Abstract: After the wind turbine blades are covered with ice, the normal operation of wind turbine generator system is affected, the wind turbine will be overloaded and the blades will be broken, which will cause safety accidents and waste of resources. Therefore, it is very important to detect the icing condition of wind turbine blades by the modal parameters. In this paper, the modal parameters of wind turbine blade under different icing thickness were measured by modal testing system and calculated by the finite element software ANSYS, and the first four vibration modes and natural frequencies of the blades are obtained. The results show that the results of simulation modal and experimental modal are close, the vibration characteristics are consistent, and the error of fundamental frequency is within 3%. The first-order natural frequency vibration mode of the blade after icing is flap-wise. Starting from the two-order natural frequency vibration mode of the blade, the coupled mode of flap-wise and edge-wise directions appears. The first four-order vibration modes of the blade remain unchanged as the increasing of ice thickness, the main vibration mode is flap-wise, and the amplitude at the tip of the blade decreases gradually. When the ice thickness is 30 mm, the fundamental frequency of the blade decreases by 28.7% compared with that without icing. These results have certain guidance on design of blade icing state detection system based on vibration detection technology.

Key words: wind turbine blade, simulation modal, experimental modal, icing, vibration mode, natural frequency