A Fault Self-healing Method For Distribution Network Based On Graph Theory And Heuristic Algorithm

Distribution network is the last link of power supply service,and the speed of fault recovery directly affects the user experience.At present,the fault disposal of distribution network still relies on manpower,which is time-consuming and has become increasingly difficult to meet the demand for power supply reliability.So it is of great practical significance to study the fault self-healing method of distribution network that has practical value in engineering.This thesis first reviews the development of fault self-healing of distribution network at home and abroad.And then,several fault location and restoration methods are introduced and analysed,combined with actual operation and maintenance experience.The topological structure of actual distribution network is generally radial and contains a large number of Tshape connection points.According to this structural feature,the knowledge of graph theory is introduced.With the controllable switches as the nodes,the topology of the distribution network is divided into multiple Y-shape tree-like structures,which are defined as Y-shape branches in this thesis.The fault location is achieved through two steps.The first step is to find out which branch the fault is in,and the second step is to complete the final fault location inside this branch.This method has great advantages in both time complexity and space complexity.It can reduce the amount of calculation and save the system overhead,and hence has good practicability in engineering.Due to the poor condition of communication in distribution network,fault information loss and distortion is inevitable.The fault-tolerant performance of the proposed fault location method is analysed and the result proves that this method itself has a good ability on faulttolerance.In order to further improve the accuracy,a two-level correction mechanism is proposed.It can be flexibly deployed according to the reliability of local communication,taking both accuracy and efficiency into account.This provides an effective way to make up for the communication short board in distribution network.Fault restoration is the key to reduce the number of time-households in the event of power supply failures.Aimming at restoring as much load as possible,and taking the actual demand of power grid enterprises for fault disposal as the starting-point,the concept of priority value of power transfer is proposed.The factors such as reserve capacity,operation risk of equipments,risk of tripping,importance of load and potential complaint are taken into account.In view of the good practicality of the heuristic algorithm,a fault restoration heuristic algorithm based on the priority value of power transfer is designed.Finally,the effectiveness of the fault restoration method proposed in this thesis is verified with practical examples consist of ome actual feeders in Guangzhou area and actual load data during summer peak load period.