A Hybrid DC Circuit Breaker Combining a Multilevel Converter and Mechanical Contactors: Verification of the Principles of Operation by Experiment and Simulation

This paper presents a new hybrid dc circuit breaker producing no conducting power loss under normal operating conditions and having the capability to interrupt a large amount of short-circuiting current within several milliseconds. It consists of two reactors for current limiting and current control, two mechanical contactors, and a multilevel converter based on the cascade connection of multiple full-bridge dc/dc converter cells. It is characterized by achieving current commutation from the main mechanical contactor to the multilevel converter with fast current control. This results in eliminating auxiliary power semiconductor switches that produce a non-negligible conducting power loss under normal operating conditions. This paper discusses both principles of operation and control method of the new hybrid dc circuit breaker. Experimental verification is performed by a downscaled system rated at 300V and 150A, along with verification by computer simulation.