Improved fractional order non-singular fast terminal sliding mode control of D-PMSG based on adaptive load torque observer

This article introduces an advanced approach in the realm of control strategies—Fractional-Order Non-Singular Fast Terminal Sliding Mode Control (IFO-NFTSMC). The foundation of this strategy lies in the combination of an Adaptive Load Torque Observer (ALTO) tailored for direct-driven Permanent Magnet Synchronous Generators (D-PMSG). The primary objective is to address the speed loop of the Machine Side Inverter (MSC) with the aim of capturing the maximum power point of the wind turbine. Central to this control paradigm is the incorporation of an Improved Non-Singular Fast Terminal Sliding Mode Surface (INFTSMS) enriched with fractional terms, introducing heightened design flexibility. Moreover, an exponential function is integrated into the isovelocity term of the exponential reaching rate, and a smooth S-function replaces the original sign function to mitigate the chattering effect inherent in the controller. Following this, the ALTO assumes a pivotal role by offering feedforward compensation for the generated q-axis current, thereby augmenting the disturbance rejection capabilities of the controller. To assess the efficacy of the proposed IFONFTSMC+ALTO in comparison with other sliding mode controllers, simulation experiments were conducted on the D-PMSG under stepped wind speeds. The outcomes underscore the exceptional performance of the controller, revealing swift response times and surpassing its counterparts in terms of vibration suppression and disturbance rejection capabilities.