Active tuned mass dampers for control of in-plane vibrations of wind turbine blades B. Fitzgerald 1 , B. Basu 1, * ,† and S. R. K. Nielsen 2 1 Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Dublin, Ireland 2 Department of Civil Engineering, Aalborg University, Aalborg, Denmark ABSTRACT This paper investigates the use of active tuned mass dampers (ATMDs) for the mitigation of in-plane vibrations in rotating wind turbine blades. The rotating wind turbine blades with tower interaction represent time-varying dy- namical systems with periodically varying mass, stiffness, and damping matrices. The aim of this paper is to de- termine whether ATMDs could be used to reduce in-plane blade vibrations in wind turbines with better performance than compared with their passive counterparts. A Euler–Lagrangian wind turbine mathematical model based on energy formulation was developed for this purpose, which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations. Also, the interaction between the blades and the tower including the tuned mass dampers is considered. The wind turbine with tuned mass dampers was subjected to gravity, centrifugal, and turbulent aerodynamic loadings. Investigations show promising results for the use of ATMDs in the vibration control of wind turbine blades. Copyright © 2013 John Wiley & Sons, Ltd. Received 25 July 2012; Accepted 10 September 2012 KEY WORDS: active tuned mass dampers; wind turbines; active control; LQR; in-plane vibration; vibration control 1. INTRODUCTION The principal objective in the design of a wind turbine is to maximize the possible power output under specified atmospheric conditions. This has led to the development of larger wind turbines with increased rotor diameters of over 120 m. Although increased rotor diameters allow more of the available wind resource to be extracted for power generation, the increased blade lengths have also increased the flexibility of the blades, which has led to increased vibrations. The blades are now a limiting factor in the design of even larger turbines. With large blades, the general assumptions made by most design codes of small deflections and the application of loads on the undeformed blade do not hold true. It has also been shown that large blade vibrations have a major influence on power production [1]. As a result, the reduction of the vibration of wind turbine blades has become an increasingly important area of research in the wind turbine industry. In this paper, the control of in-plane blade vibrations (which are predominantly edgewise with some flapwise contribution) is considered, that is, reducing blade vibrations that occur in the blade rotation plane. In the in-plane direction, the modal damping is low due to low aerodynamic damping. Aeroelastic stability problems arising from edgewise vibrations were first noticed in the early 1990s [2]. Since then, problems caused by edgewise blade vibrations have been investigated by several researchers. Thomsen et al. investigated the problems caused by edgewise vibrations in stall-regulated wind *Correspondence to: B. Basu, Department of Civil, Structural & Environmental Engineering, Trinity College Dublin, Dublin, Ireland. † E-mail: basub@tcd.ie STRUCTURAL CONTROL AND HEALTH MONITORING Struct. Control Health Monit. 2013; 20:1377–1396 Published online 11 January 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/stc.1524 Copyright © 2013 John Wiley & Sons, Ltd.