In this paper the low frequency oscillations damping of a single machine infinite bus power system which includes a UPFC is investigated by applying the adaptive backstepping control approach. Using the third order model of synchronous machine, the nonlinear state equations of the system are derived first. Then, based on adaptive backstepping control the UPFC injected control inputs as well as the system parameters estimation law are designed based on Lyapunov stability theory. Moreover considering the sixth order model of synchronous machine, simulation results are obtained for some faults. These results show the validity and effectiveness of the proposed control approach.

Keywords: Nonlinear control, Power system stability, Unified power flow controller (UPFC)