RETRACTED: Maximizing output power and reducing tower oscillations: Controller design for a gearbox-free wind turbine

Abstract

This study focuses on the development of a dynamic wind turbine system without a gearbox, with the primary objectives of adjusting output power, and generator torque and reducing tower oscillations through the design of an effective controller. The design of the controller faces challenges in selecting an appropriate mathematical model that strikes a balance between simplicity and comprehensiveness while accounting for the essential physical phenomena affecting the system. Enhancing the accuracy of the system model is crucial to improve the controller's efficiency and achieve a better approximation of the system dynamics. Therefore, this study addresses the two-fold problem of maximizing modeling accuracy while maintaining model simplicity. To capture the dynamic behavior of the wind turbine, the analysis considers three degrees of freedom: rotor rotation, kinetic pitch chain, and reciprocating motion of the tower. The tower and kinetic chain are modeled as flexible components to accurately represent their behavior. The objectives of designing controllers for wind turbines encompass maximizing output power and reducing structural vibrations, aiming to minimize the total cost associated with energy generation and turbine maintenance. To achieve this, the mathematical models developed for turbine modeling need to account for the flexibility of components that exhibit high flexibility in practical scenarios. Notably, the tower is modeled as a separate flexible object, considering its degrees of freedom, while the kinetic chain is modeled as a flexible object due to the high damping coefficient and flexibility of the shaft in a gearbox-free wind turbine. In addition to maximizing output power, ensuring system stability is of paramount importance in the absence of a gearbox. Fluctuations in generator rotational speed can escalate rapidly, leading to system instability. Therefore, precise adjustment of generator speed and torque plays a critical role in maintaining system stability. The results show that the proposed method could model the wind turbine in a better way that the maximum error of rotational speed in comparison with the real data is about 3.4%. In addition, the oscillation speed error of the tower top is about 2.3%.