Dual-voltage high power converter for a distributed power system in heavy traction, using high-voltage IGBT's

The design of a two-stage power converter for heavy traction applications, using 3.3 kV 1200 A IGBT modules is presented. The power converter is designed for a dual voltage traction system (3 kV DC, 25 kV AC), so that the first stage is configurable as a step-down or as a four quadrant power converter, whereas the second is an inverter. Initial tests on modules and a thermal analysis revealed that such modules suffer from high losses, so their switching frequency must be kept low, and the employment of liquid cooling is suggested in order for junction temperature and ripple to be limited, and reliability improved.