Research And Application Of Three-phase VSR In The Wind Power Generation

With the increasingly serious problems of energy crisis and environmental pollution, the research and application of wind energy which is a renewable source has aroused widespread concern.In order to realize effective grid-connection, the structure of back to back PWM rectifier is widely used in modern wind turbines. The control algorithm of PWM rectifier can simulate the droop characteristics of the traditional power grid, and improve the capability of Low Voltage Ride-Through, so that the wind generation system is becoming grid-friendly. This paper focuses on the PWM rectifier which is connected to the generator. The PWM rectifier has many advantages including the input sinusoidal current, power factor adjustable and energy flow in opposite direction. Besides, it is useful to eliminate the grid harmonics and improve the power factor and the efficiency of energy.Based on the DSP controller, a three-phase voltage PWM rectifier with low power was designed in this thesis. The major works are as follows:Firstly, this paper made a detailed analysis of topologies, working principles and the conversion current process of the three-phase Voltage Source PWM Rectifier. In order to realize the dual closed-loop control strategy, three high-frequency mathematical models about the Rectifier were established respectively based on three different coordinate systems.Secondly, two different control strategies were designed and detail analyzed by the use of the PI control method and feedback linearization control method separately in framework of dual closed-loop control strategy.The orientation of voltage space vector was achieved through methods of the direct voltage orientation and virtual flux orientation respectively, and each design principle was carefully described. Space Vector Pulse Modulation (SVPWM) was applied in the switch modulation, which was adjusted according to the requirement of the rectifier.Thirdly, two MATLAB/SIMULINK models using SVPWM modulation were established based on combination of two different dual closed-loop control strategies and voltage space vector orientation methods. At the same time, some results and references for the selection of devices in the rectifier design were obtained through the comparative analysis of simulation.Fourthly, the hardware design including the core control circuit, MOSFET driver circuit, detection circuit, protection circuit, buffer circuit was elaborated. The range of AC reactor and capacitor were determined by the method of main circuit parameters design according to requirements of the control system.Fifthly, the software design of three-phase voltage source PWM rectifier which includes voltage and current A/D sampling procedures, SVPWM program, protection algorithm and double closed-loop PI control strategy was carried out based on CCS3.3.Finally, a1kW three-phase voltage source PWM rectifier prototype was accomplished. In the process of debugging, the key parts which involves the exact location of the sampled values, the adjustment of PI parameters, the layout of the system and determination of the experimental procedures were detailed analyzed. Good results were achieved by adjusting PI parameters with tools such as oscilloscopes and the host computer.