Study on Characteristics of Modes Instability in Power System with Close Modes

When there exist close oscillation modes in power systems, modes instability may occur due to small changes of system parameters. The mechanism of modes instability in power system with close modes is analyzed using perturbation method and Modal Assurance Criterion is presented to measure the modes instability. New England 10-machine system is applied to analyze characteristics of modes instability by perturbing system parameters. The results show that modal interaction is a crucial factor in the modes instability, and the characteristics of modes instability may be different because of the different interaction happened between close modes.