Definition of a voltage-source converter dc-side admittance and its impact on dc-network stability

The aim of this paper is to provide a definition of a parameter that can be used for the study of the dc-network dynamics in VSC-HVDC systems. Through an appropriate selection of subsystem within a point-to-point VSC-HVDC system, a dc-side power dependent admittance is defined. The particularity of this admittance is that, if negative, there is a risk that a dc-side resonance becomes amplified. The dc-side power dependent admittance is measured in a EMT model and compared with a linearized mathematical model, showing good agreement between them. The usefulness of the defined admittance is shown through the assessment of various controller modifications on the dc-network stability enhancement. Finally, the conclusions from the analysis are verified through time domain simulations.