Research On Intelligent Control Of Large-scale Wind Turbines

Energy and environment are pressing problems that must be settled by human beings for future survival and development. Wind power has preferable economic and social benefits because of its cleanliness and free pollution, short construction period, flexible investment and few occupation of land. At present, there are big gaps between china and developed countries in wind turbine's theory and application research, because wind power has disadvantage with thermal power and hydropower in cost, power quality, equipment manufacture and control technology. Research of wind turbine in china is very weak and many advanced wind turbine technologies are not solved such as high power capacity, pitch control and variable speed constant frequency etc. Thus, almost all advanced large-scale wind turbines are imported from overseas. In all, indepth research of wind turbine technology has very important meaning for persistent wind turbine development and home production. Wind turbine is a comprehensive system engineering of high technology which deals with aerodynamics, automatic control, mechanical drive and generator etc. The research difficulties and hot pots of wind power are focused on high power capacity, advanced control and optimization etc. Control is crucial to the efficiency and reliability of wind turbines. Wind energy has lower density, instability and randomicity, wind turbines have strong nonlinear multivariable with many uncertain factors and disturbances. The thesis expands its investigation on relevant control problems of wind turbines, main contents can be concluded the following: (1) Nonlinear mathematical model of large-scale wind turbine is established by combining analysis modeling with experimental data verification to reveal the dynamic behavior of complete wind turbine. The model has generality to different wind turbine control concepts. It reflects the basic dynamics and is suitable for control purpose. Model validity is tested by measuring field data of wind turbine. Main reasons of model mismatch are analyzed. The model can be used for the validity of control strategy. (2) The estimation of effective wind speed of large-scale variable speed variable pitch wind turbine is regarded as a standard soft sensor problem to aim at measuring inaccuracy of an anemometer. Soft sensor of effective wind speed is proposed based on support vector machine (SVM). The core of soft sensor is mathematical model to realize optimal estimation of dominant variable by assistant variables. The algorithms of SVM and least square SVM for regression are derived in the paper. The detailed steps of SVM soft sensor model are presented. (3) Nonlinear predictive functional control (NPFC) based on SVM and PFC for doubly-fed induction generator are proposed for the first time. A predictive model is established by nonlinear system identification with SVM based on linear kernel function. An explicit control law is obtained through the predictive functional control mechanism with both one base function (step function) and two base functions (step and ramp functions). The algorithm for nonlinear system has light online computational burden, good reference tracking and efficient disturbance rejection. Doubly-fed induction generator has fast dynamics. Control system design for generator must be comprehensively considered on the requirements of reference tracking, sensibility to perturbations and robustness. PFC is proposed for active power and reactive power of doubly-fed induction generator based on the stator flux-oriented vector control model combining with the dynamic linearization and decoupling state feedback. (4) On the basis of power flow analysis of wind turbine, a new method for estimating the optimal rotating speed at low wind speed is proposed by an application of fuzzy inference system. The method can realize maximum wind energy capture and avoids the inaccuracy by measuring the wind speed. It need not know the aerodynamic characteristics of wind turbine. (5) Adaptive optimal fuzzy system for speed control is proposed base...