A nonlinear control scheme for extremum power seeking in wind Turbine Energy Conversion Systems

A novel nonlinear control scheme for maximum power seeking in wind turbine energy systems is presented in this paper. In the proposed control scheme, the wind turbine power coefficient is estimated using a Lyapunov-based adaptive control technique. The power coefficient estimation procedure differs from previous estimation strategies. The estimated power coefficient is used to determine a desired turbine rotor speed which is based on an estimate of the power coefficient gradient with respect to rotor speed. The desired rotor speed moves the turbine operation in the direction of increasing power coefficient and a PI controller causes the turbine rotor speed to track the desired rotor speed. The presented extremum seeking procedure differs markedly from the well-known perturb and observe scheme and does not require the addition of a dither signal. The NREL FAST numerical results are presented to demonstrate the validity and robustness of the developed control scheme.