Simulation Analysis Of Voltage Sag

With the development of the national economy and society,microelectronic technology has made great progress,computer,automatic control technology and a large number of devices and high-power electronic technology are widely applied to various sectors of the national economy in various fields.These microelectronic devices and device performance is very sensitive to the voltage change,even a little bit of voltage fluctuation will have a significant impact on their accuracy,longevity and normal work.Thus,compared to the traditional power users,these sensitive load has put forward higher requirements for the power system and power quality.Maybe just a few cycles,a few milliseconds voltage sag will have a significant impact on these devices,and creat irreparable economic losses.Therefore,it is particularly important to have a depth study on the voltage sag,including the causes,the hazards and propagation.This paper mainly introduces the concept of voltage sag,the source of the voltage sag,the harm of voltage sag,the measurement and calculation of the value of voltage sag and the measure to restrain the voltage sag.The cause of voltage sag generally have fault, air-dropped transformer and large capacity motor starts,etc.This paper built the simulation model for transformers,single phase short circuit fault, drop and short-circuit fault, bus and motor starting,etc in Matlab module,to study the cause of the voltage sag, duration and sag depth and so on,and to verify the accuracy of the results by comparing simulation results with actual field wave record.A specific point in a power system failure will cause voltage sag.The voltage sag can spread along the transmission line in power system,expand the range of voltage sag, and cause greater harm.Finally,the paper has made a deep research on the propagation rules of voltage sag in electric power system,summarized the changing rule of the voltage sag characteristics when voltage sag through all kinds of transformer,and carried on the Matlab to verify the correctness of the theoretical analysis and calculation.