Test Rig for Investigation of New Generation of 3.3kV SiC MOSFET Based Traction Converters

Abstract:
This paper introduces the test rig for investigating high-power full-SiC traction converters equipped with 3.3kV SiC MOSFET power modules developed by Mitsubishi Electric. The traction converter has been configured as a 3-phase 2-level voltage-source converter employing two power modules in parallel, which is the most common topology in the target traction applications with a rated dc-link voltage of 1.5 kV. The test rig allows complex testing of the traction converters under full-power (> 1 MW) and full-voltage conditions (dc-link voltage up to 2.4kV). The converter under the test can be loaded by both passive RL load and 3-phase ac traction motor mechanically coupled with the variable speed drive emulating arbitrary mission profile. The parallel power module operation in the converter legs aims to investigate unbalanced behavior (currents, temperatures) between SiC modules during critical traction inverter operating conditions. The test rig design makes possible easy changes of the traction converter as well as its auxiliary systems setup – e.g. variable gate driver parameters (Rgon, Rgoff, Lg), liquid cooling system allowing independent control of a junction temperature for each power module in parallel and precisely pre-set temperature difference between power modules under investigation, both artificial mis-sion profiles as well as mission profiles recorded on the real tracks.