Research On High Voltage Ride Through Technology Of MW Large Wind Turbine

At present,with the depletion of fossil energy,environmental issues have attracted widespread attention,and the use of clean energy has become increasingly diversified.Wind power generation,as a clean energy utilization form with earlier application,is relatively mature.At present,the installed capacity of wind turbines has reached MW level,but the following problems are also reflected.The main problem lies in the grid connection: due to the particularity of wind energy,the controllability of wind farm is poor,especially after the grid failure,if the wind turbine is not controlled by special means,the wind turbine will be off-grid operation.If the MW-class large-scale wind turbines fail to disconnect,it will cause secondary hazards to the power grid,and even a large-scale chain reaction.In serious cases,it will cause large-scale accidents such as grid disintegration,which will pose a greater threat to the safe operation of the power grid.Therefore,the research of wind turbine's Fault-Crossing capability has attracted wide attention at home and abroad.At present,the research on low voltage traversal of wind turbines has become more and more mature,and many wind farms have already possessed the ability of low voltage traversal.However,the problem of high voltage disconnection of wind turbines due to the delay in switching of reactive power compensation devices or excess reactive power in power grids has not yet been solved.In order to make the operation of wind turbines more stable,it is necessary to study the high voltage crossing of wind turbines.In this paper,two kinds of MW class large-scale units,namely doubly-fed units and direct-drive permanent magnet units,are studied in order to improve the high voltage ride-through capability of large-scale wind turbines.Firstly,starting from several wind power off-grid accidents,this paper discusses the necessity of high voltage ride-through capability of wind turbines,and points out that wind power will become one of the important power sources in the future,which provides a basis for the research value of this topic.Then,the high voltage traversing standards of different countries are analyzed to provide reference indexes for solving the problem of high voltage traversing.Secondly,two kinds of MW wind turbines,including doubly-fed units and permanent magnet direct drive units,are selected to establish their mathematical models and corresponding converter control strategy models.According to the established model,the transient transition process of the two types of wind turbines during power grid voltage surge is analyzed separately.Based on the characteristics of the two types of units in the transition process,the paper puts forward the following conclusions: Two high voltage traversing schemes of improved converter control strategy for generating units are proposed.In addition,from the point of view of grid-connected point voltage control of wind turbine,a high voltage traversing scheme based on fuzzy self-tuning PI control STATCOM is proposed.This scheme improves the response speed of reactive power compensation device in wind farm,enables reactive power compensation device to follow the reactive power change of the system quickly,and realizes the purpose of stabilizing grid-connected point voltage,so as to realize the high voltage of wind turbine.Pass through.Finally,the theory proposed in this paper is simulated in MATLAB/Simulin environment,which proves that changing the control mode of the unit itself can achieve the control requirements of high voltage traversing when the grid voltage is slightly surging.The high voltage traversing scheme of STATCOM based on fuzzy self-tuning PI control can help the unit achieve high voltage traversing when the grid voltage is deep surging.