Analysis of extremum seeking control for wind turbine torque controller optimization by aerodynamic and generator power objectives

TL;DR

This paper investigates extremum seeking control for wind turbine torque optimization, analyzing the effects of using aerodynamic versus generator power objectives, and proposes a new aerodynamic power-based measure for improved convergence.

Contribution

It introduces a novel aerodynamic power-based objective measure for extremum seeking control, enhancing torque gain optimization in wind turbines.

Findings

Generator power limits dither frequency, reducing convergence speed.

Aerodynamic power objective allows higher dither frequencies, improving convergence.

Phase adjustment of the ESC signal is crucial for effective optimization.

Abstract

Wind turbines degrade over time, resulting in varying structural, aeroelastic, and aerodynamic properties. In contrast, the turbine controller calibrations generally remain constant, leading to suboptimal performance and potential stability issues. The calibration of wind turbine controller parameters is therefore of high interest. To this end, several adaptive control schemes based on extremum seeking control (ESC) have been proposed in the literature. These schemes have been successfully employed to maximize turbine power capture by optimization of the $K\omega^2$-type torque controller. In practice, ESC is performed using electrical generator power, which is easily obtained. This paper analyses the feasibility of torque gain optimization using aerodynamic and generator powers. It is shown that, unlike aerodynamic power, using the generator power objective limits the dither frequency to lower values, reducing the convergence rate unless the phase of the demodulation ESC signal is properly adjusted. A frequency-domain analysis of both systems shows distinct phase behavior, impacting ESC performance. A solution is proposed by constructing an objective measure based on an estimate of the aerodynamic power.