A Decentralized Control Strategy Based on V-I Droop for Enhancing Dynamics of Autonomous Hybrid AC/DC Microgrids

Abstract

This article presents a GPS-based decentralized control strategy for hybrid ac/dc microgrids. The proposed method uses V-I droop characteristics for the distributed energy resources (DERs) in each of ac and dc subgrids. In particular, the output voltage of each DER is adjusted as a piecewise linear function of the per-unit (pu) output current. In addition, a droop control method is proposed for the interlink converter (IC) to attain global power sharing among the dc and ac DERs. The IC controller changes the deviation of the ac bus voltage as a function of the deviation of the dc bus voltage. This way, the power flow between ac and dc subgrids is adjusted such that the ac and dc DERs experience the same pu voltage deviation and hence deliver the same pu current and active power. In contrast with the existing control approaches, the proposed method does not require frequency or power calculations but directly uses voltage and current measurements in the control loops. So the delay associated with the feedback signals is minimized, which avails accurate load sharing during transients. Experimental results show the proposed method eliminates the transient overshoots of DERs' output powers by offering a fast and overdamped dynamic response.