Research On High Reliability Distribution Network Planning Method Considering Distributedpower Supply

As the development speed of the distribution network accelerates,new elements such as distributed power sources and electric vehicles are gradually connected,and the reliability of the distribution network is increasingly affected by many factors.On the other hand,the rapid development of urbanization and the growing demand for diversified users have further increased the requirements for power supply reliability.How to meet the development requirements of high reliability through scientific and rational distribution network planning has become a difficult problem to overcome.Therefore,this thesis has carried out research on the high reliability distribution network planning method considering distributed generation.Specific research works are as follows:(1)Analysis of correlation factors of distribution network reliabilityAiming at the influencing factors of distribution network reliability in planning stage,this thesis proposes a comprehensive grey relational model of distribution network reliability based on DS evidence fusion.Through the quantitative analysis of the model results,the influencing factors with large correlation degree are extracted,and the key measures for improving the reliability are positioned in order to provide a theoretical basis for high-reliability distribution network planning.The effectiveness of the model is verified by an example of a medium voltage distribution network in Suzhou.The results show that grid structure,equipment and distributed generation have important influence on reliability.The following three aspects will be studied in this thesis.(2)Active distribution network reliability assessment methodThe uncertainties of distributed generation and load are transformed into deterministic models,and the reliability models of various power components and distributed generators are established.According to the minimum area division of distribution network,the islanding and load reduction strategies based on association matrix are proposed.Considering the transfer of distributed generations and tie lines,the reliability of the active distribution network is evaluated by the sequential Monte Carlo simulation method.(3)Distribution network grid expansion and DG deployment planning with reliabilityThis thesis establishes a two-layer planning model for the distribution network grid expansion and DG distribution problem considering reliability.The upper layer is the extended planning model of the grid,which is solved by the genetic algorithm considering the optimal retention strategy,and the random generation tree method is used for line coding,which avoids the repair of the infeasible solution while takes the radial and ring network modes into account;Based on the grid scheme of the upper layer,the lower layer establishes the optimal configuration model of DG,and uses the K-means clustering method to deal with the uncertainty of DG output.The problem is transformed into the second-order cone programming problem by the relaxation transformation of the Distflow power flow equation.The Gurobi solver is called to determine the capacity and position of the DG,and the planning result is fed back to the upper layer.The reliability calculation of the entire network is implemented by the active distribution network reliability assessment method proposed in this thesis,then the reliability result is taken as the constraint or goal of the upper model,and finally the comprehensive optimization scheme is found.An example shows that reasonable tie lines and DG planning can improve the level of reliability.(4)Unit system planning and modular design method for distribution network in high reliability power supply areaBased on the strong grid structure and perfect equipment level of the high-reliability power supply area,it is proposed to further improve its reliability from the perspective of unit planning and modular design.Firstly,the concept of unit planning and modular design is explained.Then,based on the present,transition and target period of the unit planning scheme,a comprehensive evaluation model involving reliability,economy and adaptability is established.According to the "component-sub-module-module" step by step method,the reliability calculation method considering the multiple outage and the inter-module transfer time is proposed.Finally,the improved entropy weight formula is used to realize the comprehensive evaluation of the module combination scheme of power supply units in different periods,so as to locate the efficient,high-quality and lean combination scheme between modules,and provide assistant decisionmaking for planners.Through the example of Suzhou area,the advantages of unit planning and modular design in improving reliability are analyzed,and the effectiveness of module-based reliability calculation and comprehensive evaluation method is verified.