Stability enhancement of DFIG wind turbines with new space-vector based nonlinear control

In this paper, a novel nonlinear control method of Doubly-Fed Induction Generators (DFIGs) is presented to replace the traditional Proportional-Integral (PI) method in the control scheme of DFIG Wind Turbines (WTs). The proposed method is based on a new hysteresis current controller, which can modulate the voltage space vector directly in the dq rotation frame. Therefore, the new method can be easily employed in the vector-oriented-control scheme of DFIG without changing the structure of the scheme. The feasibility and performance of the proposed method are examined by using Matlab/Simulink. The simulation results demonstrate the very fast transient response of the proposed method under step-changes of power demands and wind speed. Also, the new method can overcome errors of machine parameters, which strongly impact traditional PI methods, to regulate the power output. Finally, the capability of low voltage ride-through (LVRT) is validated in the simulation study. With this capability, the proposed method can improve stability of DFIG WTs during voltage dips.