State-Space Formulation and Analysis of Distributed Control for Voltage Restoration and Proportional Current Distribution in DC Microgrids

Current allocation and voltage restoration pose intrinsic challenges in autonomous DC microgrids (DC-MG) featuring multiple parallel distributed energy resources (DERs). Hence, droop control has predominantly been employed as a control technique for MG. Although droop control facilitates current distribution among multiple DER operating within the MG, it results in a deviation from the rated DC bus voltage. To tackle this issue, a secondary control is introduced with the aim of preserving the bus voltage at the rated voltage while also ensuring proportional current allocation. To improve plug-and-play capabilities and to circumvent the single-point failure associated with centralized controls, this paper adopts a distributed scheme. In addition, to facilitate control design and stability analysis, a state-space (SS) technique is employed for the formulation of the DC-MG. The DC-MG SS model formulated and the proposed distributed secondary controller were simulated using MATLAB/Simulink®. The findings indicate that the newly devised distributed control effectively overcomes the constraints inherent in the droop control mechanism.