Determination of voltage stability limit in multimachine power systems

A method of determining the load limit and the critical state of a general multimachine power system is presented. In the method, the search for the load limit is formulated as an optimization problem. With this formulation, difficulties related to singularity of the load-flow-equations Jacobian matrix, and convergence of the load-flow solution around the voltage stability limit, are avoided. Modification to the basic formulation to allow consideration of load-voltage characteristics is also shown. A voltage stability margin is defined which may serve as a measure of the security of a given operating condition from voltage instability or collapse. Results of application of the proposed method to the AEP 14-bus network are presented