A DC Hybrid Circuit Breaker with Buffer Capacitor and Vacuum Interrupters

DC circuit breakers are important parts to protect multi-terminal high voltage DC transmission system. A DC circuit breaker is required to interrupt the fault current fast and its power losses under normal conduction should be low. The objective of this paper is to propose a hybrid circuit breaker to meet the above requirements. The proposed DC hybrid circuit breaker includes two vacuum interrupters, power electronic devices and a buffer capacitor. In hybrid DC circuit breaker, the two vacuum circuit breakers are connected in series. The power electronic devices are in paralleled with one of the vacuum circuit breakers, the buffer capacitor and the two vacuum circuit breakers are connected in parallel. Low voltage DC current interruption experiment was done based on the proposed topology. The results show that the proposed DC hybrid circuit breaker can successfully interrupt 50 V/50 A. In the current interruption progress, there is nearly no voltage applied on the power electronic devices. An external transversal magnet is helpful for the current commutating from the vacuum interrupters branch to the power electronic devices. The higher the applied flux density is, the faster the vacuum arc voltage grows, which helps the current commutation. When the current is 100 A, and flux density is 0 mT, 250 mT, 400 mT, the maximum arc voltage is 39 V, 98 V and 120 V, respectively.