Robust wide-area TCSC controller for damping enhancement of inter-area oscillations in an interconnected power system with actuator saturation

Actuator saturation is an inevitable phenomenon in control system which degrades the system performance if it is not considered in the controller design. In this paper, a robust wide-area damping controller is designed for a thyristor controlled series capacitor (TCSC) to enhance the damping of inter-area oscillations when the power system is subjected to actuator saturation. A generalized sector condition is used to represent the nonlinear effects introduced by the actuator saturation in the closed-loop system. By using these conditions, the stabilization conditions for ensuring asymptotic stability of the closed-loop system are derived based on an quadratic Lyapunov criterion. The design of damping controller that maximizes the region of attraction is formulated in the form of linear matrix inequality (LMI) and solved as an optimization problem to achieve damping of inter area oscillations. In addition to the damping controller, further, a robust pole placement approach is employed to place the closed-loop poles in a prescribed stability region. Two case studies, namely, a two-area four-machine power system and 16 machine 68 bus power system are considered to evaluate the performance of the proposed damping controller.