily research the dynamical response under condition of gust. This modeling not only inherits the simplicity of the beam element, but provides rich information on the displacement and stress as well.(2) The dynamic of drivetrain of wind turbine. Firstly, the kinematic of an object with arbitrary spatial movement is defined based on theory of multibody, and then the constraints are exerted on condition of characters of each component movement within the drivetrain and thus formed the system's governing equation. Finally the natural frequencies and mode shape are described; the influence of bearing stiffness on the natural frequency are shown; the floating of planet and sun are pictured and the dynamical transmission error varying with the frequencies are given.(3) The dynamic of the wind turbine. Through coupling the mathematical modeling of rotor, drivetrain as well as generator, the modeling of wind turbine is obtained. Applying this modeling, we investigated the mode shape of the rotor, simulated the start process of the wind turbine, research the floating of planet and sun under the condition of constant wind speed and finally analyzed the dynamical contact force between planet and sun and planet and ring respectively.(4) The deformation and stress distribution of flexible component at wind turbine. As the most flexible components at the wind turbine, tower and blade play a critical role in the dynamical behavior of wind turbine. Due to the fact that both of them are thin-walled structures, the kinetic energy and potential energy of tower, blade and nacelle are obtained by defining the consistence deformation expressions for them. The system governing equation is gained by applying Lagrange function. Using them as foundation to analyze the natural frequency and mode shape of tower and blade, calculate the distribution of the displacement and deformation of tower and blade and compare the influence of various tower stiffnesses on the blade's tip dynamical response.(5) The coupling of bearings and gear chain at drivetrain of wind turbine. At many previous research works, the stiffness of the bearing was simplified as linear infinite spring, and obviously the structure characters of bearing make this simplification have limitation. In this paper the bearing's nonlinear relationship between force and deformation is established according the bearing's geometry and Hertz contact theory, then the system equation is induced which govern the coupling behavior of bearing and gear chain.This thesis is focus on the mechanical dynamic behavior of wind turbine, the establishment of the component's mathematical modeling, simulation of the wind turbine's operation and the analysis of the mechanical characters of wind turbine... |
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