Research On The Fault Location And Fault Restoration Method For Smart Distribution Network

With reliable, high-quality, efficent, interactive and other characteristics, smartgrid is the development direction of modern power grid, which caught the highattention of electric power industy at home and abroad. Self-healing is the focus ofsmart grid technology research as the key to ensure the reliable and high qualitypower supply function. Traditional fault location and fault recovery method is nolonger applicable as the basic means to realize self-healing of smart distributionnetwork, because a lot of distributed generations are connected to distributionnetwork. Therefore, it is necessary to study the fault location and fault restorationmethod for smart distribution network under the new situation.This paper firstly introduces the research status of fault location and faultrestoration method for distribution network, then fault location and fault restorationmodel and algorithm for smart distribution network are analyzed, in order to realizefault location, isolation and restoration as soon as possible, and restore power tocritical load as much as possible. The main work of this paper includes the followingaspects:(1) The model based on bilateral power flow is estabilised, suited for not onlysingle-source-single-fault situation, but also the situation of multiple distributedgenerators with multiple faults. A regional processing method for DG distributionnetwork is raised, which divides the network into active trees and passive branches.The solution’s dimension is reduced by eliminating the passive branches free of faultcurrent, so as to improve search efficiency. This method takes fault position asvariable, so a large number of infeasible solutions are eliminated by limiting thefault number. It applies harmony search algorithm on global optimization due to itsspeed and accuracy. The validaty and rapidity are confirmed by example analysis.(2) Distribution network has the characteristics of closed loop design, open loopoperation, this paper proposes a coding method to avoid the infeasible solution indistribution network reconfiguration based on harmony search algorithm, in order toavoid topological constraint scheme in network reconfiguration. Defines the singletie loop and its matrix, on this basis proposes the method to generate the effectiveinitial population and new effective solution of harmony search algorithm, whichused to quickly restore network connectivity and avoid infeasible solution encodingin the process of fault recovery. The validaty and rapidity are confirmed by example analysis.(3) This paper proposes a phased distribution network fault restoration methodwhich integrates the heuristic search algorithm with optimization algorithm. Eachstage is determined to operate or not through indexes. The restoration scheme ofdifferent fault is different. In the first stage,the heuristic search algorithm is adoptedto restore connectedness of network; in the second stage,the harmony searchalgorithm is adopted to restore stability with the objective of voltage and linecapacity being within limits; in the third stage,the overload is rejected based on thedepth first search and priority level of load. The effectiveness of the proposed methodis verified by simulation results of improved IEEE33-bus system.(4) To make full use of the ability of DG to enhance the reliability of powersupply, this paper proposes fault restoration method with planned island ofdistributed generation for smart distribution network. N-X verification is taken fordistribution networks, all of the accidents which restore power need the island areput into accident contingency set, and develop island scheme in offline. When a faultoccurs in real time, the islanding scheme can be fast matching. A method thatcombine island load index and depth first search is proposed to divide islands, andtake the maximum amount of protection to critical loads for the target. The recoveryprocess is divided into four stages: island matching, the second to the fourth stageare the same with (3). Simulation results of PG&E69-bus system show that theproposed method is effective.