Combined Pitch and Trailing Edge Flap Control for Load Mitigation of Wind Turbines

Keshan He,Liangwen Qi,Yan Chen,Liming Zheng

doi:10.3390/en11102519

Abstract

Using active control methods for load mitigation in wind turbines could greatly reduce the cost of per kilowatt hour of wind power. In this work, the combined pitch and trailing edge flap control (CPFC) for load mitigation of wind turbines is investigated. The CPFC includes an individual pitch control (IPC) loop and a trailing edge flap control (TEFC) loop, which are combined by a load frequency division control algorithm. The IPC loop is mainly used to mitigate the low frequency loads, and the TEFC loop is mainly used to mitigate the high frequency loads. The CPFC adopts both an azimuth angle feed-forward and a loads feedback control strategy. The azimuth angle feed-forward control strategy should mitigate the asymmetrical loads caused by observable disturbances. and the loads feedback control strategy should decrease asymmetrical loads by closed loop control. A simulation is carried out on the joint platform of FAST and MATLAB. The simulation results show that the damage equivalent load (DEL) of blade root out-of-plane bending moment is reduced by 53.7% while using CPFC, compared to collective pitch control (CPC); and the standard deviation of blade tip out-of-plane deflection is reduced by 50.2% while using CPFC, compared to CPC. The results demonstrate that the CPFC can mitigate the fatigue loads of wind turbines as anticipated.

Highlights

Wind turbines are always suffering aerodynamic loads, gravitational and inertial loads, actuation loads and so on. during their lifetime [1]
The aerodynamic loads active control technology could dynamically regulate the aerodynamic properties of blades based on appropriate sensor inputs [3], so active control methods, such as individual pitch control (IPC) and trailing edge flap control (TEFC), are more suitable for handling the complex and unsteady aerodynamics loads of wind turbines
The simulation results by collective pitch control (CPC), IPC and combined pitch and trailing edge flap control (CPFC) are demonstrated

Summary

Introduction

Wind turbines are always suffering aerodynamic loads, gravitational and inertial loads, actuation loads and so on. during their lifetime [1]. The aerodynamic loads are the main source of fatigue loads in wind turbines. The asymmetrical loads caused by wind shear, tower shadow effects, turbulence and other factors will lead to fatigue damage of blades, towers, drive trains, etc. Veers pointed out that if innovative blade design and control methods could result in decreased aerodynamic loads, the fatigue loads of wind turbines would be significantly mitigated [2]. The aerodynamic loads active control technology could dynamically regulate the aerodynamic properties (such as change angle of attack or lift coefficients) of blades based on appropriate sensor inputs [3], so active control methods, such as individual pitch control (IPC) and trailing edge flap control (TEFC), are more suitable for handling the complex and unsteady aerodynamics loads of wind turbines. The IPC and TEFC are widely studied for their engineering prospects

Methods

Results

Discussion

Conclusion