Frequency-Domain Modal Analysis for Power-Electronic-Based Power Systems

This letter presents two frequency-domain modal analysis methods, 'peak-picking' and 'circle fit' methods, used for current control interactions of grid-connected voltage-source converters (VSCs). Differing from the conventional resonance mode analysis, the modal impedances are analyzed with their Nyquist plots, instead of the magnitude-frequency response, which leads to an accurate prediction on the damping behavior of system. Experimental tests verify the theoretical modal analysis methods.