Low-Frequency Instability Induced by Hopf Bifurcation in a Single-Phase Converter Connected to Non-Ideal Power Grid

With the high-density operation of China Railways High-speed (CRH) series vehicles in railways, a large number of power electronic converters are connected to the traction network. Due to the nonlinear characteristics of power electronic converter, it is easy to cause the low-frequency oscillation (LFO) in the single-phase vehicle-grid system of high-speed railways when the converter is connected to a non-ideal power grid. In order to solve this problem, the time domain nonlinear dynamic average model is proposed in this paper. Given Jacobian method to probe into the low-frequency stability of single-phase vehicle-grid system based on Hopf bifurcation, the characteristics and applicability of this method is summarized. The effects of electrical and control parameters can be analyzed with this model. In addition, with the emergence of LFO, the stability boundary leading to catastrophic bifurcation is discussed in detail. In the end, theoretical analysis results are verified by simulations and hardware-in-the-loop (HIL) platform.