Abstract: The distributed control strategy with the supervision system has effectively solved the problem of voltage deviation brought by conventional droop control method. Considering the drawback of the previous distributed control strategy in voltage drop compensation and energy storage management, this paper proposes a novel hierarchical control strategy to achieve the reliable and optimal operation of stand-alone DC microgrid. The proposed control strategy includes two hierarchical layers. The primary control layer, which is the local control layer, uses bus voltage signal as an indicator of the power balance to change the operation modes of system. The secondary control layer is the system control layer based on communication links, which can achieve real-time bus voltage regulation by low-bandwidth communication technology, and adjust the drop control coefficient based on the battery state of charge (SOC) to balance the SOC between different batteries. This paper constructs the model for PV storage DC microgrid in MATLAB/simulink, whose simulation results verify that the primary control layer can ensure the reliable operation of the system without communication links, and after the addition of the second control layer with communication links, it can solve the problem of voltage deviation brought by conventional droop control method, and realize the balance of the SOC between different batteries.

Key words: DC microgrid, hierarchical control, voltage regulation, SOC balance