A Transient-Minimized DC Fault Protection with Z-Source Circuit Breakers in Hybrid Microgrids

With the growth of emerging data centers and electric vehicles, DC power distribution and hybrid microgrids are attracting growing attention. Due to the lack of a natural zero-crossing point in DC current, reliable DC fault protection is critical. This paper introduces a transient-minimized fault protection scheme utilizing Z-source circuit breakers (ZCBs), leveraging their unique features during the activation process. These features are analyzed to provide the theoretical foundation for achieving transient-minimized DC fault protection, which eliminates high spikes in fault current, relieves stress on power devices in the system, and enhances transient stability. The effectiveness of this method is validated through simulation tests of a 100 MVA islanded hybrid microgrid using ZCBs based on experimentally verified models. Test results demonstrate that system oscillation is reduced by 13% in frequency and 74% in voltage, while completely eliminating voltage sags. With the help of ZCBs, the system also recovers more quickly after fault clearance. The results also demonstrate that the proposed method remains effective under various fault and load conditions.