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High-Frequency Instability Evaluation in Railway System Considering Frequency-Coupling Dynamics

Over the past years, the high-frequency instability issues, beyond half the switching frequency, have been aroused frequently in several railway systems. The averaging model has been continuously developed for exploring the origin of small-signal instability issue. However, since the inherent sampling nature has been neglected by averaging process, the small-signal averaging model is a single-frequency model and omits frequency-coupling components. Hence, by considering the high-frequency coupling components, this paper proposes a 2-order multi-frequency matrix model that can analyze the instability issue at high frequency range. Moreover, the frequency scan result is obtained, which denotes that the multi-frequency model can accurately evaluate the input admittance of the locomotive beyond half the switching frequency, and further analyze the high-frequency instability issue. Hardware-in-the -loop (HIL) experimental results validate the theoretical analysis.