Control Strategy of DC nanogrid Based on hierarchical bus voltage control and droop control

According to the flexible characteristics of DC nanogrid, the operating principles of different functional modularized units in DC nanogrid and switching priorities in different power consumption and generation states are studied in this paper. Then a control strategy based on hierarchical DC bus voltage control and converter droop control is put forward. The dc side voltage references of different units are stratified according to priority. Each module is regulated by droop control regarding on the PCC voltage and current signals. Through the design of droop coefficient, the current sharing between different modules of the same kind unit can be realized. Then the operation state of multi-module combination system is analyzed and corresponding state equation and module droop coefficient are derived. Finally, the effectiveness of the proposed control strategy is verified by simulation.