Development of Compact Variable-Voltage, Bi-Directional 100KW DC-DC Converter

Abstract : This paper reports the status and recent progress in development of a 100kW variable bi-directional DC-DC converter with input voltage ranging from 200 to 300Vdc, output voltage ranging from 300 to 600Vdc, a total efficiency > 95%, a power density > 4kW/liter, and a specific power density > 4kW/kg with a high coolant temperature of > 90 deg C. Multiple approaches are being studied to reduce power losses, increase operation frequency, decrease converter weight and size, including (i) a novel yet simple approach developed to achieve zero-voltage soft-switching with synchronous mode operation for high efficiency without adding any extra switch or other major components, which has led to reduce the Si IGBT switching loss by near 50% and making it possible for the converter to operate at 25KHz, (ii) an interleaving 3-phase design and implementation leading to the elimination of the ripple current going into the sensitive voltage source, (iii) designing and building compact nano-inductor with discontinuous conduction mode operation and compact bus capacitor size with ripple cancellation, and (iv) packaging and implementation of SiC Schottky diode-Si IGBT power modules with minimized thermal resistance. Experimental results of the bidirectional DC-DC converter achieving a total efficiency of 97% operating at 100kW with a coolant temperature of 90 deg C and a power density better than 4 kW/liter will be presented.