A DC Solid-State Transformer With DC Fault Ride-Through Capability

This article investigates a dc solid-state transformer (DCSST) with dc fault ride-through (FRT) capability for medium-voltage dc (MVDC) systems. The FRT requirement for DCSST in dc grid is investigated. Short-circuit fault clearance on the medium-voltage (MV) side is realized by introducing full-bridge converters with cascaded dc converter modules on the MV side of the DCSST. The FRT strategy under typical voltage sags is analyzed. Factors affecting the fault clearing and system recovery are considered, including the number of full-bridge converters, the values of dc inductance, and the dc-link bus voltage. The concept is verified with both simulations and experiments.