Regulating rotor aerodynamics and platform motions for a semi-submersible floating wind turbine with trailing edge flaps

The coupling effects between rotor aerodynamics and platform motions are being focused for floating offshore wind turbines (FOWTs). Ignoring these effects during the controller design can deteriorate some essential loads or lead to aero-elastic instabilities. Superimposed proportional model-free adaptive control (SP-MFAC) is pro-posed to cope with these effects by simultaneously optimizing blade root moments, rotor speed, platform-pitch and-yaw motions. Trailing edge flap (TEF) is used as the active flow control device. Actuators' saturation and energy consumption are considered by introducing penalty factors into control cost function. A typical semi-submersible FOWT is selected for simulation study. A comparison is made against proportional-integral-differential-based (PID-based) TEF control and baseline control in turbulent and extreme gust conditions. Numerical results reveal that SP-MFAC costs less in TEF deflection activity, but realizes better overall performance than PID-based TEF control. Further, the physical mechanisms of load reduction are analyzed with cross-wavelet transformation. The original in-phase aero-hydro-elastic mechanisms in the semi-submersible FOWT are crippled by the TEF deflection activity.