Impact Characteristics and Identification Method of Accelerator Magnet Power Supplies

Accelerator magnet power supplies are typical high-power power electronic impulsive loads in large scientific facilities. During fast excitation, the rapid rise of magnet current may cause transient power impacts and voltage sags at the point of common coupling, which can be easily confused with traditional disturbance sources such as motor starting, transformer inrush, and short-circuit faults. To support power-quality evaluation and disturbance-source tracing in distribution networks, this paper investigates the grid-side impact characteristics of accelerator magnet power supplies and proposes a physically interpretable identification method. Different current ramp-rate cases are analyzed to reveal the relationship between fast excitation, PCC power impact, and voltage fluctuation. The results show that increasing the current ramp rate significantly intensifies the active-power impact and PCC voltage fluctuation, with the maximum voltage fluctuation reaching 10.20% under the high-ramp-rate case. Based on these characteristics, a two-layer identification method combining S-transform-based voltage-sag detection and fuzzy comprehensive evaluation is proposed. The method uses multidimensional electrical features, including power change rate, three-phase unbalance, power factor, active/reactive impact ratio, and current harmonic distortion, to distinguish different disturbance sources. Verification results show that the proposed method can effectively identify fast-excitation disturbances of magnet power supplies and distinguish them from typical traditional voltage sag sources. The study provides a reference for power-quality evaluation and disturbance-source tracing of accelerator magnet power supplies connected to distribution networks.