Research On Protection And Control Strategy For Smart Grid To Deal With Abnormal Sampled Data

With the development of smart grid,computer technology and communication technology continue to integrate.Many new relay protection strategies and engineering application have been studied and put into practice.Such as station protection and wide area protection,which utilize the features that the total station or the whole network information can be achieved instantly.Compared with the traditional relay protection technology,the new relay protection technology under the background of the smart grid is on a higher platform and it has a completely new and broader room for development.However,both the traditional relay protection and the new relay protection are facing a same problem: the reliability of sampled data.Electromagnetic transformer is prone to saturation,resulting in the misoperation of protection;electronic transformers are vulnerable to environmental impact,which is the reason why it has not been widely used.To solve the problem of abnormal sampled data,work can be done from two aspects.The first is to study the method to identify abnormal data,the second is to study the new relay protection algorithm with fault tolerance,which can make sure that the relay protection can operate correctly when some pieces of sampled data are wrong.In this paper,the working principle of the data sampling terminal equipment used in the power grid is analyzed,and the equivalent circuit and mathematical model are also given.In addition,this paper briefly introduces the mathematical methods for analysis and identification of abnormal signals used in the power system.In this paper,the concept of adjoint fault of electronic transformer is presented.On the basis of qualitative or theoretical analysis of the dynamic characteristics of the power grid caused by line fault or shedding and inception of large-scale loads and large-size power sources,a new method of fault diagnosis for electronic transformer is proposed,and a quantitative evaluation method for the fault degree of electronic transformer is presented.The PSCAD modeling and simulation show that the method presented is feasible.On the basis of the analysis of the basic principle of power frequency variation protection,The influence of the system impedance,the reliability coefficient and the saturation of the transformer on the operating characteristic of power frequency variation protection and the relationship between these factors are studied.The saturation scene of transformer on transmission line is analyzed,The optimal selection scheme of the threshold value of power frequency variation protection is proposed.A new protection strategy based on the maximum and minimum setting system impedance is proposed.The simulation results shows,this method can give out the right decision when the transformer saturated,and also maintain all the merits of the traditional methods...