Blade pitch

About: Blade pitch is a research topic. Over the lifetime, 5321 publications have been published within this topic receiving 63134 citations.

Disturbance Tracking Control and Blade Load Mitigation for Variable-Speed Wind Turbines

Abstract: A composite linear state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances A limitation in the theory for common multi-state models is described; this led to the design of a complementary pitch controller The goal of the independent blade pitch design was to minimize blade root fatigue loads A SymDyn model of a two-bladed, 600-kW machine was used for the simulation studies Results indicate a 24% reduction in blade fatigue damage using the proposed controllers, compared to a conventional torque-only design However, energy capture was not improved as much as expected, partly due to nonlinearity effects degrading the performance of the state-space estimator design Tower base fatigue damage was shown to decrease significantly using active pitch

Vertical speed and flight path command algorithm for displacement collective utilizing tactile cueing and tactile feedback

Abstract: A flight control system includes a collective position command algorithm for a lift axis (collective pitch) which, in combination with an active collective system, provides a force feedback such that a pilot may seamlessly command vertical speed, flight path angle or directly change collective blade pitch. The collective position command algorithm utilizes displacement of the collective controller to command direct collective blade pitch change, while a constant force application to the collective controller within a 'level flight' detent commands vertical velocity or flight path angle. The 'level flight' detent provides a tactile cue for collective position to reference the aircraft level flight attitude without the pilot having to refer to the instruments and without excessive collective controller movement.

Combined Feed-forward/Feedback Control of Wind Turbines to Reduce Blade Flap Bending Moments y

Abstract: In above rated conditions, wind turbines are often subjected to undesirable high structural loading. We investigate two feedback control techniques in combination with a feedforward control method for reducing blade ap bending loads in above rated wind conditions. The feedback controls studied include both disturbance accommodating/tracking and integral augmented/repetitive types that incorporate models of persistent disturbances at DC (step changes in wind) and at the once per revolution frequency. Each method is combined with a feed-forward method utilizing the wind speed as measured at the blade tips and also based on the blade tip average wind speed. Performance is assessed by simulating the combined feed-forward/feedback systems on a three bladed turbine model with the National Renewable Energy Lab’s FAST wind turbine code. It is found that feedforward of blade tip average wind speed measurements can provide signicant reduction of blade root loads and improved speed regulation in time varying wind that is uniform across the rotor plane. However, the improvements are not as great in non-uniform and turbulent conditions in which case the blade tip average wind speed measurements provide incomplete information for conditions that can be unique at each blade. We use an extension of the linearized turbine model to design feed-forward compensation that uses individual measurements of the wind at each blade tip. Results suggest that using blade local measurements provides substantially greater reduction in blade loads, but assessing the full potential of using this more detailed information requires more accurate modeling of the way perturbations local to each blade couple into the turbine.

Multi rotor wind turbine

Abstract: A wind turbine arrangement comprises a tower 5 and at least two arms 3 projecting outwards there from. A wind turbine 1, 2 is attached to an end of each arm 3, with means being provided to selectively lower each turbine 1, 2 towards the base of the tower 5 to allow for easier maintenance. The arms 3 may be rigid with one another and pivoted to the tower 5 such that each turbine can be lowered in turn. In this arrangement two or three arms 3 and wind turbines 1, 2 may be provided. Alternatively the arms may be independent from one another and as such may both be lowered at the same time. The turbines 1, 2 may also be lowered whilst the arms 3 remain in a substantially horizontal position. A method of control is also disclosed which can align the turbines 1, 2 with the wind direction by means of blade pitch adjustment. The tower 5 may be mounted on land or at sea.