Current sharing control modeling and design for power supplies in nuclear fusion applications

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.