Controller design for a wind farm, considering both power and load aspects Maryam Soleimanzadeh Controller design for a wind farm, considering both power and load aspects Rafael Wisniewski Maryam Soleimanzadeh

Contents: Introduction & Overview Wind farm control Control strategy Load Power Results

Introduction Motivation: A wind flow model in the form of The wind farm controller should (based on the model): Provide power reference for each WT Minimize load

Overview

The Wind Farm Controller block controls the power production of the wind farm by sending out reference signals to each individual wind turbine. Wind turbine controller: responsible to execute the references sent from the wind farm controller Wind Farm Control

Wind Farm Configuration

Structural Loads (dynamic): The tower fore-aft motion The blade flap motion The tower side-to-side Blade edge & Drive train torsion Reducing the tower fluctuations (fore-aft and side-to-side), will significantly reduce fatigue loads Load Reduction

Depending on wind turbines operating region Control Strateg y Control Strateg y

Farm control Strategy : (Idea from WT control strategy, following figure) Below rated wind speed wind turbines are to produce as much power as possible the pitch angle is kept almost constant. Above rated wind speed wind turbines are to follow the power reference signal the rotor speed is kept almost constant. Wind Farm Control Figure: Bianchi, F. et al., Wind turbine control systems, 2006 Farm Controller produces: Power reference signals Pitch angle reference Farm Controller produces: Power reference signals Pitch angle reference Farm Controller produces: Rotor speed reference signals Farm Controller produces: Rotor speed reference signals

Below rated Wind speed: pitch angle: constant, Additional thrust by rotor speed variations: to increase damping Wind Farm Control

Below rated Wind speed: Wind Farm Control

Below rated Wind speed: S.T. x = V (Wind Speed), u= Ct Maximize Power Minimize load Increasing tower fore-aft damping Increasing tower side-to-side damping Minimize load

Above rated Wind speed: Rotor speed: constant, Additional thrust by pitch angle variations: to increase damping Wind Farm Control

Above rated Wind speed: S.T. x = V (Wind Speed), u= Ct Increasing tower fore-aft damping Increasing tower side-to-side damping Power Reference Determination Minimize load

Wind Farm Control Optimal control solution for below rated wind speed Comparison of total produced power by each WT in low wind speed, with and without wind farm controller

Wind Farm Control Optimal control solution for above rated wind speed Total power reference for each wind turbine in high wind speed, with and without controller. Total demanded power from the wind farm for both cases are equal.

Conclusion It is founded on the dynamical model of the flow in wind farms. The wind farm controller focuses on optimization of both power and load simultaneously. Determines the reference signals for each individual wind turbine controller in two scenarios based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted. In high wind speed, the power and pitch reference signals are determined. But It does not consider the interactions between wind turbine controllers and the farm controller.

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