Back-to-back converter state-feedback control of DFIG (doubly-fed induction generator)-based wind turbines

• DFIG control regarding MPPT and power quality by means of real-time digital simulation.
• Classical PI, sliding-mode based, and state-feedback control strategies comparison.
• Classical PI presented low robustness and sliding-mode presented chattering in reactive power waveform.
• The proposed state-feedback presented the best performance.

Control of DFIG (doubly-fed induction generator) is traditionally based on PI (proportional-integral) controllers and recently many papers have proposed sliding-mode based controllers. However, such controllers may excite unmodeled high-frequency system transients due to chattering, resulting in oscillations or even in unforeseen instability. In order to overcome these drawbacks, this paper proposes a internal model state-feedback control strategy for regulation of rotor direct and quadrature currents for wind driven DFIG, which can keep the smooth control signal of the classical PI controller and, at the same time, provides robustness to external disturbances. The currents are controlled in order to accomplish reactive power support to the grid and MPPT (maximum power point tracking). The proposed state-feedback control strategy as well as the classical PI and the VS-MRAC (variable-structure model reference adaptive control) sliding-mode strategy were discretized and implemented in a digital signal processor in order to interact with a real-time digital simulation of the DFIG-based wind energy conversion system. The proposed control structure achieved the fastest and the most robust dynamic response without stressing the converters or deteriorating the power quality.