Impedance-Matching Analysis of Wideband Harmonic Disturbance Generator for Railway Train-Network System

Accurate impedance measurements of the train and traction network are crucial for small-signal stability analysis of railway train-network system (RTNS). Although impedance measurement methods for four-quadrant converters (4QCs) in electric trains based on harmonic voltage disturbance injection have been proposed, few studies have investigated the impact of integrating a harmonic generator on RTNS stability. To address this issue, this article proposes a wideband harmonic disturbance generator (WHDG) and evaluates its impact on RTNS stability. The WHDG primarily comprises the back-to-back converter-based cascaded H-bridge (CHB) structure and a wideband coupling transformer. This generator can produce multifrequency perturbations with uniformly distributed spectrum energy. Subsequently, an accurate output impedance model is established based on the detailed topology and parameters of the WHDG. The model accounts for the impact of the dc impedance of the front-stage rectifier on the post-stage inverter. The close alignment between the modeling and simulation results demonstrates the accuracy of the deduced impedance model. Furthermore, an impedance-matching analysis of the RTNS with integrated WHDG is performed, indicating that the internal impedance of the WHDG weakens the stability of the tested RTNS. Finally, the effectiveness of the proposed WHDG is validated via a hardware-in-the-loop (HIL) experimental platform, and the impedance-matching analysis results are verified.