WindAdmittance:

--------------------------------------------------------------------------
   Creates a wind admittance filter.

   If dT is entered

   x[k+1] = a*x[k] + b*u[k]
   y[k]   = c*x[k] + d*u[k]

   else

   dx/dt  = ax + bu
       y  = cx + du;

   Type

   WindAdmittance

   for a demo

--------------------------------------------------------------------------
   Form:
               WindAdmittance
   [a,b,c,d] = WindAdmittance( harm, dTF, dT )
--------------------------------------------------------------------------

   ------
   Inputs
   ------
   tau        (1,1) Time constant
   dTF        (1,1) Frequency scaling constant = Blade radius/mean wind
   dT         (1,1) Sample time

   -------
   Outputs
   -------
   a          (1,1) State transition matrix
   b          (1,1) Input matrix
   c          (1,1) Output matrix
   d          (1,1) Feedthrough matrix

--------------------------------------------------------------------------
   Reference: Rosas, P., "DYNAMIC INFLUENCES OF WIND POWER ON THE
                          POWER SYSTEM", Orsted DTU, PhD Thesis,
                          March 2003, pp. 47-53. Figure 3.14.
--------------------------------------------------------------------------

Children:

Common: Control/C2DZOH
Common: Control/FResp
Common: Control/ND2SS