Proportional droop index algorithm for load sharing in DC microgrid

This paper gives an overview about droop based power sharing issues of parallel connected dc-dc converters in low voltage dc microgrid. Droop control is the popular technique for power sharing in dc microgrid. The main drawbacks of the conventional droop methods are, poor current sharing and drop in dc grid voltage due to large droop gain. In this paper, a modified figure of merit called proportional droop index (PDI) is introduced in order to improve the power sharing performance of the dc microgrid, which is a function of normalized current sharing difference and losses in the output side of the converters. This proposed control method which calculates instantaneous virtual resistance, R_droop, and allows the converter to share the load current based on input power to the converters. By using R_droop shifting, the proposed method also eliminates the tradeoff between current sharing and voltage regulation. The detailed analysis and design procedure are explained and the effectiveness of proposed method is verified by detailed simulation analysis.