| Railway transportation, as an important means of transportation, played an irreplaceable role in promoting human life. After a development process of steam, internal combustion and electrification, electric railway has been and will continue to serve as a significant transportation system of a sustainable future. At present, current traction power supply system is dealing with more and more serious problems of crossing neutral section, power quality and overloading ability, and cannot fulfill the demand for high-speed and heavy-haul railway. Although the co-phase traction power supply system which was transformed from the current system is capable of improving the power quality, it still cannot cancel all the neutral sections to link up the whole traction network and enhance the heavy-haul and high-speed operation ability.With blossom of power electronics, the advanced traction power system based on three-phase to single-phase converter can completely cancel all the neutral sections, improve the power quality, enhance the heavy-haul and high-speed operation ability and link up the entire traction network. It will be the next generation of traction power supplying.This thesis firstly studied on the advanced traction power system based on three-phase to single-phase converter, deeply analysed the topological structure and mathematical model of three-phase rectifier and single-phase inverter of the three-phase to single phase converter, researched the control and modulation strategy applied to the advanced traction power system, and the simulation verified the feasibility and validity of the circuit structure and control strategy.Then, the theoretical derivation of harmonic character of the three-phase to single phase converter is independently analyzed when using the SPWM inverting strategy,45°&60°conversion of coordinates SVPWM rectifying strategy and the2nd ripple voltage in the DC side. The simulation of the5-level simulation model confirmed the correctness of the theoretical analysis.In addition, two types of electric locomotive loads, the AC-DC load and the AC-DC-AC load, were summarized and analyzed individually. And for specific, two typical model, the SS8AC-DC locomotive and CRH2, were reviewed in detail. The simulation model of the advanced traction power system was built up and simulated combining with the locomotive load models. The simulation results show the system could operate normally and stably.Finally, an experiment of the three-phase to single-phase converter was conducted through the FPGA chips. The experimental results demonstrate the effectiveness of the control algorithm and validate the theoretical analysis on the three-phase to single-phase converter harmonic characteristics theoretical analysis.Through the research on the harmonic characteristics of the advanced traction power supply system in this thesis, the advanced traction power supply system based on three-phase to single-phase converter is able to efficiently improve power quality of both the traction network and the public utility grid comparing to the current traction power supply system. It is just an efficient, green and next generation traction power supply system and promised huge development prospects. |
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