An adaptive LVRT control for DFIG wind power system

For the doubly fed induction generator (DFIG), the rotor side Crowbar with constant resistance is a popular approach to protect the wind turbine and improve lower voltage ride through (LVRT). However, the responses of the DFIG are different according to the different degree of voltage dip. In addition, in certain condition, the constant Crowbar resistance may be over-estimated or down-estimated and result in damage to the DFIG. By recognizing this, this paper proposes an adaptive LVRT controller which using the voltage dip degree to determine the resistance of the Crowbar resistor (CR). In detail, it first gets the resistance of worst fault with a simplified calculation for the worst fault, and then, obtains voltage dip degree by detection, and then, through PWM control generating the control signal to control the resistance of the Crowbar resistor. It builds the simulation model based on Real-time digital simulator (RTDS). The simulation results show that the proposed adaptive controller could improve the ability of LVRT for the DFIG.