A Switching Thrust Tracking Controller for Load Constrained Wind Turbines

TL;DR

This paper presents a novel switching control system for wind turbines that limits thrust to reduce structural stress, balancing load constraints with power output using a linear thrust tracking controller.

Contribution

It introduces a new closed-loop switching control architecture inspired by reference governors, specifically designed for load constrained wind turbines.

Findings

Effective thrust constraint satisfaction demonstrated in simulations

Reduces aerodynamic loads with acceptable power losses

Can be integrated into wind farm control strategies

Abstract

Wind turbines are prone to structural degradation, particularly in offshore locations. Based on the structural health condition of the tower, power de-rating strategies can be used to reduce structural loads at the cost of power losses.This paper introduces a novel closed-loop switching control architecture to constrain the thrust in individual turbines. By taking inspiration from developments in the field of reference governors, an existing demanded power tracking controller is extended by a thrust tracking controller. The latter is activated only when a user-defined constraint on fore-aft thrust force is exceeded, which can be set based on the actual damage status of the turbine. Having a down-regulation with monotonic aerodynamic load response, a simple linear thrust tracking controller is proposed. Such a scheme can reduce aerodynamic loads while incurring acceptable losses on power production which, in a wind farm setting, can be compensated for by other turbines. Large eddy simulations demonstrate the performance of the proposed scheme on satisfying thrust constraints.