SEISMIC VIBRATION CONTROL SYSTEMS FOR WIND TURBINES

Abstract eng:
During the last decades the wind energy production rate has reached remarkable results also in seismic prone regions. Because of the minor damping capacity and the slender structure, earthquakes cause a further challenge for the design and analysis of the wind turbines (WT). Depending on the dynamic characteristics of the earthquakes, the tower vibrations of the WT can impair the fatigue life or the structural stability and can even cause a total collapse of the structure. In order to protect the WT, structural methods are conventionally being used, which primarily include the adaptation of the tower stiffness according to the properties and dynamic excitation of the structure. Because of the current economic challenges, these methods are not sufficient, thus limiting the realization of higher turbines, which could use the wind potential more efficiently. Therefore, several research groups and WT manufactures are working on the development of innovational solutions to mitigate wind, wave and earthquake induced tower vibrations. Hereby the use of sophisticated computational methods plays a major part for the prognosis of realistic results. Several passive, active, hybrid and semi-active tuned mass dampers and other energy dissipation systems, such as elastic or viscoelastic dampers and hydraulic dampers, are convenient for the seismic vibration control of the WT. Hereby the research concentrates especially on the development of the active and semiactive vibration mitigation methods. In particular, a semi-active version of the tuned liquid column damper, which can adapt its frequency and damping behavior depending on the structures current state and loading situation, has recently been proposed. This research work summarizes the recent developments regarding the mitigation of seismic loading of the WT and present numerical calculation methods, which can simulate aeroelastic interaction of rotor blades using blade element theory. The results of the parametric investigations of simultaneous wind, wave and earthquake loading for the WT, considering soil-structure interaction effects, will be presented.

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