Research On Chopper-based Full-scale Grid-connected Power Conversion Technology For Permanent Magnet Wind Turbine Generation

At present, variable speed constant frequency wind power system has become the main trend of wind power development with its obvious advantage in wind power converter system connected to grid. In the various implementations of variable speed constant frequency wind power system, there are two converter system topologies of the wind power market in the current main stream: double-fed induction wind generator system and permanent magnet direct drive wind power system. Among them, because of eliminating susceptible to failure the gearbox, the direct drive permanent magnet synchronous wind power system improves power system stability and reliability, and has a rapid development.Firstly, this paper analyses different topologies of direct-drive wind power system, and gives advantages and disadvantages of various topological structures. And then, the wind turbine, permanent magnet synchronous generator, three-phase uncontrolled rectifier, the Boost circuit, voltage source full-bridge inverter circuit compose of the main circuit as the background.For the boost chopper-based direct-drive wind power system, this paper analyses mathematical models of the wind power system various parts in detail, as the foundation for the later chapters. In order to capture wind energy as much as possible, maximum power point tracking techniques are more and more attention. After the introduction of several common maximum power point tracking algorithms, the presented tracking method used in this paper is given: by regulating the duty cycle of the boost circuit to achieve the maximum power tracking, but this method is mainly applied to the rated wind speed the following. For more than rated wind speed, variable pitch control technology is adopted. Next, control strategies connected to grid are studied, using the program of the voltage directed to achieve the unity power factor, DC voltage control and stability, so smoothly the whole system into the grid. Finally, this article studies the two interleaved Boost control, which effectively improves the magnification and adjusts the duty cycle and reduces the current ripple, achieving current sharing. Using Matlab/Simulink to establish a simulation model of the above control strategies, the feasibility of the control strategies is verified.