Effects of Induction and Wake Steering Control on Drivetrain Fatigue and Wind Farm Power Production

Abstract

Power optimization through wake steering and axial induction control is a well investigated topic in wind energy, which is generally proven to work. The influence of control manoeuvres on the fatigue of static components is generally discussed, but drivetrain fatigue due to wake steering and axial induction control is rarely discussed, while it is known that the drivetrain is a highly vulnerable part of the wind turbine and its downtime can result in a significant increase in cost. Having a better understanding of turbine wake interaction and wind farm power optimization and its influence on drivetrain dynamic behaviour serves as a reference for future wind farm cost optimization and predictive maintenance. The main research question answered in the thesis is as follows: To what extent does wind farm power optimization increase profit when wind farm power production and drivetrain bearing fatigue damage is considered? Multiple test cases for wake steering and axial induction control are considered, where different yaw angles, γ, and the blade pitch angles, β, are chosen for the upwind turbine. For each test case, power production and bearing damage is studied. A cost estimation is made and for a range of energy prices, the most profitable test case is found. For verification, a two and four wind turbine case in an uniform wind field is considered. Power production results for this low turbulent case are studied and compared to literature. Turbulent wind field results show that both wake steering and induction control result in a limited power production increase of 0.78% for γ = 7° and 0.17% for β = 1°, shown in the Figure below. The power production increase for the two and four wind turbine case in the uniform wind field for wake steering and induction control are 4.78% for γ = 15°, 16.6% for γ = 20°, 0.19% for β = 1° and 5.04% for β = 3° respectively. Overall absolute bearing damage of WT1 and WT2 increases with increased yaw angles for WT1 and the overall bearing damage of WT1 and WT2 decreases with increased blade pitch angles for WT1. INP-A and PLC-B bearing damage significantly increased for the downwind turbine. In the high turbulent wind field (TI = 0.2), when considering two wind turbines, wake steering can result in an increase of profit ranging from -€3,70 to €4,-, while axial induction control can result in an increase in profit ranging from €3,- to €40,-. In the low turbulent wind field (TI = 0), when considering four wind turbines, the power production increase for wake steering can result in a profit increase ranging from €30,- to €130,-, while axial induction control can result in a profit increase ranging from €15,- to €60,-. Both wake steering and induction control can result in increased profit. The desired control manoeuvre is highly dependent on the ambient wind, wake overlap of the downwind turbine and the wind farm arrangement.