Harmonic Propagation And Resonance Analysis For Traction Power Supply System Of High-Speed Railway

With the rapid development and adoption of large-capacitor, high-speed, high-density time-varying nonlinear loads (NLLs)--high-speed trains (HSTs), the power quality of trac-tion power supply system (TPSS) are getting more serious. In order to make the HSTs lighter and more reliable, LC or LCL high-pass filters, which have been installed to mitigate high-order harmonics, are not installed in most of China HSTs. Therefore, harmonic problem is a concern, because of the significant adverse impacts they have on the tractive drive system of the train and power quality of the utility system. The harmful harmonic distortions and their studies in high-speed railways (HSRs) are mainly characterized by:(1) rich high-order char-acteristic harmonics injected from the 4-quarter converter (4QC) of the HST; (2) the parallel resonance happened between distributed capacitor of the tractive conductor and inductive supply system. (3) dynamic variations in harmonic distortions caused by dynamic operation NLLs of HSTs. The harmonics generated from such high-speed trains inject into traction network and distort the power system. These two causes have resulted in the concerns about harmonic modeling, harmonic power flow, harmonic resonance and mitigation of the cou-pling system of HST and TPSS.Therefore, this thesis focused on the theorical studies dealing with the harmonic-related issues for the TPSS of China high-speed railway (HSR) systems. Especially, the "fundamen-tal/harmonic modeling-harmonic power flow-harmonic resonance-harmonic mitigate" under dynamic operations. The thesis consists of the following chapters.(1) Fundamental/harmonic modeling of HST-TPSS coupling system:The thesis has built the nodal admittance matrix model for V/x type and Scott-transformer with secondary midpoint drawn-out type transformers. According to different constructures and materials of tractive conductors, the thesis has calculated the equivalent radius and skin depth of three-type conductors, respectively. The calculated impedance and capacitance matrixes of the lines take account the skin-effect. Meanwhile, the thesis also described the modeling of lines under viaducts, and Tunnel geographical surfaces. With considering the long-line effect, the nodal admittance matrix for a MTL was presented to represent such tractive lines. Moreover, the whole system modeling——"utility system-tractive transformer-tractive lines-AT sub-station-section post" was then approved. The Norton equivalent circuit was adopted to rep-resent the HSTs in frequency-domain. The parameters of Norton model for CRH trains are computed on the field test and simulation. Therefore, the train-TPSS system uniform model was identified.(2) Time-varying numbers, positions of HSTs running on the tracks, which results in the serious harmonic distortions of the whole system. The train timetable and operation pa-rameters of HSTs are used here to determine each operation conditons-e.g. "starting-acceleration zone-steady zone-braking"-of the entire operation period and then to de-termine the in/out-put power in each operation zone. The measurement data is employed to correct the magnitudes and angles of fundamental and harmonic components. The dynamic fundamental/harmonic power flow method was proposed here to calculate the voltage pro- files at each time step. The 95% maximum index was adopted to evaluate the power quality issues in both power system and TPSS caused by the HSTs.(3) As for harmonic resonance analysis, the thesis had built the the simulated model for train-TPSS system and obtained the the harmonic propagation and harmonic amplification. This information also can be used to determine the harmonic resonance of the simulation system. Moreover, resonance mode assess method is described here and used to analyze the harmonic resonance infortion of the TPSS. The method can further calculate the effects of coupling levels of right and left supply phases, catenary length, the system capacitor, trans-former impedance, AT leakage impedance and HST impedance on the harmonic resonance. And we also assessed the characteristics and key impactors for harmonic resonance in TPSS.(4) As for resonance sensitivity study, the thesis adopted the resonance sensitive indices to find the resonance information involved in the system with considering the problems of frequency scan method. The complex admittance matrix based resonance sensitive indices are presented and used to measure the sensitive levels of different electric parameters with respect to resonance (magnitude and frequency). After searching the most sensitive pareameters, the thesis proposed the idea of resonance frequency shift based on Newton-Raphson method.(5) As for harmonic mitigation, after comparing the typical current spectrum of the HST and the voltage spectrum of the measured busbar, the harmonic problems in TPSS can be determined as the harmonic resonance and characteristic harmonic. In order to address such problems, the thesis has analyzed the resonance-and high-frequency-damping perfor-mance and then designed the filtering unit and its parameters. The results of the dynamic harmonic power flow illustrate that the C-type filter unit can be effective in degrading the resonance amplification and the distortions of high-order harmonics. And it achieved the good filtering performance.The thesis has developed the fundamental/harmonic model for TPSS, dynamic har-monic power flow and assessment method, harmonic resonance analysis, and harmonic miti-gation scheme. Both theorical analysis and measurement results made a good agree.The measured data is also used to determine the parameters of the HST. The proposed methods in this thesis can improve the power quality of TPSS and degrade the problems caused by har-monic distortions.