Comparative admittance-based analysis for different droop control approaches in DC microgrids

In DC microgrids, virtual resistance based droop control is broadly used as the fundamental coordination method. As the virtual resistance guarantees load sharing effect in steady states, the output admittance determines the dynamic response of converters in transient states, which is critical in stability analysis and system design. So far, two different approaches of droop control (i.e. V-I droop and I-V droop) are proposed. Although they can achieve the same steady-state power sharing effect and fully compliable with each other, the output characteristics are not the same due to significant difference in control architecture. In this paper, a comparative admittance-based analysis is carried out between these two approaches. State-space models and more general analytical models are established to derive the output admittance of droop-controlled converter in DC microgrids. Simulations and impedance measurement is carried out using PLECS to validate the analytical results.