Fuzzy sets-a natural way to describe power system voltage profile

Presents a way of power system voltage profile modeling, based on fuzzy sets. It is used for decentralized secondary voltage control purposes, where advantages of fuzzy models are demonstrated. Electric power system voltage profile is by its nature a fuzzy value, since it contains different voltage values at different network points. All existing secondary voltage control schemes were based on voltages of some or all power system buses, not considering voltages on connecting lines. If this was done, it would change the nature of electric power system voltage profile from a set of crisp values to an interval. When considering also voltage influences of particular voltage controlled buses on the other parts of the power system, which is an essential property in voltage control, a fuzzy set is formed from the voltage interval. Therefore, a fuzzy set model can be recognized as a natural model of the power system voltage profile.