| Abstract |
A numerical method has been suggested and applied to
simulate the operation of a stand alone Doubly-Fed Induction
Generator, in a wide range of sub and super synchronous
operating speeds. The stand alone operation is achieved through
vector control, by imposing the alignment of the d-axis of the
synchronously rotating reference frame along the stator flux
vector. Twenty seconds simulations are presented by feeding the
stator d and q current components, and artificially generated
wind speed. For the sake of demonstration of the operation in all
speed ranges, the input current components have been drawn
from the simulation of a rotor short circuited, grid connected
DFIG, starting from rest. The synchronous frequency s, and
stator voltages Vds
ref and Vqs
ref are imposed as constant demands in
the control equations. Simulations are carried out by
independently iteratively solving three differential equations for
magnetizing current Ims, and rotor current components Idr and Iqr,
respectively. Solutions of these equations respectively generate the
demands for the rotor current Idr, and rotor voltage components
Vdr and Vqr. The demand for Iqr is obtained directly from the field
alignment condition. The stator current input data includes a 150
millisecond fault induction response to a stator voltage step
change from 1 to 0.5 per unit. |
