Research On Comprehensive Evaluation Method For The Reactive Power And Voltage Control Capability Of Mountain Wind Farms

In recent years,the development of wind energy in low wind speed areas has received much attention.Mountain dispersed wind farms are the main form of wind power in the low wind speed areas which terrain conditions are complex.The fluctuation of wind power output brings problems such as voltage deviation and voltage fluctuation to the voltage stability of the gr id.The randomness and intermittency of mountain dispersed wind farms are more significant,so their grid-connection brings more challenges to the operation control of the grid.Not only the reactive power and voltage control(RPVC)capability and other gr id adaptability of wind farms but also the wind turbines in mountain dispersed wind farms have considerable residual reactive power capacity bring more possibilities for them to participate in the grid control and dispatching.In order to improve the relia bility of grid operation with wind power and promote the transformation of wind farms from passive grid-connection to active and friendly grid-connection,this paper has done the following studies on the RPVC capability of mountain dispersed wind farms:Firstly,the RPVC mechanism of the Permanent Magnet Synchronous Generator(PMSG)and wind farm is analyzed to lay the theoretical foundation for the follow-up research work.In order to study the PMSG capability and grid connected with mountain dispersed wind farm conveniently,the response characteristics of the detailed and simplified model of PMSG are analyzed.Based on the DIg SILENT/Power Factory software platform,a detailed model of the actual mountain dispersed wind farm is built,and the RPVC capability of the wind farm is studied.Combined with the actual power grid topology in a certain region of China,a distribution network test system connected with mountain dispersed wind farm was established by using the simplified model of PMSG.The validity and representativeness of the test system are verified by the power flow simulation and the index evaluation of grid structure,load distribution,wind farm distribution and permeability among different systems.It can provide a general test model for grid-connection research of distribution network and mountain dispersed wind farms.Then,based on the effects and the factors affecting the RPVC capacity of wind farms,a comprehensive evaluation system for the RPVC capacity of wind farms is proposed,it includes power index,power quality index and regulation index.The evaluation results are graded based on probability statistics,and the indexes are weighted by the combination weighting method.Taking the actual mountain dispersed wind farm as an example,the proposed method of comprehensive evaluation of RPVC capability is used to analyze it,and the effectiveness of the method is verified.This evaluation method provides a theoretical basis for the division of secondary RPVC areas of wind farms.Finally,a method for double partition of the RPVC area of mountain dispersed wind farm is proposed.The primary RPVC area of wind farm is divided according to the hierarchical clustering analysis algorithm of condensation based on the Q-U sensitivity of the system.So as to achieve the purpose of local balance of reactive power of the system connected with the wind farm.In order to assign the wind farms in the region to participate in the RPVC in priority,based on the reactive power margin,RPVC capability of the wind farm and the influence of the reactive power of the wind farm on the voltage of nodes,the secondary zoning index of the RPVC area of wind farm is proposed.The primary RPVC area with two or more wind farms is divided by comparing the secondary zoning index.The effectiveness of this method is verified by the double partition of the distribution network test system connected with mountain dispersed wind farms.