A Novel Series-Type Hybrid Circuit Breaker with Simple Start-Up Operation and Low Device Cost for Low-Voltage DC Distribution Networks

The series-type hybrid circuit breaker (S-HCB) is an effective solution for ultrafast dc fault protection. However, the introduction of multiple energy storage (ES) capacitors and fully controlled power devices for zero-current modulation leads to complex startup operations and significant-increased costs. In this article, a novel S-HCB with simple startup operation and low device cost for low-voltage dc distribution networks is proposed. The proposed design introduces an auxiliary coupled inductor into the voltage injection circuit to generate a multilevel injection voltage with only a single ES capacitor, which simplifies S-HCB's startup operation. Meanwhile, through comprehensively analyzing and designing the operating conditions for each device, some fully controlled power devices are replaced by low-cost SCRs and the required current ratings are reduced, obtaining significant device cost reduction without sacrificing performance. The operation principle and complete design consideration are detailed, and simulation and scaled-down experimental results are presented to verify the proposed concept. Compared to conventional S-HCB, the proposed design remains the inherent fast current breaking ability (300 V/30 A/14 $\mu$ s) and efficient energy transmission (99.2%/6 kW) while simplifying the startup operation and achieving over 40% cost reduction in power devices.