Delay-Dependent Small Signal Stability for Power System with Constant and Time-Varying Delays

Conventional small signal stability (SSS) model for power system is a kind of linear control system that uses 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 SSS and even cause power system instability. This chapter investigates delay-dependent SSS 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 ensures power system to maintain stability, is defined as the delay margin for SSS analysis. 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 SSS and verify the correctness and effectiveness of the proposed model and its SSS criterion.