The stability research of high-speed railway EMUs and traction network cascade system

Due to the voltage low-frequency oscillation (LFO) of high-speed railway traction network and Electric Multiple Units (EMUs) coupling system, many EMUs in different EMU depots appear the traction blockade. First, the mathematical model and small-signal analysis model of EMUs-traction network cascade system (ETNCS) are built. Second, considering Auto-transformer (AT) leakage reactance, traction network impedance and distributed capacitance, the output source module resistance of ETNCS is calculated based on the generalized symmetrical components method (GSCM). With the generalized Nyquist criterion and Bode diagram, the system stability is analyzed and the quantitative indicators of system impedance matching are given. Third, the theoretical analysis and the feasibility of inhibition for LFO are verified using Matlab/simulink simulation platform. Finally, the oscillation signals are respectively analyzed by Fast Fourier Transform (FFT). The proposed stability analysis could be used not only to understand the LFO clearly, but also provide technical reference for the stable operation of high-speed railway¹.