Development of a 90 kW bi-directional DC-DC converter for power dense applications

This paper presents the relevancy, design, and test results of a 90 kW continuous duty, three-phase, bi-directional, DC-DC converter for hybrid electric vehicles. Nominal low-side and high-side voltages of 320 V and 600 V, respectively, were used. Continuous boost-mode operation at 90 kW, and continuous buck-mode operation at 45 kW were demonstrated using 80 degrees C (inlet temperature) Castrol 399 oil coolant. The volumetric power density of the three-phase test-bed was 2.7 kW/l in boost-mode at a coolant temperature of 80 degrees C. Based on two-phase tests, the power density at a coolant temperature of 25 degrees C is projected to be 4.1 kW/l. To increase power level and power density, custom IGBT modules have been built and tested. A design layout for a packaged four-phase converter, using the custom IGBTs, including sensors and control hardware, indicates that a volumetric power density of above 4 kW/l is feasible at an 80 degrees C coolant temperature.