Dynamic Response Analysis and Vibration Control for A Fixed-Bottom Offshore Wind Turbine Subjected to Multiple External Excitations

For the offshore wind turbines installed in earthquake areas, their operation is affected by seismic loads in addition to wind and wave loads. Therefore, it is necessary to study the dynamic responses and vibration control of the wind turbines. In previous studies, the structural responses of offshore wind turbines are usually investigated in the parked case, while the blade rotation effect is usually not considered. The evaluation on the structural responses may be inaccurate under this condition, further affecting the evaluation on the vibration control performance of a control system. In view of it, this paper established a complete multi-body model of a fixed-bottom offshore wind turbine considering pile-soil interaction, and then performed simulations when the wind turbine was subjected to multiple external excitations. Continued, a single tuned mass damper(STMD) system and a multiple tuned mass dampers(MTMDs) system were applied to control structural vibrations of the wind turbine. Then, based on the construction of a simplified main structure-TMD system, TMD parameters were optimized. Finally, twelve load cases including operating and parked conditions were selected to perform simulations. Results show that the influence of the seismic excitation on blade responses is greater under the parked condition than that under the operating condition.Moreover, STMD/MTMDS exhibit better performance under the parked condition than that under the operating condition. Compared with STMD, MTMDS can better suppress the vibrations at both the fundamental and highorder modes, and exhibits significant robustness under the condition of changing soil parameters.