Decoupling control of the rotor cross-coupling voltage for doubly-fed induction generator based on multiple Degree-Freedom Internal Model Control

In a vector-controlled doubly-fed induction generator (DFIG), the cross-coupling voltage between the M and the T components of the rotor current impairs the characteristics of DFIG. The principle and the deficiency were analysed for the feedforward and feedback decoupling, and the decoupling control strategy was discussed based on the Internal Model Control (IMC). Theoretical analysis and simulation results show that, with non-synchronous changes of the parameters, the One-Degree-Freedom IMC (1DOF-IMC) decoupling of DFIG still exists coupling in the rotor current. Because of only one parameter, the adjustment is easy, but there is less effective decoupling. In Two- Degree-Freedom IMC (2DOF-IMC) decoupling method, there are two adjustable parameters, but there is still a compromise selection in robust performance, it is difficult to obtain satisfactory decoupling results. Three- Degree-freedom IMC (3DOF-IMC) decoupling is presented, by the feedforward controller, internal model controller and feedback filter, the 3DOF-IMC decoupling is implemented from multiple directions. The simulation showed that the 3DOF-IMC decoupling method has better decoupling and realizes dynamic decoupling control.