Cascade Internal Model Control scheme for PID feedback control on Keda Torus eXperiment

KTX, a reversed field pinch (RFP) device, is equipped with a robust Magnetohydrodynamic (MHD) magnetic field feedback control system, which comprises two distinct loops: an inner loop used for current control to generate a magnetic field, and an outer loop dedicated to magnetic field control; these loops operate in a cascading manner. The Proportional–Integral–Derivative (PID) control methodology is employed. In the pursuit of achieving superior performance, mathematical analysis is conducted on both control loops. This rigorous examination culminates in the design of an Internal Model Control (IMC) PID controller. Simulations are employed and further verified through experimental investigations. A magnetic field with fast and accurate response time has been successfully achieved. •Develop a cascade PID controller system for KTX to improve boundary magnetic field control and reduce MHD instability.•Mathematical model analysis and IMC Control method were applied to optimize PID parameters to enhance the control efficiency.•Experiments and simulations demonstrate significant improvements in both response time and control accuracy within the two control loops.