Engineering Design and Verification of Toroidal Field Magnet Power Supply for EXL-50U Spherical Tokamak Device

This paper presents the systematic engineering design and verification of a megawatt-level pulsed power supply system tailored for the toroidal field (TF) magnet of the ENN Xuanlong-50 Upgrade (EXL-50U) spherical tokamak. The system is engineered to meet stringent operational demands, including a high current of 150 kA, second-scale pulse durations, and high robustness. To overcome the engineering challenges of input frequency fluctuations and complex parameter coupling inherent to pulsed generator supplies, a system-level hardware selection and parameter-matching methodology was established. This framework comprehensively integrates five core components: the pulsed generator set (PGS), phase-shifting transformer (PST), thyristor converter (TC), interphase reactor (IPR), and overvoltage protection circuit (OVPC). Furthermore, to resolve the inherent trade-off between high-precision tracking and system robustness when driving large inductive loads, a compound control strategy based on a feedforward-feedback architecture was proposed and implemented. Commissioning and experimental data demonstrate that the dynamic response and flat-top current-regulation accuracy of the power supply fully satisfy the physical experimental requirements of the EXL-50U device, thereby verifying the effectiveness and engineering applicability of the proposed design.