VOLTAGE STABILITY CONDITIONS CONSIDERING LOAD CHARACTERISTICS

It is shown that when the characteristic of the composite load of a typical utility system is taken into account, large disturbance voltage stability is assured by the existence of the stable equilibrium state of the post-disturbance system, as determined from the standard power flow model. When the load contains static components, stability limits extend considerably. The exact limit for such loads can also be determined from a power flow model, properly modified to reflect the static component of the load. In specific situations, when the bulk of the load is composed of fast response loads, a correct assessment of voltage stability would require comprehensive analyses, employing detailed dynamic models of all system components. The use of the conventional power flow model may lead to considerable error.