A Gate Drive with Active Voltage Divider Based Auxiliary Power Supply for Medium Voltage SiC Device in High Voltage Applications

The emerging medium voltage (MV >= 10 kV) Silicon Carbide (SiC) devices are promising device candidates for high voltage applications, such as high voltage direct current transmission (HVDC) systems and flexible alternating current transmission systems (FACTS), where multilevel converters are often employed. Two main prerequisites for successful implementation of MV SiC devices in these high voltage applications are 1) a gate drive circuit with high common mode transient immunity (CMTI) and fast protection functions and 2) a high-reliability auxiliary power supply (APS) circuit for the gate drive circuit that can satisfy the insulation requirement. This paper presents the development of a gate drive system, targeting the utilization of 10 kV SiC devices in multilevel converters for high voltage applications. The developed gate drive system includes a gate drive circuit and an APS circuit. The APS circuit is based on the active voltage divider concept and it can harvest energy from a MV (>= 7 kV) dc bus to provide an isolated low voltage output to gate drive circuits with simple circuit structure and control scheme. The developed gate drive circuit features high CMTI (> 200 kV/mu s) and comprehensive protection functions, including overcurrent protection, isolated gate drive failure protection, active miller clamping, under-voltage lockout, soft turn-off, and fault reporting. The working principles and design considerations for the gate drive and APS circuits are presented in this paper. To validate the circuit design, the gate drive system was tested in a 10 kV SiC device based double pulse tester with 7 kV dc voltage.