SVC is composed of a controllable shunt reactor and shunt capacitor(s). Typically, the
power system control variable controlled by SVC is the terminal bus voltage. Total
susceptance (Be) of SVC can be controlled by controlling the firing angle (α) of thyristors.
Consequently, it represents the controller with variable impedance that is changed with the
firing angle of Thyristor-Controlled Reactor (TCR).
During the normal operation, the total susceptance can be controlled according to the
terminal voltage. However, at limits, minimum or maximum susceptance, SVC behaves
like a fixed capacitor or an inductor. At point Bmax, all thyristor switched capacitor are
switched on, with SVC providing rated capacitive current at specified voltage. At point
Bmin, the thyristor-controlled reactor is fully switched on, and all thyristor switched
capacitors are off to give inductive current at a defined voltage.
SVC can increase voltage stability of the system by immediately providing reactive power
support when the system has voltage problems such as due to a trip of an important
generator or transmission line, etc.
Appropriate model including appropriate representation of SVC can be incorporated in
static voltage stability study by adding SVC equations in the power flow equations. The
validated p.u. Differential-Algebraic Equations (DAEs) corresponding to this model are
[15]-[16]: