The impact of different battery charging rates of Plug-in Electric Vehicles (PEVs) on the power quality of smart grid distribution systems is studied in this paper. PEV battery chargers are high power nonlinear devices that can generate significant amount of current harmonics. PEVs will be an integral component to the operation of smart grids and therefore their power quality impacts must be thoroughly analyzed. Based on decoupled harmonic load flow analysis, different PEV charging scenarios (e.g., time zone scheduling, charging rate and penetration level) are tested for a typical large distribution network topology. The impacts of PEV charge rate on voltage profile, fundamental and harmonic losses, transformer loading and total harmonic distortions are demonstrated.