Harmonic distortion and unbalance rejection with a sliding mode controller applied on a Doubly Fed Inductor Generator

In this work, the implementation of a sliding mode controller (SMC) on the current loops of a double fed induction generator (DFIG) is discussed, this improvement intends to mitigate the effects produced by unbalanced grid voltages, where the stator currents as well as the torque are strongly impacted by such unbalance. When analyzed at the synchronous reference frame (dq) the unbalance appears as a ripple with a frequency of 2ωs, such imbalance can be mitigated by implementing a sliding mode controller at the (dq) components of the rotor current control loops, of a vector control scheme. The system is also aimed to reduce the distortion in the stator currents produced by grid voltages polluted with harmonics. The use of a SMC provides the current controller with a high speed response that allows it to perform a precise tracking of the rotor current references, this is done by controlling the rotor side currents, where the cancelation can be applied from the rotor side, and its effects are observed on the stator side currents.