Single-Stage Multiport Solid-State Transformer Based Medium-Voltage DC Interconnection System and Coordinated Control Strategies

Decentralized integration of distributed generation (DG) units and loads are increasing in the modern distribution grid. Maintaining the power flow and power quality within their accepted limits is a challenging task. This article proposes a medium-voltage dc (MVDC) interconnection system based on the single-stage multiport solid-state transformers (SST). First, the single-stage multiport SST’s coordinated control strategies and energy management method are discussed, aiming at the flexible power flow control between the utility grid, MVDC grid, and the low-voltage ac/dc microgrid. Second, the MVDC controller parameters and SST passive components are optimized based on the impedance interaction characteristics between the two SSTs’ MVDC ports, thereby enhancing the stability margin of the interconnected system. Then, the operation modes of the interconnected system are defined. Finally, the effectiveness of the proposed operation modes and control strategy is verified through a 1-MW simulation platform, while a 1-kW scaled-down experimental prototype is built to further validate the single-stage multiport SST and the MVDC interconnected system.