Relationship Between Voltage Instability and Multiple Load FLow Solutions in Electric Power Systems

There have been observed several voltage instability phenomena in electric power systems where receiving end voltages oscillate remarkably or get much lower than the nominal values. Those phenomena tend to occur in heavy loaded conditions and seem to be related to the multiple load flow solution problem for the following reasons. It has been confirmed analytically and by simulations that the multiple load flow solutions are likely to appear under the heavy-loaded conditions, and that the individual solutions of the solution pair have different features from each other, from the standpoint of stability, although they are close to each other.