Two-Degrees of Freedom Control add Repetitive Controller for Inverters Working in Island Mode in Microgrids

This paper presents the analysis and design of an innovative control scheme that significantly reduces the Voltage Total Harmonic Distortion (THDv) of power inverters connected to microgrids working in island mode. The proposed Repetitive Two-Degrees of Freedom (R2DOF) control scheme combines the advantages of both repetitive and two-degrees of freedom control techniques, both controllers reduce the THDv in the presence of nonlinear loads. As it is shown in the paper, the inverter performance is improved by the proposed concept even when strongly nonlinear loads are connected to the microgrid. The analysis and design of the whole control system is presented in detail.