New control of the 50-years-old flywheel generator EZ2– a necessary update to the latest industrial state of the art for the toridal field of ASDEX upgrade

The drive train of the "Energiezentrale 2 – EZ2″ has served as the core of the power supply for the toroidal field coils of ASDEX since 1973, utilizing its 167 MVA generator. The last upgrade was carried out in 1998. Due to the combination of power electronics failures and the steadily worsening availability of replacement parts in recent years, the ASDEX Upgrade team decided to renew the power electronics and control systems for the drive, generator, and auxiliary systems, bringing them up to the latest state of industrially available technology. This paper specifically focuses on the implementation of the non-trivial current control for the main field coils of ASDEX, which is achieved solely through the control of the generator’s excitation current. It provides a detailed description of the process from concept development to the validation of the generator control system, laying the foundation for future work.