Applying multiple tuned mass dampers to control structural loads of bottom-fixed offshore wind turbines with inclusion of soil-structure interaction

Abstract

Using structural control methods to suppress structural loads of offshore wind turbines is an economical and feasible solution. Note that the dynamic responses of offshore wind turbines are generally analyzed under the parked condition, and the blades are usually modeled with a lumped mass. Actually, the geometrical properties and rotational speed of blades can significantly affect the wind turbine performances. Therefore, these simplifications may result in inaccurate evaluation for the wind turbine dynamic responses, and then further influence the evaluation of the load mitigation effect of a control system. Moreover, the vibration behaviors and structural responses of the wind turbine can be influenced by soil-structure interaction. In this work, the structural responses of a bottom-fixed offshore wind turbine that suffers combined wind and wave excitations are explored. The blade model is explicitly established and soil-structure interaction is also taken into account. The dynamic responses of the wind turbine as well as the vibration mitigation effects of a single tuned mass damper (STMD) and a multiple TMDs (MTMD) system are examined. Furthermore, the sensitivity analysis for the TMD tuning frequency and the robustness of the MTMD system are investigated under the assumption that some TMDs in MTMD do not work properly.