Research on Low Voltage Ride through Characteristics of Doubly-Fed Induction Generator Based on Wind Power System

Doubly-fed induction generator is widely used in the wind power generation system due to its advantage of controlling active and reactive power independently, and only a percentage of the power produced by the generator has to pass through the AC excitation converter. However, the converter is quite sensitive to grid disturbance because of its limited partial capacity compared with the generator rating. Nowadays the grid code demands that the wind power generator possesses the ability of riding through the grid voltage dips, in order to prevent the more severe successive grid faults. To protect the converter and to support the grid, it is needed to limit the high inrush rotor current and provide a bypass for it via a crowbar, which is connected to the rotor windings. In this paper, a novel crowbar control strategy is proposed to limit the over current in the rotor, the over voltage of the DC bus. Experiment results prove that crowbar circuit is able to improve the LVRT of DFIG system.