Real-Time Transient Stability Assessment Using Dynamic Equivalents and Nonlinear Observers

Ali Iravani, Francisco De Leon

Research output: Contribution to journalArticlepeer-review


This paper presents a new method for detecting the early stages of unstable conditions in large-scale power systems. A reduced order dynamic model is introduced for each control area that includes an aggregated generator and associated controllers. An innovative nonlinear observer proposed that can simultaneously estimate the parameters and states of the model benefiting from available online measurements. A sensitivity analysis is used to improve the efficacy and performance of the proposed estimator. The estimated states of the proposed equivalent generator model are then used to define a Real-Time Transient Stability (RTSA) index. The recommended RTSA index demonstrates to be a clear measure of the distance to instability and prevents economic losses due to blackouts and cascading system trips. The PSS/E simulation results on two case studies using show the excellent performance of the proposed index.

Original languageEnglish (US)
Article number8964490
Pages (from-to)2981-2992
Number of pages12
JournalIEEE Transactions on Power Systems
Issue number4
StatePublished - Jul 2020


  • Dynamic equivalents
  • observability
  • parameter identification
  • simultaneous state and parameter estimation
  • stability index
  • transient stability assessment

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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