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Significant structural responses pose potential hazards to the safe operation of floating offshore wind turbines (FOWTs). To effectively mitigate the motion of FOWTs using conventional passive vibration control methods such as tuned mass damper (TMD) and multiple tuned mass damper (MTMD), an optimization method for TMD and MTMD in a barge-type FOWT is proposed in this study. A simplified dynamic model of a barge FOWT with MTMD, which includes the tower first bending and floating platform degrees of freedom (DOFs), in addition to the simplified DOF of the MTMD, is derived. The corresponding fully coupled numerical model is established using the updated simulation tool FAST-SC. Subsequently, the unknown parameters and accuracy of the simplified dynamic model are validated via comparison with the results of the coupled numerical model. Moreover, an optimization method is proposed based on the simplified dynamic model considering the prominent coupling effects of FOWT and computational expense, and the GA algorithm is used for TMD and MTMD optimization. Furthermore, the effectiveness of the optimized TMDs and MTMD is evaluated based on the reduction in the coupled responses of the barge FOWT under the selected environmental conditions. Compared with the optimized TMD in the nacelle, the optimized TMD in the platform and MTMD are proven to be more feasible for vibration mitigation under complex environmental loads. Moreover, an improved steady output is obtained using the optimized vibration control methods, in addition to the excellent mitigation effects on structural responses.

As a complex multi degree of freedom coupling system, floating offshore wind turbine usually works in complex and changeable marine environment. The research of floating offshore wind turbine often needs to consider the coupling effect of wind, wave and current at the same time. Under the action of wind and wave load, floating offshore wind turbine will produce a large motion response. Generally, the surge motion and pitch motion are the most obvious aspects, and their motion amplitude is also the largest, and large-scale motion of the floating platform will directly affect the relative velocity of the wind loaded flow. Therefore, the surge motion and pitch motion usually have the most obvious impact on the aerodynamic load of wind turbine. In this paper, the motion characteristics and aeroelastic responses of the DTU-10MW semi-floating offshore wind turbine under coupling action of wind and wave are simulated. The motion characteristics and aeroelastic responses of floating offshore wind turbine are calculated under different wind and wave combination conditions, and the influence law of wind and wave action are summarized. The results show that wind load affects the mean value of motion of the floating offshore wind turbine, and wave load affects the amplitude of motion; Finally, the dynamic response of the wind turbine with the included angle of the wind and wave load is discussed and analyzed, and the influence of the incident angle of the wind wave on the motion response of the floating offshore wind turbine is analyzed.