Characteristic Research For Low Voltage Ride-Through Of Wind Turbine With Double Fed Induction Generator

Wind power generation is a clean and non-pollution renewable energy technology. At present, wind power has become the fastest growing clean energy in the whole world annual which growth rate by more than 30%. With the technology developing and the capacity increasing, wind power in the power grid with the proportion is increasing, significant impact between the large-scale wind farm and regional power grids are more remarkable.Doubly fed induction generator(DFIG) wind turbine is the main type both at home and abroad which owns advantages such as variable speed operation, independent regulating of active and reactive power, the small capacity of converter, etc. However, it has weakness in dealing with grid fault yet. The voltage sag is the most important one which caused by short circuit or open circuit. When voltage sag deeply, it brings great threaten to the wind turbine safety and grid stability. As a result, improving low voltage ride through ability has proved to be a hot topic. In this paper, on the basis of grid codes from different countries, a research has been made to improve low voltage ride through ability of doubly fed wind turbines.First of all, a doubly-fed induction generator vector model was established which has been used in deriving transient electromagnetic relations of doubly-fed induction generator and explaining transient physical processes. On the basis of understanding of transient physical processes of short circuit failure, doubly-fed induction generator keeping connect with grid excitation control strategy was proposed during power grid fault. The new excitation control strategy that aiming at the transient characteristic of the generator electromagnetic variable, the flux generated by generator control rotor current to offset the harmful impact on rotor and to control the rotor over-current, at the same time, the stator side resistance was ultimately used to carry out deexcitation. Finally, effectiveness of this control strategy was verified by Matlab/Simulink simulation which provided a theoretical basis in improving low voltage ride through ability of doubly fed wind turbines.