Design and Analysis of a Bidirectional Hybrid DC Circuit Breaker Using AC Relays With Long Life Time

This article presented a new hybrid circuit breaker solution for using in dc microgrids. The proposed solution can offer a high-reliability protection feature for the dc microgrid with low conduction loss, bidirectional current flow, and galvanic isolation function. In the design, it is combined with a group of mechanical switches and semiconductors, where the mechanical switches handle the current conduction during normal operation and the semiconductors handle the breaker response during transient operation. The design fully utilizes the advantage of both types of switches and maximizes the performance and life time of the system. Throughout the design, it maintains only one mechanical switch in series with each power line; thereby, the high conductivity of the circuit breaker is maintained. At the same time, through the hybrid design, the electrical stress applied to the mechanical switch is eliminated. Thus, an effective and high-reliability solution is provided for the design of dc circuit breakers. The operation principle is explained in detail and the design guideline is provided. A 150/380 V and 15 A circuit breaker is successfully implemented, and the performance is experimentally verified, which shows good agreement with the theoretical findings.