Research On Transmission Characteristics Of Nacelle Wind Speed Of Wind Turbine

Wind energy is currently one of the most widely developed and utilized renewable energy sources.In order to implement the goals and tasks of "carbon peaking" and "carbon neutrality",China will vigorously promote the development of wind power industry.The upwind horizontal axis wind turbine is currently the most widely used wind turbine,typically using a nacelle anemometer for real-time measurement of wind speed.For mainstream wind turbines,the nacelle anemometer is usually located at the top of the nacelle and downstream of the blades.Therefore,the measured wind speed is influenced by blade rotation,separation flow,nacelle flow,and unit control laws,and there is a significant difference in wind speed from the incoming flow far ahead of the unit.In order to improve the accuracy of wind measurement,it is necessary to analyze the structure of the near wake near the nacelle to understand the transitive relation between the incoming wind speed and the nacelle wind speed.The pitch control and speed control of wind turbines can change the relative position and speed of the blades,significantly changing the flow around the blades,and thus affecting the near wake flow.In this paper,CFD simulation was used to study the wind speed characteristics of a 2-megawatt wind turbine under different pitch,variable speed,and yaw conditions,and the flow structure above the nacelle was analyzed.Research has found that an increase in the speed of the wind turbine will increase the fluctuation of the nacelle wind speed.The deviation of pitch angle from the design value will increase the fluctuation of nacelle wind speed,and at the same flow speed,an increase in pitch angle will increase the intensity of blade flow separation,resulting in a lower measured nacelle wind speed.Yaw control can weaken the impact of rotor rotation on nacelle wind speed fluctuations.Based on the calculation results,a nacelle transfer function was established between the incoming wind speed and the nacelle wind speed,which to some extent corrected the nacelle wind speed.The corrected nacelle wind speed can effectively replace the incoming wind speed of the wind turbine rotor,and provide certain theoretical support for advanced control and power prediction of the unit.Under the interference of upstream wind turbine wake,there is a significant change in the inflow characteristics of downstream wind turbines.The high-frequency fluctuations in wind speed and direction may have a significant impact on the nacelle wind speed.This article studies the wind speed characteristics of the nacelle of two tandem units.The nacelle wind speed and wake characteristics were analyzed under multiple stable and time-varying inflow conditions.Research has found that the wind speed fluctuations in the nacelle of both units are mainly affected by the fluctuation of incoming wind,and the fluctuation frequency is consistent with that of incoming wind.The incoming wind speed of downstream units is weakened,and the fluctuation of nacelle wind speed is smaller than that of upstream units.The fluctuation periods of the two units are consistent,and there is no difference in phase.The research in this paper provides a new approach for virtual wind measurement of wind turbines.The feedforward control of wind turbines requires wind speed prediction as a feedforward signal,and the nacelle anemometer provides a low-cost option for wind speed prediction.To achieve wind speed prediction,it is necessary to study the transmission characteristics of the nacelle wind speed of the unit and establish the connection between nacelle wind speeds.