Evaluation of damping controls of a unified power flow controller

With its unique capability to control simultaneously the real and reactive power flows on a transmission line, as well as to regulate voltage at the bus where it is connected to, the unified power flow controller (UPFC) has a potential to create a tremendous impact on power system stability. This paper examines the control capabilities of its various control variables, viz. shunt converter voltage magnitude and phase angle, series converter voltage magnitude and phase angle, capacitor control and power system stabilizer. Their effectiveness in damping improvement has been studied through singular value decomposition, Hankel singular value decomposition, and residue methods. From a number of studies it has been observed that the shunt transformer phase angle control provides the best damping properties amongst the set.