Structural vibration monitoring and operational modal analysis of offshore wind turbine structure

In order to reduce the structural failure and accident occurrence of the offshore wind turbine, the researches on structural operational safety of offshore wind turbine based on the measured data during the operation periods should be carried out and considered as the key way to solve these problems. However, the current researches are only focused on numerical simulation, model experiment and theoretical analysis and ignore the structural vibration characteristics analyzed from condition monitoring and prototype observation data from the actual wind turbine structure. To compensate for this study defect, the structural vibration displacement signals of one Chinese offshore wind power prototype under different conditions were obtained based on a long-term prototype observation in order to achieve the comprehensive and systematic research on vibration response characteristics and operational modal analysis of measured structure. Considering the complicated operational environment of offshore wind turbines, the structural response regular pattern and vibration safety are also discussed emphatically under different conditions such as standstill, normal operational, startup, shutdown and extreme typhoon status. Simultaneously, the integral operational modal identification method of offshore wind turbine in the range of full power is proposed based on traditional and modified stochastic subspace identification technologies, and further the modal identification results and the relationship between structural modal parameters and environmental/operational factors are also illustrated in this paper. The researches on the structural vibration characteristics and operational modal analysis of offshore wind turbine not only provide powerful data and technology support for the operation safety evaluation, but also provide the necessary theoretical and practical bases for the design and maintenance of wind turbine structures.