| Traction power supply system of Nanjing metro is thoroughly studied in the dissertation. Comparing to other load kinds, metro load has its special characteristic. On one hand, metro load becomes very fluctuant as time pass by. On the other hand, since traction power supply network is a AC-DC network, its running modes are complicated.First, based on the analysis of the working conditions of metro trains and the vehicle traction calculation theory, the dynamic model of metro trains is built. Also a software which has good-interface and running environment is programmed.Second, with the result of traction calculation of metro system and dynamic-topology technology, complicated and variant network can be changed into a invariant, linear and fixed-topology network. As a result, the mathematical model of DC traction power supply network is constructed. AC network with DC network are also combined in a AC-DC iterative power flow calculation program through the detailed model of 24-pulse bridge rectifier. Besides, the equivalent model of the external power network of metro system is researched, and the impact and influence of the metro load to external power network is analyzed.Third, based on the results of fundamental power flow calculation, the harmonic mathematical model of traction power supply network of metro system is created. The skin effect is also under consideration during the model-creating process. Moreover, injection of harmonic current to the external network is calculated.Furthermore, mathematical model of 24-pulse bridge rectifier, the core of the traction power supply simulation and calculation, is presented. The mechanism of interactions between the four six-pulse bridges is discussed. As the load current varies from no-load to the complete short-circuit value, thirteen modes of operation are recognized. Equations describing the mean output voltage and various operating angles of the rectifier circuit are given in terms of a reactance factor.According to the metro load model that is presented in the dissertation, a set of metro load calculation and simulation software is programmed. The software is already adopted by the Jiangsu Electric Power Test & Research Insititue(JSEPTRI), and achieved good effects. Through the comparation of simulation data and pratical data, it is proved that the mathematical model is able to reflect the change of metro load.Finally, future work and expectancy fruits are pointed out according to the understanding of the research problems and a summary of this dissertation.
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