Droop voltage range design in DC micro-grids considering cable resistance

Droop control is used in dc micro-grids to share load among multiple sources but practical factors deteriorates the performance. In this paper, the impact from cable resistance and voltage regulation error is analyzed. Cable resistance introduces extra output resistance thus changes the load sharing ratio while voltage error introduces a constant current deviation. To suppress the sharing unbalance from cable resistance, larger droop voltage range is preferred, but the tightness of voltage regulation is sacrificed. The possible voltage range for droop control in a dc system is analyzed. The quantitative relation between droop voltage range and unbalance current is derived for 2-source system. The worst scenarios for 3-source and multi-source multi-load system are identified. Dc system designers can use the relation between droop voltage and current sharing error from this paper to choose proper droop voltage range and guarantee sharing error within designed range.