Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil that has been cryogenically cooled to a temperature below its superconducting critical temperature. This use of superconducting coils to store magnetic energy was invented by M. Ferrier in 1970.
An adaptive power oscillation damping (APOD) technique for a superconducting magnetic energy storage unit to control inter-area oscillations in a power system has been presented in . The APOD technique was based on the approaches of generalized predictive control and model identification.
The authors in proposed a superconducting magnetic energy storage system that can minimize both high frequency wind power fluctuation and HVAC cable system's transient overvoltage. A 60 km submarine cable was modelled using ATP-EMTP in order to explore the transient issues caused by cable operation.
The superconducting coil, the heart of the SMES system, stores energy in the magnetic fieldgenerated by a circulating current (EPRI, 2002). The maximum stored energy is determined by two factors: a) the size and geometry of the coil, which determines the inductance of the coil.
A SMES operating as a FACT was the first superconducting application operating in a grid. In the US, the Bonneville Power Authority used a 30 MJ SMES in the 1980s to damp the low-frequency power oscillations. This SMES operated in real grid conditions during about one year, with over 1200 hours of energy transfers.
In SMES systems, energy is stored in dc form by flowing current along the superconductors and conserved as a dc magnetic field . The current-carrying conductor functions at cryogenic (extremely low) temperatures, thus becoming a superconductor with negligible resistive losses while it generates magnetic field.