Techniques for the monitoring and control of voltage stability in electric power systems operating in a stressed environment will be developed. Emphasis will be placed on the use of probe signals to detect impending loss of stability and using the resultin warning signals in closed-loop control for system stabilization. Through such a signal-based approach, reliance on availability of accurate models and on extensive off-line computations is reduced. New control laws for stabilizing power systems near voltage instability will be developed. In previous research, the PI and his students have made important contributions to the theory of bifurcation control and, more recently, have coupled this with stability monitoring. In this proposal research project, these results will be applied to detection and control of impending instability in stressed electric power networks. One major departure from previous work is the emphasis on detection of instabilities before they are actually encountered, and achieving this with a signal- rather than purely model-based technique. Additionally, it is expected that new contributions to the theory will also naturally result from analytical problems motivated by the power system application.