Cable connected active tuned mass dampers for control of in-plane vibrations of wind turbine blades B. Fitzgerald, B. Basu n Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Ireland article info Article history: Received 28 April 2013 Received in revised form 17 January 2014 Accepted 16 May 2014 Handling Editor: D.J. Wagg Available online 29 July 2014 abstract In-plane vibrations of wind turbine blades are of concern in modern multi-megawatt wind turbines. Today's turbines with capacities of up to 7.5 MW have very large, flexible blades. As blades have grown longer the increasing flexibility has led to vibration problems. Vibration of blades can reduce the power produced by the turbine and decrease the fatigue life of the turbine. In this paper a new active control strategy is designed and implemented to control the in-plane vibration of large wind turbine blades which in general is not aerodynamically damped. A cable connected active tuned mass damper (CCATMD) system is proposed for the mitigation of in-plane blade vibration. An Euler– Lagrangian wind turbine model based on energy formulation has been developed for this purpose which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations and also the interaction between the blades and the tower including the CCATMDs. The CCATMDs are located inside the blades and are controlled by an LQR controller. The turbine is subject to turbulent aerodynamic loading simulated using a modification to the classic Blade Element Momentum (BEM) theory with turbulence generated from rotationally sampled spectra. The turbine is also subject to gravity loading. The effect of centrifugal stiffening of the rotating blades has also been considered. Results show that the use of the proposed new active control scheme significantly reduces the in-plane vibration of large, flexible wind turbine blades. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction The reduction of vibrations in wind turbine blades is of topical interest. Wind turbine blade lengths have increased exponentially in the past two decades in order to maximize power output under specified atmospheric conditions. Several researchers have attempted to mitigate blade vibrations [1,2]. Uncontrolled vibrations can lead to structural damage which could reduce the life of the blades and increase maintenance costs. Ahlstrøm [3] has also shown that large blade vibrations have a major influence on power production. Therefore the reduction of the vibration of wind turbine blades has become an increasingly important area of research in the wind turbine industry. The main modes of vibration for wind turbine blades are flapwise and edgewise. In this paper, the control of in-plane blade vibrations (which are predominantly edgewise with some flapwise contribution) is considered, i.e. reducing blade vibrations which occur in the blade rotation plane. It is well known that in the in-plane direction the modal damping is low Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jsvi Journal of Sound and Vibration http://dx.doi.org/10.1016/j.jsv.2014.05.031 0022-460X/& 2014 Elsevier Ltd. All rights reserved. n Principal corresponding author. E-mail addresses: fitzgebr@tcd.ie (B. Fitzgerald), basub@tcd.ie (B. Basu). Journal of Sound and Vibration 333 (2014) 5980–6004