Power Characteristics Analysis Of Wind Turbine Under Wake And Terrain Coupling Effect With Experimental Study

With the rapid development of wind power industry,there are more and more wind farms with complex terrains compared with flat terrains where wind farms are increasingly saturated.The distribution of wind speed in the internal flow field is mainly affected by multiple factors such as wake effect,topography effect and wind turbine operating state.Therefore,it is very important to study the wake characteristics of wind turbines under different terrain complexity conditions.Considering the two main factors of wake and terrain effect,this paper studies the wake and power characteristics of unit under the influence of complex terrain.The specific work includes three aspects:Firstly,aiming at the problem that most of the mainstream 3D wake models are single wind turbine wake models,the 3D Jensen-Gaussian(3DJG)model based on the velocity distribution characteristics of wake region arranged by multiple wind turbines and the modification of wake expansion coefficient,the 3D wake models of tandem multi-wind turbines and stagger dual-wind turbines were proposed.The expansion coefficient K in wake region is modified.At the same time,two Light Detection and Ranging(Li DAR)were used to measure the wind in a wind farm in Zhangjiakou,and the wake model of multiple wind turbines was verified according to the measured data.Results show that the proposed multi-wind turbine wake model is in good agreement with the measured data which can be used to predict the three-dimensional distribution characteristics of downstream wind turbine wake well.Secondly,in order to explore the interference degree of topographic conditions on wind turbine wake characteristics,two Li DARs were used to measure the wind turbine wake in three wind farm areas with different topographic complexities.Three wind farm areas of different terrain complexities in North China were selected and wake expansions were detected by three Li DARs over a six-month measurement period.Three wake interaction conditions of separate,full,and half wakes were discussed separately in the aforementioned three wind farm areas of different terrain complexities with a total of nine different cases.Results show that under the condition of single wake,the attenuation trend of wake velocity of wind turbine on flat terrain is gentle,and the decreasing rate of velocity attenuation curve in medium and complex areas is 0.1243 and 0.0082,respectively.The wake width becomes wider with the increase of terrain complexity,and the more complex the terrain is,the faster the wake width changes.In the single wake region,upstream of full wake and half wake,the wake widths of wind turbines in medium and complex regions show the same increasing trend,with an increase of 87.5%,twice of that in flat terrain.Finally,the power generation performance of wind turbines under different working conditions is compared and studied.Meanwhile,the feasibility of multi-wind turbine wake model in Chapter 2 and the comparative study of wind turbine wake characteristics under different terrain complexity in Chapter 3 are verified to further increase the persuasion.Results show that the utilization rate of upstream wind turbines is higher than that of downstream wind turbines under three wake conditions in different terrains.The errors between the power calculated by the multi-wind turbine wake model in Chapter 2 and the actual power are 11% and 9%,respectively.In addition,with the increase of terrain complexity,wake recovery is faster.Under the independent wake condition,the actual power and theoretical power ratio of wind turbines in region A,B and C are 0.59,0.6 and 0.74,respectively.It can be seen that with the increase of terrain complexity,the performance of wind turbine is more fully played,and the acceleration effect of complex terrain can increase wind speed and bring more power generation.Through theoretical research,experimental measurement and data analysis,this paper studies the influence of wake characteristics and topographic effect on power characteristics of wind turbines in wind farms.The research results of this paper provide a certain theoretical basis and preliminary exploration of engineering application for the safe,reliable and efficient operation of wind turbine in complex terrain wind farm.