Circulating current minimization based adaptive droop control for grid-connected DC microgrid

In this paper, a distributed circulating current minimization method is proposed for parallel converters in grid-connected DC microgrids, where adaptive droop control and tertiary control have been presented to eliminate the trade-off between current sharing and voltage regulation. By introducing a dynamic averaging circulating current, the proper load current sharing with reduction in circulating currents will be achieved. Different from the fixed PI droop control, our adaptive PI droop method can dynamically adjust the droop resistance values according to circulating current control, which minimize steady state oscillation and guarantee the proper current sharing ratio with changing loads and uncertain variations in system parameters. Moreover, stability analysis of the proposed system is performed with the consideration of the variation in system control gains, droop gains and communication delay. Finally, the performance of the proposed method is validated through simulation and experimental results.