Online estimation of controlled islanding time intervals using dynamic state trajectories through cascading failures from WAMS data

Abstract

• Use the wide area measurement system to evaluate the system dynamic stability. • A new concept of estimating islanding time. • Proposing an islanding identification time (IIT) index based on the system dynamic behaviors. • Presenting an adaptive concept of IIT scheme with respect to fault severity. • Presenting an online and non-model-based index through real-time evaluations. • Online evaluation of Unstable Equilibrium Point (UEP) to estimate the stability margin of each created island. Islanding strategy is the last controlling action performed through different phases. In this case, fast and secure estimation of the islanding identification time (IIT) are two emergency parameters which play important roles on wide area stability. Due to nonlinear behaviors of the power system generators through severe faults, determining the best islanding scenario remains as an important challenge. By using wide area measuring system (WAMS) technology, an online and adaptive concept of IIT scheme is presented in this paper. To do this, at each time window, considering a set of proper IITs, the best islanding times are estimated. In this case, considering each islanding scenario, based on concept of Unstable Equilibrium Point (UEP) through online evaluations, the synchronism and stability margin of each created island is evaluated. By this way, the corresponding synchronous generators (GSs) are separated though a set of secure islanded subsystems which are operated within different stable operating points. In the case of estimating unstable islanding cases, by rescheduling GSs islanding scenarios through real-time evaluations, the most proper IITs are estimated and performed. Simulation results indicate the effectiveness of provided scheme for online estimation of proper islanding times through different wide area instability scenarios.