Research On The Grounding System Applicability Of EMUs For Sichuan-Tibet Railway

With the rapid growth of China’s economy,high-speed railways have developed rapidly.In terms of the production and operation of EMUs,China has introduced and digested advanced foreign technology,which has significantly improved the reliability of EMU operation.At present,there are different technical routes for the grounding system of EMUs,which exhibit different performances in practice,and the grounding system’s applicable conditions and parameter settings are worthy of further discussion.As a major national engineering project,the Sichuan-Tibet Railway is of great significance to the economic development of Tibet and even the southwestern region.Taking into account the long ramp and the possible bilateral traction power supply method,the situation of EMU traction return current is more complicated,and further study is needed to analyze its applicability.Aiming at the EMU grounding system,this thesis analyzes the law of the grounding return current,which lays a foundation for exploring the problems of the EMU grounding current,and also provides a basis for optimizing the grounding system in the future.First,the grounding system structure and key technical issues of the existing EMUs of electrified railways was summarized,and then the main factors that affect the regularity and performance of grounding return current was deeply analyzed.Then,in view of the uncertainty of the grounding return current of the EMUs,a dynamic simulation method combining the main circuit modeling and the random modeling of the traction load was proposed.By derivating circuit and modeling main circuit respectively,the characteristics of typical EMU grounding return current were analyzed.In order to obtain the dynamic change characteristics of the grounding current,the load datas of the EMUs from the traction calculation method were obtained,and then this datas were imported into EMU grounding system through an interface.Furthermore,the influence of the local circuit represented by the boosting wire on the grounding return current was studied,which provided a technical means for analyzing the problems caused by circuit defects.This thesis uses the grounding return current data from test and BP neural network optimized by genetic algorithm to build a forecast model of grounding return current.The magnitude of the grounding current was predicted by the primary current of the traction transformer and the position of the EMUs in the boasting wire section.Forecast results were in line with expectationsAiming at the special power supply mode of the Sichuan-Tibet line,this thesis analyzes the impedance and network loss of the bilateral power supply system,and simulates and analyzes the magnitude of the equalizing current under different load currents and transformer ratios.Finally,this thesis simulates the performance of the EMU grounding system in the bilateral power supply mode on the Simulink platform.