25 th Iranian Conference on Electrical Engineering (ICEE20 17) The Effect of Turbulence and Wake on the Power Fluctuation in the Wind Farms M. Gholami Department of electrical engineering Amirkabir University of Technology Tehran, Iran s. H. Fathi, J. Milimonfared Department of electrical engineering Amirkabir University of Technology Tehran, Iran z. Chen, F. Deng Department of Energy Aalborg University Aalborg, Denmark, Email: zch@et.aau.dk. fde(Q)et.aau .dk Email: mehrdad.pr@gmail.com. Email: fathi@aut.ac.ir. monfared@aut.ac.ir Abstract-The intermittency in wind power can face electrical network with some challenges such as power quality, frequency deviation and reliability of the system. So estimated power fluctuation in wind farm has to be known in order to reach to the grid integration requirements. In this paper the wind farm power fluctuation is investigated by considering the three factors; wake effect, turbulence and spatial smoothing, simultaneously. The wake effect is investigated for the mean value and turbulence part of the wind speed separately because of different effects of the wake. The engineering models in fluid mechanics is used for analyzing the wake effect and spatial smoothing. The proposed approach is sued for a 160 MW wind farm as a case study. Keywords- wind speed; power intermittency; spatial smoothing; turbulence; wake effect; wind/arm. I. INTRODUCTION Among the renewable energies, the wind power is more interested. There are some countries in which the wind power constitutes up to 40 percent of the total energy. But the intermittency in wind power can face electrical network with some challenges such as power quality, frequency deviation and reliability of the system [I]. The power fluctuation of wind turbine is due to intermittency in wind speed profile. Temporal variations in wind speed may be in the range of year, seasonal, month, day or several hours, because of atmospheric variations such as differential heating of the earth's surface during the daily relation cycle. In addition, there is small time scale variations in wind because of boundary layer conditions that includes turbulence in wind [2]. On the other hand a wind farm includes several wind turbines, the output powers of which are gathered to form the total farm power. The wind speed profiles over the different locations are not same and the correlation factor is not unit, so consequently the power profiles for individuals wind turbine have not the same variations. Therefor the total power of wind fann, that is the summation of uncorrelated profiles, has less fluctuation compared to summation of correlated profiles. This phenomena is known as spatial smoothing i.e. the power smoothing because 978-1-5090-5963-8/17/$31.00 ©20 17 IEEE of space distribution of wind turbines over a farm [3, 4]. In addition to temporal variation and turbulence in wind speed, there is another factor that affects the wind speed profile over the wind fann. A wind turbine extracts energy from the wind and consequently slows down the wind field behind the turbine. Another turbine positioned in the wake of the first one will generate less energy for a given free stream wind speed [5]. The wake behavior is different for average wind speed and turbulence so that there is an increment in the turbulence level together whereas the mean wind speed is decreased in wake. Therefore, it leads to significantly larger turbulence intensities in comparison with free flow [6]. Therefore wake effect can effect power fluctuation in wind fann because of changing the turbulence level in different locations. There are a few papers that consider short time variations in the wind power, e.g. [7], which only analyzes the effect of turbulence on available power of a single wind turbine. In the present paper, not only the dynamic model of wind speed is used, but also the wake effect on mean wind speed and the turbulence part are analyzed and the effect of instantaneous wind profile on the wind farm power fluctuations is investigated simultaneously. In fact in this paper the effect of three factors; wind speed turbulence, wake effect and spatial smoothing, on the output power of a wind farm are investigated, simultaneously. In section II the principles of wind and wake effect are presented. Then in section III the wind farm power is analyzed. In section IV the results are shown and the average wind speed mode is compared with instantaneous mode. Finally in section V the conclusion is presented. II. WAKE EFFECT In this section, first the wind speed profile is surveyed and then the wake effect for mean and turbulence speed is analyzed according to the engineering model in fluid mechanics. 1148 Downloaded from https://iranpaper.ir https://www.tarjomano.com/order