Soft Turn-Off DC Solid-State Circuit Breakers With Flexible Dual Tripping Schemes

A novel solid-state circuit breaker (SSCB) topology with two combined tripping schemes is proposed in this article: 1) fault current bypass (FCB) tripping and 2) soft turn-off tripping by transient commutation current injection (TCCI). There are four main contributions in this work: 1) flexible combined dual tripping schemes are realized by one single topology and 2) the traditional monotonous hard-switching FCB tripping with fast isolation speed cannot handle heavy load faults due to gate oscillations caused by higher
$\text{d}i/\text{d}t$
and
$\text{d}v/\text{d}t$
. Compared to pure FCB tripping, the combined soft turn-off tripping by TCCI in this work realizes zero current switching (ZCS) for the semiconductor switch to suppress its gate oscillations at heavy load fault interruption; 3) the capacitors in the TCCI circuits are automatically self-charged by the dc bus during the OFF-state of SSCB, which greatly simplifies the design by getting rid of external capacitor charging circuits; and 4) reclosing and immediate reopening operations are realized, which enhances the practicality of this work A 375-V/20-A SSCB is designed and developed to experimentally validate the proposed dual tripping schemes at light load fault (57 A) and heavy load fault (325 A). The SSCB demonstrates an ultrafast response speed of
$5.2 ~\mu \text{s}$
with FCB tripping and
$19.6 ~\mu \text{s}$
with TCCI soft turn-off tripping. The reclosing and reopening operation is also validated based on the IEEE Standard C37.14. This article is accompanied by a slide as multimedia material demonstrating the contributions of the presented work.