Loop-at-a-Time Stability Analysis for Grid-Connected Voltage-Source Converters

The instability phenomena caused by converter–grid interactions can be prevented designing controllers with adequate stability margins. Yet, the multiple-input–multiple-output (MIMO) dynamics of grid-connected voltage-source converters (VSCs) complicate analysis for controller design. To tackle this challenge, article presents a loop-at-a-time VSCs, which not only shows close correlations generalized Nyquist criterion MIMO systems but also enables to quantify margins individual closed loops. Moreover, between loops analyzed. Test cases numerical sensitivity analysis, simulations, and field measurements converter validate theory.