Development of a New DC-to-DC Converter for Ultra-Fast Charging of Electric Vehicles Using Superconducting Inductors Cooled With Liquid Hydrogen

Toward the 2050 net-zero goal, an increasing number of battery electric vehicles (BEVs) must be achieved to reduce CO₂ emissions out of the mobility sector. One of the barriers for spreading BEV use is definitely long charging time. Shorter charging times would be realized with very high power, higher voltage, and higher current. Although conventional chargers, which are based on ac-to-dc power converters, receiving power from utility grids show technologically high efficiency, the overall efficiency from power generation to battery charge is not so high due to multiplied efficiency through the power path going down, typically below 90%. DC-to-dc (dcdc) boost converter technology is widely deployed as a power conditioner for photovoltaic power plants, which draw maximum power from the renewable sources. When the circuit is used not only as a power conditioner but as a battery charger, a sophisticated dc power system would be realized. Our group has designed and demonstrated a superconducting dcdc double-boost superconducting boost converter (SBC) converter to prove the excellent potential as an ultra-fast charger providing high voltage with large currents with high efficiency. We designed the SBC using Bi2223 and MgB₂ coils. The converter with the MgB₂ inductor, which has already demonstrated nominal operation with liquid hydrogen cooling in a previous research, showed high efficiency larger than 95% up to 15 kW of output power operations with liquid helium cooling.