An Active Oscillation Compensation Method to Mitigate High-Frequency Harmonic Instability and Low-Frequency Oscillation in Railway Traction Power Supply System

This paper investigates the high-frequency harmonic instability (HHI) and low-frequency oscillation (LFO) phenomena in high-speed railways, and proposes an active oscillation compensation method to mitigate these HHI and LFO. Such mitigation method introduces the input voltage oscillating components of grid side to the control loop of the grid-side converter, which helps to mitigate the voltage oscillation variables and restore the steady state of the train and traction network (simplified as “train-network”) system. From the perspective of train-network impedance, this paper proposes the train impedance models with and without the mitigation process. The generalized Nyquist analysis method is used to analyze the stability of the system with and without the mitigation. Finally, the mitigation method is verified by simulated and experimental data, to be capable of suppressing both HHI and LFO effectively.