Overvoltage protection scheme for three-phase current source converter built with SiC MOSFETs

The overvoltage caused by dc-link inductor current interruption is a serious problem in the current source converters. It becomes an even more challenging issue when the fast-switching SiC MOSFETs are applied as switches in these converters. The protection is required to have nanosecond-level response time to protect the devices. Addressing this challenge, this paper proposes a novel overvoltage protection scheme constituted by a diode bridge and the high-power transient-voltage-suppression (TVS) diodes. It can detect and clamp the overvoltage within less than 50 ns to protect the device from breakdown. When the energy in the inductor is small, it can be dissipated in the TVS diodes. Otherwise, a capacitor in series with a thyristor can be added to absorb the energy. The effectiveness of the protection scheme has been verified by experiments in a 7.5 kW current source rectifier built with SiC MOSFETs.