An Enhanced Droop Controller for Accurate Transient and Static Current Sharing and Power Quality Improvement in DC Microgrids

In dc microgrids (MGs), droop control is commonly used for load current sharing. However, conventional droop-controlled dc MGs have two drawbacks: dc bus voltage deviation and degraded current-sharing performance. Even worse, due to mismatches between the actual and desired output impedances of distributed generators (DGs), their transient performance tends to deteriorate, causing significant overshoot or undershoot in their output currents. This issue can adversely affect the dc MGs’ operation, yet it is frequently overlooked. To address these issues, this article proposes an enhanced droop controller that improves the traditional design by incorporating voltage compensation and both transient and static current-sharing compensation loops. It eliminates the impact of line resistances on steady-state current sharing accuracy without requiring prior knowledge of them, enhances the transient performance of DGs, and reduces dc bus voltage variation. Moreover, it exhibits strong robustness and mitigates the impact of parameter variations in DGs on the transient current-sharing performance. A 1.35-kW test rig was designed to verify the effectiveness of the proposed controller. The experimental results show that, compared to the existing methods, it reduces DGs’ overshoot or undershoot by at least 68% and decreases the dc bus voltage drop and surge by at least 18.6%.