| When the atmospheric inflow blows through the wind turbine,it will produce wake effect.The wake effect will reduce the wind speed and increase the turbulence intensity,which makes the flow field inside the wind farm complex.At the same time,the wake effect will also increase the fatigue load of the unit,shorten the service life of the unit and reduce the output power of the wind turbine,thus affecting the internal output power of the whole wind farm.At the same time,in complex terrain,the atmospheric environment of wind field is more complex and changeable.The wake effect and complex terrain simultaneously make the flow field inside the wind farm in complex terrain more complex and changeable.Considering the joint action of the two,the following research is carried out in this paper:Firstly,on the basis of the traditional Jensen wake model,considering terrain effect and wind shear effect,and assuming that the wake profile is Gaussian rather than "top-hat" distribution,an improved three-dimensional Jensen-Gaussian wake model for wind turbines located at the top of a mountain in complex terrain is proposed.After that,the wake expansion coefficient k is modified,which is no longer an empirical constant,but is related to the turbulence inten sity of the incoming flow and the downstream distance of the wind turbine,that is,the wake radius expands nonlinearly.Secondly,in order to obtain the real three-dimensional wake distribution of wind farms with complex terrain,and provide the wind farm field data to verify the derived three-dimensional wake model,two LiDARs were used in a wind farm in Zhangbei County,Hebei Province.Firstly,the accuracy of wind speed and wind direction of two laser radars is verified to make sure that they have good measurement accuracy.Then,based on the historical wind speed and direction data of the wind tower of the wind farm in January and December,it is determined that the north wind and North northwest wind are the prevailing wind directions of the wind farm in the experimental month,so as to determine the layout and experimental scheme of the lidar and set the measurement mode of the LiDAR.Wind data measured by Wind Mast WP350 LiDAR is used to fit the incoming wind profile,and the wind shear coefficient is obtained.Using the data measured by Wind3 D 6000 LiDAR,the flow field of wind turbine tail is analyzed.Finally,the wake of wind turbine in complex terrain is analyzed by using the measured experimental data of wind farm.Using the data measured by PPI m ode and RHI mode,the horizontal cloud images of horizontal plane and vertical height plane are drawn.The wind turbine selected in the experiment has a complete and independent wake area under specific wind conditions,and the wake tends to change with the trend of terrain.Results show that the assumed sinking height of the wake center is more in line with the actual situation,but there is a slight deviation in the prediction of near wake area and far wake area.The wake sinking phenomenon is not obvious before about 3D position behind the wind turbine but is obvious after 3D position,and more after about 10 D position.In the terrain with larger slope,the wake sinking phenomenon is more obvious than that in the terrain with slower slope.The three-dimensional Jensen-Gaussian prediction of wake wind speed in horizontal plane and vertical height plane in complex terrain is compared with the field measured data.Results also show that the wake model can predict the wake of wind farm in complex terrain,especially the wake near the wake center.Finally,the error analysis of the prediction results of the wake model is carried out.The maximum errors of the horizontal and vertical altitude plane predictions are 13.1% and 11.2% respectively,and the data with the prediction results less than 10% account for 82% and 90%respectively.Moreover,the prediction results of the wind speed in the far wake area are better than those in the near wake area.In this paper,the wind farm measurement experiment is carried ou t by using LiDAR.The wake center of wind turbine in complex terrain is studied,and the deduced three-dimensional Jensen-Gaussian wake model in complex terrain is verified,which provides a reference for the layout optimization and collaborative control of wind farm in complex terrain. |
