Decoupled control techniques for dual flying capacitor bridge power supplies of large superconductive magnets

The dual flying capacitor (DFC) was developed in 1976 as a method of supplying efficient bilateral power to large superconductive magnets. This power supply concept uses a second superconductive coil for energy storage. Large reversable power demands of the load magnet are met by energy exchange between the storage and load coils, through the DFC bridge. This paper will show that the DFC circuit can be decomposed into two elementary single flying capacitor (SLC) circuits which can be controlled independently. The discovery of this decoupled control concept is the origin of several new control strategies which significantly improve the performance of DFC power supplies, microcomputer controllers containing the decoupled control algorithm were tested on a DFC system simulator. The results show that time optimal load coil current and voltage control is now achievable by a robust bang-bang control technique. Furthermore, load coil current ripple and voltage spectrum can be independently controlled, while following an arbitrary reference signal. The DFC bridge, with the decoupled controllers, is a high performance power supply candidate for superconductive magnets of fusion reactors, particle accelerators and other systems.