Community Research and Development Information Service - CORDIS

TURBU Offshore, Computer Program for Frequency Domain Analysis of Horizontal Axis Wind Turbines

The computer program TURBU Offshore has been developed for frequency domain analysis of offshore wind turbines. Next to load calculation via power spectral density functions, TURBU Offshore allows for:
(i) the computation and analysis of modal properties, and
(ii) time-domain simulation with feedback loops for control included under stochastic excitation from a wind field and sea waves.

The structural dynamics are catered for by multi-body models of the blade and tower structure, which consist of mass/spring/damper-elements with up to six degrees of freedom (DOF). Lumped DOFs are included for:
(i) yaw, roll and tilt of the nacelle,
(ii) bending and torsion of the rotor shaft,
(iii) control of the generator counter torque, and
(iv) flap and lead oriented hinges in the rotor blades and pitch actuation.

The aerodynamic forces are uniformly distributed over a blade element while tip and root losses are taken into account via Prandtl's correction factor; unsteady aerodynamic forces can be included in accordance with the ECN dynamic stall model The dynamic inflow is included as the linearised version of the ECN cylindrical wake model.

The equations of motion are derived in accordance with Newton's first and second law. The thus formulated equations of motion (EOM), together with the strongly automated generation of the implementation of the EOMs, allows for convenient incorporation of uncommon distributed actuation mechanisms on the rotor blades. The linear equations of motion without periodic coefficients are derived by transforming the rotating blade and shaft DOFs into coordinates in a fixed frame of reference. These fixed-frame coordinates also apply for input and output variables related to the rotor blades, such as the wind speed as experienced by the blades, the pitch angles and the blade bending loads. This coordinate transformation allows for traditional Eigen value analysis as well as for time-domain simulation with a linear time-invariant (LTI) system. In this LTI time-domain simulation the rotor azimut dependent operations are moved to the boundaries of the system: the blade inputs are demodulated before they enter the LTI-system and the rotor blade outputs from the LTI-system are remodulated in order to get the meaning of variables on the rotating blades.

After further development, the TURBU code will be part of a control development software environment in which controller synthesis, stability analysis and time-domain evaluation are integrated. It is pursued to offer this software environment when cooperating with medium to large wind turbine manufacturers for identifying and addressing mid- and long-term research items. This cooperation intends to make wind turbine manufactures conscious of the potential of control and of interweaved control/aero-elasticity problems. The software will be offered in a 'laboratory version' without so called help desk function. Some kind of license agreement will apply. A user should be moderately to high experienced in the field of wind turbine control and aero-elastics.

Related information

Reported by

Energy Research Centre of the Netherlands
Westerduinweg 3P.B. 1
1755 ZG Petten
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