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This paper proposes an optimal efficiency control scheme for a wind system with doubly fed induction generator (DFIG). The suggested control scheme combines loss minimization (LM) in the DFIG and maximum power point tracking (MPPT) in the wind turbine and therefore maximum electrical energy generation, by the same wind energy potential, is achieved. Moreover, since the cut-in wind speed is reduced, extension of the exploitable wind speed range toward the lower speed region is attained. The LM is achieved by properly controlling the flux-linkage of the DFIG with respect to the stator current and the MPPT is accomplished by regulating the rotor speed through the rotor current. The parameters of the LM and MPPT controllers can be determined experimentally, and thus, the knowledge of the wind energy conversion system (WECS) model is not required. For the implementation of the proposed control strategy, a new structure of the WECS has been adopted. However, the hardware requirements of the WECS and considerably the cost have not been considerably affected compared to the conventional configuration. Selective simulation and experimental results are presented to validate the effectiveness of the proposed control strategy and demonstrate the operational improvements. [ABSTRACT FROM AUTHOR]

This paper highlights key contributions in extremum seeking (ES) control and ripple correlation control (RCC). Maximum power point tracking (MPPT) utilizing the 120-Hz inherent inverter ripple is shown to be developed in the early 1980s. Even though that specific MPPT development did not explicitly mention ES control, the analysis presented there shows otherwise. RCC stability and operating properties are also addressed where the fundamental difference between RCC and popular ES control methods is the perturbation source. Since RCC utilizes inherent switching ripple in power electronics, the high ripple frequency leads to fast RCC convergence. [ABSTRACT FROM AUTHOR]