An Adaptive Droop Control Method for Interlink Converter in Hybrid AC/DC Microgrids

Abstract

The conventional control scheme of hybrid microgrids (MGs) uses active power-frequency and reactive power-voltage droop control methods to realize proportional active power sharing in ac and dc MGs, respectively. In order to equate the percentage loadings of dc and ac subgrids, the power transfer through the interlink converter is controlled such that the per-unit frequency deviation of ac MG is equated to the per-unit voltage deviation of dc MG. The main drawback of the mentioned strategy is the poor dynamic response caused by the slow dynamics of the conventional droop method as well as the delay associated with frequency measurement in the interlink converter (IC) controller. To enhance the dynamic response, a control scheme based on voltage-current droop characteristics is proposed in this paper. In this method, the d and q axis V-I droop control schemes are adopted for proportional active and reactive power sharing among ac Distributed Energy Resources (DERs), and the dc V-I droop control method is used for coordination of dc DERs. Furthermore, a novel control strategy based on d-axis voltage/dc voltage droop characteristics is proposed for the IC to realize global power sharing with a fast dynamic response. Experimental results are presented to showcase the efficacy of the proposed scheme.