Combined optimization of SSCB snubber and freewheeling path for surgeless and quick bus fault interruption in low-voltage DC microgrid

When a bus fault occurs in a low-voltage DC microgrid, solid-state circuit breakers (SSCB) on either end of the DC bus assume the responsibility of the isolation of the faulted section, while the freewheeling path attached between SSCB and the bus takes on the task of fault energy absorption and fault current damping. However, during fault interruption, the snubber attached in parallel with SSCB for overvoltage suppression will influence the fault energy absorption performance of freewheeling path, while the resistance of the freewheeling path will also influence the overvoltage suppression capability of the SSCB snubber. Hence, this paper analyzed the interaction between the two and proposed a combined design so as to optimize the fault interruption performance for minimum SSCB overvoltage, and shortest fault clearing time, with less cost and size. Preliminary experiments are conducted on a ±200V/DC prototype, and the experimental results demonstrated the effectiveness of the design.