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Investigation of renewable energy generation and load impact on the grid impedance at different points of connection in public low voltage grids to support grid integration of renewable energies

Due to an increasing number of distributed energy generation systems connected to low voltage grids, further investigations are required to ensure high power quality and power system stability. One important power system parameter is the frequency depending grid impedance at the points of connection referred to as grid impedance. This impedance considerably affects power quality and system stability especially if remarkable resonances occur. In this paper, the grid impedance composition of different public low voltage distribution systems is measured and analyzed. The primary objective is to reveal the contribution of load and solar power generation to the grid impedance and especially to resonances. This case study shows that grid impedance resonance strongly depends on loads and inductance of the upstream network in low voltage power systems. However, if the load impedance is very high or no load is present, solar power plants lead to remarkable grid impedance resonances especially during nighttime.