Performance assessment of floating wind turbines during grid faults

This paper presents an evaluation of the response of a
floating wind turbine to a grid fault. A multi-MW wind turbine
mounted on a spar-buoy type floater is simulated. The generator
is a permanent magnet synchronous machine connected to the
grid with a full converter. The electrical grid is modeled as a stiff
grid behind an impedance, a suitable setup for transient fault
studies. Sub-models of generator and converter controllers and
the power network are combined with a state-of-the-art numerical
simulation of the hydro-, aero- and structural dynamic behavior
of the floating wind turbine, using FEDEM Windpower software.
The response of the floating wind turbine was studied for a
100 ms grid fault that resulted in 50% residual voltage at the grid
connection point. From the simulation results, it was found that
the turbine is capable of riding through voltage-dips without
severe effects on the electrical or mechanical systems. A significant
dip in the tower bending moment was observed, however the
magnitude was not found to be critical. The most affected component
of the bending moment is around the axis of the rotor,
and is directly related to the loss of generator torque.