Power rectifiers are widely used in different industrial applications that deliver DC voltage supply for many types of loads like electrolysis cells, metal electroplating and other DC loads. These rectifiers act as nonlinear loads injecting harmonic currents to the AC mains with lots of troubles and negative impact on the utility grid and the load itself, like increasing losses, measurement error, protection device false tripping and distortion of the voltage at the PCC affecting other loads at the same point. For this reason, many researches focus on this problem and how to mitigate it. In this research, power analysis measurements are taken for 750 KW power rectifier feeding electrolysis cells and define the power quality indices compared to IEC 519 Standard. Passive filter is selected to mitigate the recorded harmonics. Two types of filters are designed. The first is three single tuned passive filter to mitigate the 5th, 7th and the 11th harmonics. The second
type is 2nd order high pass filter to mitigate harmonics equal and greater than 13th harmonics. MATLAB simulation is performed to validate the proposed solution. The current total harmonic distortion can be reduced from 29.6 % to 1.5 % and supply voltage total harmonic distortion is also improved from 3.25 % to 0.62% which meet the international standard and improve the power quality of the voltage at point of common coupling.