Research On Key Technologies Of Closed-Loop Operated Medium-Voltage Distribution Network

With the economic and social development of our country,power users are more and more demanding on power supply reliability.Closed-loop operated medium-voltage distribution network can effectively improve the power supply reliability.However,because of the very difference between closed-loop operation and open-loop operation in connection modes and operation modes,closed-loop operated medium-voltage distribution network may bring some new problems to grid operation.It is of important theoretical and practical significance in studying on some key technologies of closed-loop operating medium-voltage distribution network.Reliability is an important index in measuring the power supply reliability level of distribution network.This thesis will first have a further study on reliability evaluation method of closed-loop operated medium-voltage distribution network.Through improving minimum-cut-set method and on basis of setting up equivalent power point and equivalent load point and obtaining bi-directional minimum cut set of main loop branch point,a method will be proposed to evaluate reliability of closed-loop operated complex medium-voltage distribution network.Through the calculation and analysis of examples,this method will be proved to be correct and superior.Usually,there is a contradiction between reliability of grid operation and economy of grid construction.Medium-voltage distribution network operating in closed-loop will bring great challenges in economy of grid construction while it can improve power supply reliability.This thesis will study on reliability cost-benefit optimization method of closed-loop operated medium-voltage distribution network.Set up an optimization mathematical model and solve this problem by using the improved partheno genetic algorithm in order to get the best planning program of closed-loop operated medium-voltage distribution network.Through the calculation and analysis of examples,the proposed model and its solution algorithm will be proved to be effective.On basis of analyzing the connection mode requirements of closed-loop operation mode,this thesis will propose two new closed-loop operated medium-voltage distribution network connection modes and analyze the advantages and disadvantages in operational characteristics of several closed-loop operated connection modes.Also,compared to open loop operation,analyze the influence of closed-loop operation mode on distribution network operational characteristicsThis thesis finally will also have a study on the problem of relay protection and feeder automation of closed-loop operated medium-voltage distribution network.Through analyzing the influence on closed-loop operated medium-voltage distribution network while using traditional open-loop operated medium-voltage distribution network relay protection and feeder automation,relay protection configuration and feeder automation will be proposed to be used in closed-loop operated medium-voltage distribution network.