Structural Performance Analysis And Wind Resistant Optimization Design Of Tower Structure For Horizontal-axis Wind Turbine

As a sustainable and renewable clean energy,wind energy has always been favored by various countries,and the development of wind energy industry is also in line with low-carbon development concept in our country.The wind turbine is a mechanical tool for capturing and utilizing wind energy.The wind turbine tower,as the main bearing capacity component of the wind turbine,accounts for nearly 20% of the manufacturing cost of the wind turbine,and its mass can weigh hundreds of tons.With the emergence of megawatt-level wind turbines,the tower structure is also developing towards the direction with more than 100 meter.The load action of wind turbines is more complicated,thus the structural damages in wind turbine tower often occur under strong winds.In this paper,the structural dynamic characteristics and the strength and stability design of the wind turbine tower structure under wind loading are numerically studied.For the structural optimization design of wind turbine tower under wind loading,a mathematical model of wind resistant optimization design is constructed to obtain the optimization results in the structural parameters of wind turbine tower,which could greatly reduces its material cost and engineering cost.The dissertation mainly includes the following aspects of work:The tower structure of a 1.5MW wind turbine is simplified into a cantilever beam model with variable sizes in cross section.The corresponding finite element model is established to check the static strength and stiffness ability of the tower under the various working cases with nominal wind speed,cut-out wind speed and maximum design wind speed.The Moore integral method is adopted to calculate the top displacement of the tower and used for the next optimal design procedure.The free vibration modes of the main tower is modeled and analyzed,and the first 6vibration free modes of the tower are solved.The value of first order natural frequency of the main tower is between the rotation frequency of the wind rotor and the passing frequency of the propeller,which means no resonance phenomenon occurs.It is also found that the mass at the top of the tower has a great influence on the first order natural frequency of the tower.Finally,the first-order natural frequency of the tower is calculated by the compliance method and selected as the optimal design constraint in the next optimal design procedure.Under the combination of dead weight and wind loading as result of rated wind speed,cutout wind speed,and maximum wind speed,the linear buckling analysis of the tower is performed.As for the buckling load coefficients,all of the working cases are larger than 1,which shows the strong buckling stability in the main tower.Taking the material cost of the tower structure as the objective function,the mathematical model of the wind resistant optimation design procedure for the main tower of wind turbine is constructed.The genetic algorithm is adopted by considering the previous constraints to carry out the optimal design of main tower under the maximum design wind speed.Meanwhile the optimal design of the tower is also conducted under the same working conditions by selecting the FMINCON function,which is compared with the results from the genetic algorithm.The optimized results from both methods show good agreement and it is shown that the optimized tower structure of wind turbine meets the safety requirements.