Measurement results and performance analysis of the grid impedance in different low voltage grids for a wide frequency band to support grid integration of renewables

Knowledge of the frequency depending grid impedance is necessary for adequate grid integration, including setting of standards, of renewable energy sources. It is also essential for the design of power converters for renewable energy sources. In this paper wide frequency range measurements of the positive sequence grid impedance in public low voltage grids with high proportion of renewable energy generation systems are presented and analyzed. This case study shows, that the impedance of a point of connection strongly depends on the low voltage grid including its sources and loads. Moreover, the impedance varies strongly during the day but shows similar recurring pattern from day to day. The used measuring system is briefly described.