Multi-Objective Control for Structural Load Reduction and Maximization of Power in Low Wind Speed Region

Abstract

In this paper, a control strategy that optimizes a trade-off between power production maximization and structural
load reduction in low wind speed region is proposed. To capture maximum power during low wind speed, an optimal operating point defined by optimal tip speed ratio, optimal rotor speed, and wind speed must be properly tracked. However, due to large inertial loads of utility-scale wind turbines as well as strong variations of incoming wind speed, the optimal operating point cannot be perfectly tracked, leading to sub-optimal operation. On the other hand, strict tracking of optimal power curve in wind turbines results to undesirable loads in its structural members; hence, it is important to balance between these two contradicting control requirements. To simultaneously realize the objective of maximizing power production and mitigation of structural loads, two control loops are proposed. Here, optimally tracking rotor (OTR) control is used to maximize power production, while perturbed individual blade pitch signals are utilized for structural load minimization. The results indicate that the proposed multi-objective control strategy can make a reasonable trade-off between power production maximization
and structural load reduction. Consequently, guaranteeing extended operational lifetime without much compromise on power production objective.