General description

iSLA is a tool for simulation, analysis and design of conventional and advanced underfrequency load-shedding (UFLS) schemes of island and isolated power systems. iSLA can handle a large amount of operating and contingency scenarios.

Isolated power systems are especially sensitive to generation-load imbalances. The small size, the relatively low inertia, and the comparatively large generation in-feeds make them more vulnerable than large interconnected systems. UFLS schemes are the last-resort tool to protect the power system in case of a severe contingency. iSLA incorporates both conventional and advanced UFLS schemes.

Key features

• Simple and quick simulation of conventional UFLS schemes: the user can either use predefined contingencies or specify them explicitly.
• Two-step design of conventional UFLS schemes: Contingencies are either selected manually or through Cluster Analysis. Different optimization algorithms and objective function formulations are available. The optimization constraints and the set of decision variables are fully modifiable.
• Monte-Carlo simulations for the analysis of conventional UFLS schemes: the user can select from a large set of distribution functions and specify their parameters. Several reporting indexes can also be specified by the user.
• Synthesis of advanced UFLS schemes: the user can quickly simulate the behavior of UFLS schemes based on Decision Trees, ANN, Regression, or Frequency Stability Boundary.
• Tuning of generator models for frequency stability studies: the user can select and fine tune generator models by using either available detailed models or field test measurements.
• Incorporation of energy storage systems.

Publications

[1] L. Sigrist, A UFLS scheme for small isolated power systems using rate-of-change of frequency. IEEE Transactions on Power Systems, vol. 30, no. 4, pp. 2192-2193, July 2015.

[2] L. Sigrist, I. Egido, L. Rouco, Principles of a centralized UFLS scheme for small isolated power systems. IEEE Transactions on Power Systems, vol. 28, no. 2, pp. 1779-1786, Mayo 2013.

[3] L. Sigrist, I. Egido, L. Rouco, Performance analysis of UFLS schemes of small isolated power systems. IEEE Transactions on Power Systems, vol. 27, no. 3, pp. 1673-1680, August 2012.

[4] L. Sigrist, I. Egido, L. Rouco, A method for the design of UFLS schemes of small isolated power systems. IEEE Transactions on Power Systems, vol. 27, no. 2, pp. 951-958, May 2012.

[5] I. Saboya, I. Egido, E. Lobato, L. Sigrist, Analysis of UFLS schemes with increased wind generation in small isolated power systems. In 17th Power Systems Computation Conference - PSCC'11.Stockholm, Sweden, 22-26 August 2011.

[6] L. Sigrist, I. Egido, E.F. Sánchez-Úbeda, L. Rouco, Representative operating and contingency scenarios for the design of UFLS schemes. IEEE Transactions on Power Systems, vol. 25, no. 2, pp. 906-913, May 2010.