A Robust Feedback Linearization Controller Design for Thyristor Control Series Capacitor to Damp Electromechanical Oscillations

FACTS devices such as TCSC are capable of controlling power flow, improving transient stability, mitigating sub synchronous resonance (SSR), and reducing fault currents. An efficient control scheme is required to ensure the best use of TCSC. Conventional control strategies are based on approximate linearized model with fixed structures and parameters. But in fact, the nature of a power system not only is highly nonlinear but also exhibits some kind of uncertainty. In this paper, a robust feedback linearization controller is designed for this purpose. First, a suitable diffeomorphism transformation is used to linearize the nominal model. Then, a recursive method is used to complete the adaptive control law. The obtained controller can stabilize the uncertain system if the value of the uncertain parameter belongs to a presupposed closed region. Two different faults have been applied in the system. A symmetrical three-phase short-circuit fault which occurs at the generator bus and at the midpoint of the transmission line as well as a sudden load removing fault are applied. By using computer simulation of different operating conditions and disturbances, the effectiveness of the proposed robust nonlinear controller is established. The designed controller is applicable as it doesn't need any complicated computation while providing good performance in different operating conditions.