Crowbar Protection Technology For Doubly-Fed Induction Generator Based Wind Turbines During Low-voltage Ride Through

At the background of conventional energy Crisis, research on the use of wind power become the hot spot. With the increasing of wind power capacity, the interaction between Wind turbine and the grid become more significant. Countries around the world have made corresponding provisions for grid-connected wind power generation. Wind power system must have the capacity to low-voltage ride through. When the power grid voltage drop in a certain range, the wind power system must connected to the grid and provide active power (frequency) and reactive power (voltage) Support.In this paper, double-fed induction generator is the research object. After analysis of the structure and basic principles of DFIG, mathematical model of an ideal motor is build. Then a improved DFIG model incorporating flux saturation is provided. On the base of stator voltage-oriented vector control, stator flux dynamic response is considered during process of grid voltage fluctuation. Then the dynamic response of DFIG is analyzed in order to find out the key factors which affect the LVRT capability.When the grid voltage drops a lot, Crowbar protection devices must used to ensure the LVRT operation of wind power system. Various factors which impact the Crowbar protective effect is analyzed. The faster DFIG operated, the deeper grid voltage dropped, the fault currents become greater and the effect of protective is worse. The choice of Crowbar resistance is neither too big nor too small. Too big resistance make DC bus voltage too high and too small resistance can not resist the fault currents. Through simulation and experimental validation, the effectiveness of Crowbar protection during DFIG's LVRT operation is verified.