| Traction power supply system and power train constitute train-network coupling system,good matching relationship of train-network coupling system is the key to ensure the traction power supply system power quality and safety, stability, continuous operation of electric trains. During the operation of electric train, the train-network coupling system appears a variety of complex abnormal electrical processes due to electrical mismatch, which seriously affecting the reliability and security of traction power supply system and operating trains.Three abnormal electrical processes about high-order harmonic resonance phenomenon,passing section over-voltage phenomenon, the inrush current and sympathetic inrush phenomenon of electric trains were studied which exist in train-traction network coupling system, and the improvement schemes were proposed. An improvement scheme is proposed.The main research contents and achievements are as follows:(1) The harmonic resonance generation mechanism of the traction power supply system was analyzed and the impedance characteristics of the traction power supply system and the transmission characteristics of the high harmonic currents in the traction power supply system are studied by constructing the simulation model of the train-traction network coupling system.The resonant characteristic of the simplified model of the traction power supply system was studied by the modal analysis real modal analysis method.The system’s complex admittance matrix was converted toa real type admittance matrix, and the key eigenvalues, eigenvectors and resonant frequencies of the system were obtained. By means of the key eigenvectors, the results show that the proposed method is as well as the existing modal analysis method. The harmonic model of impedance-matching balanced transformer was established to analyze the permeability characteristics of high-order harmonics for public grid high-voltage three-phase system,and the harmonic model of the inverse Scott transformer was established to analyze the permeability characteristics of high-order harmonics for the low-voltage three-phase system of traction substation. The traction substation with severe harmonic distortion was measured, and the harmonic measured data were analyzed and compared with those resulted from harmonic models of impedancematching balanced transformer and inverse Scott transformer. The results show that the high-order harmonics less penetrate into the high-voltage three-phase system,but significantly into the low voltage threephase system of traction substation.(2) Though building the mathematical model and simulation model of a new bilateral power supply system,the resonance mechanism, impedance-frequency characteristic and harmonic current transmission characteristic of the new-type bilateral power supply system were studied. Based on the simulation model of the new-type, long distance and non-phase separation cable power supply system, the impedance frequency characteristics at different locations of the traction network were analyzed. The characteristics of two kinds of new traction power supply modes were evaluated through mathematical modeling and simulation analysis.(3) The equivalent model and simulation model of transient processes in the automatic passing neutral section of on-board and the ground were established respectively, and the generation mechanism, characteristic, influencing factors of transient overvoltage in two kinds of automatic passing phase insulator were analyzed. The results show that the maximum overvoltage occurs when the peak value of the voltage and the neutral section is directly connected with the catenary, the higher the voltage phase difference between the two ends of neutral section, the higher the maximum overvoltage amplitude is. Under the same conditions of voltage phase difference, the maximum overvoltage at the outlet of the traction substation is higher than that in section post, and the duration is longer and the oscillation is stronger. The amplitude, duration of the overvoltage and the harm to the system of the traction substation are much higher than that of the section post.(4) The equivalent circuit model and the simulation model of traction power supply system when the train transformer close were built, the key factors affecting the train inrush current were studied, including the locomotive breaker’s closing phase,space position,transformer remanence, transformer internal parameters and multiple train closing. The influence of inrush current of electric Locomotive transformer on the system was analyzed. In order to research the mechanism of sympathetic inrush occurs in electric locomotive transformer, the mathematical model include of traction power supply system, closing locomotive and operating locomotive was established, and the influencing factors of the sympathetic inrush were analyzed. The results show that, the inrush current not only can cause the voltage of the traction network and the voltage of the secondary side of the transformer to fall and serious distortion, but also cause the sympathetic inrush of the operating locomotive. The impact of the size is related to the magnitude of the inrush current, train position and transformer parameters and so on.(5) The impedance-frequency characteristic, transient characteristic, filtering characteristics and resonance suppression characteristic of the new wave-trap High-Pass Filter(WHPF)were studied, the results show that, the WHPF exhibits high impedance at the power frequency and does not exchange the reactive power with the system. It can effectively filter the high-frequency harmonic currents and shift the first resonance frequency of the traction power supply system to a higher frequency band to avoid the power train harmonic current frequency range, thereby suppressing traction network resonance. A filtering scheme based on Y-type WHPF was proposed to decrease the too high contents of high order harmonics in the low-voltage three-phase system of traction substation, and a set of engineering test device was developed. The operation results show that the device can effectively filter the harmonic voltage, and the power quality can be improved significantly, which solves the the electrical equipment burning problems in the subsition.(6) The study is focused on the new type of co-phase power supply scheme, which the single phase transformer is used in the traction substation in this design. When the negative sequence exceeds the standard, the neutral section at the exit of the traction substation can be cancelled by using the combined co-phase power supply system. The bilateral power supply technology can be applied at the section post which the neutral section is also cancelled.Benefit from the bilateral power supply technology, a few hundred kilometers of no neutral section, continuous uninterrupted power supply is realized, and the interruption and transient process of power supply because of the electrical sectioning is also avoided. As a result, the various problems brought about by the electrical sectioning are solved.When the bilateral power supply is not allowed by the power system, a new automatic passing neutral section scheme was proposed, which is suitable for the section post. The structure and working principle were introduced, and the simulation of the process of the train with continuous electric current passing through the neutral section was analyzed.According to the simulation results, it could be seen that the train with continuous electric current passing through the electrical sectioning can be realized by using the thyristor switch,and the series resistance of the system can restrain the transient process of the equilibrium current and the abnormal condition.In this paper, the generation mechanism and influencing factors of electrical transient phenomena such as harmonic resonance, excessive phase overvoltage and inrush current and synergic inrush current appear in the car- net coupling system are analyzed,The effective control measures are put forward to realize the good electric coupling relationship between the traction power supply system and electric trains, which provide the support for the safe operation and maintenance of the electrified railway. |
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