Comparison of Methods for Calculation of Margins to Voltage Instability

Abstract

The paper describes and compares three methods for calculation of margins to voltage instability: a second order optimization formulation successive linearizations and sensitivity calculations fast decoupled load flow (FDLF) combined with curve fit They are all based on the static load flow equations, and voltage instability margins are given in terms of MW, MVAr or MVA load increase. The comparison focuses on: initiation requirements, flexibility to increase the load, load modelling, reactive power generation limits, speed, accuracy and convergence robustness. Also included are example calculations on a Norwegian 51 1 -bus system.