PROJECT TITLE :

Modeling and Analysis of VSC-Based HVDC Systems for DC Network Stability Studies

ABSTRACT:

A modeling approach is presented in this paper in order to analyze instabilities originating from dc-network resonances in voltage-supply converter HVDC (VSC-HVDC) systems. Through frequency-domain modeling, it is shown that the VSC-HVDC system can be represented as a feedback interconnection of 2 subsystems. These subsystems are defined during this paper as a dc network impedance connected to a VSC dc-aspect power-dependent admittance. The conditions in which this admittance encompasses a negative conductance are investigated since they will amplify dc network resonances. It's found that when the VSC that controls the direct voltage injects power into the dc network, the mentioned conductance becomes negative on top of bound frequencies. Additionally, the impact of weak ac grids, management system delays, and alternative direct voltage controllers on the studied conductance is investigated. The theoretical findings are verified through time-domain simulations.