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Research Of Algorithms For Distribution System Reliability Assessment Based On Network Reconfiguration

Posted on:2003-03-13Degree:MasterType:Thesis
Country:ChinaCandidate:Z F LuFull Text:PDF
GTID:2132360092465929Subject:Power system and its automation
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The research object of the dissertation is the reliability evaluation of distribution systems. To reduce the complexity and to increase the precision of computation, systematical studies on theory of reliability assessment and its applications are conducted. In this precondition, flow computation of radial and meshed configurations are studied theoretically, the flow calculation efficiency is improved, and so is the reliability assessment efficiency. In addition, the reliability assessment model of distribution systems with multi-source reservation in great power station is developed. The details are as follows:Using recursive function with the breadth first search and the depth first search, the dissertation presents an effective method to identify network configurations speedily and easily. The program has clear thoughts and concise codes, and it only needs basic input data of the network. The method is prepared for flow computation and reliability assessment.Concepts of the breakpoint and the breakpoint port are put forward, so that forward/back sweeping load flow method that is only used in radial configuration before is expanded and applied in meshed configuration. Not as NR and FDLF, it requires less computer time and has good convergence. Because the relation between voltage and current of the breakpoint port is linear, the sensitivity matrix between voltage and power of the breakpoint port is the thevenin equivalent impedance matrix in theory. Therefore, it is proved that the iterative calculation of correction of the breakpoint power injections is convergent. As examples, load flow calculation for IEEE 33node and 90node test systems show that the load flow solution of distribution systems has excellent convergence characteristics and speediness.Based on the failure-mode-and-effect-analysis(FMEA) technique, the load-point is regarded as the analysis object, and the method of area partition of component failure-mode for system configurations which expanded the idea of reliability assessment is proposed. It is an excellent solution in application to distribution-system-reliability evaluation considering switch failure, bus failure, switch-stuck, switch-misoperation and misoperation ofrelay protection device.In order to improve the assessment precision further, a hybrid algorithm of distribution systems reliability is put forward. The excellence of the AC load flow and the network flow method are integrated. Before reliability calculation with the network flow method, the affective area of tie switch is knew through computation of the AC load flow. It is analyzed that the computation time of the algorithm is linear to the number of nodes and tie switches theoretically. Therefore, the algorithm greatly alleviates the "dimension catastrophe" with considering failure of more components. In the end, the program's speediness, utility and veracity are indicated through computing indices of the IEEE 6 bus reliability test system (RBTS) and actual system. It's characteristics are embodied much more in the case of large-scale distribution systems reliability assessment and considering failure factors thoroughly.The dissertation presents an effective model of reliability evaluation to systems with multi-component in reserve, that is to say, using Poisson distribution model, reliability formula of irreparable systems with different components in reserve has been deduced; and Markov stochastic model of reparable standby systems has also been presented. By emulating the time (T) of irreparable systems to reparable systems, the deduced formula can compute reliability for reparable systems with different components in reserve. A new model of reliability evaluation for reparable systems with different components in reserve is developed. Finally, the method's rationality is indicated through computation of examples and application in an actual project which is the distribution systems of water power plant in the three gorges.
Keywords/Search Tags:distribution systems, reliability, AC power flow, FMEA, hybrid algorithm, systems with multi-component in reserve
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