Influence of adaptive controlling strategies of floating offshore wind turbine on corrosion fatigue deterioration of supporting towers

Abstract

Floating offshore wind turbines (FOWTs) demonstrate very promising potential in unlocking the plentiful wind resource in deep-water oceans. Meanwhile, the combination of the harsh marine environment and strong dynamics complicate the long-term deterioration of FOWT-supporting towers, specifically the escalating corrosion fatigue (C-F) coupled deterioration in critical connections. Unlike traditional engineering structures, an interoperable control is available in FOWTs, such as the pitching, yawing and torque controllers, which can mitigate structural oscillation and loads. With the recent advances in smart sensing, a better prognosis of current and future deterioration can be guaranteed with increasingly accessible data. Thus, a refined adaptive control strategy is hence deemed essential based on the site-specific data, to curb the operation and maintenance (O&M) costs of FOWT towers based on the structural condition. The present work elaborates on the influence of various adaptive controlling strategies of FOWTs on the C-F deterioration of supporting towers, lending itself to preliminary references for balanced trade-offs between power generation and structural reliability. Multi-physics simulations of FOWTs are initially carried out to establish fatigue stress spectra from site-specific wind-wave distribution, using various types of control strategies. Structural reliability assessment is then conducted by incorporating the spectra into a time-variant C-F deterioration model in which the ambient corrosivity is accounted for. The result suggests a compelling C-F deterioration faced by FOWT towers due to strong wind-wave loads, high corrosivity and improved structural flexibility. More critically, the finding underscores the apparent influence of controlling strategies on the C-F deterioration of FOWT structures, especially under certain regimes of wind velocities. In addition, preliminary but innovative perspectives are elucidated on the delicate balance and conflict between generation efficiency and structural reliability.