“…It should be noted that in the study of dynamic stability, the linearized model of the system is used, and in order to design the controllers that dampen fluctuations based on FACTS devices, these devices must be included in the linear model of the system. Among the works in the field of linearization of FACTS devices, we can refer to [44], which deals with the linear modeling of synchronous series compensator (SSSC), static synchronous compensator (STATCOM), and UPFC in single-machine and multi-machine power systems and the modification of the Heffron-Phillips model so that all three devices have reached a similar structure with minor differences for the modified Heffron-Phillips model [1], [3], [10], [15], [17], [22], [25], [27], [31], [45]- [71]. In these articles, several methods have been used to select the feedback signal for the complementary controller.…”