Abstract Summary
Wind Turbines (WT) are rapidly becoming a significant contributor of the total energy produc-tion grid. Nowadays, a typical WT has the capability of 15MW power generation with larger rotors and towers with the average tower height being 120m. These slender and flexible struc-tures are vulnerable to external vibration sources such as wind gusts and earthquake excita-tions. To ensure safety and sustainability, it is necessary to mitigate the dynamic responses of the WT. The integration of dynamic vibration absorbers (DVA) to WT towers has the potential to significantly improve the damping of the tower and the nacelle dynamic responses, increas-ing thus the reliability of WTs. Current research is focused in studying the dynamic response of WT with DVA being installed at the top of the tower. In that case, DVA is indeed effective in suppressing the fundamental vibration mode of the tower, in which the maximum displacement occurs at the nacelle. However, when the WT is subjected to earthquake excitation, higher vi-bration modes are also excited. These modes may further contribute or even dominate the dy-namics of the tower. In this study, the structural response of WT with DVA installed at various positions along the tower height, is presented. Results indicate that in order to effectively con-trol the tower vibrations, two DVA need to be installed, one below the nacelle and one at the base of the tower. Further investigation is being performed to identify the optimum location and design of these DVAs. Finally, it is shown that vibration control can extend the lifetime of the structure increasing the WTs reliability.
