Study On Systematic Dynamic Model And Key Part Optimization Analysis For Wind Turbine

In recent decades, the rapidly development of wind energy in China and the increasing of size and complexity of homemade wind turbine have requested the improvement in wind turbine systematic design technology and manufacturing capacity. A reasonable systematic dynamic model is an important part for systematic design of MW-class wind turbine. According to its results, engineers not only can predict the time-series data of loads on different parts, but also can conduct stability analysis and control design. Therefore, the construction of wind turbine's systematic dynamic model has an important significance for the development of wind turbine systematic design and manufacturing capacity.The dissertation proposes a study entitled"Study on Systematic Dynamic Model and Key Part Optimization Analysis for Wind Turbine", sponsored by Chongqing Science and Technology Key Project (CSTC20073052). Based on preliminary studies, a wind turbine systematic dynamic model including wind field model, rotor aerodynamic model and structural dynamic model has been established and a composite optimization method is presented for the key parts of wind turbine. In wind field model, the influence of blade's rotation motion on wind speed PSD has been analyzed. In rotor aerodynamic model, the original BEM theory has been modified to account for tip-loss correction, yaw error correction and periodic change of blade azimuth position, and the modified BEM model has been set up in Simulink. In structural dynamic model, the flexibility of blade and tower is represented by presumed mode shapes, and with the Kane Equation, the full wind turbine systematic dynamic model has been established. Using the model, the total wind turbine modal analysis has been conducted and the loads on key parts of a stall-regulated 600kW wind turbine and a pitch-regulated 2MW wind turbine have been simulated. With the load simulation results, the fatigue analysis and composite optimization including topological optimization and wall thickness optimization analysis of a hub has conducted. In the dissertation, the major work and tasks are summarized as follows:1) Wind field for wind turbine was set up for its systematic dynamic model. Based on the motion of wind turbine's components, the similarities and differences between stationary components and ones with period motion have been investigated. According to standard von Karman power spectral density (PSD) model and rotationally sampled PSD model, the PSD matrixes of turbulence on components of wind turbine has been setup, and longitudinal turbulence's time serials have been generated based on the superimposition of harmonic waves. The results from statistical analysis of simulated data and comparison with target spectrum demonstrated the validity of the presented method. The wind field model can describe the characteristics of wind speed on wind turbine and can be used in wind turbine systematic dynamic model.2) The original BEM theory for wind turbine's rotor was introduced and was modified to take the tip loss correction, yaw error correction and blade azimuth into consideration. The modified BEM model was set up in Simulink. Using the model, the inflow factor, the tangential factor of blade, rotor's torque and output power was calculated. The Simulink model has taken more correction factors into consideration, and can simulate aerodynamics more correctly; besides, the model is easy to understand and to expand. Comparison between the results and Blade's showed that the model was credible.3) Based on presumed mode shape method, the structural dynamic equations of wind turbine including the first and second flapwise mode shape of blade, the first edgewise mode shape of blade, the first and second fore-to-aft mode shape of tower and the first and second side-to-side mode shape of tower were constructed. Along with the wind field model and BEM model, the wind turbine aeroelastic systematic dynamic model was constructed, the model can describe the dynamics of wind turbine more correctly than subsystem model. Using the model, the deflections, speeds and load of tower, blade and hub of a stall-regulated 600kW wind turbine and a pitch-regulated 2MW wind turbine have been calculated. The results were compared with that of Blade.4) For a stall-regulated wind turbine and a pitch-regulated wind turbine, linearization analysis of wind turbines was conducted at steady operation points, and the first-order linear period equations for wind turbines were obtained. With the multi-blade coordinate transformation method, the degree of freedom of blade's rotation motion was converted into stationary frame where the tower-nacelle subsystem existed. In the stationary frame, mode frequencies and damp ratios for wind turbine were calculated through modal analysis, and the Coleman diagrams were drew for two kinds of wind turbines under two situations, with aerodynamics and without aerodynamics. The results can be used in control design and stability analysis.5) According to the simulation results of hub from wind turbine systematic dynamic model, the fatigue analysis was conducted, and a composite optimization model including a topological optimization model and a wall thickness optimization model was constructed to reduce the weight of hub. In the optimization model, the objective was the minimum weight of the hub, while the design variables are the wall thicknesses of the hub. With the optimization model, the weight of hub is reduced with 29%, while the fatigue life is still sufficient. The method of fatigue analysis and optimization analysis for hub can be applied to other key part of wind turbine as well.