Mechanism on Voltage Low Frequency Oscillation of High-Speed Railway Traction Network and EMU Coupling System

Traction blockades in many EMU in different place appear due to voltage Low Frequency Oscillation in High-speed Railway Traction Network and EMU Coupling System. The research of the mechanism of this phenomenon is currently still in its early stages. In this paper, firstly, the state equations and the transient energy balance equation of traction network and EMU coupled system are derived. Secondly, the open-loop stability of the traction network and EMU system is determined and the factors causing voltage oscillations are analyzed with the small gain theorem. Thirdly, the all-parallel connected autotransformer traction supply model is precisely built using a 10-conductor chain circuit and CRH3 EMU electrical model is established based on the transient current control. On this basis, the interconnected system of the traction network and EMU is implemented, and voltage oscillation phenomenon is reproduced. In addition, voltage oscillation is suppressed with adjusting EMU controller parameters and load distribution. By analyzing the PI controller parameter adjustment, it is found out that this suppression measure has its limitations. Finally, the frequency of the oscillating voltage is accurately extracted by using FFT method and Prony method.