Research On Full-scale Grid-connected Power Conversion Technology For Direct-driven Wind Generation System Based On Back-to-Back PWM Converter

As a kind of pollution-free and green renewable energy, wind power has a very promising future, many countries attach great importance to the development and use of wind energy, As wind power industry develops rapidly, direct-driven wind power system attracted wide attention for many advantages, it is now one of the current research focus, while the full-scale power converter control technology is the core technology of direct-driven wind power generation system.This dissertation researches on full-scale grid-connected power conversion technology for direct-driven wind generation system based on back-to-back PWM converter.Firstly, the direct-driven wind turbine with permanent magnet synchronous generator(PMSG) is discussed, which includes the feature of variable speed constant frequency, the topological structure of D-PMSG wind turbine systems converter, base on the topological structure of back-to-back PWM convertor. The power conversion technology for D-PMSG base on the topological structure of back-to-back PWM convertor is built as the core of this dissertation;Secondly, the mathematical model of D-PMSG wind turbine systems, which includes the model of wind turbine, the mathematical model of shaft-line, the model of full-scale power convertor is analyzed through the research on the principle of D-PMSG wind turbine systems based on back-to-back PWM convertor;Thirdly, aims at the back-to-back PWM convertor of D-PMSG and reposes on the technique of vector control, mainly analyzes on the control principle of the zero d-axis current vector in the motor-side and the voltage-oriented vector control principle for the grid-side. The validity of these two control methods is confirmed through the Matlab/Simulink simulation;Finally, the operational aspect of the converter of directly-driven wind generation system when grid voltage dips is analyzed in detail, then the running state of the D-PMSG when grid voltage dips is simulated by Matlab/Simulink, describes the possible damages of the system if we don't take any effective measures. After introducing the concept of LVRT, a method of adding a damping load to protect the system based on power dissipative crowbar is analyzed, and the related module of control methods is designed, this method is confirmed effective and reliable through the Matlab/Simulink simulation, it can help the D-PMSG to ride through the low voltage during the breakdown time.