MEST multi-coil system control and application study to a PILOT FFHR with a RFP fusion core

The Magnetic Energy Storage and Transfer (MEST) system is a newly developed scheme to supply the superconducting (SC) coils in large-size tokamak and Reversed Field Pinch (RFP) reactors, to cope with the issues related to electrical power handling in this application. It is a very promising alternative to face both the issues related to high active power peaks, required during plasma formation and control, and the huge reactive power demand, linked to the use of traditional converters. The MEST system operating principle and control strategy supplying a single SC coil has been already outlined and studied in previous works. From this starting point, the MEST control system has been expanded to supply a complete set of SC poloidal field coils, considering the magnetic coupling and the energies associated with the magnets-plasma system, essential to control the overall system energy and achieve a certain degree of decoupling between the grid and the coils. This paper presents and discusses the principles to control the currents of a complete set of poloidal field coils using the MEST system, with efficient electrical power management, that could be transferred to different tokamak or RFP reactors, featuring similar poloidal magnet systems. To assess the control operation the application study to PILOT Fusion-Fission Hybrid Reactor (FFHR) is reported using analytical calculations and numerical simulations.