Medium-voltage semiconductor-based circuit breakers for DC grids, offering faster, efficient switches.
Researchers at the US Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed medium-voltage semiconductor-based circuit breakers designed to protect DC grids at lower cost.
Medium-voltage DC systems are designed to reduce transmission losses and to integrate with modern loads and renewable sources like large-scale solar power stations. The technology aims to support the expansion of DC power distribution by providing a faster response time than mechanical switches.
ORNL’s design uses thyristor-based semiconductor switches capable of interrupting DC current in under 50 microseconds, approximately 100 times faster than mechanical devices. Conventional mechanical breakers cannot react fast enough to prevent heat build-up and arcing.
They can reduce conversion losses between DC-based electronics and the alternating current (AC) grid, increasing efficiency and lowering energy costs, particularly for energy-intensive applications such as data centres.
Previous semiconductor-based DC breakers have been too costly for widespread deployment and typically limited to under 2,000V. ORNL’s approach uses thyristors for their robustness and lower cost, combined with an external circuit to force current reduction since thyristors cannot switch off directly.
A prototype achieved interruption at 1,400V, with reaction times four to six times faster than earlier thyristor-based designs. To scale up voltage handling, the team connected breakers in series, ensuring even voltage sharing and maintaining response speed. Testing reached 1,800V, with work underway to extend capability towards 10,000V.
