Delay-dependent Small Signal Stability Criterion for Power System with Time Delays

Abstract Small signal stability (SSS) deals with the problem of state evolution with time when power system is subjected to small signal disturbances .Conventional SSS model for power system is a kind of linear control system by using Taylor's formula at equilibrium point without considering time delay influence. However, time delay, existing in transmission of data from the measurement location to a control center and communication of these data to control devices, would degrade stability performance and even cause power system instability. This paper investigates delay-dependent SSS problem by constructing a new SSS model for time-delay power system. A novel LMI based SSS criterion is derived by adopting an improved Lyapunov-Krasovskii functional method. The upper bound of time delay, which guarantees power system to maintain stable, is defined as delay margin for SSS evaluation. Case studies are carried out on synchronous-machine infinite-bus power system and multimachine power system. Satisfactory results demonstrate the influence of time delay on power system stability and verify the correctness and effectiveness of the proposed model and its SSS criterion.