Direct lyapunov theory-based method for power oscillation damping by robust finite-time control of unified power flow controller

Unified power flow controller (UPFC) is one of the most versatile and complex flexible AC transmission system (FACTS) devices. It is emerged with a proven capability of instantaneous control of transmission line parameters. This study presents an approach based on the direct Lyapunov stability theory with finite-time convergence and chattering-free characteristics to improve damping of power oscillations using UPFC. A state-variable control strategy is derived and implemented to tackle the problem of finite-time convergence of system states. In the suggested method, the chattering phenomena and discontinuity of the controller, that is common in finite-time controllers, are removed to obtain a continuous and smooth controller. The suggested controller is simple and clear than the conventional famous finite-time controllers for double-integrator systems. Simulation results are given to illustrate the effectiveness and robustness against parameter uncertainty and external disturbances of the proposed algorithm. It is shown that the settling time of the system, enhanced with the proposed controller is significantly less than the conventional non-linear controllers. The proposed controller is investigated on UPFC connected to a two-bus power system.