Resonant Frequency Identification Based on Harmonic Injection Measuring Method for Traction Power Supply Systems

Accidents related with high-order harmonic resonance seriously threaten the safety and stable operation of traction power supply systems (TPSSs). Generally, the resonant frequency of a TPSS, which is the crucial information for resonance suppression, cannot be accurately obtained through model-based methods due to the TPSS complexity. This study proposes a direct measuring method that harmonic currents at different frequencies and amplitudes are injected into the TPSS by a harmonic generator (HG). Then, the resonant frequency can be identified by measuring the harmonic response. The HG based on a single-phase cascaded H-bridge converter and its control algorithms are developed. Both simulations on a railway system model and experimental results on an equivalent resonant circuit are carried out to validate the feasibility and effectiveness of the proposed method.