A Study Of AC Excitation Wind Power Generation System And Its Excitation Control Strategies

As one kind of the most important renewable energy, wind power is of significance in alleviating the world's energy crisis and environmental crisis, and has attracted a great attention around the world. Almost 378 Wind Farm will be built in 2010 in China.Ac excitation generator,was called doubly-fed generator in many articles,has been used in most wind farms. With the development of high-efficiency and high-capacity for wind turbine, ac excitation wind power generation system becomes the main trend of nowadays wind power generation technology for its advantages of its inverter with small size, light weight, low cost and high efficiency. For these reasons, studying of excitation control technology for ac excitation wind power system is necessary.Firstly, the operating principle of ac excitation wind power system is analyzed in this paper, and then the wind model theory and wind machine model are introduced for the simulation of wind turbine control.Secondly,the scheme for cutting in of ac excited wind turbine generator is proposed by studying the cutting-in control strategy based on stator flux linkage orientation; then control strategy of cutting in that does not depend on the parameters of the generator or the position of the rotor is proposed. The control strategy of ac excitation after the generator that has been connected to the power grid is analyzed.Then, based on the theory of ac excitation wind power system, stator flux oriented vector control strategy and direct power control strategy have been studied and compared briefly, then the linear optimal control strategy was proposed to ac excitation wind power system for its transient stability.The transient process of ac generator under low vltage fault is analyzed. The ac excitation control performance of the generator under low vltage fault was simulated in Matlab/simulink. At last, experiments are carried out on a 5.5kW generator test rig to test the theories.