There have been a number of attempts to derive an accurate
analytical model of a TCSC that can be employed in system
stability studies and controller design [3-6]. The model
presented in [3] uses a special form of discretisation, applying
Poincare mapping, for the particular Kayenta TCSC
installation. The model derivation for a different system will
be similarly tedious and the final model form is not convenient
for the application of standard stability studies and controller
design theories especially not for larger systems. A similar
final model form is derived in [4], and the model derivation is
improved since direct discretisation of the linear system model
is used, however it suffers other shortcomings as the model in
[3]. The modeling principle reported in [5] avoids
discretisation and stresses the need for assuming only line
current as an ideal sine, however it employs rotating vectors
that might be difficult to use with stability studies, and only
considers the open loop configuration. The model in [5] is also
oversimplified because of the use of equivalent reactance and
equivalent capacitance that might be deficient when used in
wider frequency range. Most of these reported models are
therefore concerned with a particular system or particular type
of study, use overly simplified approach and do not include
control elements or Phase Locked Loops (PLL).