Small-Signal Stability Analysis of Grid-Following Converter via Inner/Outer SISO Feedback Loops

Multiple-input multiple-output (MIMO) frequency-domain models are often used to analyse the small-signal stability of grid-connected converters. The limitations of standard MIMO analysis tools have spurred the development of methods that reduce systems to equivalent single-input single-output (SISO) systems. This paper presents a novel equivalent model structure for a grid-following converter containing two SISO inner feed-back loops and a single SISO outer feedback loop. The simple algebraic relationship between the original and equivalent model allows insight into effects such as that of varying power angle, as well as controller design based on classic loop shaping principles.