Investigation on vibration behavior of onshore wind turbine tower based on long-term monitoring data

To study the structural characteristics of onshore wind turbines under a range of environmental and operational conditions, a 2.0 MW onshore wind turbine tower was monitored for a period of 3 years. Based on the long-term field monitoring data, a statistical analysis of the vibration of the wind turbine and environmental factors was conducted. Then, a method based on covariance analysis was applied to determine the modal parameters of the wind turbine tower. In addition, the operating conditions of the wind turbine were divided. The effects of different operating conditions on the first three orders of frequency and damping ratio of the wind turbine tower were thoroughly examined. Finally, Campbell diagrams for the wind turbine in the X and Y directions were generated. The results indicate that the wind turbine blade speed at the third frequency (0.35 Hz) was nearly identical to the tower's fundamental frequency, which could potentially lead to structural resonance. Additionally, the blade speed of 7 rpm in the wind turbine causes the jump phenomenon, which is consistent with the non-linear jump phenomenon observed in the Sommerfeld effect during the transition from pre-resonance to post-resonance. This phenomenon provides an explanation for the peak of the RMS (root mean square) of the tower at wind speeds of 3 and 8 m/s vibration amplitude, thereby confirming the existence of resonance in the wind turbine. Consequently, the long-term monitoring of the wind turbine provides a basis for the design and assessment of the condition of wind turbine towers.