Automated OMA for monitoring wind turbine blade modes from the tower during operation

For wind turbines installed in the built environment, the risk of ice throw is a concern to operators. Large pieces of ice being thrown from the blades poses a severe risk for damage on infrastructure and, worse, personal safety. In industry several solutions do exist to detect the build-up of icing using operational modal parameters obtained from sensors on the blades. In this research project an alternative strategy to detect icing is investigated. Using a sensor on the tower, to detect variations in the frequency of so-called rotor whirling modes as an indicator for ice. Previous results on parked turbines proof the concept of this method. In this follow-up research the possibility to estimate and track the rpm-dependent whirling modes from measurements on the tower is investigated. The paper primarily aims to detect and quantify the uncertainty in the estimation of the whirling modes' frequencies during operation of a wind turbine. © 2019 International Group of Operational Modal Analysis.