Nonlinear Control of Power Coefficients in Wind Turbines

Abstract

Wind speed above rated value causes high power and generator over speed. This leads to overloading and breakdown of the generator. As a result, control is required to maintain the desired generated electrical power. Many papers use the blade pitch angle, which is highly non-linear as control input to achieve this goal. In this paper, the power coefficient is used for the first time as the control input due to its simplicity, noting that power coefficient is a linear coefficient of the rotor power. A non-linear controller called Sliding mode is used to command the power coefficient to regulate the rotor speed to the desired value. The actual pitch angle for every wind speed is determined by designing some algorithms which are used with the power coefficient from the controller. The simulation results show that this control strategy is able to regulate the generator power by setting the rotor speed to its desired value. Another non-linear controller called feedback linearization is also used to compare its results to the sliding mode controller. This is to show that other controllers can also be used. The simulation results of the two controllers are indistinguishable.

Keywords

• wind turbine electrical power,generator speed,power coefficient,pitch angle,sliding mode control

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