| With the extensive application of AC-DC-AC electric locomotives and electric multiple units(EMUs),the high-order harmonic resonance(HOHR)in traction power supply systems(TPSSs)and interference on on-board and ground signal receiving equipment caused by high-order harmonic seriously threaten the safe and stable operation of electrified railways.Based on actual engineering cases,aiming at attacking above problems,a series of research work,such as generating mechanism of high-order harmonic and HOHR,lateral transmission characteristics of high-order harmonic,harmonic impedance identification of TPSS,mechanism analysis of high-order harmonic interference on on-board track circuit reader(TCR)receiving coil and choke transformer signal winding,modeling of induced harmonic voltage and comprehensive treatment of high-order harmonic,were carried out in this thesis.The generating mechanism and characteristics of high-order harmonic were analyzed by using bilateral Fourier series,and the correctness of analysis was verified by combining HX_D1 and HX_D2 simulation models.The harmonic coupling relationship of network-train system(NTS)was established and analyzed.The mechanism of HOHR was analyzed by using single-phase distributed parameter simplified circuit.And the defect of HOHR traditional analysis methods was analyzed,i.e.,the harmonic interaction between feeding section on both sides of unbalanced traction transformer(UTT)is ignored.According to the parameters of a TPSS,the NTS simulation model was built to reproduce the HOHR.Based on field tested data,the lateral transmission phenomenon of harmonics between the feeding section on both sides of the V/v UTT was analyzed,the key to identify the harmonic impedance of the TPSS is the total harmonic impedance of traction transformer port.Based on the harmonic lateral transmission mechanism,the harmonic coupling model of a TPSS was established,and the complex independent component analysis(CICA)was utilized to decouple the model yielding separate harmonic impedance of system side and load side.The total harmonic impedance seen from a UTT secondary side was obtained through paralleling the two sides.Simulation results verified that the proposed method,compared to several more conventional methods,is with greater applicability in a wide frequency range when the impedance ratio of the two sides and the background harmonics are uncertain.The identification results combined a low-power experimental platform and the field tested data validated that the proposed method can accurately find the resonant frequency of an actual TPSS.According to the field tested data and the structure of the switch section without track circuit codes,the generating mechanism of the unbalanced traction current,unbalanced traction harmonic interference on the on-board TCR receiving coil and the voltage difference fluctuation of rail surface were analyzed.The magnetic flux of the on-board TCR receiving coil was calculated,showing that the effective range of the traction harmonic current on the TCR receiving coil is determined to be 3 meters.The induced harmonic voltage models of the TCR receiving coil and the choke transformer signal winding were established,showing that the induced harmonic voltage amplitude of the TCR receiving coil and the traction harmonic current amplitude of the rail meet the linear relationship(about 1.26 times),the induced harmonic voltage phase of the TCR receiving coil lags the phase of traction harmonic current of the rail byπ2,and the induced harmonic voltage of the choke transformer signal winding is linearly related to the voltage difference of rail surface.The correctness of the theoretical research was comprehensively verified by combining the simulation results and the field tested data.The comprehensive treatment technology of high-order harmonic was studied for HOHR and signal interference.A passive second-order high-pass filter(2-HPF)was designed,whose parameters were optimized through analysis of simulations.Tests on the effect of the 2-HPF on HOHR and signal interference were conducted at Ningke line and Guangzhou east railway station respectively:for Ningke line,the 19th to 25th harmonics were filtered out when 2-HPF was applied;for Guangzhou east railway station,the 2000Hz traction harmonics in lead wire of the choke transformer were significantly reduced,and the filtering effect of the 40Ωresistance filter was better than that of the 80Ωresistance filter.Based on railway signal system,by studying the influence of traction current unbalance coefficient and choke transformer excitation current on traction harmonic current interference signal,the protection measures were given through optimizing the track structure and signal equipment parameters. |
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