Research On The Strategy Of Large-scale Wind Farm Participating In Power System Frequency Regulation

Due to the intermittent and fluctuation of wind energy,the power system needs to set enough frequency regulation Capacity in order to keep the frequency of system stable,which increases the operating cost.Moreover,with the integration of regional large-scale wind power,both inertial response and primary frequency regulation of the power system areweakened seriously.Therefore,how to flexibly control the active power output of large-scale wind power clusters within the forecast range of effective wind power output,so that it has effective inertial response and primary frequency regulation capability has become a key point of current research.Firstly,the mathematical models of ordinary asynchronous wind turbines and variable-speed wind turbines are established respectively.Based on this,the differences of the frequency response characteristics between the two models after connecting grid were analyzed.Ordinary asynchronous wind turbines have a strong relationship between the rotor speed and the system frequency.The coupling relationship appears to the system as "inertia".However,because of the existence of the machine-side converter,the variable-speed wind turbine shows "weak inertia" or "no inertia" when the system frequency fluctuates.For the wind farm composed of variable-speed wind turbine,the larger-scale of wind power connecting to grid,the worse of the frequency stability and recovery effects of the system after large disturbance.Secondly,based on the traditional zonal control principle of variable-speed wind turbines,the power output characteristics of variable-speed wind turbines were analyzed.By analyzing the working principle of several mature load shedding control modes,the frequency response characteristics and applicable conditions of each load shedding control mode are analyzed,compared and simulated.Finally,according to the characteristics of variable speed wind turbines and comparisons of advantages and disadvantages of each load reduction control mode,under the premise of considering as much as possible the economics of wind turbine load reduction operations,a frequency-variable load reduction strategy for variable speed wind turbines based on wind speed segmentation was proposed.In order to avoid frequent switching of load reduction modes due to noise caused by frequent changes in wind speed and wind speed measurement errors,a Pearson morphological index of unit operation wind speed clustering and clustering was introduced.The improved Eulerian moving average prediction model is applied to coordinate the frequency regulation output of the system in different time scales for the grouped units,so that the inertia and primary frequency regulation are combined to realize the optimal frequency adjustment of the system.The simulation results show that the multi time scale coordinated optimization strategy based on the improved Eulerian moving average prediction model can make the large-scale wind power cluster have controllable inertial response and fast and accurate primary frequency regulation ability.The large-scale wind power cluster meets the requirements of providing continuous and effective primary frequency regulation service for the system through the coordinated output of internal units,and effectively solves the problems of insufficient equivalent rotational inertia of the system after large-scale wind power is connected to the grid and secondary frequency drop of the system caused by the variable-speed wind power unit participating in frequency regulation only by using analog inertia control.Among them,according to the wind speed segmented variable speed wind turbines frequency regulation and load reduction strategy,the complementary advantages of traditional load reduction and frequency modulation methods of variable speed wind turbines are realized.Under the premise of storing active backup power as much as possible,the large-scale wind power cluster is equivalently reduced the phenomenon of abandoning wind energy and electricity has improved the economics of wind power operation.