Development of new solutions for high voltage power supplies of Neutral Beam Injector for nuclear fusion experiments

The DTT test facility has the goal of solving one of the critical challenges in harnessing of nuclear fusion energy: the extraction of the heat generated by the fusion process for future fusion reactor. This research is particularly relevant in view of DEMO, which will be the intermediate step between ITER and commercial power plants. A significant portion of substantial additional heating power required will be supplied through Neutral Beam Injection. This thesis focuses on the development of a high-voltage power supply for the Neutral Beam Injector of DTT, with particular emphasis on the challenge posed by handling arc breakdowns at the output of the converter. The application of Modular Multilevel Converter technology is explored within the context of the Acceleration Grid Power Supply for the Neutral Beam Injector of DTT. Such power supply produces a high voltage, and has demanding requirements in terms of voltage ripple, voltage regulation range and energy delivered to the arc. The research investigates a specific topology designed to minimise the number of semiconductors. The work includes the design of the converter, the development of a custom control scheme, and the verification of performance through numerical simulations. Additionally, layout studies are conducted to have an initial estimate of the volume required for the installation of such converter. Protection strategies against severe overvoltages, overcurrents and to limit the energy delivered to the arc during breakdown events are also evaluated.