Fuzzy PID control on the load current of a linear-motor type flux pump

Flexible and precise current control of high temperature superconducting (HTS) loads based on flux pump is critical in many applications, which stabilizes both the generated magnetic field and operating current. For HTS loads with small inductances, such as small coils and single cables, it is difficult to stabilize the load current at a specific value without a current controller. Existing works have rarely studied methods to control such currents in HTS loads, prohibiting flux pumps from being used in high precision applications. This paper proposes a fuzzy proportional-integral-derivative (PID) control strategy to regulate the closed-loop load current of a small HTS coil and an HTS single cable, by controlling the DC bias field of a linear-motor type flux pump. The proposed control method enables stabilization of the load current at a preset level in HTS load with small inductance. The experimental results validate the effectiveness and robustness of the proposed control method, which enables the HTS flux pump to be potentially used for highly stable HTS magnets, or as a testbed current source for HTS cables, such as CORC ® , etc.