The Load Characteristic Analysis Of Large Wind Turbine Tower

Wind turbines absorb wind energy with the rotating rotors, which is changed into mechanical energy and then sent to the electricity transmission grid. Towers are the main supporting components in wind turbines with a thin, cylindrical and towering structure. For towers being in the natural environment for long time with the effect of turbulence, wind shearing, wind direction and tower shadow, etc. All of the phenomena result a very complicated aerodynamic loads effect, which has a large impact on the aerodynamic performance and the lifetime of wind turbines.In the process of wind turbine designing, for ensuring the safe, reliable and effective running, and avoiding the accidents happenning, the loads of towers should be analyzed. Above all, the performance and the safety of structures should be improved and optimized, which are especially important to the large and medium-sized wind turbines.A type of 2 MW wind turbine is shown as an example in this paper, and the steady-state turbine model and dynamic turbine model are both established with the GH-Bladed software, and then the simulation experiment is carried out effectively. Based on the theory of gas dynamics and structure dynamics, with the IEC and GL standard files, the tower loads are analyzed and validated in detail. In the process of research, some conclusions are obtained, and summarized as follows:(1) According to the establishment of coordinate system, the transmission and the simplified process of turbine loads are researched deeply. All six kinds of tower loads are summarized with the load characteristics, which include:aerodynamic load of tower top, hub torque, tower wind loads, imbalance point of nacelle mass, nacelle gravity and tower gravity. With all the loads being simplified along the coordinate system, the concentrated force and the moment can be calculated.(2) The impact factors of power are the main consideration in the steady state performance analysis of wind turbines. The main factors affecting power are the tip speed ratio and pitch angle. For reaching the best tip speed ratio to attain to the maximum power, the pitch angle should be adjusted according to the control system.(3) The bending vibration rule of the four cross-sections is similar with the limit load analysis of these four tower sections. The engine parts in nacelles will change in different wind conditions, which result in the changing of the bending moment and the maximum bending moment section. In addition, the vibration problem is always the main safe factors of turbines from operational state to stop-state.(4) The relational curves of stress and cumulative cyclic frequency are shown with the GH-Bladed software in fatigue load analysis ofd towers. In the fatigue test, the tower is under the action of a given stress again and again, and the tower will be broken when the damage accumulate to a certain critical value.