Research on power conditioning systems for superconductive magnetic energy storage (SMES)

Several converter/inverter circuit topologies using silicon controlled rectifier (SCR) and gate turn off (GTO) devices have been developed for operating a superconductive magnetic energy storage (SMES) coil with an electric utility. Control of real and reactive power and shorting switch and current bypass techniques have been investigated. Experimental tests of independent real and reactive power control have been successfully performed using an 8-h superconducting coil and 10-kVA power conditioning circuits. In typical studies, the real power was cycled from zero to a peak charging power of 7 kW and then the discharging power was held constant at 3 kW, while the reactive power was independently held constant at various values between 0 and +or-5 kvar. A technique for zero current opening of a mechanical bypass switch using converter control to cancel the coil current in the closed bypass switch was also successfully demonstrated using the 8-h coil.