Power quality measurements performed on a low-voltage grid equipped with two wind turbines

The power quality of a low-voltage grid with two wind turbines is investigated. Slow voltage variations as well as transients and harmonics are measured and analysed. Furthermore, the spectrum of the power is determined so that the presence of periodic power components can be investigated. Although periodic power fluctuations reaching 10 % of the rated power are registered, voltage variations are lower than the prescribed IEC flicker limit at steady-state operation. As the turbines are put on-line, the voltage level is lowered by 3 %, which exceeds the flicker limit. The risk for flicker increases if the X/R ratio of the grid is low and if turbines which have a tendency to produce large periodic power fluctuations are used