Study And Simulation On Variable Speed Constant Frequency Doubly-fed Wind Power Generating System Excited By Matrix Converter

The problem of energy and enviornment is the urgent problem which threatens human surval and development. Wind energy, as an inexhaustible, clean and cheap "green energy", on which the research has become an important subject in the field of renewable energy. Increasing the capacity and technical level of wind power generation plays an important role in improving China's energy structure, constructing energy security system and building a harmonious society. Based on the analysis and study on relevant literature and the research status of wind power technology at home and abroad, this thesis presents a deep study on the excitation control technique of VSCF doubly-fed wind power generator.This thesis did a research on the basic theory of VSCF DFIG wind power generation system, analysed sub-synchronous, synchronous and super-synchronous three work mode of DFIG, and discussed the flowing rule of power in the wind power system firstly. Then the basic features and operating principles of DFIG and wind turbine were studied to find the largest wind power point tracking strategy.Using the stator field orientation vector control theory, the mathematic models of DFIG in the d-q axis synchronous rotating reference frame are deduced, which effectively reflect the function of amplitude, phase angle and frequency of the rotor excitation current for controlling the output power. The rotor exciting current is decomposed to exciting and torque components, then the rotor current forward fed back compensation are added to the rotor exciting and torque components respectively. This control method makes the active and reactive power be controlled respectively, and track the largest wind power point. As wind power system is multi-variable, non-linear and large inertia, the adaptive fuzzy PI controllers are used in the wind power generating system.After comparing and analyzing the advantages and disadvantages of various frequency converters, matrix converter is used as the rotor exciting device of wind power generating system. Chapter 3 discusses the principle and control method of matrix converter in detail, and selects the space vector modulation (SVM) act as the modulating strategy. The mathematic model of SVM is deduced. Finally, the matrix converter is simulated, and the simulation results indicate that matrix frequency converter has better performance. According to the mathematical model in stator flux orientation synchronous rotating reference frame, the system control diagram and system simulation flowchart were designed. The feasibility of control algorithms and control technique proposed by this thesis and the ability of wind power point tracking and the power factor control were studied by simulation. The simulation program was written in C language, it's output datum were called by MATLAB to draw simulation curves. The simulation results prove that the system tracked largest power point effectively, stator active and reactive power could be regulated respectively, indicates that the VSCF control target was realized and the control scheme of this system is feasible.