Multivariable Control of Large Variable-Speed Wind Turbines for Generator Power Regulation and Load Reduction

Abstract

In this paper a multivariate control strategy for regulating generator power and minimizing rotor blade loads during high wind speed is proposed. Due to high demand on wind energy, the current trend is to manufacture larger wind turbines with higher ratings. Consequently, structural loads and flexibility increase as the turbines size increases. Notwithstanding these emerging challenges, wind turbines have to cope with seasonal and intermittent wind variability. For this reason, innovative control strategies to limit power generated to the rated value and to mitigate the structural load are required. To achieve these objectives, generator torque is held constant at the rated value, and a fusion of two control algorithms working in tandem is used for pitch control: A proportional-integral (PI) baseline controller is used to generate demanded collective pitch angle for regulating generator speed and independent pitch control (IPC) is utilized to reduce structural load. To compute the overall instantaneous turbine control input, collective pitch angle is added to the perturbed IPC pitch angle demand input. The core contribution of this paper is realization of a multi-objective control strategy using IPC. The performance of the proposed scheme is compared with that of PI controller. The results indicate improved performance in terms of controlling speed/power and mitigating structural loads.