Analysis On Vibration Characteristics Of The Megawatt Class Wind Turbines

In recent years, with the continued growth demand for energy around the worldand the increasingly stringent environmental regulations, the wind power has beendeveloping rapidly in the energy industry, However, in the process of starting andbraking of the yaw system, the vibration of the yaw system will make serious impacton vibration noise, fasteners, the fatigue life of the wind turbine, and so on.vibration relates to the safe operation of the megawatt wind turbine, it willeventually lead to the short of life of the wind turbine. It is necessary to study thereason of vibration and vibration characteristics for megawatt wind turbine yawsystem, and There is a need to put forward scientific ways to solve this seriousproblem.Therefore, supported by the renewable power technology key laboratory openfund project of hunan province [2011KFJJ001] and university-enterprise cooperationproject“The reliability research of high strength bolt of megawatt wind turbine”.The vibration of the yaw system was studied from the dynamics, the virtualprototype dynamics model of the megawatt wind turbine was built, To reduce thevibration and improve its dynamics performance was taken as the starting point.Focus on the influence of the flexible tower for active yaw. The primary works andinnovation of this thesis are as follow:(1) The static analysis of flexible tower was carried. The distribution laws ofstress and displacement of the tower under different conditions was obtained. Theresults validated that static strength of the tower and displacement of top tower wasin the engineering permissible range, which laid a foundation for the followingsystem dynamic analysis.(2) The modal analysis of the rigid-flexible coupling model was processed, themodal shapes and corresponding natural frequency were obtained. The results showthat the natural frequency of the tower was outside±10％of the rotationfrequency of the wind wheel and the blade passage frequency, the resonance thatcould have been avoided.(3) The step function was used to simulate the process of starting and brakingof the Megawatt-class Wind Turbine. The dynamic analysis had investigated the influences of the stiffness of the tower, the preload of the spring, yaw drive torqueon the vibration of yaw system when wind turbine startup and braking.