Modeling And Power Quality Simuliation Of AT Traction Power Supply System For Railways

Power plays an important role in the social life, and high speed and heavy haul railway undertakes the main carrying task of modern life, electrified railway is very popular for the advantage of lower energy consumption and huger capacity. With the rapid development of industrial technology, the power quality pollution which caused by the impact of the high speed and heavy haul railway on the grid is becoming more and more obvious. As the energy core of the railway transportation, the accurate and effective analysis of the traction power supply system has the great significance on enhancing the comprehensive power quality of the power supply system.In this thesis, the first part is about the theoretical analysis of the connection form on the traction transformer; and then the authors will establish a four wire system by equivalently simplifying the traction network which composed by the multi conductor transmission according to the Carson Theory; construct the model of the equivalent harmonic source according to the nonlinear load characteristics of electric locomotive at the same time; and build a comprehensive simulation model of traction power supply system on the AT power supply mode by MATLAB.Based on the integrated simulation model, the author will give a theoretical simulation analysis on the factors which affects the quality system of electric directly. The simulation model is applied by analyzing the distribution of harmonic current and the voltage of the traction network in different conditions; magnetizing inrush current of the transformer and analyzing the distortion rate of the power system. The results show that the greater distortion of harmonic current when the locomotive is farther to substation. Harmonic is transmissed from the locomotive location to the distance,and it is not obvious that the effect of lengths of traction network on the harmonic distortion. The minimum voltage in the traction network is the location of load.The voltage fluctuation less than5%is allowed when two trains running at the same section. The excitation of transformer will be greater than the rated current when the closing angle is0°or the transformers have larger capacity.However,remanence have a little effect on the size of the inrush current.The unbalance degree of current in three-phase YNd11connection transformer is greater than Scott transformer.The results of the analysis of the transient simulation signal,analyzed by fast fourier transform and Hilbert-huang transform respectibely, indicates that Hilbert-huang transform can pinpoint the start and end time and frequency variations of signal disturbance,which have a very superior performance on the analysis of nonstationary signals in ectrified railwayFinally, a summary analysis of the development trend of power quality management is made and the electrified railway system simulation modelest is established by using SVG to filter out harmonics.SVG results show that the system can filter out98%of harmonics; SVC,one of TCR type, implements hardware simulation which has a better effect on filtering out3,5harmonics.We also compare the usefulness and advantages and disadvantages of the two methods, which contribute to the security and stability of railway transport capacity and providing a reference on compensation governance programs.