Wide-Area Detection of Voltage Instability From Synchronized Phasor Measurements. Part I: Principle

TLDR

Early detection of impending voltage instability is addressed using synchronized phasor measurement system states. The paper develops theoretical foundations for sensitivity calculation along the system trajectory, derives an algebraic model, and demonstrates it on a five‑bus system with load‑tap‑changer and field‑current‑limiter dynamics. The method fits algebraic equations to sampled states, computes sensitivities efficiently to detect when load powers reach a maximum, accounts for over‑excitation limiters, and requires no load model.

Abstract

This two-part paper deals with the early detection of an impending voltage instability from the system states provided by synchronized phasor measurements. Recognizing that voltage instability detection requires assessing a multidimensional system, the method fits a set of algebraic equations to the sampled states, and performs an efficient sensitivity computation in order to identify when a combination of load powers has passed through a maximum. The important effects of overexcitation limiters are accounted for. The approach does not require any load model. This first part of the paper is devoted to theoretical foundations of sensitivity calculation along the system trajectory, derivation of the algebraic model, and illustration on a simple five-bus system involving the long-term dynamics of a load tap changer and a field current limiter.