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. This work is supported by National Basic Research Program of China (973 Program) (No. 2014CB247400).