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

Abstract

Toward 2050 carbon neutral, an increasing number of Battery Electric Vehicles (BEVs) must be achieved to reduce CO₂ emission out of the mobility section. One of the barriers for spreading BEV use is definitely long charging time. Shorter charging time would be realized with very high power, higher voltage and higher current. Although conventional chargers, which are based on AC-to-DC (ACDC) power converters, receiving power from utility grids shows technologically high efficiency, the overall efficiency from power generation to battery charge is NOT so high due to multiplied efficiencies through the power path going down, typically below 90%. DC-to-DC (DCDC) boost converter technology allows us not only to make good use of renewable energy but to achieve very high charging efficiency by the way of direct power receiving from renewable sources. The bottle neck for large current charging is the current capacity of conventional inductors, which would be drastically improved by replacing the normal inductor to “superconducting coil”. Our group has designed and demonstrated a superconducting DCDC (SCDCDC) double-boost converter to prove the excellent potential as ultra-fast charger providing high voltage with large currents. We designed the SCDCDC by 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 efficiencies larger than 95% up to 15 kW of output power operations with liquid helium cooling.