Dynamic Security Analysis Of Wind Turbine Tower Structure

The rapid development of modern society is based on the adequate energy. Asthe shortage of fossil energy and environment pollution become more and moreserious, the wind energy, which is a new clean and sustainable energy, is got moreattention. In recent years, wind turbines are widely used in the world, and it has abroad prospect. With the gradually development of the wind power technology, thewind turbines tend to be giant in order to obtain greater economic benefits. Becauseof the complicated working environment and special structural form, wind turbineblades are prone to occur fatigue failure, menwhile, the development of the giantwind turbine makes the incentive of wind wheel for the tower increasing. Therefore,the problem of how to ensure the safety of the tower after a blade fatigue failure isstanding out, especially for the giant wind turbines.In this paper, a security analysis for the2MW horizontal axis wind turbinetower was conducted by using the finite element software ANSYS. The impact forthe tower’s safety due to the leaf abscission are investigated in three aspectsincluding dynamic characteristics, wind-induced response and the structure stability.Then a concept of transient influence coefficient after leaf abscission was proposed.Firstly, the dynamic characteristics analysis mainly summarized the impact forthe dynamic characterisics of the wind wheel and tower after the leaf abscission.The analysis shows: Both the wind wheel and the tower vibration modes can beaffected by the leaf abscission. The transient influence coefficient is directly relatedto its corresponding number of modes, the position of shedding blade, bladevibration frequency, the number of blades and the tower oscillation frequency. Byinvestigated the leaf abscission’s impact for the system resonance range throughdrawing the CAMPBELL Chart, obtained that leaf abscission has a weak impact onthe wind wheel resonance speed, but it may increase the possibility of resonance ofthe wind wheel-tower system;Additionally, the wind-induced response analysis mainly analyzed the windwheel and the tower’s wind-induced response before and after the leaf abscission,the results showed that the leaf abscission has little effect on the mechanicalproperties of the wind wheel, but it has a great influence on the mechanicalproperties of the tower. This paper provided the basic changing law for the transientinfluence coefficient according to the variation on the blade’s stiffness, rotor speedand wind speed, and moreover, combined the resulting law with the actual projectconditions, the paper made reference to proposals to the existing wind turbine and future wind turbine tower design, to avoid the damage of the tower caused by theleaf abscission;In the end, the tower’s stability analysis contrasted the tower’s buckling modebefore and after the leaves fall off. The analysis shows: Leaf abscission cause greatchanges to the tower buckling modes and buckling eigenvalues. The tower’sbuckling eigenvalues after the leaf’s drop is much smaller than the characteristicvalues before shedding and the buckling failure location is switched from the centraltower to the top, furthermore, the analysis researched the basic changing law for thetransient influence coefficient according to the variation on the cabin quality, rotorspeed and wind speed, respectively.