Power conditioning and characterization for superconducting magnetic energy storage

Superconducting Magnetic Energy Storage (SMES) is being considered for use by both the electric utility industry and the high energy physics community. The utility industry is interested in SMES for load leveling and system stabilization. The high energy physics community is interested in SMES as a burst-discharge energy store to power high-energy physics devices. SMES offers attractive costs for energy storage in the range of a gigawatt-hour (3.6 TJ), high diurnal energy storage efficiency (92-95%), and rapid response to variations in load demand. The difficulty with utilizing SMES as a burst-discharge energy store is that in this mods SMES must have the capability to disconnect from the utility grid and operate as a stand-alone power source. When used as a stand-alone power source, the SMES power conditioning system must be able to maintain a constant voltage, constant-frequency, self-commutated 60 Hz bus for driving loads which vary from zero demand to the peak capacity of the device. The SMES power conditioning system must provide this type of performance from a SMES coil which stores direct current. Power conditioning for Inductive energy stores is complicated by the necessity for maintaining a closed path for circulation of the storage current. This paper involves research in the problems inherent in designing such a power conditioning system. Topics to be addressed in this report include self-resonance of the SMES coil, transient behaviorof theSMES coil, and power conditioning issues.