Unified Analysis of Low‐Frequency Oscillation and High‐Frequency Resonance in Train‐Network System Considering Decoupled Model of AC–DC Converter

Low‐frequency oscillation (LFO) and harmonic resonance (HR) caused by AC – DC converters in train‐network system (TNS) degrade power quality, and threaten operational safety. This paper conducts a unified assessment based on the commonalities between LFO and HR. First, based on harmonic linearization, first‐order decoupled models for LFO and HR are established, respectively, through disturbance frequency approximation. Next, through feature extraction, evaluation indices oscillation gain (OG) and oscillation frequency (OF) are defined and solved. The amplification effect of train oscillation transmission in the network on the voltage harmonics of traction substations is quantified. Meanwhile, combined with the division of active/passive systems to reconstruct the system structure, the recovery time (RT) is derived, which reflects the RT after oscillation occurs when the train raises its pantographs to draw power. Furthermore, an oscillation indices prediction model is built to predict the oscillation trend. Finally, security domains for LFO and HR are designed according to standards and evaluation indices, and the proposed method is verified through engineering test and hardware‐in‐the‐loop experiment.