Integration of multi-terminal DC to DC hub architecture with solid state transformer for renewable energy integration

In this paper an alternate to the DC to DC stage of a single phase solid state transformer is proposed comprising of a Multi limb core (MLC) transformer. Further two important operation conditions of a single phase solid state transformer (SST) with cascaded series connected converter topology is studied: soft startup from auxiliary DC source to avoid any inrush current on the DC capacitors and the control interaction between the cascaded converters under severe voltage sag. The voltage balance in the cascaded structure under extreme voltage sag is the primary concern and a solution is proposed.