Abstract. This paper
studies a closed-loop wind farm control framework for active power control
(APC) with a simultaneous reduction of wake-induced structural loads within a
fully developed wind farm flow interacting with the atmospheric boundary
layer. The main focus is on a classical feedback control, which features a
simple control architecture and a practical measurement system that are
realizable for real-time control of large wind farms. We demonstrate that the
wake-induced structural loading of the downstream turbines can be alleviated,
while the wind farm power production follows a reference signal. A
closed-loop APC is designed first to improve the power-tracking performance
against wake-induced power losses of the downwind turbines. Then, the
nonunique solution of APC for the wind farm is exploited for aggregated
structural load alleviation. The axial induction factors of the individual
wind turbines are considered control inputs to limit the power production of
the wind farm or to switch to greedy control when the demand exceeds the
power available in the wind. Furthermore, the APC solution domain is enlarged
by an adjustment of the power set-points according to the locally available
power at the waked wind turbines. Therefore, the controllability of the wind
turbines is improved for rejecting the intensified load fluctuations inside
the wake. A large-eddy simulation model is employed for resolving the
turbulent flow, the wake structures, and its interaction with the atmospheric
boundary layer. The applicability and key features of the controller are
discussed with a wind farm example consisting of 3×4 turbines with
different wake interactions for each row. The performance of the proposed APC
is evaluated using the accuracy of the wind farm power tracking and the
wake-induced damage equivalent fatigue loads of the towers of the individual
wind turbines.
Wind tunnel validation of a closed loop active power control for wind farms