Harmonic filtration by current injection and shunt capacitors technique

The controlled and uncontrolled converters or inverters loads are widely used in industrial applications and especially in producing electric energy from renewable sources. These types of nonlinear loads generate harmonics, with damaged effects, lead to voltage and current distortion at utility and load sides, in addition to high amount of losses in distribution system. The source currents of single phase and three-phase controlled or uncontrolled bridges contains high level amount of harmonics and consequently the total harmonic distortion is greater than the allowed values according to all international standards. This paper is proposed a new scheme based on triplet injection technique in addition to a passive filter connected to the ac utility side. This technique is based on Injecting the harmonic components from the DC side back to the line through the boost circuit and zigzag transformer in presence of line capacitors, as shown in Fig. 1 to control the injection of the harmonics, the final scheme will reduce the total harmonic distortion of the line current to an acceptable value that meet the requirements of international standards and especially IEEE standard.