A Modular Bidirectional Solid-State DC Circuit Breaker for LV and MVDC Grid Applications

Abstract

Direct current (dc) microgrids are increasingly gaining attention in industrial applications due to their simpler and more efficient integration with renewable energy resources and energy storage elements. The dc grid demands a faster, compact, cost-effective, and fault-tolerant protective system for reliable operation. To address the above challenges, this article proposes a bidirectional solid-state dc circuit breaker topology that guarantees reliable operation of dc grids [low voltage dc (LVDC) and medium voltage dc (MVDC)]. A modular extension of the proposed circuit breaker is also presented, resulting in better reliability, scalability, and fault-tolerant operation. The circuit breaker is derived using power semiconductor devices [silicon-controlled rectifiers (SCRs) and insulated-gate bipolar transistors (IGBTs)], with SCR acting as a main power interruption device. Salient features of the proposed topology include modularity, use of low-power rated devices, low-current rated sensors, and pre-fault interruption. A detailed mathematical analysis validating the design and operation of the proposed modular circuit breaker is presented. Moreover, the article also highlights the merits and limitations of the proposed concept. Finally, a laboratory prototype is developed with a system specification of 400 VDC/14 A to validate the performance of the proposed circuit breaker with single and modular operations, which is in line with the obtained simulation results. To verify current sharing between the modules, a few non-ideal conditions such as the use of non-identical main SCRs and turn-on delay are considered and tested on the developed prototype.