Effect of blade pitch control on dynamic characteristics of a floating offshore wind turbine under platform pitching motion

Abstract

Blade pitch control (BPC) is an indispensable part of a variable speed wind turbine, which maintains a stable power output by adjusting the blade pitch angle to adapt to the changing inflow speed introduced by the platform pitching motion (PPM). An integrated aeroelastic-servo transmission system of a floating offshore wind turbine (FOWT) is established and validated. Comparing with existing models, our model considers the effect of the BPC on the FOWT, apart from the dynamic characteristic of the drivetrain and the aeroelastic coupling of the blade. Firstly, dynamic behaviours of the FOWT under different tip speed ratios are compared. Then the performance of FOWT with and without the BPC influence is compared, followed by a dynamic analysis of the FOWT under a varying platform pitching amplitude. Results show that the tip speed ratio slightly alters the FOWT performance under the PPM. Considering the effect of the BPC, the fluctuation of the generator power reduce, but the aerodynamic thrust tends to enlarge the PPM. The non-torque loads induced by the PPM are insensitive to BPC. Fluctuation of the system response increases with increasing platform pitching amplitude.