Absence of pure voltage instabilities in the third order model of power grid dynamics

TL;DR

This paper demonstrates that pure voltage instabilities are not physically consistent in the third order power grid model, but voltage collapse phenomena can still occur without such instabilities, refining understanding of grid stability.

Contribution

It clarifies that pure voltage instabilities are nonphysical in the third order model and shows voltage collapse can happen independently of these instabilities.

Findings

Pure voltage instability is inconsistent with Kirchhoff's law.

Voltage collapse can occur without pure voltage instability.

Refines the understanding of stability routes in power grid models.

Abstract

Secure operation of electric power grids fundamentally relies on their dynamical stability properties. For the third order model, a paradigmatic model that captures voltage dynamics, three routes to instability are established in the literature, a pure rotor angle instability, a pure voltage instability and one instability induced by the interplay of both. Here we demonstrate that one of these routes, the pure voltage instability, is inconsistent with Kirchhoff's nodal law and thus nonphysical. We show that voltage collapse dynamics nervertheless exist in the absence of any voltage instability.