Abstract—This paper analyzes the extent to which the low
voltage ride through (LVRT) capability of wind farms using
squirrel cage generators can be enhanced by the use of a
STATCOM, compared to the thyristor controlled static var compensator
(SVC). The transient stability margin is proposed as the
indicator of LVRT capability. A simplified analytical approach
based on torque-slip characteristics is first proposed to quantify
the effect of the STATCOM and the SVC on the transient stability
margin. Results from experiments with a STATCOM and a 7.5 kW
induction machine emulating a wind turbine are used to validate
the suggested analytical approach. Further verifications based
on detailed time-domain simulations are also provided. Calculations,
simulations and measurements confirm how the increased
STATCOM rating can provide an increased transient stability
margin and thus enhanced LVRT capability. Compared to the
SVC, the STATCOM gives a larger contribution to the transient
margin as indicated by both calculations and simulations. The
inaccuracies introduced by neglecting the flux transients in the
suggested approach are discussed and found reasonable for an
estimation method when considering the simplicity compared to
detailed time-domain simulation studies. A method for estimating
the required rating of different compensation devices to ensure
stability after a fault is suggested based on the same approach.
Index Terms—Grid code, induction machine transient stability
limit, low voltage ride through (LVRT), voltage source static var
compensator (SVC).