Research On The Cause And Location Of Voltage Sag In Liquefied Natural Gas Receiving Terminal

In recent years,power quality has been paid more and more attention by many relevant researchers,the power supply companies and all kinds of users at home and abroad.There are many types of power quality problems.Voltage sag is one of the common power quality problems.The frequency of voltage sag is high,which is serious to economic losses,and the damage to the large equipmentis especially serious.So,as a continuous production enterprise,Liquefied Natural Gas(LNG)receiving station is affected frequently by voltage sag.The causes of voltage sag in LNG terminal are analyzed,and the upstream and downstream locations of voltage sag sources are located,divide the responsibilities between power supply companies and users,is the research significance of this topic.According to the main wiring diagram of primary side of LNG substation,the power system simulation model of LNG terminal is built.Analysis the cause of voltage sag in power system of LNG receiving station,laying the foundation for the detection and location of voltage sag.The voltage sag caused by the start-up of large equipment in LNG terminal,the switching of transformer outside the plant and the short circuit of overhead line is studied and simulated.The characteristics of voltage sag caused by different reasons are different.Detection of different types of voltage sag is helpful to analyze the characteristics of voltage sag.For voltage sag data of LNG terminal,the starting and ending time of voltage sag can be detected by wavelet transform,and the effective value and phase jump of voltage can be detected by dq transform.The combination of the two can clarify the characteristics of voltage sag.The voltage dynamic monitoring system is installed on site,analyze the stored field data.Due to the low accuracy of traditional voltage sag source location methods,this paper proposes a voltage sag source location method based on comprehensive criteria and neural network.The voltage sag data is obtained by using the above model,the characteristic value of voltage sag is extracted.The neural network is trained by the characteristic quantity of voltage sag and the characteristic criterion of traditional voltage sag source location,and the trained neural network is used to locate the voltage sag source of LNG terminal.Compared with the traditional voltage sag source location method,the results show that the neural network algorithm based on the typical LNG terminal voltage sag source location accuracy and effectiveness.