Structural Shapes and Loads for Steel Wind Turbine Towers

The article deals with the issue of analyzing the structural design of towers for wind power plants (WPP), as well as the loads acting on them. When it is necessary to locate wind turbines at a height of up to 40 m, towers are usually designed as lattice towers (trihedral or tetrahedral). Tubular design of towers is used when their height exceeds 40 m. Russian wind farms mainly use tetrahedral lattice towers with a crossed variant of lattice organization, firstly, because of the relative complexity of manufacturing trihedral supports, and secondly, because of the possibility of the effect of wind shading of the wind turbine unit by a tower of tubular design. The height of the tower is based on the diameter of the wind wheel and the required height of the wind turbine to ensure its performance. The optimum base width of wind turbine towers is usually small and the D/H ratio is shifted to 1:20. Tubular towers are designed most often with a simple weakly conical shape or have a stepped-cylindrical outline. Currently, the most promising are wind turbines with variable rotor speed and direct power transmission. The frequency parameters of towers, as well as the loads on the wind turbine tower, are primarily determined by the characteristics of the wind turbines used. The main loads absorbed by the tower are the result of the operation or aerodynamic resistance of the wind turbine generator or its parts. Loads on the tower, especially in dynamic formulation, should be determined only taking into account the joint operation of the system “support - wind turbine”. A special problem in determining the loads on wind turbine towers is the determination of loads from a particular type of wind turbine. In addition to the rotor pulling force, foreign standards regulate the determination of loads associated with the friction of parts of mechanisms during tower rotation, eccentric application of the rotor pulling force and other similar aspects. In operating mode, wind turbines are a source of rather strong vibrations, which are composed of a main frequency, determined by the number of rotor revolutions per unit time, and an additional frequency, determined by the number of blades passing by the tower. Necessary conditions for dynamic behavior of the tower can be achieved by adopting new design solutions, increasing its stiffness, as well as by using frequency tuning techniques.