Abstract: The power of the distributed generation in the grid-connected mode was usually controlled by the grid current. As the grid impedance changes, the steady-state errors and the content of total harmonic distortion will increase when conventional proportional-integrator controller is used. Based on the robust control technique, an improved control scheme is proposed in this paper. By properly designing the weighting functions, the proposed controller exhibits high gains at the vicinity of the fundamental frequency and the sufficient high-frequency attenuation characteristics within a certain range of the grid impedance changes. In this paper, the influence of the grid-impedance variations on system stability is analyzed when conventional proportional-integrator controller is used, and the design principle of the improved control scheme is given. In the end, the simulation and experimental results verify the effectiveness of the proposed scheme.