Optimal Power Control in Wind Farms for Gearbox Load Reduction

Rapid power and torque fluctuations in time-varying conditions increase the fatigue load and failure rate of wind turbine (WT) gearboxes. In this study, an optimal power control method is proposed for a wind farm (WF) to improve the power flow and service quality, allowing the WF to track the power demand instructions from the transmission system operator while minimizing the fluctuations of vibration displacements inside the gearbox. A comprehensive dynamic model of the gearbox is developed by analyzing the transmission mechanism of key gearbox components, such as the planet carrier, planet gears, sun gears, and spur gears, describing the correlation between the internal vibration and mechanical torque and power output. Then, an optimal power control problem is formulated based on model predictive control to suppress the fatigue load while tracking power. Furthermore, a fatigue evaluation system is built based on the real-time vibration state inside the gearbox to characterize the service quality of WTs and guide the power generation of the WF. This approach provides a safety-oriented boundary regarding the WT fatigue load in the optimal power dispatch issue of WFs to suppress potential WT failures. Case studies in MATLAB/Simulink demonstrated the effectiveness of the proposed method.