Power system small signal stability region with time delay

With the rapid development of phase measurement unit and wide area measurement system (PMU/WAMS), power system coordinated stability control has been paid more and more attention. Since there is obvious time delay in WAMS measurement, it is important to properly evaluate the impact of time delays on power system stability analysis and controller design. In this paper, influence of time delay on power system small signal stability region is deeply investigated. Small signal stability of differential algebraic equation with time delay is first reviewed as the necessary theoretical background. Then an optimal-based algorithm is given to trace boundaries of the small signal stability region with considering the time delay. Finally, two simple systems are employed to do some verification studies. It is found that time delay has significant influence to the boundary of the small signal stability region, especially when the time lag is large. This paper is helpful to properly consider the effect of time delay in power system controller design and small signal stability studies. (c) 2007 Elsevier Ltd. All rights reserved.