Individual pitch control design of wind turbines for load reduction using

Abstract

The modern large wind turbines (WTs) are subject to large asymmetric loads, as a result of rotational wind field sampling, wind shear, tower shadow and yaw misalignment. Such asymmetric loads will produce large fatigue damage to blades, hub, shaft and yaw bearing. To mitigate such problem, sliding mode control (SMC) is applied to design individual pitch control (IPC) strategy of WTs in this paper. First, an extended linear model of WT accounting for dynamics of actuators and integral of output errors is derived for control design. Afterwards, a SMC-based IPC strategy is proposed for asymmetric load reduction. Poles assignment method is used to design the SMC switching function, and terminal sliding mode method is utilized to obtain the control law. Finally, the control performance of proposed method is compared to traditional collective pitch control (CPC) and proportional-integral (PI)-based IPC through simulations using FAST software. The simulation results show that the proposed SMC-based IPC can further reduce asymmetric loads compared to CPC and PI-based IPC in both steady and turbulent wind conditions.