A novel compensation approach for DC current component in a grid-connected photovoltaic generation system

A Photovoltaic inverter directly connected to the grid can cause, besides the generation of several current harmonics, a DC current component injection. The benefits of avoiding the use of power transformers in photovoltaic applications are higher conversion efficiency of the photovoltaic system and lower costs. Excessive DC current injection into the AC network can result in problems such as increased corrosion in underground equipment and transformer saturation. In literature some methods are proposed to use a current controller to force the output dc current to zero. Current controllers are prone to errors associated with nonlinearity and offsets in the current sensors. In order to overcome those problems, in this paper the application of the compensation approach of the shunt active filter illustrated by the authors in a previous paper is proposed. The proposed DC current compensation strategy was embedded in the inverter of a grid connected photovoltaic generation system.