A novel topology and control strategy of DC fault current limiter

DC power distribution network is widely used in long-distance and large-capacity transmission, undersea transmission, and interconnection system for its small system loss and high controlled characteristic. The fault current limiter (FCL) takes a very important part in the DC distribution system. Since there is no natural zero crossing point of the current in DC system, it is more difficult to limit fault current in DC system than in AC system. Low shortcut impedance could lead to a high current rate of rise, which can cause heat, arc and electrical stress damage to the DC system in such a short time when the breakers are not ready to act. This paper proposed a new type of solid state fault current limiter to restrain the shortcut current and to make sure the breakers act correctly. In normal situation, the limiter plays as a transmission tine. But when fault occurs, it works as a buck circuit to control the fault current within a certain desired range. In this way, the fault damage can be reduced. Experiment results can be taken to prove the limiter.