1Impedance Based Resonance Analysis in a VSC-HVDC System

Abstract—Resonances can limit power transfer in a Voltage Source Converter-High Voltage DC (VSC-HVDC) system. The objective of this paper is to develop impedance models for the rectifier AC system and the inverter AC system for a VSC-HVDC system. Resonance stability will be examined using Nyquist stability criterion and impedance frequency responses. The impedance models considers the outer control loop and the inner current control loops of VSCs. Impacting factors are then examined. Stability analysis demonstrates that the feed-forward filter, line length and power transfer level have significant impact on resonances. Time-domain simulation results obtained Matlab SimPowerSystems are used to validate the analysis. Index Terms—Admittance, impedance, resonance stability, VSC-HVDC. I