Novel dc/dc choppers with circuit breaker functionality for HVDC transmission lines

•Proposed two converter topologies used as dc circuit breakers for HVDC transmission.•Proposed configurations are promising for future practical development as they are less costly.•Proposed auxiliary controller ensures the short-circuit faults shut-down completely.•An isolation time of 6.5 ms has been achieved by proposed controller.•The proposed circuit breaker can switch between step-up and step-down modes smoothly.

This paper proposes two novel dc/dc choppers with dc circuit breaker functionality for HVDC transmission lines. These converters feature step-up and/or step-down functions with instant interruption of short-circuit faults. Compared to other state-of-the-art converter topologies described in the literature, the proposed topologies have better control functions, lower manufacturing costs and reduced energy losses. A double closed-loop controller is designed to regulate the inductor current and output voltage of the converters. An auxiliary controller is also proposed to ensure proper shut-down of the circuit breaker in the event of dc short-circuit faults. The simulation and experimental results are presented to validate the effectiveness of the proposed converter configurations and control scheme.