Impedance shaping method for system-level stabilization of droop-controlled DC microgrids

DC microgrids (MGs) based on distributed energy resources (DERs) are prone to stability issues due to the negative impedance characteristics of some interface converters. Large-scale MGs need to be compatible with various operation modes and integrate the DERs with different structures, thereby increasing the difficulty of stabilization design. To address this problem, this paper proposes a novel impedance shaping method to achieve system-level stabilization by designing feedback laws for the droop-controlled sources. An impedance shaping criterion is first proposed for the decoupling design of multiple droop-controlled sources. Compared with existing impedance shaping methods, the proposed criterion can be more flexibly applied to a large-scale DC MG. An efficient algorithm is further developed to design the primary droop control by combining the proposed criterion and linear matrix inequalities. The proposed method features a simpler control architecture and can be directly applied to the DERs with different interface converters. Case study based on experiment and benchmark system shows that the DC MG designed by the proposed method has a high stability margin and good transient performance.