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Power electronics converters employed in nuclear fusion applications have been recently assuming a crucial role for coils power supplies as they are particularly challenging not only due to the very high current amplitude, but also to guarantee a proper plasma confinement and control for tens of years. To face such demanding requirements, with focus on the Central Solenoid power supplies of the Divertor Tokamak Test (DTT) facility, this paper analyzes a parallel-connected H-bridges (HBs) DC-DC converter characterized by relatively low voltages and very high current ratings (tens of kiloamperes), quite unusual in industry applications. A specific mathematical model, including the high frequency disturbances identification, has been pointed out for the first time in literature. A control strategy, which also aims to maximize the current sharing among all HBs legs, is proposed and tuned through a model-based design. The Hardware-in-the-loop test facility has confirmed the validity of the presented control by keeping the load current error below DTT requirements and by correctly balancing each HB leg current. These results have been furtherly experimentally validated through a Prototype test bench.

The state-of-the-art power supplies for superconducting magnets are bulky, expensive, and subjected to hundreds of kilowatts of power losses during operation producing significant reactive power absorption and harmonic distortion on the power grid. Moreover, current is injected from room temperature to 4 K coils through current leads, which represent a major source of heat load for the cooling system. Flux pumps are contactless, compact power supply systems able to operate superconducting magnets in a nearly persistent current mode with practically negligible operation losses. Although several small-scale experimental tests already proved the concept of flux pumps, no demonstrators suiting the current and voltage rating of fusion magnets have been built, nor a proper design has been developed. In this study, we developed an application-oriented modelling framework for optimized design of linear flux pumps. This paper presents the framework and a design of a linear flux pump demonstrator with a current capability of 2000 A to be integrated into the Frascati Coil Cold Test Facility. Simulations reporting its performance when employed for the energization of a toroidal field coil of the Divertor Tokamak Test (DTT) are described, both for the ramp up and current maintenance regimes, and its efficient modularity exploitation is analyzed.