Research On The Rotor Aerodynamic Optimal Design And Control Optimization Of Low-Wind-Speed Turbine

With the consistent promotion of wind resource exploitation, conventional development of comparatively high-wind-speed wind power projects is getting harder and the wind power transmission cost is getting higher. Hence, it becomes a new direction to tap low-wind-speed wind resource. In order to realize distribute wind power feeding into grid, wind power local utilization, to make up for the shortcomings of conventional wind energy utilization, and to complement the deficiency of fossil energy, tapping low-wind-speed wind resource is of great significance.The kernel of exploitation of low-wind-speed wind power lies in the energy capture efficiency of wind turbine generator system (WTGS), optimization of low-wind-speed blade airfoil, and optimization of WTGS aerodynamic characteristics of wind turbine. These are the key to enhance low-wind-speed wind energy conversion efficiency, to lower WTGS costs, and to balance WTGS load. Sponsored by the National Science and Technology Support Project "5.0MW Doubly-Fed Variable Speed Constant Frequency Offshore Wind Turbine Design, Integration and Demonstration"(2009BAA22B02), this research involved optimization method, theoiy and key techniques of aerodynamic design of low-wind-speed rotor and WTGS control. The main contents are as follows:Based on aerodynamic design theory of blades and genetic algorithm optimization, the blade airfoil parameters were optimized, using the mid-low wind speed blade airfoil as the reference base, lift-drag ratio as fitness function, geometric control parameter of upper and lower surfaces as design variables for airfoil optimization. After100generation of generic evolution, finally the low-wind-speed series optimized blades airfoils were obtained. Compared to the reference base airfoil, optimized airfoils had higher lift-drag ratio and better lift coefficient.Based on numerical simulation method of Navier-Stokes equation, softwares GAMBIT and FLUENT were used for simulating air flow field of optimized airfoils and studying their aerodynamic characteristics, which included the pressure distribution around airfoil, speed distribution, lift-drag ratio. The numerical analysis results verified the validity of optimized airfoils.Based on Blade Element Momentum (BEM) theory, the blade aerodynamic design was optimized with genetic algorithm, using rotor power coefficient variable dCpmax as the optimization objective function, geometric chord and twist of airfoil distribution function coefficient as design variables for blade optimization. After generic evolution, the low-wind-speed blade aerodynamic model was obtained. Based on this blade, software GH Bladed was used for constructing a3MW low-wind-speed wind rotor dynamics model to analyze aerodynamic characteristics of the rotor. The results showed low-wind-speed wind rotor had higher efficiency and wider high-efficiency-region, less thrust load, therefore the validity of blade aerodynamics optimization was verified.Fuzzy control was applied in maximum wind energy capturing and dynamic load control of doubly fed induction wind generator system (DFIG). In environment of software GH Bladed, a3MW low-wind-speed WTGS mathematical model was constructed. Fuzzy controller of speed and dynamic load was designed and analyzed using them. Simulation results verified that the optimal wind energy curve occurred with fuzzy control and therefore highest wind energy capturing efficiency. Also, a dSPACE control system based DFIG in the loop test platform was constructed, and tested the characteristics of DFIG. The tests verified further the significant advantage of fuzzy control on onlinear time-varying wind generator control system.