Mitigating Control Loop Interactions in Grid Forming Inverters using Fullstate Feedback Control with Reduced Sensor Requirements

Grid-forming inverters play a vital role in facilitating the incorporation of distributed renewable energy sources into microgrids by regulating the AC voltage output of inverters. Traditionally, LCL filters are preferred due to their exceptional ability to attenuate harmonics. However, the conventional control approach for grid-forming inverters faces challenges in achieving desired performance due to interactions between control loops and low bandwidth limitations. To overcome this issue, this study proposes using an integral full-state feed controller that is tuned using the linear quadratic regulator approach. Moreover, implementing a full-state feedback controller requires measuring various parameters such as inverter side current, capacitor voltage, grid side current, and point of common coupling voltage. However, the integration of these measurements adds complexity and increases costs in system design. To address this challenge, a proposed solution called the Generalized Extended State Observer eliminates the requirement for current sensors on the inverter side and voltage sensors at PCC. The effectiveness of this control scheme is demonstrated through MATLAB/Simulink simulations.