Research On Control System Of The Converter For Doubly Fed Induction Generator

ABSTRACT:At present, the problem of energy shortage and high price of oil become more and more serious. So it is important for human to consider how to make full use of renewable energy. With the problems exposed by the leak of nuclear power generation station in Japan recently, wind power generation, which has been widely used in commercial applications as one kind of renewable energies, will attract more and more attention.On account of the advantages as wide range of operation speed, high efficiency, low capacity of power flow and low cost of system, doubly-fed induction generator (DFIG) based wind turbine has been widely used in wind power generation systems, and become an important research field of wind power. This dissertation focuses on the operation and control of doubly-fed wind power generation system and carried out theoretical analysis, simulations and experiments on DFIG wind generation in detail.First, this dissertation analyzed the operation principle of doubly-fed induction generation (DFIG), including the mathematical model, coordinate transformation and power flow which make a theoretical basis for the study of the whole dissertation.Second, based on the back-to-back structure of dual PWM converter and the difference between rotor side converter and grid side converter in performance and control, this dissertation discussed the control method of rotor side converter including the stator flux oriented vector control and stator voltage oriented vector control. The grid voltage.oriented vector control for grid side converter is also analyzed in this thesis. The theoretical analysis and control strategies have been validated by simulations of a 1.5MW DFIG wind power generation system.Besides, several stator flux observer methods of DFIG are studied and compared. After compared several observers, this dissertation pays more attention to the full order flux observer, and its effectiveness under dynamic status and steady-state is investigated by simulations.The theoretical analyses of DFIG wind power converter system are carried out with lots of experiments. The validity of the theory and the control strategy are verified through experiments.