Adaptive Solid-State Circuit Breaker Without Varistors in VSC Interfaced DC System

The rapid discharge of the dc-link capacitors during the short-circuit fault would cause the transient current with fast propagation speed in the VSC based dc system. It is necessary to limit the dc fault current and lower the requirement of fault detection speed. However, the traditional fault current limitation method with directly installed inductors in the dc line will prolong the fault isolation time, resulting in the system instability during the power flow shifting. In this paper, an adaptive solid-state circuit breaker (SSCB) is proposed for the low and the medium voltage dc system, bypassing the installed inductors during the normal state and connect them into the dc line when the fault occurs. Besides, the energy dissipation circuit and the snubber circuit are applied to release the energy stored in the installed inductors and the dc line inductance after tripping. Hence, the fault isolation speed can be accelerated, and it is not necessary to use the metal oxide varistors in the proposed SSCB. By comparing with other SSCB schemes with the fault current limitation function, the effective fault current limitation, fault isolation and the ride-through of the proposed SSCB is verified in the OPAL-RT based simulation and the hardware test.