Experimental Validation of a High-Frequency Full-SiC Auxiliary Converter for AC Railway Supply Systems

This paper presents the experimental validation of a high-frequency full-SiC railway auxiliary converter power module intended as a building block for modular multi-system railway auxiliary converters. The proposed architecture employs a unified SiC-based power conversion platform that integrates an active front-end single-phase PWM rectifier with a galvanically isolated high-frequency DC/DC stage operating at 90 kHz under zero-current switching (ZCS) conditions. Although the converter is designed for both AC and DC traction systems, this study focuses primarily on its operation under single-phase AC railway supply conditions, which are representative of practical applications. A hybrid bipolar–unipolar modulation strategy is used to reduce the RMS voltage stress on the input inductor while preserving controllability of the input current near the voltage zero-crossing regions. Special attention is given to operation under distorted railway supply voltages, which are common in real traction systems. The control structure combines a proportional–resonant (PR) current controller, harmonic compensators, feedforward voltage compensation, and MSOGI-based synchronization to ensure stable synchronization and low-input current distortion even under non-ideal conditions. Experimental validation was performed on a 10 kW laboratory prototype. The results demonstrate a peak efficiency of 98.4% and near-unity input power factor. Under heavily distorted supply conditions THDv>30%, the input current distortion remained below THDi=2.3%. Harmonic and STFT analyses confirmed the robustness of the proposed synchronization and current control structure. The obtained results indicate that the proposed high-frequency full-SiC converter topology is a promising solution for future modular railway auxiliary converters, offering high efficiency, reduced passive component volume, and high power density. Full-scale high-voltage validation under both AC and DC traction systems remains the subject of further work.