A novel 60 MW Pulsed Power System based on Capacitive Energy Storage for Particle Accelerators C. Fahrni*, A. Rufer*, F. Bordry**, JP. Burnet** *EPFL, Ecole Polytechnique Fédérale de Lausanne 1015 Lausanne, Switzerland Tel.: +41.21.693.26.28 **CERN, European Organisation for Nuclear Research 1211 Geneva 23, Switzerland Tel.: +41.22.767.61.11 E-Mail: claude.fahrni@epfl.ch, alfred.rufer@epfl.ch, frederick.bordry@cern.ch, jean-paul.burnet@cern.ch Keywords «Energy storage», «Particle accelerator», «Power cycling», «Pulsed power converter». Abstract Large Physics experimentation as in particle accelerators or in nuclear fusion is often characterised by a strong and modulated power demand, incompatible with the power availability of the grid. Therefore, large facilities for short-term energy storage have been used, traditionally based on rotating machine. Several new solutions of power supply are studied and especially a new solution for energy storage is presented, where capacitors are used as energy storage elements. They are integrated in the static power converter. The energy- and instantaneous power-demand are presented, and then the global storage system with a dedicated multilevel DC/DC converter with flying capacitors is described. A specific control strategy for voltage balance, together with an adapted loss compensation method is also introduced and developed. Introduction The PS accelerator (Proton-Synchrotron) was the first large accelerator built at CERN [1]. It has been in operation since 1959 and is part of the LHC (Large Hadron Collider) injector chain, see Fig. 1. It receives beam from the Proton Synchrotron Booster (PSB) at the momentum of 2.12GeV/c and accelerates it up to 26GeV/c. It is a cycling machine with a pulse repetition time of multiples of 1.2 seconds. Cycles up to 20GeV/c can be done in 1.2 seconds. Above 20GeV/c, the minimum cycle duration is 2.4 seconds. The PS accelerator has 101 main magnets connected in series making an impedance of 0.9H and 0.32Ω. They are supplied with current by a dedicated power system. The shape of the current, the voltage and the active power at the load for a 26GeV/c cycle are shown in Fig. 2. The maximum active power at the magnet terminals varies from plus to minus 40MW. As this large active power variation during a cycle was not acceptable to the electrical network, a Motor-Generator set (M-G) was chosen to act as kinetic storage. The present M-G set from SIEMENS has been in operation since 1968 and has reached its end of life and CERN has decided to replace it. CERN launched many studies to find solutions for a new power system [2]. The results of these studies are presented in this paper. At first, the present power system is described. Then, the study’s results of new solutions is analysed. Finally, the study for a solution based on capacitive energy storage is presented. This last study has been done in collaboration with EPFL (Swiss Federal Institute of Technology). Authorized licensed use limited to: CERN. Downloaded on December 15, 2008 at 05:37 from IEEE Xplore. Restrictions apply.