Research On Electromagnetic Transient For Passing Neutral Section Without Power Interruption Of Electrified Railway

At present,the on-board neutral-section passing method is widely used in China.But it has some drawbacks such as it needs frequent operation the main breaker of locomotive which will causes the speed loss and difficult to reach the expectation.The technology of passing neutral section with neutral section and locomotives charged is the future development trend.This method is switched by the ground sensor with the switch so that the locomotive is passing neutral section without power interruption.But throughout the process,the locomotive will switch from one stable state to another,accompanied by a transient proeess with overvoltage and overcurrent,which will threatens the safe operation of the traction net and the electric locomotive in severe cases,and also restricts the application of this method in China.Therefore,this thesis studies the electromagnetic transient of the passing neutral section process,which plays a certain role in promoting and referencing the development of ground automatic passing neutral section technology.Fisrtly,this thesis introduces the technology of auto-passing neutral section,including different structures and schemes,and compares the advantages and disadvantages of three kinds of schemes in detail.The transient processese of passing neutral secion without power interruption are divided in detail in the first.After the dynamic circuit analysis of the transient process is carried out respectively,the generation mechanism of its overvoltage and inrush current is expounded.The mathematical model is established and the mathematical expression of neutral section overvoltage and inrush current is deduced.At the same time,the reasonable time interval of switch separation under the principle of passing neutral section with non-blocking traction pulse of locomotive is studied.Based on Matlab/Simulink platform,a multi-conductor chain traction network model,electric locomotive model and neutral section system model with switch control logic are established and realized the dynamic simulation of locomotive passing neutral section.All transient processes are studied in detail by using the built model.The level and probability in different transient processees are investigated by combining the simulation data.The influence of transformer wiring mode and positon of neutral section on overvoltage amplitude is analyzed.In addition,according to the inrush current,the influence degree of acting angle,neutral section position,residual magnetism size,locomotive transfonner parameter and power supply voltage fluctuation on excitation inrush current is studied.Finally,aiming at the problem of overvoltage and inrush current in passing neutral section without power interruption system,this thsis puts forward the optimization strategy of combining switching action time with installation suppression device.Eliminate the generation of inrush current during closing by selecting the moment of switch closing.Using electronic switches to suppress the overvoltage in the second process.Installing the RC absorver in neutral section,MOA arrester in locomotive and closing resistances in overlapping section to suppress the overvoltage of switch closing.The mechanism of three measures is analyzed,and the value of its parameters is discussed,and the inhibition effect under the optimal parameters is verified by simulation.In addition.In addition,three kinds of measures are compared in different aspects,and based on the actual project,the optimization strategy is selected.