An Improved Droop Control Method for Accurate Dynamic and Static Current Sharing in DC Microgrids

In DC microgrids (MGs), droop control is a commonly used method for load current sharing among parallel distributed generation (DG) units. However, it has two inherent drawbacks: 1) DC bus voltage deviation caused by virtual and cable resistances, and 2) degraded dynamic and static current-sharing performances due to discrepancies between the actual and desired output impedances of DG units. Especially under source or load current fluctuations, the dynamic performance of DG units tends to deteriorate, potentially leading to significant overshoots in their output currents. Such occurrences can have adverse effects on the operation of DC MGs. Currently, two methods are employed to address these issues: one utilizes secondary control strategies to correct the voltage offset of droop control methods, while the other adjusts the droop coefficient by using the estimated cable resistance. However, these methods often rely on communication networks, central controllers, or estimated cable impedances. This paper presents an improved droop control method to achieve accurate dynamic and static current sharing and DC bus voltage restoration. Without prior knowledge of cable resistances, the proposed method not only eliminates the impact of cable resistances on the current-sharing accuracy but also significantly enhances the dynamic performance of DG units. The effectiveness of the proposed method is validated through hardware-in-the-loop simulations.