Microgrids operation based on Master-Slave Cooperative Control

Low-voltage microgrids can be seen as the basic tiles of the smart grid patchwork, owing to their capability to efficiently manage their distributed energy resources in aggregate form. They can support the grid in terms of demand response, power quality, ride through capability, etc., and at the same time they can ensure electrical continuity to the loads even in case of grid failure. This paper describes a simple and effective approach to manage microgrids by synergistic control of the power electronic interfaces acting therein, i.e., the Utility Interface (UI) installed at the point of common coupling with the utility, and the Energy Gateways (EGs) interfacing distributed generation units and energy storage devices with the distribution grid. In our approach the UI acts as control master for the microgrid: in grid-connected operation, the UI dispatches active and reactive power references to the EGs so as to improve energy efficiency and voltage; in islanded operation, the UI performs as grid-forming voltage source and assures the power balance by exploiting any local energy storage. The paper describes the theoretical background of the proposed control approach and demonstrates the system performance by MATLAB/Simulink simulation.