Fault characterization and protective system design for a residential DC microgrid

Abstract

A residential DC microgrid is being built in an underserved community in Milwaukee, Wisconsin. The short circuit protection for this DC system and discrimination of faults along the interconnecting cables is a significant challenge. This paper addresses discrimination of sudden short circuit faults using an ultra-fast normally-on Silicon Carbide (SiC) Junction Field Effect Transistor (JFET)-SiC based solid state circuit breaker (SSCB). JFET gating for turn-off is self-powered from the drain to source voltage that occurs during a high current fault. Fault characterization of the system is performed using PLECS — a high resolution power electronics systems simulation platform. Fault discrimination of series connected SiC JFETs, with settings adjusted by a simple resistor change, is a validated both using an LTSPice model and a laboratory test fixture.