Unlike fixed-base offshore wind turbine, the soft floating platform introduces 6 more degrees of freedom of motions to the floating offshore wind turbine. This may cause much more complex inflow environment to the wind turbine rotors compared with fixed-base wind turbine. The wind seen locally on the blade changes due to the motions of the floating wind turbine platform which has a direct impact on the aerodynamic condition on the blade such as the angle of attack and the inflow velocity. Such unsteady aerodynamic effects may lead to high fluctuation of the loads and power output. The present work aims to study the high unsteady aerodynamic performance of the floating wind turbine under platform surge motion. The unsteady aerodynamic loads are predicted with a lifting surface method with a free wake model. A preview predict control algorithm is used as the pitch control strategy. A full scale U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) 5 MW floating wind turbine is chosen as the subject of the present study. The unsteady aerodynamic performance and instabilities have been discussed in detail under prescribed platform surge motions with different control targets. Both minimizing the power output and rotor thrust fluctuation are set as the control objectives respectively. The theory analysis and the simulation results indicate that the blade pitch control can effectively alleviate the variation of the rotor thrust under platform surge motions. Larger amplitude of the variation of blade pitch is needed to alleviate the variation of the wind turbine power and this leads to high rotor thrust fluctuation. It is also shown that negative damping can be achieved during the blade pitch control process and may lead the floating platform wind turbine system into unstable condition.

与固定基座海上风机不同，软浮动平台为海上浮动风机引入了6个以上的运动自由度。与固定基座风力涡轮机相比，这可能导致风力涡轮机转子的流入环境复杂得多。在叶片上局部观察到的风由于浮动风力涡轮机平台的运动而改变，这直接影响叶片上的空气动力学状况，例如迎角和流入速度。这种不稳定的空气动力效应可能导致负载和功率输出的高波动。本工作旨在研究在平台喘振下浮动风力涡轮机的高非定常空气动力学性能。不稳定的空气动力学载荷可以通过带有自由尾流模型的升力面法进行预测。预览预测控制算法用作俯仰控制策略。本研究的主题是美国能源部的国家可再生能源实验室（NREL）5兆瓦浮式风力发电机。在具有不同控制目标的规定平台喘振运动下，已经详细讨论了不稳定的空气动力学性能和不稳定性。分别将功率输出和转子推力波动最小化两者作为控制目标。理论分析和仿真结果表明，叶片俯仰角控制可以有效地减轻平台喘振运动下转子推力的变化。需要叶片桨距变化的较大幅度以减轻风力涡轮机功率的变化，并且这导致较大的转子推力波动。