| This dissertation is sponsored by the project ("Study on Optimal Switching Model and Algorithm for Electrical Distribution Networks Using Immune-Algorithm", No.50307015) of the national natural science fund of China. In this paper, the computer calculation technique, power flow estimation, load shedding strategy and reliability evaluation of complex electrical distribution networks (EDNs) are studied.The EDN is connected directly with customers. The research results show that 80% of the total customer interruptions results from EDNs. At present, the electric power utilities are focusing on satisfying the demands of the customers and transmitting the electricity with high quality and reliability to customers. In this paper, the novel technique of complex EDNs reliability evaluation has been integrated with theories, such as power system analysis, power system planning, data structure and algorithm design, to improve the performance of the proposed algorithm. The EDNs reliability evaluation considering the load curve has been realized, and the main results are as follows:①It is difficult for the engineering data stored in files or database to reflect the practical topology structure of EDNs directly. The large-scale storage capacity and complicated search process of data usually result in the calculation complexity of EDNs reliability evaluation. According to the topology structure characteristics of EDNs, radial link table (RLT) and recursion search technique are proposed to solve this problem. The RLT storing the EDNs data has the advantages of isolating the relationship-data from the input data, reflecting the topology structure of EDNs directly, and avoiding the large dimension matrix calculation. Based on the data structure of RLT, a node-to-node or section-to-section recursion search technique is proposed to improve the efficiency of EDNs power flow calculation and reliability evaluation.②The relationships among the voltage, transfer power and branch impedance of EDNs are analyzed using the models of node voltage drop and branch power loss. Based on the definition of node-load-moment (NLM), models of the equivalence power and the equivalence impedance are formulated to estimate the node voltage and branch transfer power after load transferring in the failure analysis process of reliability evaluation. The models have the advantage of high precision, simple calculation process, and linear character to improve the efficiency of EDNs power flow calculation in failure analysis process.③The configuration of EDNs is simplified using the section-link table. A section load shedding strategy, which has been compactly modeled by the section-link table, is proposed to simulate the load transferring process of practical EDN. Many test and engineering cases show that the power flow estimation model and load shedding strategy are with high precision and effectivity in EDNs reliability evaluation, and have the engineering practicality.④An EDN reliability evaluation algorithm considering the load curve is proposed to analyze the rule of the reliability indices changing with the variation of load demands. The EDNs reliability indices are classified and discussed according to their definitions and calculation formulas. Based on it, the calculation formulas of load-reliability curves are proposed. The node voltage estimation method is discussed using NLM model in the model of load tinily increasing. In order to analyze the critical characteristics of EDNs reliability, the EDNs reliability evaluation algorithm considering the load curve and the calculation algorithm of reliability index curves are implemented using the NLM model and clustering algorithm.⑤The applications of the above models, methods, and techniques to IEEE33-nodes test system, RBTS_BUS6 test system and a practical EDN with 1013 nodes has verified their correctness and advantages. According to the comparison and analysis of practical engineering system planning cases, factors, such as configuration of EDNs, allocation of switches and transferring capacity of tie lines, which influence the EDNs reliability index curve are discussed. Based on these analysis, a principle for EDNs medium-term or long-term planning is summarized as"Enough sections, tie lines and standby capacity"to improve EDNs reliability.A software named"Complex EDNs Reliability Evaluation and Analyses"has been developed by VC++6.0, which contains all the programs discussed above, such as power flow calculation, reliability evaluation considering the constraint of power flow, reliability evaluation considering the load curve, and reliability index curve calculation. The practical engineering applications show that the software is effective and practical.
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