Research On Multi-fault Sets Selection Based On The Searching Of Transmission Sections

Faults selection is the basic and important step for the transient stability of power system risk assessment.With the continuous expansion of network scale and complexity increasing,"N-1" security constraints has been unable to meet the actual requirements of the power grid safe and stable operation,and cascading failures or multiple faults have become a more important issue.At present,most of the fault sets used in transient stability analysis in practical power grid is selected by historical data and expert experience,which is too dependent on the subjective judgment of the relevant personnel.For this reason,this paper presents a method for screening multiple fault sets for power grid security analysis.Blackout mainly begins with a single fault,and then a series of chain reactions may lead to the occurrence of multiple faults,or cause system instability.Therefore,it is an important method to prevent power grid from blackouts to find the path of fault development and find the weak link of power system and take corresponding measures to make it stronger.In this paper,according to this idea,we search the weak sections of the power grid,and then select the multiple faults based on the sections.The main research contents are as follows:Study on the transmission sections search method based on the complex network theory.The power grid is divided into several subareas based on the complex network theory,considering both the network topology and the current operating state,and then search for the transmission sections.This method neither depends on the selection of overload branches,nor requires the calculation of all cut sets,and the problems of current cross sections search methods are improved to some extent.This paper proposes an index-weighted maximum edge betweenness-to search the shortest paths of the whole network.The ending criterion of subarea division is proposed to improve the GN algorithm,which speed up the subarea division.Finally,transmission sections are obtained by searching the cut sets of network based on the subarea division.By using the example of the 220kV grid of Hebei south network,the results of the partition and the search results are given.By comparison of two algorithms on the southern Hebei network also section search,the search results were compared with the results of this chapter,this chapter search section and more weak in transient margin and critical fault clearing time.Then,study on the selection and ranking method of multi-fault sets based on the transmission sections.The weighted maximum edge betweenness is used as the index to select the key branch,and the end criterion of the division is put forward.The n-order important fault domain is formed by searching the transmission sections based on the corresponding subarea division.Then,the n-order fault set is formed in the n-order important fault domain,and the importance degree of fault sets is sorted according to the proposed index.A case study is carried out in the East China 2020 planning grid.After simplifying the network,the topological graph of 291 nodes and 375 lines are formed.The fault sets of "N-2" and "N-3" are selected according to the method of this paper,and the partition results of "N-2" and "N-3" fault sets,the searching results of the cross section,the selection and sorting results of fault sets are carried out.The results show that the proposed method can filter out the more serious faults which lead to the system instability,and the fault set sorting can further filter the fault set,thus further reducing the number of faults to be concerned.