Experimental Study on Dynamic Characteristics and Vibration Mitigation Strategy of Jacket Offshore Wind Turbines Under Typical Normal Operating and Mechanical Fault Conditions

Based on a 1/75 jacket offshore wind turbine (OWT) fully coupled test model, fault and vibration-reduction dynamic model tests of a jacket OWT were conducted under typical wind and waves. The structural responses under grid loss and blade pitch faults were compared with those under normal operating conditions, and the coupled dynamic characteristics of jacket OWTs were analyzed under normal operating and mechanical fault conditions. Subsequently, a tuned-mass damper (TMD) model was designed and manufactured to evaluate the vibration-reduction effect of the TMD on the structural response of a jacket OWT under fault conditions. The results showed that the proposed fully coupled test design method for OWTs based on aerodynamic performance and hydrostructural elastic similarities can accurately simulate the normal operating and fault conditions of OWTs. Under fault conditions, a blade pitch-to-feather control strategy significantly reduces the structural response of an OWT; however, the load on the OWT requires further attention under blade pitch faults. Moreover, when the wind speed is not lower than the rated wind speed, the TMD exhibits a good vibration-reduction effect on the structural response of the jacket OWT under normal operating and fault conditions. Meanwhile, attention should be paid to the limitation of TMD frequency detuning when the wind speed is lower than the rated wind speed.