A Virtual Impedance Based Control for Power Sharing in a Microgrid with Uncertainty in Line Impedance

In a microgrd, power sharing among different power converters with different energy sources is important especially when it works in the island mode. The droop control which is broadly used in the microgrid has the merits of simplicity since it only uses the local signals and does not require communication. However, in the conventional droop control, there is inherent trade-off between the power sharing and the voltage regulation in selecting the droop coefficient. In this paper, a virtual impedance-based control for sharing power is proposed for improving the voltage various while maintaining power sharing among different power converters when there is uncertainty in the line impedance. Experiments are carried out to compare with the conventional droop control method. It shows that the virtual impedance based decentralized control has drastically decreases the voltage variation from 5% to 0.8% while maintaining the same power sharing, which demonstrate its superiority over the conventional droop control when there is impedance uncertainty in the grid.