Study On The Mechanism And Effect Of Voltage Sag In Distribution Network

The power quality problem in power system has been paid more and more attention by domestic and foreign researchers,power supply departments and users,with the rapid development of economy.Compared with power supply interruption,the frequency of voltage sag is very high,and it has a serious impact on the sensitive load,which causes huge economic losses.Voltage sag has gradually become one of the most attentions in the dynamic power quality problems.Study and analyze the influence and propagation mechanism on voltage sag play a crucial role for enhancing asset utilization ratio of power system and reducing economic losses,so study of this subject will have a very important significance.The occurrence of voltage sag is randomly.Voltage sag has become a great hidden danger to the safe operation of electrical equipment,with the wide application of power electronic equipment in power system.The voltage sag can be caused when the events occur in the transmission and distribution system,such as short circuit fault,induction motor starting and transformer switching.Among them,the short circuit fault and induction motor starting are the two main causes of voltage sag.The characteristics of voltage sag caused by different short circuit faults are different,and the transmission mechanism of different voltage sag is studied to help to identify the type of fault.Using the model built in simulation software to analyze the propagation characteristics of voltage sag,which caused by different short circuit faults,through the transformer with different winding connections,and to summarize the propagation law of voltage sag,based on the derivation of the voltage transfer matrix of transformer with different winding connections.The load characteristics of the user terminal will have a certain impact on the characteristics of voltage sag,when the voltage sag is transmitted to the user.This paper focuses on the influence of dynamic load characteristics of induction motor on voltage sag waveform,caused by short circuit fault,and voltage recovery after fault removal.Furthermore,the mechanism of the variation of characteristic parameter of voltage sag causing by induction motor dynamic load characteristic is analyzed.Finally,the voltage sag caused by three typical events are detected by S transform,then analyzed the mitigation effect of distributed generation on voltage sag,through the simulation of modified IEEE-33 nodes model with distributed power grid system.