Fault Ride-Through Testing of Wind Turbines

Grid codes concerning low-voltage fault ride-through capabilities of wind turbines are not (yet) harmonized, varying from country to country. Full-scale field testing of wind turbines with respect to all such codes may therefore not be practical. IEC 61400-21 is currently under revision, and the last committee draft (CD 2006) presents a standardized physical test for characterizing a wind turbine's response to a voltage-dip. The results of such physical tests may be used to validate numerical models of the turbine, which in turn can be used for modelling grid code compliance assessment of particular country codes. Success with such modelled validation will provide confidence in numerical simulations. The hypothesis of this paper is that the use of numerical models, that have been validated against the standardized tests, can reduce the number of physical full- scale tests needed. This paper assesses to what degree a validated simulation model is capable of predicting the fault ride-through capabilities of a fixed speed induction generator. This is done by comparing measurements on a wind-turbine emulator in a laboratory with predictions from a validated simulation model of the laboratory emulator. Simulations and laboratory measurements show excellent agreement. The validated simulation model accurately predicts the fault ride-through capability of the direct grid connected induction generator. It is concluded that the proposed methodology is promising and thus has the potential to increase the efficiency of grid code assessments. Full-scale field tests will still be required to validate the modelling completely, but using numerical models reduces the number of field tests needed.