This paper proposes a modified fractional order PI controller (MFO-PI) for grid connected variable speed wind energy conversion system (WECS). The proposed MFO-PI employs an integer integral action and fractional order integral action, and a supervisor to select the more suitable integral action looking to the working conditions. The parameters of the MFO-PI controller have been tuned using frequency method to realize the isodamping feature. The MFO-PI controller is used to guarantee maximum power extraction on the first and obtain power factor unity on the other hand. To investigate the efficiency of the proposed controller, an experimental bench has been carried out. The experimental results demonstrate the superiority of the proposed controller over integer order controllers for a wide range of wind speed.

Keywords: Wind energy conversion, Fractional order proportional-integral (PI) controller, Switched controller, Switching algorithm, Grid connected