Multi-level control of grid-tied DC microgrids

Increase of DC-compatible loads, popularity of distributed renewable energy sources (RESs) and development of power electronic converters are boosting the applications of DC microgrids (MGs). Multi-level control is proposed to realize the coordination among RESs, battery energy storages (BESs), DC loads and utility grid in distributed manner. System elements are prioritized to schedule different operation modes with bus voltage variation. Bus voltage band is divided into a few sub-regions so that operation could be realized in distributed manner. Droop control is implemented to realize power sharing among system elements in monitoring bus (MB) mode based on their capacities. System and individual converter response regarding variation of load power, RESs generation and operation modes transition between grid-tied and islanded are investigated. Lab-scale DC MG is developed to verify the feasibility and effectiveness of proposed control method.