**6. Conclusions**

The grid-connected inverter control is studied in this paper. To solve the nonlinearity and uncertainty issues of GCIS, an AFC approach for GCIS is proposed. The developed controller relies on two principles: namely, the input-output feedback linearization principle and the approximation capability of the fuzzy system. The GCIS is modeled as a nonlinear MIMO system. A fuzzy system with weighted average defuzzifier, singleton fuzzifier, and product inference rule is utilized to develop the AFC law through approximation of the unknown nonlinear functions that appear in the input–output linearizing model. Due to the ability of the proposed controller to estimate unknown parameters for different operation cases, the controller is robust against parametric uncertainties. The closed-loop stability using the Lyapunov function analysis is established to show that the output tracking error is globally ultimately bounded. To test the effectiveness of the proposed approach, the proposed AFC was implemented and tested in the MATLAB/SIMULINK environment for a GCIS for different operating cases as unity power factor tracking, tracking of power factor changes and robust tracking. The obtained simulation results showed that the proposed AFC provides excellent tracking performance with bounded tracking error and bounded control signals. In comparison to the PI control and TSKPFNN controller, the proposed AFC showed superiority in terms of response and reduced fluctuations in case of power factor change tracking. Moreover, the results showed that the proposed AFC is very robust against parametric and model uncertainties.

**Author Contributions:** Methodology, H.Y. and M.S.; Software, M.S.; Validation, H.Y., R.A.A. and A.A.-H.; Writing—original draft preparation, M.S.; Supervision, H.Y.; Writing—review and editing, H.Y., R.A.A. and A.A.-H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Sustainable Energy Research Center (SERC) at Sultan Qaboos University (SQU) under gran<sup>t</sup> number IG/DVC/SERC/18/01.

**Acknowledgments:** The authors acknowledge the financial support provided by Sustainable Energy Research Center (SERC) at Sultan Qaboos University (SQU) under gran<sup>t</sup> number IG/DVC/SERC/18/01.

**Conflicts of Interest:** The authors declare no conflict of interest.
