Analysis of lower frequent vibration of large wind turbine tower

Tower of modern large wind turbine are made of flexible steel tubular structure. Its first nature frequency is normally lower than the blade pass frequency and even lower than the wind rotor rotating frequency, therefore the vibration feature of the tower is important for the running condition of the wind turbine set. This paper discusses the lower vibration feature of the tower of a large MW wind turbine by means of analyzing the measured tower vibration signal. The non-stationary vibration feature was discussed based on modern spectral analysis and time-frequent analysis. The lower frequent resonance of the tower was identified.