Researches On The Control Strategies Of Direct-drive Wind Power Generation System Based On Buck-boost Matrix Converter

With the increasing demand on energy, it is imminent for countries to develop new renewable energy resources. Wind energy, which is a kind of renewable energy resources, has the following characteristics:reserve largely, renewable, no pollution and so on. Meanwhile, owing to the way of generating which is a kind of low cost and has a commercial prospect, countries all over the world pay much attentions to the wind power generation. In wind power generation system, direct-drive wind power becomes the mainstream of the wind power development because of its simple structure, high efficiency and low maintenance costs. Grid-connected inverter, which connects the wind generator and the power grid, is the core component of the wind power. Double current transformers PWM are adopted widely as the grid inverter in wind power generation system at present. The inverter not only can operate in four quadrants, but also has high conversion efficiency, small content of harmonic, adjustable power factor features. However, the volume of the inverter is larger, and the cost is higher. A new type of buck-boost matrix converter (BBMC) is adopted as the grid-connected inverter in this thesis and its control strategy is also studied.Firstly, the develop situation of the wind power generation is introduced. And the current research status of the wind power grid-connected converter is expounded. What’s more, the characteristics of BBMC are introduced also. Furthermore, adopting BBMC as the grid-connected inverter of the direct-drive wind power system is presented in this thesis.Secondly, the fundamental features of the wind turbine are introduced. And the principle of capturing maximum wind energy is expounded also. According to the coordinate transformation technology, the mathematical model of the permanent magnet synchronous generator under the synchronous rotating coordinate system is established. The Zero d axis current vector control strategy is adopted on the electric generator. The fuzzy PI current regulator is designed and its effect is simulated and verified.Thirdly, the web side mathematical model of BBMC is analyzed. Power grid voltage is considered as a given signal. Based on the capacitor voltage and inductor current of the network side converter, double-loop control strategy is adopted. According to the basic request of the grid-connection control, fuzzy PI voltage regulator is designed and the control effect is simulated and verified also.Lastly, with DSP as the controller and with MOSFET as the main circuit power switch, the experiment system which is based on BBMC web side converter is developed. Meanwhile, the corresponding control software is developed. The experimental system is tested which shows that the related indicators meet the requirements of the design.