Study On Fault Section Location And Restoration Control Methods Of Distribution Network With Distributed Photovoltaic

Fault restoration of distribution networks requires rapid supply recovery through network reconfiguration or reclosing method after faulted line-section located and isolated,which is essential for improving the power distribution reliability.However,with a high penetration of distributed photovoltaic(dPV)generation,the fault current of the distribution network presents "multi-source" feature.The change makes it difficult for the traditional fault location and restoration control methods oriented to passive distribution network to correctly locate the faulted line-section and restore power supply quickly.This problem seriously affects the safe operation of distribution networks and power distribution reliability.Therefore,it is in urgent need to study the faulted line-section location and restoration control methods of distribution network with dPVs.This dissertation carries out the research on faulted line-section location and restoration control methods of distribution network with dPVs along the route of"characteristic cognition-faulted line section location-restoration control".The research would provides technical support for the rapid fault restoration and reliable operation of distribution network with high proportion of dPVs.The specific research work and innovative achievements are as follows.(1)Based on the mechanism analysis of coupling relationship between dPV and grid-side voltage,the dynamic characteristics of dPV during fault and restoration stages of distribution network are investigated.Equivalent analysis models for dPV in multi-fault scenarios considering control differences are constructed,revealing the mechanism that the network voltage one-way determines the fault characteristics of dPV in the fault stage.And there is two-way closed-loop coupling of dPV and network in the restoration stage.The dynamic characteristics of dPV are concluded which should be considered in the design of control methods in each stage of distribution network.It solves the problems of unclear spatial distribution of fault features of distribution network with dPV and lack of considering dynamic characteristics of dPV in restoration control methods,lays a foundation for the study of faulted line-section location and restoration control methods.(2)The faulted line-section location method based on limited meters and compressive sensing is proposed.By analyzing the fault location model of distribution network with dPV under limited meters,the underdetermined equation mapping relationship between low-dimensional measurements and high-dimensional fault location information is clarified.Then,the Bayesian Compressive Sensing(BCS)algorithm is introduced to solve the underdetermined equation to locate the faulted line-section.Furthermore,based on the partition of the dPV-connected nodes and the restricted isometry property of BCS,the optimal layout scheme of the least meters is designed.The proposed method can achieve a correct location rate of more than 95%using only 25%penetration of meters in the distribution network,indicating the fault position for restoration control.(3)An adaptive reclosing method based on voltage rise time-limited detection is proposed.The instantaneous fault clearance in the dPV connected system after tripping can be identified by the voltage rise feature.In view of this feature,a fault state criterion based on voltage difference integral is proposed to detect the clearance of instantaneous fault reliably.By furtherly integrating the protection action information and the time limitation of dPV fault ride-through,an adaptive setting scheme of reclosing delay is designed.Compared with the traditional reclosing method with fixed time-delay,the instantaneous fault recovery time can be shortened from more than 3 seconds to within hundreds of milliseconds,enabling fast restoration of instantaneous fault in distribution network with dPVs.(4)A power supply path reconstruction method for dPV-connceted distribution network based on double time-section constraint check is proposed.A mathematical model of distribution network restoration control is constructed by taking into account the output recovery process of dPV within a few minutes of grid connection time.A double-time section constraint check method is proposed to check the constraint conditions at the initial and late restoration period to guide choice of the distribution network reconstruction schemes.In addition,by introducing the pre-scheme initialization and Gaussian variation,an improved Binary Particle Swarm Optimization algorithm is applied for rapid reconfiguration plan decision.The proposed method can reduce the calculation time of network reconfiguration plan from several minutes to a dozen seconds,while avoiding the restoration failure which may be caused by the low output of dPV in the early stage of distribution network restoration.The proposed method provides technical support for the reliable load-transfer after permanent fault isolation in distribution networks with dPVs.