Modeling On Traction Power Supply System Of Metro And Analysis Its Influence To The Power Network

With the rapid rail transit subway construction, on the one hand promote the development of the city, on the other hand promote the social and economic development, The influence of metro traction power supply brought to the public power grid is concerned highly. The characteristics of Metro DC traction system is that, strong fluctuations, rich in harmonic content, and large cable capacitive current. In addition, the metro system is among the densely populated city, if the accident happens, there is great impact on the public power grid supply and social stability in entire city. taking preventive measures, it required to make systematic analysis and appropriate preventive measures in advance to reduce the current harmonics, resonance over-voltage, cable capacitive current and stray current hazards on the power system to improve power grid power quality,reliability and stability, and eliminate the potential risk of power grid of causing the accident. Therefore, this thesis is researching for the effect of power supply system of metro to the public grid by simulation with examples.24 pulse rectifier and subway electric locomotive simulation model is constructed in Matlab/simulink environment. The harmonics of the DC system, transformer winding and AC side is analysed. The results show that the simulation system can be truely reflecting the actual rectifier and locomotive work by running.Taking the analysis the example of putting into operation of Xi'an Metro, and application of practical design parameters, the harmonic quantitative is analysed when load operation during the day and low operation during the night by the connecting simulation model, that contains metro traction power supply system and power netting,then evaluates the harmonic hazards of different load. based on PCC point harmonic standards and operational characteristics of metro, this paper presents a specific harmonic control project, then shows the correctness of the program by simulation results. Simulation shows, the installation of passive filters on 35kV high-voltage bus can achieves better results for harmonic control.The capacitive current of cable is calculated in frequency and single-phase fault condition. the PCC power factor impulsion is analysed along with traction load change. Using a resonant circuit equivalence principle, the relationship between the cable capacitive current and the resonance is researched. calculated the capability of line terminal parallel reactors. the method of installing parallel reactor can inhibit the production of resonance over-voltage. The voltage fluctuation and power quality are analysed along with the change of load and short-circuit capacity of the system by simulation model.Finally, metro stray current equivalent circuit is established by CDEGS software, using Xi'an design parameters, including rail model, drainage net model, underground transmission cable model, the thesis have resarched the distribution of rail potential,stray current and the potential of buried cable shield, and stray current preservation method is advanced.This thesis provides theoretical basis for metro traction system supply system connecting to power network. Meanwhile, provides a good foundation for the planning for metro construction and design.