Higher-Harmonic Load Control of Wind Turbine Blades with Actuator Saturation

Dynamic loads on the wind turbine blades result in structural fatigue, which is harmful to the longevity of a wind turbine. The fatigue damage on the blades correlate with fluctuations in blade-root bending moments. Dynamic load control aims to reduce such load fluctuations. In this paper, higher-harmonic load control is developed to target the first two harmonics of the dynamic loads at blade roots. Sectional Lift Actuators (SLA), which are a proxy for on-blade flow control devices, are utilized. The SLAs are assumed to have finite actuator authority. This paper compares two nonlinear saturation management schemes that allocate the available actuator authority towards controlling the different harmonics. These schemes are compared based on damage equivalent fatigue loads and turbine performance. The relative efficacy of the saturation management schemes proposed is evaluated.