Design And Research On Dual PWM Converter Of Wind Turbine Based On Soliding Mode Control

With the rapid development of global economy, the demand for energy is increasing. Due to the coal, oil and other conventional resources increasingly scarcing on earth, and the use of conventional resources will also brings a lot of pollution to the environment. Therefore, in order to solve the problem of energy and the environment, we should not only reasonably take advantage of the coal, oil and other conventional resources, but also must develop the use of renewable resources. Wind energy is a safe, environmentally friendly and new renewable energy, inexhaustibly. With the mature of wind power technology, the cost of wind power generation has also been reduced constantly. In the field of wind power, the direct-drive wind power generation system has become an important research direction. This thesis analyzes and studies the control strategy of dual PWM converter, applying the sliding mode variable structure control strategy to the dual PWM converter control system, building the simulation models of wind power generation system in MATLAB and proving the proposed design method is feasible through simulation experiment.Firstly, the thesis describes the basic structure and its related properties of the direct-drive permanent magnet wind power generation system. For the poor dynamic performance of nonsingular terminal sliding mode in the far, the thesis designs a nonsingular terminal sliding mode surface with rapid convergence. The thesis introduces the basic principles of the various components, establishes the mathematical model of each component, specifically including the mode of wind turbine, the mode of transmission system, the mode of PMSM, the model of dual PWM converter, and the model of intermediate DC link.Secondly, the thesis mainly introduces the basic principle of sliding mode variable structure control, and designs DC-side voltage, d-axis currentand q-axis current sliding mode controller of grid side PWM converter based on this principle.Thirdly, the thesis introduces the method of maximum power point tracking (MPPT) and the vector control principle of the permanent magnet synchronous generator, and mainly expounds the implementation method of MPPT based on the best tip speed ratio and zero d-axis current vector control. The thesis also introduces the double-loop control structure including speed outer loop and current inner loop. Then, the thesis designs speed, d-axis current and q-axis current sliding mode controllers of the motor-side PWM converter. At last, the control of sensorless permanent magnet synchronous generator is studied in the wind power system. The sliding mode observer model is designed and the model is used to estimate rotor speed and rotor position of the permanent magnet synchronous generator, to replace the role of the position sensor and to implement the sensorless control of PMSG.Finally, the thesis builds simulation models of grid-side PWM converter control, motor-side PWM converter control and the sliding mode observer in MATLAB. Then, the thesis makes simulation experiments of the whole model for wind power system. According to the simulation analysis, the control strategies of the dual PWM converter can achieve a maximum power point tracking in the wind, and realize interconnection with the grid under unit power factor, ensuring control system good dynamic and steady-state performance. And on this basis, the thesis establishes the simulation model of wind power generation system based on the SMO, according to simulation analysis, showing that the wind power generation system based on the SMO can accurately estimate the rotor speed and rotor position and implement the sensorless control of PMSG.