High-frequency Harmonic Resonance Analysis And Suppression In China’s High-speed Railway

High-frequency resonance is one of the urgent problems arising from the high-speed railway development. Inability to give a reasonable explanation and effectively suppress high-frequency resonance makes traction power supply systems (TPSSs) and high-speed trains take a security risk, and the protection of travelers and the punctuality operation to be challenges. In this paper, based on the National Natural Science Foundation (Modeling of Dynamic and Nonlinear High-Speed Train Load and Harmonic Resonance Suppression Based on Optimizing its Characteristics 51207131), high-frequency resonance in high-speed railways is studied. The study focuses on high-frequency harmonic loads of a traction drive system (TDS) of a high-speed train, resonant characteristics of a coupling system comprised by a TPSS and TDSs, and suppression methods of high-freqeuncy resonance. It provides theoretical support for practically solving resonance problems, and has important theoretical and practical value.This dissertation first analyzed the pulse voltage generated by a TDS four-quadrant converter (4QC) of a high-speed train based on the mathematical sinusoidal cutting model, and deduced the high-order harmonic spectrum formula of the 4QC input current corresponding to different sampling techniques. Then taking CRH3-type train as a case, the load current spectrum was calculated by the formula, and it was compared with that obtained by the Fourier transform of the simulated and experimental results. The result verifies the correctness of the formula, and shows that the pulse voltage generated by the 4QC is the harmonic source of the high-speed train load. On this basis, the high-order harmonic spectrum formula of the input current of four 4QCs was deduced, and the current harmonic spectrums under the normal condition and the fault condition were respectively calculated and compared. The comparison result shows that the multiple technology increases the equivalent switching frequency of the converters and effectively suppresses the low-order harmonics, and that unexpected low-order harmonics generates with incorrect carrier phases. Since a TPSS and a TDS usually have high power and complex structure, field testing and experimental research go on with complex environments, great loss, low efficiency and high risk. If we can establish transient simulation models for both a TPSS and a TDS, we could reproduce high-frequency resonance in a laboratory environment with the simulation method, and research the mechanism and the suppression technology of high-frequency resonance. Therefore, this thesis describes the structures of a typical autotransformer-fed TPSS and TDSs of some typical high-speed trains, models each component of the TPSS, and presents the control strategy of the TDSs. All these are the basis for high-frequency resonance related problems. Taking the leading segment of Beijing-Shanghai high-speed railway as an example, the harmonic resonance of the high-speed railway was studied. First, based on the working mechanism of the TDS of a high-speed train, the coupling model of a traction power grid and a train for harmonic resonance analysis was established, and the mechanism and the characteristic of high-frequency resonance were analyzed based on it. The analysis demonstrates that the harmonics of the 4QC pulse voltages are the excitation sources of the resonance and the shifting of the resonant frequencies and the elimination of the resonant harmonics in the source will suppress the resonance. A combined simulation system for the autotransformer-fed traction power grid of the leading segment of Beijing-Shanghai high-speed railway and the CRH380AL-type high-speed train was established based on MATLAB / Simulnk, and it was verified by the experimental results. Then the characteristic function to identify the resonant frequency and assess the resonant intensity was proposed. Based on the characteristic function, simulation analyses of the resonance characteristics were performed when the line length varies and when the train worked in different power, different locations, and different conditions, and the results were explained with the vehicle-grid input impedance (VGII).To transfer resonant frequencies and achieve high-frequency resonance suppression, a theoretical grid input impedance calculation method was proposed for an autotransformer-fed traction power grid with multi-conductor transmission lines, and then VGII was achieved considering the reactance of vehicle-mounted transformers. Based on VGII, the sensitivity of the resonant amplitude and frequency to the critical component parameters of the given coupling system was calculated. The results show that the primary leakage of the V/X transformer makes the greatest influence, the secondary side leakage of that has a slightly less influence, the leakage of the vehicle-mounted transformer only has a little influence and the leakage of the autotransformer has nearly no influence on resonance. However, the adjustable range of the critical components is too limited to guarantee the effective resonance suppression. Further, a parameter design method for resonance suppression filters was also suggested based on the least total VGIIs. By investigating the total harmonic distortion of the pantograph voltage in the combined simulation system, it was verified that the designed filter not only achieves resonance suppression, but also gets a better performance compared with the filter designed by the traditional method.In order to eliminate resonant harmonics in the harmonic source and achieve high-frequency resonance suppression, specific harmonic elimination pulse-width modulation was introduced into multiple 4QCs, and resonant harmonic elimination pulse-width modulation (RHEPWM) was proposed. Initial switching angles of RHEPWM were decided based on carrier-shifting based sinusoidal pulse-width modulation (CSBSPWM) technology. The optimal target function was set for eliminating the specific low-order harmonics and the harmonics around the resonant frequencies simultaneously, and the optimal switching angles corresponding to all the modulation degrees were solved by the Levenberg-Marquard method. The real-time vehicle-grid combined simulation model was created with the RT-Lab simulator. The high-frequency resonance suppression ability of RHEPWM was verified by comparing the harmonic spectrum and the total harmonic distortion of the pantograph voltages and currents as CSBSPWM and RHEPWM were respectively adopted in the trains worked under different conditions (traction and braking), different powers, and different positions.