Nonlinear coupled dynamic response of TLP wind turbine with redundant mooring under complex environmental loads and multi-tendon failures

Abstract

The nonlinear coupled hydrodynamic performance of floating wind systems under extreme sea loads is strongly affected by tendon stiffness degradation and failure-induced restoring-force redistribution. Tendon failure can threaten the stability and safety of tension-leg platform (TLP) wind turbines, particularly in non-redundant mooring configurations. This study investigates the NREL 5 MW wind turbine mounted on the UMaine-TLP platform and proposes a redundant tendon system to separate the platform natural frequencies from the rotor excitation range. A fully coupled aero-hydro-servo-control dynamic model is established in SESAM and validated against OpenFAST. The effects of wind-wave-current misalignment and single- and double-tendon failure on platform motions, tendon tension redistribution, and transient responses are examined under operating and shutdown conditions. Results show that the redundant tendon system maintains dynamic stability after tendon failure. Tendon failure has limited influence on horizontal motion but significantly amplifies rotational responses owing to stiffness degradation and asymmetric restoring-force redistribution. Under operating conditions, windward tendon failure increases resultant horizontal displacement by only 12.91%, whereas the maximum rotational response increases by more than 100%. Adjacent tendon tensions reach 2.06 and 2.12 times the intact values under operating and shutdown conditions, respectively, while the minimum safety factor remains 1.95.