Analysis of harmonic voltage distortion simulation study results compared to actual levels measured at the 383 MW nearshore wind park Fryslân

In 2021 the 89 WTG, 383 MW nearshore Wind Park Fryslân (WPF) in the IJsselmeer, the Netherlands became operational. The electrical infrastructure of the wind park can be regarded as a worst-case for harmonic voltage distortion. Extensive simulation studies have therefore been done by WPF using impedance loci to represent the transmission network. The studies confirmed that the capacitive behavior of the wind park electrical infrastructure, in combination with a weak inductive high-voltage grid, result in amplification of background harmonics and harmonics emitted by the WTG. However, comparing harmonic distortion measurements with the simulation results for Windpark Fryslân, the paper identifies specific limitations of the existing approach for proving grid code compliance regarding harmonic voltage distortion. Since background harmonic distortion is currently not considered in load flow studies, small changes in assumptions (for example WTG impedance) can cause an amplification or damping of the background distortion of a certain harmonic order. This means that overall harmonic voltage distortion may be both under- and overestimated. To mitigate this risk, more precise impedance data could be made available by the grid operator. Also, background harmonic distortion at the PCC should be considered in harmonic studies to improve both the correctness and the accuracy of simulation results.