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A Low-Loss Low-Cost DC Circuit Breaker for Power System Protection

DC circuit breakers (DCCBs) are key components for the protection of dc power networks, such as high and medium-voltage direct-current (HVDC and MVDC) systems. Mechanical based DCCBs are relatively economic but their speed of operation is slow. Conversely, DCCBs based on semiconductor switches are expensive and can cause high power losses, although their speed is fast. To combine the advantages of these devices, this paper presents a low-cost integrated circuit breaker (ICB) with comparable power losses to mechanical DCCBs and a fast protection speed. This is achieved by sharing semiconductor switches to block faults at any line connected to the ICB, with current flowing through mechanical components only during no fault conditions. The topology design and operating sequence of the ICB are presented. The ICB has been modeled in PSCAD/EMTDC and its effectiveness for isolating a dc fault is demonstrated through a simulation study.