Control architecture and hierarchy division for renewable energy DC microgrids

The hierarchical control architecture for a renewable energy microgrid is developed, which combines the advantages of centralized and distributed control to enhance reliability and flexibility. According to the physical characteristics of a DC microgrid, the control architecture is divided into three levels, namely, the converter control level, bus regulation level and dispatch managing level. At the converter control level, various kinds of converters in a microgrid system can be categorized into terminal regulating converters and bus regulating converters according to external control targets. At the bus control level, the DC bus voltage of the microgrid system is divided into three ranges corresponding to three system operation modes. Each unit switches adaptively between the terminal regulating converters and bus regulating converters according to the variation of DC bus voltage. At the dispatch managing level, the microgrid control center adjusts the output characteristic curve of each unit to achieve further advanced functions. The converter control level at the bottom ensures high reliability operation by distributed autonomous control; the dispatch managing level at the top promotes global optimization by centralized decision making, whilethe intermediary bus control level serves as a bridge in between. A test platform is implemented to verify the effectiveness of the control hierarchy. © 2015 State Grid Electric Power Research Institute Press.