Research on H_∞ Pitch Control of Floating Offshore Wind Turbines via Self-triggered Mechanism

The random characteristics of offshore wind and wave can increase the aerodynamic load on floating offshore wind turbines, leading to frequent adjustments to the pitch system parameters and fluctuations in power output. To cope with this issue, this paper presents an H_∞ pitch control strategy for floating offshore wind turbines based on a self triggering mechanism. By employing the variational mode decomposition method, wind and wave signals are separated into low-frequency and high-frequency components. The low-frequency component serves as the steady-state input for the Markov process, while the high-frequency component functions as the disturbance input, then a Markov model for floating offshore wind turbines that accounts for wind and wave disturbances is proposed. Based on this, resorting to Lyapunov stability theory, a criterion for the H_∞ stochastic stability of floating offshore wind turbines is established. Furthermore, an algorithm for designing a self-triggered H_∞ pitch control feedback gain matrix is introduced. The proposed algorithm can reduce power fluctuations while decreasing the update frequency of the controller. Finally, the NREL 5 MW floating offshore wind turbine is simulated and validated using the FAST model combined with the MATLAB/Simulink platform. The simulation results demonstrate that the control strategy proposed in this paper can significantly enhance the dynamic response performance of the floating offshore wind turbine under wind and wave disturbances, thereby ensuring the stable operation of floating offshore wind turbines.