Studies On Analysis And Optimization Of Distribution Network Reliabllity

To ensure a reliable consumption for electric power users is a core task for distribution system planning,construction and operation.In order to conduct the planning and operation in distribution networks,explicit indicators had been set to assess the reliability of power supply for it.In this paper,the reliability problem in distribution network was researched as a main issue,which embodies in the performance improvement of reliability evaluation algorithm and reliability optimization by means of optimization-based switch allocation.Considering that redundant analyses are widely existed in existing reliability access algorithms,an equivalent superposition algorithm for distribution network reliability evaluation based on switch characteristics,which takes into account the operating characteristics associated with the switch type after the fault occurred and combined the network partition and minimal path ideology,has been constructed.In the process of network partition and regional minimum path formation,the system component indices was superimposed on the switch elements equivalently,which derived an equivalent switch reliability matrix.The reliability indices was calculated by taking switch elements as analysis object and equivalent switch reliability matrix along with regional minimum path matrix as medium.Test results of IEEE RBTS Bus 2,4 and 6 show that the proposed algorithm can avoid redundancy analysis and effectively improve calculation speed and efficiency.Notice that traditional mathematical analysis method is inefficient in solving complex optimization-based switch allocation problem,a differential evolution algorithm with an individual-dependent mechanism and a successful-parent-selecting framework was introduced in this paper.Individual-dependent mechanism was integrated to remedy the influence toward the performance of algorithm brought by parameters setting and mutation strategy,and successful-parent-selecting framework was adopted to escape the stagnation in the process of iteration.The performance of the proposed algorithm was tested from many aspects,results show that the proposed method is feasible and benefit both in success rate of optimization and convergence speed of iterations.In order to resolve the problem of load fluctuation and invalid of annual equivalent method brought by load growth in optimization-based switch allocation problem,a polymorphic model of load and power failure losses was constructed,a multi-objective optimization-based switch allocation model considering load growth was constructed by taking the total switch costs and blackout costs in planning period as elements.The requirement of single-load-point toward reliability,namely the customer choice on reliability,and the reliability constraints of systems,were both considered.The results of feeder F4 in IEEE RBTS Bus 6 has validated the influence of weight factor,customer choice on reliability and load growth in objective function to the result of optimization-based switch allocation.