Research On Maximum Power Point Tracking Control Of Doubly Fed Wind Power Generation System

Although the massive use of fossil fuel promotes the rapid development of global economy,it also pollutes the living environment of the world and poses a great threat to the sustainable development of mankind.With the depletion of fossil fuel and the increasing awareness of environmental protection,the searching for renewable clean energy has become the consensus of many countries.As an environmental friendly large-scale energy source,wind energy has broad space for development.Also,wind energy is of great significance for solving the energy crisis and environmental pollution problems.With the wide application of wind turbines,how to capture wind energy as much as possible and obtain the electrical power output as much as possible has become the focus of wind power generation control technology.The thesis investigates the maximum power point tracking control for doubly fed induction wind power generator system.Firstly a brief summary of the domestic and overseas development situation on wind power,related works on control of wind power system and the research status of the maximum wind power tracking control is provided.Then the thesis introduces the structure and principle of doubly fed wind turbine,and establishes the mathematical model of wind turbine,transmission system and doubly fed induction generator.Finally the five operation areas of the wind turbine are analyzed.For the power capture control of variable-speed wind energy conversion system,the thesis proposes a control method with guaranteed performance by employing a prescribed performance function and the output error transformation technique.By utilizing the extended state observer(ESO)to estimate the system uncertainties including aerodynamic torque and friction,it eliminates the dependence of the controller on the aerodynamic torque and system parameters.The cascade system theory and input-to-state stability(ISS)are used to analyze the stabilization of the closed loop system.Finally,the feasibility of the proposed method is demonstrated on Matlab/Simulink.For the power control for variable speed wind turbines equipped with Doubly Fed Induction Generator(DFIG),the thesis proposes a novel control strategy with guaranteed transient and steady-state performance based on the reduced-order extended state observer(RESO).Compared with most existing studies,the thesis is capable of quantifying and further guaranteeing the system performance on both transient and steady state stages.The new error transformation technique is used to remove the correlated relationship of the constraint functions,which renders this method more practicable and general.By utilizing RESO to estimate and compensate the system uncertainties in real time,it eliminates the dependence on system models and parameters,and improves the tracking performance of the system.Meanwhile,compared with the conventional ESO,RESO reduces the adjustment parameters,which renders it easier to implement in practice.The effectiveness of proposed scheme is validated via the theoretical analysis and simulations.