Hierarchical distributed control approach for multiple on-site DERs coordinated operation in microgrid

Micro grid (MG) is a self-controllable small-scale network developed to flexibly manage distributed energy resources (DERs). In this paper, an interlinked three-layer distributed control framework is proposed for the coordinated operation of multiple DERs in MG. In the bottom layer, an inner double-loop voltage and current controller is incorporated with a power droop controller for DER primary voltage and frequency regulation, which explores the fast response capability of DERs to counterbalance load fluctuations in MG. In the middle layer, a distributed secondary frequency and voltage control strategy based on the finite-time discrete consensus theory is implemented to correct the DER frequency and voltage offset in the bottom layer, and the proportional allocation of MG reactive load demands among multiple DERs is also achieved. In the upper layer, a distributed economic dispatch algorithm based on finite-time discrete consensus is implemented to minimize DERs total generation cost by optimizing DER active power reference coupled with the middle and bottom layers. Simulation results demonstrated that the proposed three-layer hierarchical distributed control approach is flexible for the plug-and-play behaviors of DERs and can achieve satisfactory reactive power share among multiple DERs; in addition, the approach effectively regulates DER voltage and frequency and ensures their low-cost operation.