A time domain simulation model which approximates the
three-dimensional velocity fluctuations of wind turbulence
has been developed. This model is used in a discrete time
control algorithm to regulate the output torque of a wind
turbine by changing the pitch angle of the turbine blade.
The wind model provides a velocity field which varies
randomly with time and space and gives the proper correlation between spatial locations and velocity components.
In addition, the spectral representations approximate
those observed from a rotating reference frame. The version of the model described in this report is a time
domain simulation. It makes use of a random number generator to construct a white noise time series with a uniform
power spectral density over the frequency range of interest. This noise source is then passed through a set of
appropriate linear filters to obtain the various wind
velocity fluctuations which would be experienced by a
rotating wind turbine blade. The blade pitch angle
remains fixed in the computation of average torque values
for each revolution which does not permit a continuous
control action to be implemented. Therefore, a discrete
control model with a time interval equal to the period of
the rotor revolution is chosen. A control action which
compensates for the flapping oscillation and induces a
torque step response with a small overshoot which reaches
steady state in a minimum number of steps is desirable.
To achieve this, an integral control action is combined
with a digital narrow band rejection filter. The integral
control action eliminates the steady error in the resulting torque response
