This paper presents a robust power control strategy using fractional order proportional-integral FO[PI] controller to enhance the performences of power control of a doubly fed induction generator (DFIG). In this paper, a new analytical design method is proposed and used to design FO[PI] controllers. The FO[PI] controllers designed in this way improve the control dynamics and robustness of the DFIG under various kinds of disturbances and parameters’ variation. The originality of the present study lies in the development the new analytical design method, which is based on five frequency specifications, namely, phase margin, gain limitation at crossover frequency, robustness to gain variation, sensitivity and complementary sensitivity functions. The proposed method offers most of the advantages of the methods reported in the literature. Indeed, it guarantees robustness using phase margin, gain limitation and robustness to gain variation and disturbance rejection using sensitivity functions. Moreover, the complex analytical derivation is simplified using a change of variables and appropriate trigonometric formulas. The power control of the DFIG is examined with both integer order proportional integral controller IOPI, and fractional order proportional integral controller FO[PI]. The obtained results show that both IOPI and FO[PI] controllers give good performance under normal operation. However, FO[PI] controller fares better than IOPI controller under gain variation and various disturbances.

Keywords: Analytical design, Frequency specifications, Proportional integral (PI) controller, Fractional order, Integer order, Power control, Doubly-fed induction generator