Research Of Ground Automatic Convert Technology

In order to reduce the influence of the electrified railway on the negative sequence of the power grid,the electrified railway usually adopts the phase changing power supply scheme,and there is an electric division phase area every 20-30 km on the contact network.The existence of electric phase separation will not only cause the speed loss of the locomotive,but also produce serious electromagnetic transient process in the phase separation area,which brings serious threat to the locomotive and power supply system.The same phase power supply technology can better solve the problem of electric phase separation at the exit of the locomotive through the substation,so it is still worth studying how to make the locomotive safely and stably through the electric division phase in the section post.This paper mainly introduces and analyzes the automatic passing neutral section.Generally,the phase of the two sides of the section post of the traction power supply system is the same,so in view of the problem of overvoltage and overcurrent in the traditional ground control automatic over phase separation scheme,this paper studies a new type of uninterrupted phase separation scheme for the new partition,which can effectively solve the problem of the locomotive passing neutral section of the section post.The new scheme uses thyristor instead of vacuum load switch,and paralleled damping device on both sides of the thyristor.It not only solves the shortcoming of short life of the mechanical switch,but also ensures that the locomotive has no transient electric phase through the disconnected angle and closed angle of the control switch.And the damping device can restrain the transient overvoltage caused by the control of the control of the thyristor.The paper first introduces the transient process of the traditional ground control automatic over phase scheme and analyzes the intercepting overvoltage and switching overvoltage during passing neutral section.The mathematical expression of neutral section voltage of each process is derived.The influence factors of transient overvoltage are summarized.The phenomenon of magnetizing inrush in locomotive main transformer is analyzed.Then the principle of the new scheme is introduced,and the transient process of locomotive is analyzed theoretically based on the new scheme.The neutral section voltage is calculated by numerical method.The relationship between transient overvoltage and switching angle and size of damping device is summarized.The restraint law of damping device on overvoltage is analyzed during passing neutral section.The new damping device,thyristor and its equalizing absorption circuit are designed.Finally,the simulation model of locomotive and traction power supply system isestablished by using Matlab/Simulink software,and the simulation of locomotive excessive phase is carried out.Through the normal working mode,the standby mode and the simulation results of the failure state,it can be seen that under the proposed parameters,the locomotive can be continuously supplied and without the transient process under the normal working mode during passing neutral section.Under other working modes or fault states,transient overvoltages can be well suppressed,and locomotives can be safely and stably through electrical separation.