A Unified Control Strategy for Three-Phase Four-Wire Inverters in Grid-Tied and Islanded Microgrids with Enhanced Harmonic Suppression

This paper presents a unified control strategy for three-phase four-wire inverters operating in both grid-tied and islanded microgrid environments. Microgrids, decentralized energy systems comprising diverse energy resources, have witnessed increased integration in modern power networks. A critical component ensuring their effective functioning is the inverter, especially when dealing with variable loads and distributed energy resources. The developed control scheme accentuates two paramount aspects: seamless transition between grid-tied and islanded modes, and superior harmonic suppression. To achieve this, the control strategy deploys an adaptive harmonic compensator combined with a novel synchronization method. Simulation results, in conjunction with experimental validation, demonstrate that the proposed methodology not only guarantees stable operation under both operational modes but also enhances the harmonic profile of the inverter's output voltage, ensuring its compliance with stringent grid codes. This work paves the way for more robust, flexible, and cleaner integration of microgrids into the main power network.