Real-time implementation of sliding-mode field-oriented control for a DFIG-based wind turbine

摘要

Wind energy has many advantages because it does not pollute and is an endless source of energy. The most used electric machines for horizontal axis wind turbine is the doubly fed induction generator (DFIG). In this paper, the authors propose a real-time field-oriented control based on sliding mode (FOC-SM) for a DFIG prototype connected to the grid via a 3-phase transmission line. To track the desired DC voltage reference at the output of the DC link and to maintain constant the electric power factor at the step-up transformer terminals controlled by grid-side converter, a vector-oriented control combined with sliding mode is introduced; and to force independently the rotor currents to track a specified reference defined from the required stator active and reactive powers, controlled by rotor-side converter, an FOC-SM control scheme is proposed. The DFIG rotor is coupled to the grid via a back to back power electronic converter, whereas the stator is directly linked to the grid. The proposed control scheme is experimentally validated on a 1/4 HP DFIG prototype and tested under constant and variable wind speed, maximum power extraction, and fault grid conditions. The real-time results show that the proposed controllers achieve a high performance under ideal and no-ideal grid conditions. Moreover, the proposed scheme is robust in presence of uncertainties, which usually exist in the real system.