Hybrid vibration control of offshore wind turbines under multiple external excitations

Abstract

Structural control methods are a promising way to improve the dynamic response of offshore wind turbines. In this study, the effectiveness of passive tuned mass damper (TMD) and hybrid mass damper (HMD) control is examined for suppressing the vibration in a monopile offshore wind turbine subjected to a combination of wind, wave, and seismic loads. A high-fidelity wind turbine model is established based on the multi-body dynamics simulation code SIMPACK. A reduced-order model of the wind turbine is, then, extracted from input-output time-domain response data, which is used to design an HMD controller using the H∞ loop shaping approach. The controller is, then, applied in the high-fidelity multi-body model of the wind turbine, and an additional control force is applied using feedback from the displacement acceleration at the tower top. The performance of the passive TMD and HMD control systems is examined and compared in terms of the suppression of tower-top displacements under normal operating and parked conditions. The results revealed that the HMD control system can better reduce the tower-top displacement as compared to the passive TMD system before and during earthquakes, albeit at the expense of high input control power and large TMD displacements. However, the two control systems have a negative impact on the dynamic response of tower after the earthquake. Moreover, the investigation of controller gains indicated that the vibration suppression effect of HMD improves with the increase in control power, leading to larger TMD strokes.