Research On Reconfiguration And Reliability Evaluation Of Distribution Networks

With the deep research of the smart grid, the important position of distributionnetwork has been paid extensive concern and attention. As the important part linkingthe transmission system and consumers, distribution system plays an important role insupplying and distributing electrical energy to users, its operation state directly affectsthe user’s reliable power and economic benefits of power supplying. The distributionnetwork reconfiguration is not only an important part of distribution managementsystem, but also an important means to optimize and control the distributionsystem.And the distribution network reliability assessment is an important part ofpower grid construction and renovation, it can guarantee the reliable operation of thegrid. This thesis does some study on the relationship between reliability andreconstruction， and fast and accurate methods for configuration and reliabilityevaluation of complex distribution system are studied.In the study of distribution system configuration, distribution networkreconfiguration algorithm based on heuristic rules and harmony search algorithm (HSA)is proposed. At first, the codification strategy based on the reconstruction loops isadopted according to the characteristics of distribution network reconfiguration andHSA. Then several special branch groups are constructed and several disconnectingrules are set to avoid the infeasible solutions. Furthermore, the initial network isanalyzed with the objective function for the minimization of power loss, and theeffective search space of each loop is shrunk by using heuristic rules. Finally, theharmony search algorithm is used to search the global optimal solution. Using theproposed method, the number of candidate solutions can be reduced greatly, theoptimal solution could be achieved rapidly and has prominent performance in thequality of solution and robustness, and the search performance will not become worsewith the expansion of the network.In the study of reliability evaluation of distribution system, a reliabilityassessment for complex distribution system based on merging of regional fault treeswitches is proposed. At first, taking circuit breakers or section switches as boundarycomponents, the distribution network is divided into fault zones according to thecharacteristics of switches. Regarding fault zones as basic units, the reliability analysismethod is proposed based on constructing regional fault tree. Reliability indices of thetop fault zone is obtained by up-stream merging of switches from the lowest level, and then downs-stream merging of switches from the top down along the branch tocalculate the reliability indices of the others by modifying the parameters in the knownupper regional indicators. Finally, the reliability indices of system is yielded andamended with the difference. This method takes into account the coordination ofbreakers and could avoid the repetitive search of the same element. It has a clearphysical concept and high calculation speed.Finally, the simulation results of IEEE typical examples and RBTS6system verifythe feasibility and effectiveness of the proposed methods.