Closed-Loop DC-Transformer Control for Dual-Active-Bridge Interlinking Converters in DC Microgrids

Phase-shift (PS) dual-active-bridge (DAB) interlinking converters (ILCs) exhibit considerable potential in linking DC buses. DC ILC control research is focused on addressing three issues, namely modular series-parallel connection, control adaptability in various microgrid-operation modes, and microgrid stability with constant power loads. However, PS DAB converters operating with open-loop control cannot maintain bus voltage when load changes. Based on the open-loop controlled resonant converters which are called DC transformers (DCXs), this study proposes a closed-loop de-transformer (CL-DCX) control method for DAB ILCs. In conventional control techniques, specialized control loops are used for addressing each control issue. It is hard to combine these loops to address all three control issues simultaneously. By contrast, the CL-DCX control method is simple and can address all three control issues simultaneously. The proposed CL-DCX control method is conducive for implementation in independent microgrids and may benefit medium-voltage applications because of its versatility and simplicity.