Enhanced Power Sharing Control of an Islanded DC Microgrid with Unmatched Line Impedances

Nowadays, the rise of DC loads along with distributed energy resources (DERs) and energy storage systems (ESSs) have led to a growing interest in using direct current (DC) microgrid systems. Conventional droop control methods face significant limitations when applied to parallel-connected distributed generation (DG) units, particularly in achieving balanced power sharing and minimizing voltage deviations. To overcome this issue, an enhanced power sharing control method is proposed in this paper to address load sharing in parallel-connected DG units based DC microgrids, considering unmatched line impedance and load variation. The enhanced control method aims to achieve balanced load power sharing and voltage control through the use of a Luenberger observer to estimate the Point of Common Coupling (PCC) bus voltage and accordingly estimate the voltage deviation. The proposed method compensates for the effects of unmatched line impedances and dynamic load variations, enabling accurate power sharing and precise DC bus voltage regulation. Various scenarios are studied to evaluate the performance of the proposed method under different operating conditions including system and load parameters variations. Finally, the performance of the proposed control method was validated through real-time simulation using OPAL-RT target, and compared with conventional droop control approaches.