Damping Inter-Area Oscillation in Power Systems Using Local PSSs based on Global Control Signals

In this paper, the concept of SMIB is generalized for inter-area oscillation consisting of two or more oscillating areas. By using the generalized SMIB (GSMIB) model the nature of inter-area oscillation and the mechanism for its damping is investigated. It is shown that the PSS of power stations are not able to damp inter-area oscillation based on the local control signals which are commonly used for damping local oscillations. Based on the derived GSMIB model it is shown that only using global control signal provided based on the concept of center of inertia (COI) of oscillating areas is able to damp inter-area oscillation. The global signals provided based on the COI can be categorized into 1-global area signals and 2- global inter-area signals. Also it is shown that depending on the pattern of the oscillating areas proper combination of both types of global signals could be able for damping inter-area oscillations. The simulation studies on IEEE 39-buses test system show the effectiveness of the proposed signals for damping inter-area oscillations.