CERN-PS Main Power Converter Renovation: How to Provide and Control the Large Flow of Energy for a Rapid Cyclic Machine?

The PS accelerator (Proton-Synchrotron) at CERN, which is part of the LHC injector chain, is composed of one hundred magnets connected in series. During a typical acceleration cycle (taking 2.4 seconds), the active power at the magnet terminals varies from plus to minus 40 MW. As this large active power variation was not acceptable to the electrical network, a motor-generator set (M-G) was inserted between the grid and the load. The M-G set (of 1968) acts as a fly-wheel with a stored kinetic energy of 233 MJ and the magnets are fed via two 12-pulse thyristor rectifiers. A renovation or replacement of the installation is planned in the near future as part of the consolidation of the LHC injectors to avoid any major breakdown, to improve overall availability and to reduce operation and maintenance costs. This paper presents a first comparison of technical solutions available to build such a power system and the strategy that will be applied for the up-grade of the system.