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Recent research has demonstrated that the rotor angle stability of a power system can be assessed by identifying the sign of the system's maximal Lyapunov exponent (MLE). A positive (negative) MLE implies unstable (stable) rotor angle dynamics. However, because the MLE may fluctuate between positive and negative values for a long time after a severe disturbance, determining the system stability is difficult when observing a positive or negative MLE without knowing its further fluctuation trend. In this paper, a new approach for online rotor angle stability assessment is proposed to address this problem. The MLE is estimated by a recursive least-squares-based method from real-time rotor angle measurements, and two critical parameters, the Theiler window, and the MLE estimation initial time step are carefully chosen to make sure that the calculated MLE curves present distinct features for different stability conditions. By using the proposed stability assessment criteria, the developed approach can provide a timely and reliable assessment of rotor angle stability. Extensive tests on the New England 39-bus system and the Northeast Power Coordinating Council 140-bus system verify the effectiveness of the proposed approach.
Wei et al. (Mon,) studied this question.