Short-Circuit Protection of Power Converters with SiC Current Limiters

In this paper, a method to limit fault current from DC side short-circuit condition in AC-DC power converters is presented. This approach is based on using Normally-ON SiC-JFETs in series with the DC capacitors as Current Limiting Diodes (CLDs). In this configuration, the gate and source contacts of the JFETs are connected together to make two-terminal devices (V-GS=0). Under a fault condition, the capacitors voltage appears across the devices causing them to operate in the saturation region where their current is limited by channel pinch-off and self-heating. Whereas under normal conditions, the CLDs operate in the linear I(V) region where they exhibit low on-state resistances and therefore, have minimal effect upon the converter operation. This paper also includes experimental results to verify the effectiveness of the proposed method in limiting capacitors discharge current during a fault and to demonstrate its small influence on normal operation.