Fault Mechanism And Suppression Strategy Of False Neutral Section In DN Power Supply Traction’s Network

With the rapid development of China ’s high-speed rail industry,the power and number of high-speed EMUs have increased,resulting in overvoltage and overheating ablation of contact line in false neutral section of DN power supply traction’s network,which has a serious impact on the normal operation of EMUs and traction network equipment.This paper studies the above problems,the specific work is as follows:Firstly,the physical and mathematical models of DN power supply power supply system,traction network false neutral section,EMU electrical primary system and EMU passing traction network false neutral section are established.the correctness of the mathematical model is verified by simulation experiments.Secondly,the process of EMU passing traction network false neutral section is studied,which is divided into four stages.Two mathematical models are established for the overvoltage of pantograph and the local temperature rise of contact line.The study of the model shows that the causes of EMU passing traction network false neutral section include pantograph overvoltage and local temperature rise of contact line.When the local temperature rise of the contact line is too large in the load difference between the left and right power supply arms,the local overheating of the contact line causes local ablation.Then,for the overvoltage and the local temperature rise of the contact line,the simulation verification is carried out in this thesis.The simulation results show that there is overvoltage phenomenon,but the amplitude is small.When the load difference between the left and right power supply arms increases,the local temperature of the contact line increases significantly.When the unilateral power supply arm runs four columns of 200km/h EMUs,one column of which passes the traction network,the local temperature of the contact line is too high to cause the contact line ablation,which verifies the correctness of the theoretical analysis.Finally,aiming at the ablation problem of contact line in EMU passing traction network false neutral section,two suppression strategies are proposed.The first is to reduce the contact line temperature below the protection temperature by reducing the EMUs speed,and the correctness of the scheme is verified by simulation.The second is to transform the false neutral section zone of the traction network into the neutral section structure of the power electronic switch,which can effectively eliminate the original overvoltage problem and the overheating problem of the contact line,and the correctness of the scheme is verified by simulation.The research results of this paper can provide reference for the safe operation of EMUs in the false neutral section zone and the technical transformation of the false neutral section zone.