Decentralized Coordination Control for Parallel Bidirectional Power Converters in a Grid-Connected DC Microgrid

Abstract

In the grid-connected mode, the dc microgrid is connected to the utility by parallel bidirectional power converters (BPCs), which provide voltage support for the dc microgrid. The coordination control for these parallel BPCs is very challenging. First, for the parallel BPCs, there is circulating current among them, which limits the total system capacity and may damage switching devices. Second, taking the constant power load into consideration, the performance especially the stability of the dc microgrid is degraded if the conventional ${\mathbf i}_{\boldsymbol {dc}}{\mathbf -}{\mathbf v}_{\boldsymbol {dc}}$ droop is adopted to share the power. Third, the voltage restoration should be faster for the better quality of dc voltage, and the restoration strategy should be scalable to the changes of the dc microgrid topology for the better flexibility. For these problems, this paper proposes a decentralized control method for the parallel BPCs, which can make the BPCs operate in coordination and provide voltage support for the dc microgrid well. Furthermore, the reliability of the proposed control method is illustrated by the stability analysis. All the conclusions are verified by the real-time hardware-in-loop tests.