Decoupled control of speed and reactive power of doubly-fed induction generator

The wind power generation system driven by a variable speed wind turbine is extensively studied for its ability of varying rotating speed to track the optimal TSR and the maximal energy capture when the wind speed is changed. Another advantage of the variable speed wind power generation system than a fixed-speed one is its capability of reactive power and voltage control. Doubly-fed induction generators are widely used in variable speed wind power generation systems, with a frequency converter connected between the grid and the rotor winding, which is used for match of variable speed and constant frequency. Additionally, the converter can act for reactive power and voltage control by feeding particular voltages on the rotor winding. Naturally, the rotor voltage may have simultaneous influence on both speed and reactive power of the generator, but the rotor voltage indeed has two freedoms. So, a decoupled control of speed and reactive power is developed in this paper, based on the nonlinear inverse system method, and simulation results show the validity of the proposed control law.