Analysis of voltage stability enhancement via unified power flow controller

This paper discusses the control of the unified power flow controller (UPFC) to improve power system voltage stability. A dynamical UPFC model is presented. The impact of the UPC model on voltage stability is clarified through bifurcation analysis. Robust techniques are employed for the series and shunt branches control and the DC capacitor voltage control. Only local measurements are required for designing the controllers. The effectiveness of the proposed UPFC control on voltage stability is examined on a three-machine power system. Bifurcation analysis indicates that the feasibility region can be greatly extended. Therefore the proposed controller is effective in voltage stability enhancement.