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영어

This paper proposes a center field compensation system using PID control with auto-tuning to improve the temporal stability of high-temperature superconducting (HTS) magnets. The proposed control system is designed to mitigate magnetic field drift induced by screening currents, as well as fluctuations resulting from power supply ripple in HTS magnets. Various auto-tuning techniques were implemented and evaluated to optimize the controller gains, thereby improving the performance of the field compensation system. A background coil, simulating a HTS coil, and a central magnetic field compensation coil were fabricated, and experiments were carried out to compare the performance of each auto-tuning method based on Settling Time and %Overshoot. Experimental evaluation of the compensation coil demonstrated that the Cohen-Coon tuning method is the most effective for central magnetic field compensation. Current distortions, replicating drift caused by screening currents in HTS magnets and fluctuations from the power supply ripple, were applied to the background coil. Using the proposed method, the central magnetic field was successfully compensated, significantly enhancing the temporal stability of the magnet. After successful validation of the auto-tuning-based central magnetic field compensation technique, a Z0 compensation coil for the 400 MHz (9.4 T) HTS NMR magnet was designed and fabricated. Applying the proposed system to HTS NMR magnets is expected to significantly enhance the temporal stability of the magnetic field.