PID Control of an Electromagnet-Based Rotary HTS Flux Pump for Maintaining Constant Field in HTS Synchronous Motors

Rotary HTS flux pumps are suitable for cryogenic applications, where it is difficult to implement direct physical connections between the device in question and an external power supply. Here we examine the proportional-integral-derivative (PID) control of a rotary HTS flux pump to compensate for a change in the current in the HTS field coil of a synchronous motor under operating conditions. The field coil current must be maintained constant to prevent output fluctuation of the synchronous motor. In this context, a prototype of the rotary HTS flux pump with rotating HTS tape is constructed for a synchronous motor in this study. A 600-turn electromagnet is used to inject magnetic flux into the HTS tape to charge the HTS coil. The magnetic field of the electromagnet is controlled via PID control with respect to the rotational speed and rotating direction of the machine. As a result, we successfully compensate for change in the current of the HTS coil by controlling the magnetic field of the electromagnet, while the rotating speed and direction are varied.