Voltage Stability Analysis in Electric Power Systems by Nonlinear Programming

ABSTRACT

Voltage instability phenomena in electric power systems are characterized by a progressive lowering of receiving end voltages beyond their nominal values.Particularly, a voltage collapse occurs at a load node when the active power fed from the load reaches a maximum value. On the basis of this observation a new method for the analysis of the voltage stability in power systems is presented.The suggested approach derives the critical voltage stability conditions for the system through the solution, by non linear programming techniques, of a non linear constrained optimization problem which considers as objective function the active power demand at a prefixed load node and as constraints the active and reactive power balance equations at the system nodes and the practical operating capabilities of generators. The method proves suitable for a rigorous individualization of the factors which affect voltage instability phenomena and can advantageously be used for planning and operation of electric power systems. Two examples are presented to illustrate the validity and the usefulness of the suggested approach.