The Research Of Voltage Sag Source Location Methods In Distribution Network

Power is an economical and clean energy situation,which is easy to transmit,easy to control,and easy to transform.It's a special commodity whose quality is maintained by both utilities and consumers.With more and more intelligent,digitally-automated and sensitive devices being used in social production and life,people are increasingly inseparable from stable power supply,and requirements for power quality are getting higher and higher.Among many power quality problems,voltage sag is one of the most serious power quality problems and one of the most frequently complained power quality problems.For a lack of correct judgment to the reasons of power quality declining,disagreement arises between the power suppliers and users.Studying voltage sag source location methods is helpful to determine who is to take the responsibility of voltage sag,help to avoid the economic disagreement between power suppliers and users,and help to find weak links in power networks,which can provide support for power network reconstruction and improving power supply reliability.This paper makes an introduction of the existing sag source location methods,through modeling and simulation analysis on 6 kinds of existing locating methods,it points out the advantages and disadvantages of those methods including disturbance power and disturbance energy(DEP),current real component polarity(RCC),investigating slope of the system trajectory(SST),distance relay(DR),resistance sign(RS)and Superposition Theorem in Linear Ciruit(STLC).Through the analysis on the equivalent circuit model of failure power network,a method of tracing voltage sag source based on the sequence incremental power current direction is proposed.The proposed method defines a three-phase power current,if symmetric three-phase voltage sag is measured,calculate three-phase positive sequence incremental power current,if asymmetric voltage sag is measured,calculate three-phase negative sequence incremental power current,through judging the change of three-phase sequence increment power current before and after fault,voltage sag source location can be realized.The correctness of the proposed method is verified by radial network simulation and large motor starting simulation.A voltage sag source locationg monitoring device is designed,and on this basis,a voltage sag source locationg monitoring system is constructed.The developed sag source location monitoring device was used to verify the laboratory physics experiment.The developed voltage sag source location monitoring system was used for the verification of the network testing.The verification results show that the proposed method can accurately locate the voltage sag source under radial network,and verify the reliability and practicability of the developed voltage sag source location monitoring device and voltage sag source location monitoring system.