Analysis Of Reactive Power-Voltage Characteristics Of Wind Farm And Research On Control Strategy

With the national wind power base projects being connected to the grid and put into operation,the newly installed wind power has increased significantly,and the proportion of wind power generation has further increased.The randomness,discontinuity,and volatility of wind energy bring some challenges to the stability of the grid.In addition,energy resources and the main forces of load consumption in China are inversely distributed,and long-distance transmission has exacerbated the adverse impact of wind power grid connection.How to sufficiently utilize reactive power compensation devices in wind farm to maintain the voltage stability at point of common coupling and reduce the voltage fluctuation of nodes in wind farms has become the key to wind power grid-connection.On the basis of studying the reactive power and voltage related characteristics of wind farm,fuzzy C-means clustering is used to analyze the regional reactive power regulation ability of wind farm.A reactive power coordination optimization control strategy based on improved second-order particle swarm optimization algorithm is proposed,which fully utilizes the reactive power regulation ability of DFIGs,retains more dynamic reactive power margin,and improves the stability of system voltage.The main contents and achievements of this paper cover the followings:(1)A method of DFIG group classification in wind farm based on fuzzy C-means clustering is designed,and the regional reactive power regulation capability considering operational constraints is studied.Fuzzy C-means clustering is used to analyze the historical data of wind farm,and the active power output fluctuation,terminal voltage margin and reactive power margin are used as clustering indexes to divide the DFIG group into different regions,and reactive output in each region is coordinated and controlled for reactive compensation.The range of reactive power regulation in each region is obtained by considering the point voltage constraint and reactive power output constraint during operation,so as to obtain the relatively reliable reactive power regulation capability of wind farm.(2)A regional reactive power optimization control strategy based on improved second-order particle swarm optimization algorithm is proposed to solve the problems of insufficient utilization of reactive power regulation capability and large voltage fluctuation at the DFIG terminals during operation.Based on the reactive power regulation ability of each region,considering the power losses,terminal voltage changes of each DFIG,and dynamic reactive power margin,then the reactive power optimization model of wind farm is constructed.The improved second-order particle swarm optimization algorithm is used to solve the optimal reactive power output scheme of each region and compensation equipment.The neural network is used to fit the active power output and reactive compensation tasks of wind farm to achieve real-time optimal reactive power distribution.(3)Taking a 100MW wind farm as an example,the effectiveness of the proposed regional reactive power coordination control strategy is verified by simulation.Firstly,the DFIGs in the wind farm are divided into different regions based on the historical data,and the reactive power control capabilities of each region and reactive power output scheme are obtained based on the predicted data.Then,different active power output scenarios and reactive power requirements are selected,and the traditional equal-margin distribution method is used as a comparison.The results showed that the proposed strategy could effectively reduce the terminal voltage of the DFIG and retain more dynamic reactive power margin,and improve the stability of wind power grid-connection under the condition of little difference in power loss.