CONTROL OF SIDE-SIDE AND FORE-AFT VIBRATIONAL MOVEMENT OF A WIND TURBINE

Aspects of the present invention relate to controlling a wind turbine having a tower damping system (57, 55) actuable to control components of vibrational movement of the tower (12), a side-side component of a vibrational movement of the tower (12) in a horizontal plane; and a fore-aft component of the vibrational movement of the tower (12) in the horizontal plane are determined; and a control signal based on the side-side and fore-aft components is determined such that the tower damping system (57, 55) produces a force that increases or decreases the vibrational movement of the tower (12) such that the side-side and fore-aft components are substantially equal.