In order to solve the control problems of matrix converter(MC) in unsymmetrical load with PI control or repetitive control (RC) strategy, a combined scheme of PI and RC method was proposed, and the quality of output voltage could be effectively promoted. The compound controller was designed by establishing the mathematical model of MC in d-q coordinates, and analyzing the stability conditions as well as the characteristics of disturbance attenuation of MC system. As a delay link was included in the internal model of the repetitive controller, an obvious lag existed in signal regulation process. Based on analyzing the harmonic features around park transformation, the harmonics in phase coordinate system was converted to 3 times harmonics in d-q coordinates by park transformation in double sequences. The internal model was improved, and the settling time of the compound controller could be reduced without affecting the performance of harmonic suppression. The simulative results indicate that the improved compound controller has a good property in the regulation capability and the disturbance suppression, the unbalanced problem of three-phase output voltage could be effectively resolved.