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Wind turbine control algorithms : DOWEC-F1W1-EH-03-094/0
Gepubliceerd door: Publicatie datum:
ECN Windenergie 1-12-2003
ECN publicatienummer: Publicatie type:
ECN-C--03-111 ECN rapport
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The objective of DOWEC task 3 of work package 1 has been defined as ?research and devel-opment of wind turbine (power) control algorithms to maximize energy yield and reduction of turbine fatigue load, and its optimisation for offshore operation?. In accordance with the DOWEC baseline turbine and the related DOWEC turbine all activities were focused on active pitch to vane, variable speed concept. The results of this task contribute to the:

? set-up of a modular control structure based on theoretical analysis and industrial needs;
? increase of turbine performance (power production, load reduction) by additional control features and actions.

It can be concluded that the control structure is superior to ordinary PD feedback control of the rotor speed. An independent comparison for the DOWEC turbine using an aerodynamic code, with a state-of-the-art control structure, has resulted in improvements concerning:

? extreme fore-aft tower bending moment (-40%);
? fatigue fore-aft tower bottom bending equivalent moment (-50%);
? variations in blade pitch rate (standard dev. -0.65 dg/s);
? tilt moment (-10%).

The mean power production (10min) in above rated wind speeds was over 99% of its rated value. Opposite to the improvements it has brought about larger variations in generator speed (standard dev. .5 rpm), increase of yaw moment (12% ) and radial blade forces (14% ).

The underlying approach of the control structure divides the multivariable wind turbine system into different independent scalar subsystems by band fil-tering. As a consequence the resulting setpoints, the pitch rate and electrictorque, consist of additive contributions of the different control actions.

Concerning power control, ordinary rotor speed feedback has proved to be a robust core. However, valuable extensions were developed by wind speed feed forward control (pitch control) and optimisation around rated condition (electric torque control).

Promising results have been achieved on fore-aft tower damping by pitch control. Electric torque control has enabled considerable damping results of (collective) drive train resonances and possibilities for badly damped sideward tower vibrations.

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