An Improved Delay-Dependent Stability Criterion for Power System with Double Time Delays

Abstract

In this paper, a Direct Method-based delay-dependent stability criterion is presented. Initially, the Lyapunov-Krasovskii functional of power system with double time delays is simplified, then the derivative of Lyapunov-Krasovskii functional along time is converted into the pattern of linear matrix inequality (abbreviated as LMI). During the process of derivative construction, an integral inequality is introduced to magnify the derivative, thus no free-weighting matrix is utilized in the new criterion. It can be proved that the new criterion, in comparison with the former ones with free-weighting matrix, has the same conservativeness and much fewer unknown variables. Finally, the proposed criterions effectiveness is validated by the typical second-order delay system and WSCC-3-generator-9-bus system. Numerical results indicate that the proposed criterion can obtain the same stability margin with the former ones with free-weighting matrix, but the improved criterion can remarkably curtail the calculation time.