μ Approach-Based Robust Stability Analysis of Weak-Grid-Connected Voltage Source Converter

Stability study for weak-grid-connected voltage source converter (VSC) has attracted extensive attention since its sensitivity to electrical network and control parameters. The existing methods mainly focus on stability analysis under nominal conditions, ignoring the multiple uncertainties, which accompany practical system inherently. In this paper, the structured singular value (SSV, also called
$\boldsymbol{\mu}$
)-based approach is proposed to study the robust stability margin of weak-grid-connected voltage source converter under multiparameter uncertainties. First, the complete small-signal model is established, and the predefined indeterminate part is pulled out from the remaining precise part of the system model using linear fractional transformation (LFT) algorithm. Then, system robust stability is evaluated through the calculated value of
$\boldsymbol{\mu}$
, under single- and multiple-parameter variations. Finally, the
$\boldsymbol{\mu}$
approach predictions results are validated by time-domain simulation.