The experimental setup is described in Fig. 6. Ratings and
characteristics of all system components are summarized in
Table III. In all measurements, the pu system is based on the VA
rating of the machine used to emulate the wind generator, which
is a 7.5 kW wound rotor induction machine with short-circuited
rotor terminals. The wind turbine is emulated by a torque controlled
dc motor. A constant torque is used to model the power
from the wind, because the analyzed transient phenomenon is
assumed to be much faster than wind variations.
A local load, having induction motor characteristics is
placed at the point of common coupling as shown in Fig. 6, in
order to force the power system towards its stability limit. The
STATCOM is an IGBT-based inverter bridge with a control
strategy based on vector control technique. The vector control
technique is implemented in a host computer and downloaded
into the processor of a DSP based control system.
A balanced three phase short circuit condition is provoked for
300 ms by operating the short circuit device in Fig. 6. The first
experiment performed is without the control of the STATCOM
and it shows to be unstable. Three other experiments are performed;
with the control of the STATCOM for different current
ratings, of 0.5, 1.0, and 1.8