Operational modal analysis in the presence of harmonic excitations: A review

Abstract

Over the past years the use of Operational Modal Analysis (OMA) for Structural health monitoring has become more and more widespread. Such a methodology would also be relevant to wind farm owners that want to monitor the integrity of their turbines' foundations. However, harmonic components, originating from the rotor and periodic aerodynamic forces, are present within the measured vibrations. The harmonics violate the set of assumptions of common OMA techniques and as a result, these techniques potentially fail. This paper explores the different techniques presented in the literature to handle these harmonics. The techniques are first presented and later applied on data of an offshore wind turbine in the Belgian North Sea.