Research On Fast Topology Analysis And Fault Location Method For Power Network

The wide area backup protection is an effective technical way to solve the problems existing in traditional backup protection, in which the multi-point information from much wider area of power network could be used. The current operation mode and topology structure of power system need to be tracking rapidly and precisely, which could supply the wide area backup protection with the latest physical network grid information. Meanwhile, the fast and accurately location of faulted components is the key function for the implementation of wide area backup protection. Therefore, in the thesis the fast topology analysis and fault location will be the two attracting aspects needed researching fundamentally and comprehensively.The hierarchical and distributed topology modeling could improve the efficiency of topology analysis process in program architecture, in which all the substation configurations could be finished in a parallel way, and then the system network topology could be implemented based on the uploaded analysis results from different power stations and plants. Hence, in order to meet the requirement of wide area backup protection based on WAMS, the following fast topology identification contents, including novel matrix-based topology analysis method for substation configuration and the concrete application of PMU information in topology analysis, have been researched. The corresponding result of this part is as following:(1) Research on fast matrix-based substation configuration method only the circuit breaker status information in utilizationA new topology tracking algorithm is proposed based on virtual impedance. Firstly, the each switch branch in electric main connection is processed as one branch with virtual impedance; then, the original topology analysis and the tracking status change in circuit breakers in stations could be finished in a similar way as the formulation and modification of the nodal matrix for power network; finally, the aim to deal with the effect from status change of breakers on the pre-existing topology results could be achieved, and the repeat operation could be avoided which existing in the process from original adjacent matrix to completed connected matrix in traditional matrix-based method.In addition, a novel integrated topology analysis scheme is founded based on the breaker connected routes. In this scheme, the relationship between the breaker connected routes among two nodes and the corresponding elements in completed connected matrix is analyzed firstly. And two routes finding algorithms are proposed respectively according to the graphical characteristic of main connection or the cofactor signing simplification of adjacent matrix. Then the completed connected matrix in function way with the breaker statuses as variables could be established systematically, to which the integrated analysis for original topology formulation and tracking status change of breakers could be accomplished based on the finding of solution by substituting the real time statues of the corresponding breakers. Moreover, the topology analysis process, formulation of breaker connected routes function in off-line and the real time tracking in on-line, could enhance the efficiency of substation configuration.(2) Research on concrete application of state and analog information from PMU in network topology analysisA fast topology analysis algorithm is formulated based on the hybrid operation of PMU information. In the step of substation configuration, based on the bus grouping for inlet and outlet lines, how many connected pieces are grouped could be formed by judging whether the line currents incident to the concentrated bus node meet the KCL. Then the task of substation configuration could be finished. In the step of topology analysis among stations and power plants, the difficulty in islands analysis is pointed as the tracking the open of tree-branch firstly; then the generalized KCL is applied to the analysis for input currents of area network, and the tracking difficulty could be overcome combining with the dynamic grouping of tree-branches and cotree-branches.In addition, an identification method based on least square principle is established to correct the topology error in circuit breaker status. In this part, the types of switch topology error are determined at the beginning. Moreover, the linear equations are formulated in complex form to associate the switch status with the current in lines and breakers. After the partition of real and imag part for plural equations, the identification algorithm for switch status could be implemented by use of the least square method. The test examples have validated the efficiency of the proposed algorithm.The rapidity and synchronism of the PMU information from the multi-point in entire power network has affected the topology analysis function deeply. The calculation simultaneity of electrical quantities is also useful to the location of faulted components, which plays the key role in wide area backup protection. The occurrence of fault in power system will lead to the broken of power network topology. According to the different process modes and the variation in size of PMU measurements, the fault location methods have been focused in this thesis as following:(1) A fault location method is proposed based on the consistency analysis of electrical topology. The different between fault in branch and node have been analyzed in the broken for power network topology structure. As to the faulted branch location, the consistency for electrical topology is used to implement the rapid and accurate fault detection. As supplements, the Bayes Discriminant theory is introduced to finish the location of nodal fault precisely and reliably, in which the combination prior knowledge with posterior probability have been utilized about electrical quantities during the pre-and post-fault.(2) Research on fault location method for entire power network based on sparse PMU placementFirstly, the invariance characteristic of the nodal matrix for power network during pre-and post-fault is analyzed by the equivalent elimination of fault point. Secondly, having taken the advantage of the nodal impedance matrix, two fault location algorithms are proposed:one is based on the adaptive searching of near and remote sections, and the other is based on the minimum variance principle. The two mentioned algorithm could provide the fault point distance with a certain precise.In the former one, the classification of fault in near and remote section is defined. According to the nodal voltage information, the adaptive searching scheme for branches has been established. In this algorithm, the fault in near section could be located with high efficiency, and in remote section also can be determined without omittance. In the last one, the statistical characteristic of nodal equivalent input virtual fault current series has been extracted. Based on minimum variance principle, the first step to locate the suspected bus and second one to determine faulted branch could be finished. In this process, the searching scope could be limited to the branch set associated with suspected bus, from which the fault location could benefit more.