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Significant barriers to interconnection are being perceived already
with the requirements of the new grid codes, and there
is a need for a better understanding of the factors affecting the
behavior of the wind farm under severe contingencies such as
voltage sags. Wind farms using squirrel cage induction generators
directly connected to the network will most acutely suffer
from the new demands, since they have no direct electrical control
of torque or speed, and would usually disconnect from the
power system when the voltage drops more than 10–20% below
rated value [5]. In general, fulfilment of LVRT by reactive compensation
will require fast control strategies for reactive power
in wind turbines/farms with cage induction generators.
Different solutions are found to support the transient behavior
of cage induction generators in case of changes in the grid
voltage. Mechanically switched capacitors, SVC, Synchronous
Condensers and Voltage Source Static Var Compensator such
as the STATCOM can be used to regulate voltage as shunt
compensator to improve the grid interface of directly connectedasynchronous wind generators. Thyristor-controlled static var
compensators (SVCs) have been reported in [6], [7] for voltage
support of critical loads, transient stability improvement and
power oscillation damping in electric power transmission systems.
The STATCOM has the same capabilities, as reported in
[8], [9], but with a higher control bandwidth and the additional
capability of providing higher currents at low voltage levels.
Studies of transient stability of induction generators related to
the use of a STATCOM have been reported in [10], [11], and
a general analysis of the ride through capability of fixed-speed
wind farms with a STATCOM is provided in
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