1.5-kV, 1.5-kW, High Voltage Ratio, Bidirectional Dc/dc Converters for Power Distribution on the Moon

Modular multilevel GaN-based isolated DC/DC converters are proposed for 1.5-kV, 1.5-kW power transmission on the lunar surface. These converters offer benefits such as a high step-up/step-down voltage ratio, low device voltage stress, and frequency multiplication. This paper details the electrical design and considerations for the converter operating in the lunar surface environment, focusing on device selection and derating, submodule design, and transformer design. The thermal analysis of the converter has been updated to account for cold-starting at cryogenic temperatures and ensuring the required cooling capability without air convection on the lunar surface to prevent overheating. Instead of using traditional heatsinks for cooling, radiation-based thermal solutions have been proposed, designed, and analyzed for effectively cooling the switching devices under vacuum conditions. To date, the converters have been validated under 1.5 kV/1.5 kW conditions in an ambient environment and under 1 kV/655 W conditions in a vacuum and 77 K temperature environment.