Iterative learning control applied to a non-linear vortex panel model for improved aerodynamic load performance of wind turbines with smart rotors

Abstract

The inclusion of smart devices in wind turbine rotor blades could, in conjunction with collective and individual pitch control, improve the aerodynamic performance of the rotors. This is currently an active area of research with the primary objective of reducing the fatigue loads but mitigating the effects of extreme loads is also of interest. The aerodynamic loads on a wind turbine blade contain periodic and non-periodic components and one approach is to consider the application of iterative learning control algorithms. In this paper, the control design is based on a simple, in relative terms, computational fluid dynamics model that uses non-linear wake effects to represent flow past an airfoil. A representation for the actuator dynamics is included to undertake a detailed investigation into the level of control possible and on how performance can be effectively measured.

Iterative learning control with applications in energy generation, lasers and health care

“…Also [23] considered the case with a simple first-order model of the actuator dynamics. Pure oscillatory flow produces a periodic fluctuation in the lift which can be successfully damped using simple-structure ILC, as in [23,24].…”

“…In normal operating conditions, the angle of attack (AoA) is not high enough to provoke separation, hence the flow remains attached, and the pressure distribution on the surface of the blade can be calculated by assuming the flow is inviscid. The model employed here is the same as used in [23] but is substantially different from that in [24] due to the inclusion of a wake generated by shedding vorticity in the form of discrete vortices from the trailing edge of the aerofoil into the flow. This vorticity then convects downstream as a solution of the Euler equations that govern inviscid flow.…”

“…The boundary conditions on the surface of the body are satisfied using a panel method (details can be found in [23,24]). The base flow consists of the free-stream velocity V 0 (t) = (V 0x (t), 0) and the velocity field generated by the vortex panels, the vortices shed into the wake from the trailing edge and also disturbances are introduced into the flow upstream of the aerofoil, also in the form of discrete vortices.…”

“…An oscillatory inflow was assumed and a range of flow conditions (amplitude and period of oscillation, AoA, flow with and without upstream disturbances) for both the simple quasi-steady flow model [24] and for the more advanced model with a dynamic wake as outlined above [23]. Also [23] considered the case with a simple first-order model of the actuator dynamics. Pure oscillatory flow produces a periodic fluctuation in the lift which can be successfully damped using simple-structure ILC, as in [23,24].…”

“…Simple-structure ILC for wind turbine blades has been investigated in [23,24], where [15] gives further background on the implementation of active load control for wind turbines. An oscillatory inflow was assumed and a range of flow conditions (amplitude and period of oscillation, AoA, flow with and without upstream disturbances) for both the simple quasi-steady flow model [24] and for the more advanced model with a dynamic wake as outlined above [23].…”