Research On Protection Scheme Of Flexible Passing Neutral Section In All Parallel At Traction Power Network

China's electrified railway adopts single-phase AC 27.5kV power supply system,and there must be an neutral section link.The flexible passing neutral section technology can well solve the problems of speed loss,energy consumption increase,transient over-voltage,and arc pull of pantograph when the locomotive is passing neutral section.Protective relaying system is the guarantee that the traction power supply system can supply power safely and reliably.Therefore,the application of the flexible passing neutral section device necessitates consideration of the protection of the device itself and the influence of the introduction of the device on the protection of the traction power network.This paper mainly studies the protection of all parallel traction power network with flexible passing neutral section devices.Firstly,the flexible passing neutral section technique is introduced in this paper.By analyzing the neutral section voltage generation theory and combining the basic working principle of the flexible passing neutral section device,the single-phase pulse width modulation(PWM)rectifier control principle and the power control algorithm of the inverter are respectively given in this paper.The frequency shift phase modulation and power control of the locomotive passing neutral section process are simulated on the RTDS,which verifies that the locomotive can realize the continuous power passing neutral section,and the arc-free and over-voltage.Then the application of the flexible passing neutral section device in all parallel AT traction power network is analyzed.Secondly,according to the flexible passing neutral section system and the all parallel AT traction power network,the fault analysis is performed,the non-metallic fault of the all parallel AT traction power network is theoretically deduced.The theoretical analysis of various faults such as converter fault,single-phase isolation transformer fault,neutral section short circuit fault and neutral section thunder strike is analyzed by the structure of the flexible passing neutral section device.The influence of the flexible passing neutral section device fault on the traction power network protection are taken into account.Based on the analysis of the mechanism of wrong-phase short-circuit of traction power network,combined with the characteristics of locomotive passing neutral section,the wrong-phase short-circuit of flexible passing neutral section system is analyzed.Considering the non-metallic fault of the traction power network and the influence of the power electronic transient response of the passing neutral section device on the protection of the flexible passing neutral section device,combined with the five phases of the locomotive passing neutral section,the non-metallic faults of the A and B two-phase traction power network are analyzed.The protection requirements of the system are obtained according to each type of fault.Thirdly,analyzing protective relaying system scheme of the all parallel AT traction power network,according to the protection requirements of fault analysis,the flexible passing neutral section device is equipped with instantaneous overcurrent protection,second harmonic blocking overcurrent protection,excess voltage protection,low-voltage protection,and phaseto-phase of voltage differential protection,reclosing protection,remote trip protection,etc.Aiming at the fault condition of train passing neutral section in the fault of traction power network,the function of remote trip protection based on wide-area measurement and control system to realize the synergistic protection of passing neutral section system and traction power network is studied.Based on the advantages of wide-area measurement and control system,the principle of feeding section protection,bus-bar protection and breaker failure protection of all parallel AT traction power network is studied.Finally,based on RTDS software,a flexible passing neutral section all parallel traction power network model is built,which simulates various faults in actual engineering,and the protection module is built according to various protection principles of protection scheme to verify the reliability and correctness of the action of protection setting in fault.