Pinning-Based Hierarchical and Distributed Cooperative Control for AC Microgrid Clusters

With the large-scale application of microgrids (MGs), interconnecting nearby MGs to form an MG cluster (MGC) enables a higher utilization of renewable sources. This article presents a pinning-based hierarchical and distributed cooperative control strategy for AC MGC, which includes distributed generation (DG)-layer, MG-layer, and MGC-layer controls. The DG-layer control regulates the local voltage/current of each DG unit. The MG-layer control is performed for each individual MG, managing DG units in a cooperative manner through several sparse communication networks. By representing each MG as an MG agent, the MGC-layer control coordinates MGs based on a higher level peer-to-peer communication network among MG agents. The interaction between MG-layer and MGC-layer is established by pinning some DG units of each MG to communicate with the MG agent. Compared with the existing literature, the contributions of this article are: 1) simultaneously realizing multiple control objectives in the MGC system level including frequency/voltage regulation and active/reactive power sharing; 2) presenting a systematic approach to construct a unified small-signal dynamic model of the MGC system; and 3) performing a detailed small-signal stability analysis to evaluate the system dynamic performance. Time-domain simulation and experiments are carried out to validate the effectiveness of the proposed methods.