Superconducting AC/DC power conversion using high-temperature superconducting components

The trend towards DC transmission of power, especially when using superconductors, has made the conversion of power from AC to DC and DC to AC a critical element of many electrical systems. We designed and tested a AC to DC and DC to AC converter which used HTS cryotron switches. The superconducting elements were made from yttrium barium copper oxide, and the converter was operated at 77 Kelvin. Both AC to DC and DC to AC conversion has been demonstrated, and the conversion has been shown to be relatively independent of frequency over a wide range. The converter was tested with a current of a few amperes, but is upwardly scalable to thousands of amperes. At larger currents the converter is more efficient as much of the power loss occurs in a separate control circuit which carries a current that does not scale with the amount of current controlled. Significant sources of inefficiencies remain which make the initial device impractical for actual use; however, the proposed improvements in material and design should allow the converter to be used in practical applications and outperform conventional methods of conversion such as thyristors.