The increasing use of grid connected power electronic systems generates a set of interference phenomena between those devices and distribution grids. Power electronic systems are both sensitive to voltage disturbances and sources of disturbances, such as current harmonic distortion, voltages unbalance and flicker. Such phenomena motivated the study of a system named Open Unified Power Quality Conditioner, based on power electronic converters, used for the improvement of the Power Quality level in low voltage distribution grids. The study, mainly theoretical, has addressed the issue of compensators coordination under different operating conditions.