Research On Power Supply Characteristics Of All-parallel AT Traction System For High-speed Railway

Along with the development of China high-speed railway Construction, the train speed and traction current are steadily picking up. High-speed train needs high power, especially with the increase of traveling density, demands for better and more reliable traction power supply system to provide the required load of Electric Multiple Unit(EMU) are increasing. Direct power feeding system and Auto-transformer (AT) feeding system are satisfied with the requirements, but AT feeding system is more suitable for high-speed Railway. For instance, it can offer an additional level of voltage and electromagnetic compatibility. It can also reduce the complexity of the catenary circuit and the engineering investment. With the adoption of integrated grounding technology, the traction power supply system is more complex. The theoretical analysis of the AT power supply system for the preliminary design of the entire system, research and rational allocation is critical, so the analysis of its power supply characteristics have important theoretical significance and applied value. At the same time, by the study of its power supply features, the running state of traction network including voltage, current and rules can be obtained. With this, it can be further obtained the setting-calculation method of various protections and accurate setting formula for microprocessor-based power relay.With the adoption of integrated grounding technology, the rail, protection wire and ground wire connected to the integrated grounding system many times by lateral link. In order to analyze the current distribution of the whole system, the self-impedance and mutual-impedance of each conductor need to be calculated respectively. Then, through proper simplification, we can obtain the simplified traction network model. Detailed theoretical derivation can derive the exact current distribution and characteristics of traction network. In practical application, for the fast analysis of the power supply characteristics, the normal running state or short-circuit current is divided into several loop current using loop analysis in this paper. By utilizing the principle of superposition and the independent loop current for normal operation and fault current, the distribution of the traction network can be obtained. This loop division method for rapid analysis according to actual situation on the failure can determine the type of fault, and thus can verify the criterion and the configuration of the protection and fault location devices. This analysis method will be affected by the impact of the actual system parameters. On the basis of the AT equivalent circuit, considering AT leakage reactance, the accuracy of the loop analysis method is further improved.Combined with the equivalent circuit of the traction transformers, the influence of the traction transformer secondary winding leakage reactance on the traction network current distribution in the actual situation is also analyzed. On the basis of theoretical analysis, we make use of the powerful tool PSCAD/EMTDC to make the model of all-parallel AT power supply system. The influence of the protection wire, ground wire and lateral link are considered. Simulation results show that the established simulation model is consistent with the actual situation of the all-paralleled AT power supply system, the resulting waveform can also verify the correctness of the circuit analysis. Finally, take the Beijing-Shanghai high-speed railway power supply system as the research object, combining the actual data of artificial short-circuit test, several typical short-circuit fault current distribution has been analyzed, and validates the correctness of the loop analysis method.