Study On The Simulation And Optimization Of The Large Wind Turbine And Its Key Components

Due to environment deterioration, energy crisis and other factors, wind power technology has been becoming more and more attractive to people. With the increment of single wind turbine (WT) capacity, complexity and the rise of offshore WTs, higher requirements are proposed in domestic independent wind turbine design and manufacturing. There's still a huge gap of synthetic wind turbine design level between China and western countries, and many problems need to be solved especially on whole turbine modeling, performance simulation, load calculation, etc. This research is under the support of Chongqing Key Technologies R &D Program titled"Wind Turbine System Design Key Technology"with focus on system simulation and structure optimization of certain 2MW variable speed-pitch horizontal wind turbine. The main content and structure of the dissertation are as follows:In chapter 1,the status and hot research topics of wind power technology is analyzed. The technical requirements of WT system simulation and optimization is proposed. The research status of wind turbine system in terms of aerodynamics, structural dynamics, system modeling and simulation, and component optimization technology is reviewed. Therefore the research of wind turbine system and key components simulation and optimization is proposed. The main content and skeleton of the thesis are given as well.In chapter 2, a new theory of WT aerodynamics - BEM GDW comprehensive theory is proposed. With respect to the extensively used and revised blade element momentum theory (BEM) on WT aerodynamic performance calculation, its defects, such as no 3D aerodynamic effects,time delay, etc. are identified. Meanwhile, another theory named generalized dynamic wake theory (GDW) is solicited. GDW, compared to BEM, can describe more general pressure distribution. It does exist time delay, and the rotor induction rate can be obtained from a series of first order partial differential equation which prevents iterations. However, its calculation is unstable under low wind speeds. To remedy the deficiencies of both theories, via combination, BEM-GDW comprehensive theory is presented. The theory is fulfilled in Matlab taking account of dynamic stall.In chapter 3, the whole WT is modeled and simulated, and loads on various key components are calculated. The typical modeling process, module characteristics and parameter definition of the 2MW variable speed-pith horizontal wind turbine generator system is elaborated. Detailed research of the effects of module characteristics and parameters on the model is conducted. Based on practical wind field characteristics, design load cases of the wind turbine under real operation in accordance with GL certification are defined. The model of the whole WT system is established, and static and dynamic simulation are conducted to obtain extreme and fatigue loads of every components. It plays a guiding role on component certification and subsequent design. Also preliminary research is performed on sea condition, and lays a foundation for off shore wind turbine system design.In chapter 4, emphasis is put on ice load investigation of WTGS (wind turbine generator system). It is the first time to investigate wind turbine under ice loads. Through numerical simulation, the effects of ice load on wind turbine airfoil, power and annual power output are studied. Using Matlab, a routine which is initially used to calculate wind turbine aerodynamic performance, power and annual power output based on BEM-GDW comprehensive theory is further developed to incorporate the effects coming from ice loads. The 2MW variable speed-pitch wind turbine is used as an example to do performance simulation. The obtained power curve is compare to the results from GH Bladed, and the accuracy and practicability of the numerical simulation method is verified.In chapter 5,based on BEM-GDW comprehensive theory, considering actual annual wind distribution probability and targeting maximum annual power output, a wind turbine blade optimization routine has been developed combined with genetic algorithm technique. The routine is applied to conduct optimization design of the 2MW horizontal wind turbine blade. Smooth geometric transition along the optimized blade span with respect to twist, chord length and thickness distribution is found which is beneficial for manufacturing. Meanwhile, the energy capturing efficiency and annual power output has greatly improved based on the current optimized design, yielding evidently practical engineering application value.In chapter 6,a new method, which constructs and solves optimization model to optimize the structure of wind turbine in order to improve the stability of whole wind turbine system with coupled blade and tower, is developed. The optimization model formulation is described as the following: minimizing system vibration is the objective function, diameter and thickness of tower are decision variables, and constraints include strength, deformation and mass. Interior penalty function technique is applied to solve the optimization model, and Campbell diagram is employed to analyze the system stability. The formulation and solution method were applied to the 2MW horizontal axis wind turbine, and the stability of the whole turbine was greatly improved and tower mass was reduced by 13%, which demonstrates the proposed method not only contributes to theory research but also leads to great benefits in practice and effectively optimizes the original design, contribute to the key components of domestic wind turbine optimum design to improve the domestic wind turbine design standards, and domestic and lay a good foundation and broaden the design ideas.In Chapter 7, the important results and conclusions of the dissertation are summarized, and the prospective research work is presented.