On the Performance of Voltage Source Converters based on Silicon Carbide Technology

Abstract:
The energy conversion efficiency of voltage source converters based on 1.2 kV silicon carbide MOSFETs and Schottky diodes have been assessed by device measurements and converter simulations. A similar measurement and simulation study has also been performed on a similarly rated 1.2 kV silicon IGBT and PiN diode pair. Transistor to diode current commutation measurements have been performed in a clamped inductive switching test rig for a temperature range between -75°C to 175°C. The measurements have also been performed with different switching rates modulated by a range of gate resistances between 10Omega to 1000Omega. The measurements show that the switching energy of the SiC MOSFETs/SBD pair generally exhibits a negative temperature coefficient whereas that of the silicon IGBT/PiN diode pair exhibits a positive temperature coefficient. Furthermore, the switching energy of the SiC devices are 80% lower than the silicon bipolar technologies. The measurements have been used as inputs into the simulation of a 3 phase, 3-level neutral point clamped voltage source converter. Results from the converter simulations show that the SiC NPC-VSC exhibits 5% higher energy conversion efficiency, 3% less THD and 500% higher maximum switching frequency on average.