Abstract
Under the isolated microgrid, the output voltage of the inverter is influenced by different load conditions; further, the unbalanced load and the nonlinear load affect the output voltage of the inverter significantly. In order to mitigate voltage unbalance rate and improve total harmonic distortion (THD) caused by the unbalanced loads under the existing converter structure, this thesis not only applies model predictive control on inner current control loop to improve the dynamic response, but also performs the repetitive control on the outer loop to improve THD. Besides, the discrete model for analyzing effect of the predictive controller and repetitive controller are constructed to prove the stability of the system. The proposed control strategy is performed by Simulink; moreover, the presented theory are also verified by different simulations such as unbalanced loads, nonlinear loads and switching loads.