Control of MW-Scale Wind Turbines for Fatigue Load Reduction and Performance Improvement

Abstract

As the size of wind turbines are continuously increasing, fatigue loads must be reduced to obtain a more reliable condition for main components. Independent pitch control (IPC) strategy, based on the collective pitch control (CPC) strategy, provides an effective solution to load reduction on WT’s components caused by asymmetry loads. Meanwhile, IPC can also improve the performance of MW-scale wind turbine. This paper presents a dynamic model for 5 MW wind turbines of CSIC (Chongqing) Haizhuang Windpower Equipment Co., Ltd. Based on the dynamic model, an independent variable pitch controller has been investigated. Non-linear dynamic analysis has been conducted on wind turbine structures. During the turbine linearization, the blade flap-wise and tower F–A bending modes are considered. The tower, main shaft and blade are regarded as rigid bodies. Based on the dynamic model, the IPC controller is designed through d–q conversion. The results suggest that the IPC technique not only works well in stabilizing the output power, but may also effectively reduce the fatigue loads on the blades, main shaft, tower and hub. Under the identical conditions, the IPC presented in this paper has more advantages than a collective pitch controller, and can further reduce loads on key components. The IPC is of greater significance in control of wind turbines, and can lead to lower maintenance costs. However, IPC will raise the pitch-regulating speed, and further increase the fatigue load on the pitch mechanism. This problem requires further studies for a solution.