The increasing of the Photovoltaic (PV) systems penetration requires study of their effects on the grid's power quality. Therefore, in this paper the grid-tied PV system is studied. This needs an appropriate simulation of the PV system. Therefore, PSCAD/EMTDC is used in this study. The paper starts with investigation of the effect of PV on the harmonic distortion of the system. Finally, a proposed low-cost series connected single tuned-filter is designed for harmonic reduction in grid-tied PV systems. The results confirm the validity of the proposed filter for wide rating of PV systems