The Research On Characteristics Of Atmospheric Boundary Layer And Its Influence On Power Of Large-Scale Horizontal Axis Wind Turbine In Qinghai-Tibet Plateau In Winter

With the scale application of large wind turbines in plateau areas,the special geographical location and climatic conditions make the wind turbines fa ce complex aerodynamic problems.Therefore,combining with the resource characteristics of China’s current wind power development and construction layout and the trend of large-scale development of horizontal axis wind turbines.In this study,we considers the many problems faced in wind turbine research,uses advanced wind measurement equipment,takes a 3.3 MW horizontal axis wind turbine with a rotor diameter of 146m and its surrounding atmospheric environmental conditions in a wind farm in the Qinghai-Tibet Plateau as the measurement and research object,and combined with the wind turbine SCADA data,and the characteristics of the atmospheric boundary layer in the Qinghai-Tibet Plateau in winter and its influence on the power of large horizontal axis wind turbine was investigated by using field experiment.The main research contents include:1.Investigate experimental equipment and develop experimental programmes;The applicability of the lidar Zephi R Dual Mode（ZDM）in the plateau area was verified from three aspects of horizontal wind direction,horizontal wind speed and wind shear exponent.As a result,the field experimental data obtained in winter based on ZDM is valid and reliable.2.Based on the inflow turbulence data（1.5D position in front of the wind turbine）and meteorological data（the top position of the nacelle）obtained by ZDM,the distribution feature of the characteristic parameters of the atmospheric boundary layer are studied.In the winter condition of the region:（1）The distribution of temperature,humidity,air pressure,and air density are concentrated between-5.5～-12.5℃,21～43%,69.4～70.3k Pa,and 0.9063～0.9338kg×m^-3.Compared with the standard value of sea level,the air pressure and air density have dropped by nearly 30%and 25%,respectively.（2）The wind direction is mainly WNW,followed by E and ENE.Shape factor and scale factor of wind speed are approximately 2.5 and 6.95,respectively.The turbulence intensity is mainly concentrated in 3～10%.Wind shear exponent is concentrated in 0～0.4.（3）In the two wind directions（65～75°and 285～295°）,the difference in wind shear is the largest and the difference in air density is the smallest.From the perspective of the change relationship between the two parameters of the characteristic parameters of the atmospheric boundary layer,in the density concentration area,under the same air density,the wind speed and wind shear in the east wind direction（<180°）are smaller than those in the west direction（>180°）.（4）The air pressure reaches the local maximum when the average daily temperature difference is 6.1℃,and the average daily temperature changes the fastest（rising or falling）.Conversely,the daily average air pressure is at its lowest when the temperature is at its respective extremes.The change trend of humidity and air density are basically the same,and opposite to the temperature change trend.Moreover,the mean values of turbulence intensity and wind shear exponent in the afternoon are8.1%and 0.066.3.Based on the data of two wind directions,the influence of the atmospheric boundary during the day and night layer on the output power of wind turbines was studied.（1）It is determined by indirect method that the atmospheric stability in the afternoon stage is dominated by convection.At night,the occurrence probabilities of strong stable,strong convection and near neutral states are basically the same.（2）The main parameters that affect the output power of a wind turbine are wind shear,air density,wind direction and turbulence intensity.In the west wind direction,the greater the air density,the greater the power,and while in the east wind direction,the greater the air density,the lower the power.（3）The spectral density function of wind turbine output power in the low-frequency region has the same dynamic characteristics as atmospheric turbulence.In the frequency range of the inertial subregion corresponding to the wind speed,there is a nonlinear relationship between power and inflow speed.In the high frequency region,the spectral density function changes significantly with the control strategy of the rotor speed.（4）From the perspective of spectral characteristics,the influence of the atmospheric boundary layer during the day and night on the turbulent inflow and output power of the wind turbine is greater than the influence of th e wake（wind direction）of the upstream turbines on the turbulent inflow and output power.（5）The output power of the wind turbine has a time lag relative to the incoming flow,and the lag time is approximately5 times the convection time.This research has an important impact on improving the power generation efficiency of wind turbines in high altitude areas and reducing fatigue load.At the same time,it also promotes the understanding of various physical processes in the atmosphere,which is of great significance to the site selection and planning of wind farms.It can provide a reference for revealing the change law of wind characteristics in the winter environment of the Qinghai-Tibet Plateau.