Decentralized Voltage Regulation and Energy Management of Integrated DC Microgrids into AC Power Systems

This article proposes a control strategy for integrated dc microgrids (MGs) into power systems. In this method, the DC MGs are capable of importing or exporting energy from or to the AC grid based on the loading conditions. The DC MGs employ an interlinking converter (IC) as a bidirectional back-to-back converter for a distributed generator (DG) unit at the point of common coupling (PCC). In a multi-DG unit DC MG, an energy management strategy should be planned by sharing network loads among dispatchable DG units, and meanwhile, the dc network voltage should be regulated. The proposed control system utilizes an ac voltage superimposed on the nominal dc voltage of the network. The frequency of the superimposed ac voltage is used to modify the conventional droop control, which leads to simultaneous accurate load sharing and regulated voltage in a decentralized manner. The IC DG unit equipped with the proposed controller interfaces the dc network through a dc/dc buck converter and the ac grid through an active rectifier. This strategy provides a seamless transition between islanded and grid-connected modes for the DC MGs. The performance of the proposed control system is evaluated through simulations studies via PLECS and a set of experimental results.