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

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.