Integrated approach to dynamic and static voltage stability

The authors formulate voltage stability as a dynamic problem and show that the excitation systems plays a key role in determining voltage stability through the relevant eigenvalues of the linearized system's A matrix. Whereas in most studies using a linearized dynamic approach the electromechanical modes are of concern for stabilizing the system, it is shown in this study that the electrical variables associated with the excitation system play a dominant role. In the limiting case when there is no representation of the excitation system, the determinant of the load-flow Jacobian becomes the key determining factor. Under these conditions, Venikov's criterion is valid. The authors consider both the limited-Q and the unlimited-Q case, i.e., the Q limits on the reactive power generation.