Study On Network Topology Analysis And Operation Modes Combination In Power System

Complicated operation mode and changeful power network topology brings some hidden trouble to power system's safety. It is very significative to analyze and make use of the network topology, and to study the combination of different operation modes and power network topology configurations, for power system analysis and safe operation. This dissertation devotes to the study of operation modes'combination and network topology analysis. The research productions have been applied in the relay coordination softwares for many provincial and regional power networks. And they improve the veracity of setting, the efficiency of relay coordination software and the reliability of relay equipments'action.Firstly, this paper exploits a novel physical topology analysis method to analyze the characteristic of corresponding geometrical topology. The elements of impedance matrix (Z-matrix) can concentratedly reflect all the electrical coupling of different buses in the systematic scale. Recurring to the global topological attributes concealed in Z-matrix, a new physical topology analysis algorithm to identify cut edges and vertices is presented, it introduces two simple equality criterions derived from the reduced Z-matrix elements. This novel algorithm adequately utilizes the physical topological properties concealed in the Z-matrix of power system. The improvement over existing graph-theoretical approaches is in that this new algorithm has more direct-viewing, simplicity, specific and important physical significance, which can borrow ideas to insight and research the topology configuration in power network.Secondly, based on the electrical coupling paths described by physical parameters of equivalent network derived from the reduced impedance matrix, this paper analyzes the representative dynamic change of mesh network topology which has an influence on the calculation of setting, a new method in combination of operation mode is presented. It introduced electric coupling of loops which cake care of the influence of mesh network selectively based on two criterions.Furthermore, according to the topology characteristic of power substations or plants considered in relay coordination, the operation mode change of elopements in the power substations or plants can be thought as a whole unit with different impedance parameters. Two types of sensitivity factors are derived that demonstrate the relationship between the fault current or coordination coefficients and different operation modes of different substations or plants. The operation mode of substations or plants which have great impact on the setting of relays will be taken into account selectivity in the relay coordination. The speed of fault calculation for relay coordination will decrease remarkably when considering varying of operation conditions including the switching of operation conditions of substations or plants and line outages simultaneously. Two methods are presented to improve the arithmetic of fault calculation based on the impedance matrix: 1) the substations and plants in various operation conditions are reduced into a single-bus or two-bus equivalence networks in advance, the switching of which are substituted by the change of the equivalence networks; 2) the elements of the partial impedance matrix for fault calculation are classified, the number of the elements need to be modified decreases gradually according to their necessary and the optimum sequence of modification. These improved methods decrease the modification of the impedance matrix and quicken the speed of fault calculation remarkably.Next, a new algorithm of network topology analysis for equivalent impedance calculation is presented. This proposed algorithm combines the physical topology and geometrical topology. Ineffective directions of geometrical path search are excluded through the judgment of electric physical paths, which ensure the search direct to the power system all along, and the complex back-tracing and the depth search of radial branches are avoided.Finally, this paper studies the determination of minimum break point set (MBPS) owning the intersectant and complicated meshed power network. Based on the of mesh network being transformed into radiate network theoretic analysis, the fastest loop opening analysis criterion principle is obtained. And an algorithm to determine MBPS for inverse-time directional overcurrent relay setting coordination grounded on analysis of opening loop is brought forward. The definition of coordination deadlock meshnetwork is analyzed according to the property of relay coordination of definite-time relays in power systems, and this paper discusses the difference between the break point set in the definite-time relay coordination and inverse-time relay coordination. By obtaining the coordination deadlock meshnetwork loop through pre-coordination, the paper improves the functional dependency methodology and proposes a new method to determine the minimal breakpoint set which is used to break the obtained deadlock loop.