Vibration Suppression of Offshore Wind Turbine Under Multi-Hazards by Active Tuned Mass Damper

Abstract Offshore wind turbines (OWTs) are subjected to multi-hazards of wind, wave, and seismic loads, and excessive vibrations may occur in the support structure. To effectively alleviate these vibrations, an active tuned mass damper (TMD) is considered to be installed in the nacelle in this study. Based on Euler–Lagrange's equations, the OWT with an active TMD is modeled by a multi-modal model incorporating the structural dynamics, seismic, hydrodynamic, and aerodynamic loads as well as the active control system. The active TMD is regulated using the linear quadratic regulator controller. In this study, the dynamic responses of the uncontrolled monopile OWT are initially examined, followed by a comparison of the dynamic responses of the controlled monopile OWT. Moreover, the performance of the active structural control strategy is evaluated as the weighting matrices and optimal TMD parameters are varied. According to the results of the study, it indicates that seismic load significantly excites the fundamental vibration modes of the support structure, resulting in a notable increase in the nacelle's fore-aft displacements. Both the designed passive and active TMDs effectively reduce these vibrations, with the active TMD providing superior vibration control performance. The vibration suppression performance of the passive TMD is severely reduced when the stiffness parameter deviates significantly from the optimal value, whereas the active TMD can effectively compensate for this drawback.