Tower of a floating wind turbine is a high-rise and slender flexible structure excited by wind,wave,turbine rotation and other complex excitation sources.A rapid evaluation of the natural frequency and mode of the tower is the key to the design of floating wind turbine system.In view of the current situation that the modal analysis of floating wind turbine tower is mostly based on the assumption of fixed tower bottom and does not consider the influence of floating foundation and operation of the wind turbine,an accurate and efficient evaluation method of natural frequency of large floating wind turbine towers is proposed.The variation characteristics and rules of natural frequency of floating wind turbine towers are studied.The results indicate that when the wind turbine is parked,there is a deviation of about 10%in the natural frequency of the tower obtained from the simplified model of the fixed bottom.The influence of floating foundation should be considered in the evaluation of the natural frequency of the tower.The natural frequency of tower slightly decreases when considering the effect of the upper rotor aerodynamic added mass when the wind turbine is in operation.The results can provide a reference for the design of floating wind turbine towers and control strategy.
floating wind turbinetowernatural frequencyfrequency-domain analysis methodaerodynamic added mass
NETL
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