A power conversion system which uses a plurality of transistors to convert DC power to AC power is made more efficient by the use of liquid refrigerant to cool the transistors. A plurality of passages are formed in a cold plate on which the transistors are mounted, and liquid refrigerant is flashed into the passages to cool the cold plate and the transistors. The liquid refrigerant can by derived from a condenser from an organic rankine cycle or a vapor compression cycle.