Research program of the Utgrunden Demonstration Offshore Wind Farm, Final Report: Part3, WP2, Electrical
The power quality impact from the 10 MW Utgrunden wind park is investigated in this work. Reactive power exchange with the grid, flicker emission, response to voltage disturbances and harmonic emission have been investigated. The measurements were made on the low-voltage side of the 55/22 kV-transformer that connects the Utgrunden wind park with the main 55 kV grid on Öland. This means that the measurements presented show the result from a weaker grid point compared to the one that actually is used.
It was found that the wind park operated well with no noticeable negative power quality impact on the adjacent grid. The flicker emission is very low, the flicker coefficient is around 2-3 for the whole park which means that this park can be connected to a very weak grid without causing flicker nuisance. The harmonic current emission was always below 1.5 % which is well within the suggested limits. The voltage THD was below 3 % which also is well within the allowed limits. Interesting to note is that the highest voltage THD-values occurred when the park was disconnected from the grid. In fact it was not possible to see any relation between the voltage THD and the level of the produced electric power from the wind park.
The wind park produces some reactive power at low wind speed and consumes some reactive power at high wind speed, the power factor is at rated operation 0.999.
The wind park is frequently subjected to voltage dips. Dips with a remaining magnitude of 85 % or higher seem not to lead to disconnection of turbines, while dips with a lower remaining magnitude leads to the disconnection of turbines.
From March 23 to August 8, 2004, about 15 dips occurred which lead to the disconnection of at least one turbine, the most severe dip noted had a remaining magnitude of 60 %.