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Disturbances from the utility grid including voltage sags, harmonics and the grid impedance will affect the LCL-filter-based grid-connected inverter's connecting to the grid. In this paper, a repetitive-based controller with dual close-loop and feedforward for a single-phase system is proposed. In the method, dual close-loop control with feedforward can limit the resonance peak of the LCL filter and brings high gain and rapid response; repetitive control can provide the system with the ability to attenuate grid harmonics and good robustness. Additionally, it is easy to design and implement for the repetitive controller. Simulation and experimental results are given to prove that the grid current quality can still satisfy the standard under the conditions of different grid disturbances.