This work presents a method of current harmonic reduction in a distorted distribution system. In order to evaluate the proposed method a grid with high-order current harmonics is assumed. The reduction of current distortion is feasible due to the pulse modulation of an active filter, which consists of a buck-boost converter connected back-to-back to a polarity swapping inverter. For a practical application, this system would be the power electronic interface of a Renewable Energy Source (RES) and therefore it changes a source of harmonics to a damping harmonics system. Using the proposed method, the current Total Harmonic Distortion (THD) of the grid is reduced below the acceptable limits and thus the general power quality of the system is improved. Simulations in the MATLAB/SIMULINK platform and experiments have been performed in order to verify the effectiveness of the proposed method.