A Cryogenic Gallium Nitride Full Bridge for Use in a Thermally Insulating Dual Active Bridge

In this paper, a Liquid Nitrogen (LN2) cooled Gallium Nitride (GaN) Cryogenic Full Bridge (CFB) is presented as part of a Dual Active Bridge (DAB) for use in a hybrid Liquid Hydrogen (LH2) High Temperature Superconductor (HTS) transmission line. The concept of a 20 kW DAB with cryogenic parts is outlined and the design of the CFB as one of the cryogenic parts is presented. Furthermore, the construction of a cryogenic test bench is described which is used to validate the functionality of the CFB and to characterize it. Finally, the first measurements of the prototype down to 82 Kelvin are presented, which confirm the increased efficiency of the GaN semiconductors at cryogenic temperatures.