Semi-active vibration control of wind turbine blades using a time-frequency approach

Abstract

This thesis proposes the use of structural control devices to mitigate the response of wind turbines, particularly the blades. Theoretical and experimental investigations have been carried out to ascertain the effectiveness of passive and semi-active dampers in controlling the response of wind turbines. A structural dynamic model was formulated using Lagrange's Equations taking account of the coupling between the blades and tower, and the centrifugal stiffening which occurs due to blade rotation. A model for both flapwise and edgewise vibrations was developed. Dampers were added to the turbine model in the form of Tuned Mass Dampers (TMDs), or equivalent Tuned Liquid Dampers (TLDs), represented by mass-spring-dashpot systems. The effectiveness of these passive devices in controlling the dynamic response of the turbine was studied in detail.