Bidirectional SSCB for Residential DC Microgrids with Reduced Voltage and Current Stress during Fault Interruption

Almost 30% of the world’s energy-related green-house gas emissions come from buildings, and by 2030, cities are projected to account for 73% of the world’s energy use. In most cities, buildings represent significant energy consumption and produce appreciable carbon emissions. Zero-energy buildings are gaining more attention with the penetration of renewable energy sources at the distribution end and increased requirements for high energy efficiency. Considering the reliability, efficiency, ease of control and integration of renewable energy sources, and direct connection of DC loads, the DC microgrid system outperforms the AC system. Moreover, the DC system protection design has remained a serious obstacle to the faster adoption of DC systems due to the characteristics of DC fault current. After an unexpected fault, the system current can rapidly develop to more than a hundred times the nominal current without a natural zero current crossing point. Therefore, DC microgrid systems require fast and reliable protection devices such as DC circuit breakers (DCCB). This paper proposes a new bidirectional solid-state DCCB incorporating MOSFETs in the main conduction path and a controlled auxiliary branch with MOSFETs and capacitors. The proposed DCCB provides current sharing between two branches at the instant of a fault and reduces current stress on the main MOSFETs during turn-off. The prototype is built, and the circuit breaker’s performance is validated for a system rating of 350V/16A, equivalent to DC building electrical specifications.