Robust design of fuzzy-based power system stabiliser considering uncertainties of loading conditions and transmission line parameters

Ensuring the efficiency and robustness of a power system stabiliser is indebted to provide a comprehensive scheme that considers significant uncertainties in variables and parameters of the model. This study proposes a robust type-II fuzzy logic-based power system stabiliser scheme that can handle the uncertainties in both loading condition and line parameters. Unlike loading condition, there are many lines in a typical power system and it is necessary to introduce an indicator that can mark lines with significant uncertainty in the parameters. Hence, a criterion based on Oscillatory Stability Index is presented in the study. On the other hand, random samples from line parameters and loading conditions are generated by the roulette-wheel using probability density functions (PDF) to form the elements of the weighting matrix. Two objective functions including weighted eigenvalue deviations and damping ratios are defined and then optimised to find the parameters of the proposed stabiliser in the uncertain environment. Simulations are carried out in different scenarios and in terms of both load condition and line parameters changes. Finally, the performance of the proposed stabiliser is assessed through comparisons with an optimised lead-lag power system stabiliser and a robust lead-lag power system stabiliser.