PMU-based model-free method for transient instability prediction and emergency generator-shedding control

摘要

Using PMU measurements, this paper proposes a model-free method to predict post-fault transient instability and develop emergency generator-shedding control. First, the multi-machine system is converted to an equivalent one-machine-infinite-bus (OMIB) system based on online generator clustering, and then the stability criteria are derived to judge the transient stability using the OMIB rotor speed (OMIB-omega) trajectory. Next, a new trajectory prediction algorithm based on ensemble online sequential learning machine (E-OS-ELM)is proposed to predict the OMIB-omega trajectory with an adaptive prediction window. The post-fault transient instability status can be detected in advance on basis of the predicted omega trajectory and the derived stability criteria. Lastly, when the system is foreseen to lose stability, an analytical generator-shedding control algorithm is presented, and the relationship between the generator-shedding amount and the time delay is illustrated. Case studies on the New England 39-bus system, the NPCC 140-bus system and a realistic province power system in China are presented to show the proposed methodology can detect the instability status early, and help the system maintain synchronism.