53 research outputs found
Convex Model Predictive Control for Down-regulation Strategies in Wind Turbines
Wind turbine (WT) controllers are often geared towards maximum power
extraction, while suitable operating constraints should be guaranteed such that
WT components are protected from failures. Control strategies can be also
devised to reduce the generated power, for instance to track a power reference
provided by the grid operator. They are called down-regulation strategies and
allow to balance power generation and grid loads, as well as to provide
ancillary grid services, such as frequency regulation. Although this balance is
limited by the wind availability and grid demand, the quality of wind energy
can be improved by introducing down-regulation strategies that make use of the
kinetic energy of the turbine dynamics. This paper shows how the kinetic energy
in the rotating components of turbines can be used as an additional
degree-of-freedom by different down-regulation strategies. In particular we
explore the power tracking problem based on convex model predictive control
(MPC) at a single wind turbine. The use of MPC allows us to introduce a further
constraint that guarantees flow stability and avoids stall conditions.
Simulation results are used to illustrate the performance of the developed
down-regulation strategies. Notably, by maximizing rotor speeds, and thus
kinetic energy, the turbine can still temporarily guarantee tracking of a given
power reference even when occasional saturation of the available wind power
occurs. In the study case we proved that our approach can guarantee power
tracking in saturated conditions for 10 times longer than with traditional
down-regulation strategies.Comment: 6 pages, 2 figures, 61st IEEE Conference on Decision and Control 202
On the Analysis and Synthesis of Wind Turbine Side-Side Tower Load Control via Demodulation
As wind turbine power capacities continue to rise, taller and more flexible
tower designs are needed for support. These designs often have the tower's
natural frequency in the turbine's operating regime, increasing the risk of
resonance excitation and fatigue damage. Advanced load-reducing control methods
are needed to enable flexible tower designs that consider the complex dynamics
of flexible turbine towers during partial-load operation. This paper proposes a
novel modulation-demodulation control (MDC) strategy for side-side tower load
reduction driven by the varying speed of the turbine. The MDC method
demodulates the periodic content at the once-per-revolution (1P) frequency in
the tower motion measurements into two orthogonal channels. The proposed scheme
extends the conventional tower controller by augmentation of the MDC
contribution to the generator torque signal. A linear analysis framework into
the multivariable system in the demodulated domain reveals varying degrees of
coupling at different rotational speeds and a gain sign flip. As a solution, a
decoupling strategy has been developed, which simplifies the controller design
process and allows for a straightforward (but highly effective) diagonal linear
time-invariant controller design. The high-fidelity OpenFAST wind turbine
software evaluates the proposed controller scheme, demonstrating effective
reduction of the 1P periodic loading and the tower's natural frequency
excitation in the side-side tower motion.Comment: This work has been submitted to the IEEE for possible publication.
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Optimal Control for Wind Turbine Wake Mixing on Floating Platforms
Dynamic induction control is a wind farm flow control strategy that utilises
wind turbine thrust variations to accelerate breakdown of the aerodynamic wake
and improve downstream turbine performance. However, when floating wind
turbines are considered, additional dynamics and challenges appear that make
optimal control difficult. In this work, we propose an adjoint optimisation
framework for non-linear economic model-predictive control, which utilises a
novel coupling of an existing aerodynamic wake model to floating platform
hydrodynamics. Analysis of the frequency response for the coupled model shows
that it is possible to achieve wind turbine thrust variations without inducing
large motion of the rotor. Using economic model-predictive control, we find
dynamic induction results that lead to an improvement of 7% over static
induction control, where the dynamic controller stimulates wake breakdown with
only small variations in rotor displacement. This novel model formulation
provides a starting point for the adaptation of dynamic wind farm flow control
strategies for floating wind turbines.Comment: 6 pages, 8 figures, accepted for publication for IFAC World Congress
202
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