Robust predefined-time fractional-order sliding mode control for performance enhancement of hydro-turbine governing system

The hydro-turbine governing system (HTGS) holds a crucial position in maintaining overall stability and security of hydropower stations. HTGS characterized by intricate dynamics involving strong coupling, nonlinearity, and non-minimum phase behavior, is responsible for regulating the frequency of the hydropower system. This article proposes a predefined-time fractional-order sliding mode controller (PTFOSMC) aimed at improving the frequency stability of the nonlinear HTGS, accounting for both internal disturbances and external noises within a predefined time. Input/output feedback linearization serves to define the explicit mapping between the HTGS control inputs and its observed outputs. Leveraging fractional calculus principles, a fractional-order controller is designed to mitigate chattering effects associated with the sign function, surpassing conventional sliding mode control (SMC) techniques. Moreover, fractional-order control methods afford greater flexibility in parameter tuning, enhancing the adaptability of controller design. The proposed PTFOSMC guarantees stability of the HTGS within a predefined time, allowing for explicit adjustment as a tuning parameter. Stability analysis of the HTGS under the proposed PTFOSMC utilizes the Lyapunov function. Numerical simulations validate the robustness, effectiveness, and superiority of the PTFOSMC relative to both finite-time control method (FTCM) and integer-order sliding mode controller (IOSMC).1