Grid impedance determination — relevancy for grid integration of renewable energy systems

As the power of renewable energy plants is increasing, their impact on the power quality becomes more and more important. The occurring grid feedback is related to the grid impedance. Therefore the exact measurement of the grid impedance is necessary. In this paper simulations of a windfarm grid integration scenario are presented that show the advantages of a grid impedance measurement in context of harmonics. In addition methods to determine the frequency dependent grid impedances are outlined and the influence of the virtual-starpoint on the calculations is examined. Based on the examinations a novel method to identify the real grid impedances is proposed.