Study On Digital Modeling And Simulation For Power Supply System Of High-Speed Railway

High-speed railway is rapidly developed in China, and traction power supply system is one important subsystem of high-speed railway, whoes safe, reliable and efficient operation is an important guarantee for the reliability of operation of high-speed railway. Digital simulation for traction power supply system is an important basis for design and scientific research of the system, having important theoretical and applied value. Effective power flow calculation of traction eletric network and harmonic analysis method are the key issues need to be researched for the digital simulation. Power flow calculation of traction eletric network and harmonic propagation etc. are focused researched.Auto-transformer power feeding (AT-fed) with many advantages is adopted in high-speed railway, but because of its specialized network structure, the analysis and calculation can be very complicated. A novel algorithm improved on the equivalent circuit of AT-fed system is researched for power flow problem of traction electric network. In this algorithm locomotives are considered as constant power model and the leakage impedance of ATs are taken into account also. The calculation with multiple trains or single train running can be carried out by the principle of superposition and Newton iterative. Moreover the leakage impedance of ATs' influence on the traction electric network can be simulated according to the improved algorithm. Train voltages and current are calculated with both single train running and multiple trains running; Voltage distributions of traction electric network are simulated. Then the results of simulating shows that the algorithm developed in this paper has a large speed of convergence and a reliable result, can solve the power flow problem of AT-fed efficiently regardless of the number of trains, the position of trains.Appropriate voltage level of traction eletric network is a necessary guarantee for high-speed train running. The ability of improving the train voltage by heightening the return feeder voltage rank is analyzed. Train voltages with both single train running and multiple trains running, current distributions of traction electric network and the average effective voltage of trains were simulated, when the return feeder voltage was 27.5kV and 55kV respectively. Results of simulation show that when the return feeder voltage is heightened, the voltage loss of traction electric network is reduced and train voltage is increased regardless of the number and position of trains. Train voltage increased by 4.29kV averagely with four trains running. It indicates that train votagle is improved with return feeder voltage heightened.With the wide application of AC-DC-AC system by high-speed train, the low-order harmonics are decreased, but a lot of high-order harmonic are contained in the traction power supply system. The harmonic current amplification may exist and the traction electric network can experience parallel resonance at a specific frequency. Traction electric network is modeled by the equivalent reduction method of multiconductor transmission line to calculate the unit length impedance and admittance of the traction electric network and analyze harmonic propagation. Harmonic current amplification is simulated with the length of traction electric network, the location of train changed and the different locations of traction electric network. It indicates that the resonance frequency does not depend on the location of the train, the farther the train is from the substation, the higer the amplification of the harmonic current is, and the longer the traction electric network is, the lower the resonance frequency is.Simulation models data of traction power system can be applied in traction power system analysis conveniently. A simulation models data of traction power system and train model are created based on matlab/simulink, a simulation system for traction power system is established using the models data. Verification results shows that simulation system is of applicability and universal. Based on this simulation model, train harmonics characteristic is analyzed, results show that the harmonic components decrease as the power level increases, and increases as the voltage increases. Harmonic current amplification and resonance are simulated, the results verify the conclusion made according to the the equivalent reduction method. The suppression measures of harmonic current amplification are discussed. The suppressive effect is simulated with the length of traction electric network and the location of train changed. Results show that the filtering device installed has a good ability of harmonic suppression.