Transient Stability Assessment of Large-Scale Power System Using Predictive Maximal Lyapunov Exponent Approach

Online assessment is important to guarantee the transient stability of power systems. The model-free maximal Lyapunov exponent (MLE) estimation approach enables accurate assessment but has time-consuming problem. This work proposes a fast online approach to transient stability assessment using Predictive Maximal Lyapunov exponent (PMLE), which significantly reduces the assessment time. It consists of relative rotor speed prediction, relative rotor angle prediction, PMLE estimation, state-plane trajectory calculation of PMLE, and stability assessment. The prediction steps and models of relative rotor speed are specifically designed according to the rotor angle undergoing first swing instability, multi-swing instability, or stable conditions. Besides, the PMLE is obtained by relative rotor speed and angle prediction based on self-memory model. Furthermore, critera for assessing stability in advance based on PMLE and the state-plane trajectory of PMLE are proposed. By solving the time consuming problem of six swing patterns identification and MLE estimation, the proposed approach improves rapidity of assessment for all stable and unstable conditions. Case studies are conducted on IEEE 39-bus system, WECC 179-bus system, and Northeast China Power System with 2131 buses. The results verify the effectiveness and rapidity of the proposed approach compared to those of other model-free methods.