HVDC Circuit Breakers Combining Mechanical Switches and a Multilevel PWM Converter: Verification by Downscaled Models

This paper presents two high-voltage direct-current circuit breakers that have the capability of interrupting a short-circuit current within several milliseconds. They consist of a current-limit inductor, a current-control inductor, one or two mechanical switches, and a multilevel converter with phase-shifted-carrier pulsewidth modulation. The two breakers can commutate an almost zero current from the main branch to the auxiliary branch. This paper proposes an original breaker with low-voltage and high-voltage mechanical switches connected in series, followed by a simplified breaker with a single high-voltage mechanical switch. Finally, this paper includes experimental verification by two slightly different downscaled breakers rated at 300 Vdc and 150 Adc, as well as confirmation of an actual original breaker by circuit simulation using the "PSCAD/EMTDC" software package.