DC Current Injection Into the Network from PV Grid Inverters

The present paper is focused on the study of the DC current injection for low voltage small grid-connected PV systems, which is one power quality requirements by the utility companies. For this aim, the existing status of guidelines and regulations in six selected countries where the development in the grid PV sector has evolved rapidly over the last decade, (Japan, Germany, USA, Australia, Spain and United Kingdom) has been viewed, according to the DC current injection into the grid. Furthermore, a grid-connected system installed in Spain has been used to perform measures about their possible DC current injection into the grid. Thus, twelve single-phase inverters (according to the transformer options: 50 Hz LF transformers, HF transformers or transformer-less) from the European market have been tested. Many groups of measurements were made, under different conditions. The results show that in all cases there is any DC current injection, even if a LF transformer inverter is used