Hierarchical Plug-and-Play Voltage/Current Controller of DC Microgrid Clusters with Grid-Forming/Feeding Converters: Line-independent Primary Stabilization and Leader-based Distributed Secondary Regulation

Considering the structure of dc Microgrids (MGs) composed of grid-forming/feeding converters, a hierarchical Plug-and-Play (PnP) voltage/current control architecture for MG clusters is proposed. In the primary level, a PnP voltage/current controller is proposed to achieve simultaneous voltage support and current feeding function according to local references. In addition, stabilizing controller is characterized by explicit inequalities which are only related to local parameters of a MG. In the secondary level, for the system with interconnection of MGs, a leader-based voltage/current distributed controller is proposed to achieve both voltage and current regulation without specifying the individual setpoints for each MG. The proposed controller requires a communication network and each controller exchanges information with its communication neighbors only. With the proposed controller, each MG can plug-in/out of the system seamlessly, irrespectively of the power line parameters and models of other MGs . The proof of the MG cluster closed-loop stability exploits structured Lyapunov functions, the LaSalle invariance theorem and properties of graph Laplacians. Theoretical results are validated by hardware-in-loop (HiL) tests.