Multi-Port Operation of Modular Bridge Rectifier Solid State Transformer with Integrated Medium-Voltage Energy Storage

Solid-state transformers (SSTs) demonstrate significant potential for hybrid power conversion systems requiring medium-voltage (MV) and low-voltage (LV) DC interfaces to a MVAC grid. The modular bridge rectifier (mBR) topology represents an emerging single-stage SST implementation, featuring just one diode and isolated DC/DC converter per submodule to achieve superior power density and modularity. This paper presents the first comprehensive exploration of mBR’s multi-port functionality for MVAC/MVDC/LVDC power conversion. The quantitative analysis of each port’s achievable power range, accounting for topological constraints and current stress limitations, is presented. A novel branch current distribution method is proposed to reduce operational voltage range of branch DC/DC converters while compensating for MVDC current disturbances. Furthermore, the islanded operation without MVAC grid is discussed, wherein the three-port mBR morphs into three parallel input-series-output- parallel (ISOP) DC/DC converters. A hierarchical control architecture capable of seamless transition between grid-connected and islanded modes is also introduced. Finally, all proposed operational modes of multi-port mBR SST are validated through a thorough simulation of a 250 kW demonstration converter connecting a 3.3 kV MVAC and a 4.67 kV MVDC grids to an 800 V LVDC load.