Stability Analysis of Two-Terminal VSC-HVDC Systems using the Net-Damping Criterion

Artikel i vetenskaplig tidskrift, 2016

This paper performs a frequency-domain investigation in two-terminal voltage-source-converter–HVDC (VSC–HVDC) systems, focusing on the use of the net-damping criterion to investigate poorly damped conditions and closed-loop stability. The system is represented as a feedback interconnection of two subsystems, defined in this paper as: 1) a dc-grid input impedance and 2) a VSC input admittance. The damping characteristics of the two subsystems are defined at critical frequencies and their separate contribution to the closed-loop stability is assessed by the net-damping criterion. A variety of study cases demonstrates the effectiveness of the latter as a powerful tool for stability investigation, while a correlation has been derived between the net-damping value and the damping factor of the poorly damped poles of the system.