Supercapacitors-based Power Supply for ASDEX Upgrade Toroidal Field Coils

ASDEX Upgrade (AUG) electrical power is provided with three Flywheel Generators (FGs) that are charged up before the start of each plasma pulse with 15 MW for 30 minutes. The stored energy is then used to satisfy the high power needs during the pulse of up to 400 MW. The biggest FG (‘EZ2’) in case of a major fault could not be replaced by any other FG of such size because no comparable devices are available on the free market. Therefore, the development of an alternative energy storage with high power and energy density and fully controllable output is planned. Supercapacitors (SCs) are well known for their high specific power. The combination of this technology and a proper power converter topology such as the Modular Multilevel Converter (MMC) represent a promising alternative to be explored to replace Tokamaks FGs. The MMC topology allows a discrete-leveled output voltage and, thanks to its high cells number, it can operate continuously even in case of fault of some cells, while a FG could not. In this paper the concept of a SCs-based power supply for AUG's Toroidal Field (TF) Coils is presented, highlighting the main advantages and challenges of this project.