عنوان مقاله [English]
The aerodynamic performance of an offshore floating wind turbine is more complicated than onshore wind turbines because of the motions of the floating platform. In this paper, the effects of a floating platform rotational motion on the performance of an offshore wind turbine are investigated. For this sake, the unsteady blade element momentum method is used as the aerodynamic modeling tool. The proposed model has been validated based on data available for the reference turbine in the ground or fixed platform. To estimate the pitch angle as the control parameter in the power adjusting system, the proportional integral controller has been utilized. This control system is utilized to maintain the rated power of the wind turbine and also to approach a closer model of the wind turbine. The rotation of floating platform including three main angular motion as pitch, roll, and yaw have been studied which are approximated by a sinusoidal function. Results showed that among rotational motions, the effect of pitch motion is more considerable than roll and yaw motions. In the case of pitching motion input, reduction of mean power coefficient for tip speed ratios less than 7 is expected. For high tip speed ratios more than a critical ratio, the trend is reversed with respect to the fixed-platform case. The magnitude of change in the power coefficient, however, depends on several parameters which are explained more in the paper. The same but degraded trend also occurs in the case of roll and yaw disturbances. Moreover, the mean value of blade pitch angle which is an index of control effort is being increased.