Model of the RFX-mod poloidal field circuit

Aiming at predictive simulation of the plasma magnetic parameters during the RFX-mod discharges, a model was designed to simulate the poloidal field power supply system, detailing each individual switching unit and the single ac–dc converter with its local control circuit, together with the magnet system and the complete multi-variable feedback system devoted to the plasma shape and position control. The model was realized by coupling a linear model of the axi-symmetric evolution of the plasma with a detailed implementation of the RFX-mod circuit developed by means of the SimPowerSystem Toolbox in the framework of the Matlab-Simulink™ package. In order to evolve the plasma current, a Bessel Function Model (BFM) is adopted to implement the energy transfer from the toroidal to the poloidal field. The axi-symmetric controller is implemented to close the loop and is the same running on the VME nodes of the real control system. The model was successfully tested against experimental data, showing good agreement between measured and calculated waveforms.