Collaborative voltage unbalance compensation in islanded AC microgrids with grid-forming inverters

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe presence of unbalanced loads in power systems creates voltage imbalances that perturb the operation of sensitive loads like induction motors, power electronics converters and adjustable speed drives. This paper presents a novel control scheme that achieves accurate voltage balance at any node of an islanded AC microgrid with seamless integration with the existing hierarchical control of the microgrid. A master-slave architecture is adopted for the unbalance compensation due to its low network traffic requirements and its modular conception. The unbalance compensation follows a collaborative principle where current injections are computed as a function of the current rating of each inverter thus avoiding the overcurrent stress of the unbalance compensation by a single inverter. The paper presents the stability analysis and the design guidelines for the control parameters. The performance of the control proposal has been successfully tested in a laboratory microgrid. Selected experimental results are presented.Postprint (author's final draft