Placement of variable impedance devices for enhancement of small signal stability in power systems

This paper presents an efficient analysis and design method, based on the analysis of controllability and observability measures to place variable impedance devices for enhancement of small signal stability in complex power systems. An advanced linear state model of the power system that includes the representation of high-speed thyristor-based control of variable impedance devices is derived. Based on this representation, a numerically stable algorithm is given for computing controllability of critical system modes as a measure of the distance of the linear state representation from the nearest uncontrollable system. This approach is then extended for computing observability. A location index for variable impedance devices is finally defined from controllability and observability measures.