Oscillation Energy Analysis of Inter-Area Low-Frequency Oscillations in Power Systems

Low-frequency inter-area oscillation is a potentially dangerous phenomenon in power systems involving exchange of power among generators in different areas. In this paper, we study the characteristics of inter-area oscillation by analyzing the distribution of the oscillation energy. First, we introduce equations for the kinetic energy of generators and the potential energy of network branches, derived from the linearization of system dynamic equations. Then, we study the mode composition and the distribution of the generators' kinetic energy during low-frequency oscillations. A modal kinetic energy participation factor is proposed for evaluating the participation of each generator in the oscillation. The relationships among electromagnetic power oscillation distribution, rotor speed deviation, and generator kinetic energy are analyzed and compared to their modal parameter left eigenvectors, right eigenvectors, and linear participation factors, respectively. The bus voltage angle deviation, active power oscillation, and branch potential energy are calculated using the right eigenvector from modal analysis. The distribution characteristics of voltage angle oscillation and branch potential energy in inter-area oscillation is developed. The simulation results for a four-generator two-area system and the New England 10-machine 39-bus system illustrate the feasibility and validity of the proposed theory and method for analysis of inter-area oscillations.