Admittance study of grid-connected VSCs for harmonic oscillatory instabilities

Abstract

Voltage source converters (VSCs) can reduce damping of grid-connected VSC systems at harmonic resonances, leading to system instability. The conductance of the VSC admittance can be shaped selecting appropriate VSC parameter values to increase VSC damping at poorly damped harmonic resonances and ensure system stability. This study extends existing findings and makes contributions in this direction. Analytical expressions of the positive- and negative-sequence VSC conductances are presented to study exhaustively the impact of VSC parameters on harmonic oscillatory instabilities. Two applications, i.e. a traction system and an offshore wind power plant, are used to show the contribution of this study. The analytical study is validated from PSCAD/EMTDC time-domain simulations.