| With the increasingly serious global energy crisis and environmental pollution, the development and utilization of renewable energy sources such as wind energy and solar energy are attracting more and more attention. For the relatively lower cost and abundant global resources, wind power generation has become one of the most promising renewable energy that could be applied on a large scale. A low speed multi-polar Permanent Magnet Synchronous Generator (PMSG) is utilized in the Direct-Drive (DD) Wind Power Generation System (WPGS) to eliminate the up-speed gearbox that is always included in traditional WPGS. The DD-WPGS has advantages such as low maintenance costs, high reliability. Furthermore, it can greatly improve the wind power capturing capability when it works in Variable Speed Constant Frequency (VSCF) mode. The PMSG-WPGS meets the requirements such as high efficiency, large capacity, high reliability and it is becoming a research hotspot in many countries. In this dissertation, couple of topology and their control strategy of the converter for DD-WPGS are comprehensively investigated. A simulation and experimental platform is built up and a lot of simulation and experimental results are obtained based on it.At the beginning of this dissertation, the domestic and overseas research status of WPGS structure and VSCF technology are summarized compendiously. Then the performance characteristic of wind turbines (WT) and the operation principle of optimum utilization of wind energy are addressed, and a method of using Asynchronous motor to qualitatively simulate WT is presented, which establishes foundation for relevant experimental study. This dissertation carries on the deep study on the control strategies of the grid-side three-phase PWM inverter. The vector regulating principle of the phase and amplitude control for three-phase grid-connected inverters is represented. To solve the problem of heavy impact current and slow dynamic response, the start voltage prediction control and the current feed-forward control are proposed, which improve the dynamic performance of the system in the phase and amplitude control. The experimentation carried out on a three-phase grid-connected inverter proved the validity of proposed methods. A direct current control strategy with fixed switching frequency is studied. The mathematic model of three-phase grid-connected inverter in synchronous rotating coordinate system is built. Based on Fourier analysis of Saddle Pulse Width Modulation (SAPWM) wave, a 0-axis harmonic injection method is presented for enhancing DC link voltage utilities. The simulation and experiment has been presented to verify the proposed theories. A virtual-flux-based sesorless control strategy of three-phase PWM converter is studied, and a teady-state error compensation method for virtual flux observer is proposed. Then, the dissertation does research on two kinds of the WPGS topology. One is the topology including PMSG linked the passive rectifier, and the other is topology including PMSG linked the active rectifier. For the former, the performance characteristic of the passive rectifier is analyzed at first. Then the system structure, control method and the MPPT strategy are researched for the topology respectively based on boost converter and Z-source inverter. Simulation and experimental results is provided. For the latter, by analyzing the mathematic model of PMSG, a rotor flux oriented vector control strategy and a MPPT strategy based on optimizing the efficiency of PMSG is designed. The simulation and experimental results prove the validity and feasibility of the presented control method. At last, to solve the problems of high harmonic and low power factor for the PMSG in the first kind of topology, a method of compensating PMSG's reactance voltage based on a novel circuit called Magnetic Energy Recovery Switch (MERS) is researched, and the simulation results prove that it has good compensation effect.
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