Abstract
Unified Power Flow Controller (UPFC) can inject voltage with the controllable magnitude and phase angle in series with a transmission line. And it can also generate or absorb controllable reactive power. UPFC is expected to be able to damp power system oscillation more effectively than power electronics applied devices such as SVG and TCSC.
In this paper, a. control system design of UPFC for power system damping enhancement based on eigenvalue control method was proposed. As a result, it was made clear that the best design method for the power system damping enhancement is to determine steady-state values of UPFC control variables and control parameters of UPFC such as gains and time constants simultaneously because controllability of UPFC depends on the steady-state values of UPFC and the power flow condition. And the effectiveness of the proposed control system taking into account UPFC inverter ratings is verified by digital time simulation. Furthermore the effects of input signals to UPFC controller on small-signal stability and transient stability enhancement were studied. And it was made clear that the controller of UPFC using global information are more effective on the power system damping enhancement than that using local information because the global information has stronger observability for power system oscillation than the local information.
