A Hierarchical Control Structure for Distributed Energy Storage System in DC Micro-Grid

To adapt to the rapid development of the renewable generations, DC micro-grid has been becoming an attractive technical route. Energy storages are widely employed in DC micro-grid to balance the power generation and usage. Therefore, the coordination and energy control among these distributed energy storage systems are critical technical issues to guarantee the overall efficiency and security. In this paper, the concept and characteristic of the distributed energy storage system in DC micro-grid are first analyzed. A hierarchical control system for power sharing is proposed to achieve the state-of-charge (SOC) balancing among energy storage units (ESU). In the lower layer of the control system, the DC droop control is applied to allocate the output power of each ESU based on its maximum output power. In the upper layer, consensus algorithm is utilized to adjust the output power reference of each ESU to reduce the SOC difference. Finally, a Matlab/Simulink model is built to verify the proposed approaches. The simulation results indicate that the proposed method can achieve the SOC balancing robust operation in distributed energy storage system.