The Interline Power Flow Controller (IPFC) is a voltage-source-converter (VSC)-based flexible ac transmission system (FACTS) controller which can inject a voltage with controllable magnitude and phase angle at the line-frequency thereby providing compensation among multiple transmission lines. In this paper, the use of the IPFC based controller in damping of low frequency oscillations is investigated. An extended Heffron-Phillips model of a single machine infinite bus (SMIB) system installed with IPFC is established and used to analyze the damping torque contribution of the IPFC damping control to the power system. The potential of various IPFC control signals upon the power system oscillation stability is investigated a using controllability index. Simulation results using Matlab Simulink demonstrate the effectiveness of IPFC damping controllers on damping low frequency oscillations. © 2008 IEEE.