In the previous chapter, we considered the application of FACTS controllers
for damping power oscillations in transmission lines caused by low frequency
rotor swings in generators. The objective is to improve small signal stability
of power systems that implies the ability of the power systems to maintain
synchronism under small disturbances that are always present (due to small
perturbations in the system load). It is essential to maintain small signal
stability for all normal operating conditions that a power system is subjected
to.