A reliable

fast and low conduction loss direct current (DC) circuit breaker plays a significant role in the development of the DC grid. The topology and operation principle of the cascaded full-bridge hybrid DC circuit breaker are described in detail. Compared with the topology that directly utilizes insulated gate bipolar transistors (IGBTs) in series connection

the voltage balance is easier to achieve for connecting FBSM in series. In order to get a quick response to the DC grid fault

the rapid fault detecting method and pre-transferring strategy are introduced. A low voltage physical dynamic model has been built to verify the operation and control strategy. This work is supported by State Grid Corporation of China.