Passive control of wind turbine tower using nonlinear magnetic vibration absorber and eddy current damping

Horizontal axis wind turbines (HAWTs) are the most widely used means of producing clean wind energy. Giant wind turbines with high production capacities are prone to degradation through environmental loads like wind and earthquake which might result in shorter machine life time or higher maintenance costs and consequently increased energy price. Vibration control methods have proven to be effective in ensuring structural integrity and general safety of wind turbine towers (WTTs) as well as the blades. There are challenges associated with employing typical linear dampers that need to be addressed such as limited available space in the nacelle, practical feasibility issues, and narrow effective frequency bandwidth of linear dampers. In this paper a new method for passive vibration control of wind turbines is proposed and a novel bi-directional design of the damping device is presented which is based on magnetic forces and eddy current damping. The proposed device is described in details and its parameters are analytically evaluated. The effect of the damper on nacelle displacement due to wind load is examined numerically and the results are compared to a typical tuned mass damper in terms of effectiveness and required space inside the nacelle. The study reveals that the magnetic damper is a competitive device for vibration control that could be as effective as a TMD with less required space.