A FLEXIBLE NEURAL CONTROLLER FOR TRANSMISSION SYSTEMS EQUIPPED WITH UPFC

Unified power flow controller (UPFC) is the most reliable device in the FACTS concept. It has the ability to adjust all three control parameters effective in power flow and voltage stability. This paper presents the establishment of a linearized Phillips-Heffron model of a power system installed with UPFC to damp low frequency oscillations in a weakly connected system. UPFC has four control loops that, by adding an extra signal to one of them, increases dynamic stability and load angle oscillations are damped. In this paper, after open loop eigenvalue (electro mechanical mode) calculations, state-space equations has been used to design damping controllers and it has been considered to influence active and reactive power flow durations as the input of damping controllers, in addition to the common speed duration of synchronous generators as input damper signals. The potential of UPFC supplementary controllers to enhance the dynamic stability is evaluated based on this model. On the other hands dynamic equations for a power system are nonlinear. To control a nonlinear system, nonlinear controllers are used. Theses controllers are designed based on system state space equations to obtain controlling signal. In this paper a proposed neural controller is used to product a supplementary controlling signal for stabilizing and oscillation damping to overcome the drawbacks of conventional lead-lag controllers in system nonlinear model. The presented control scheme not only performs damping oscillations but also the voltage and power flow control can be achieved. Simulation results carried by Matlab, show the proposed strategy has fast dynamic response.