All-Port Unterminated Small-Signal Stability Analysis of Multi-Port Grid-Connecting Converters

This article investigates the use of an all-port unterminated (black-box) representation for small-signal stability analysis and robust, termination-independent controller design of grid-connecting (interlinking) converters with an arbitrary number of dc and ac ports. In this regard, an impedancebased stability assessment method and an associated admittance passivity criterion are established for general multi-port dcdc, ac-dc, and ac-ac converters. The proposed methodology is exemplified and validated using analytical models, control-hardware-in-the-loop simulation results and experimental results, demonstrating its effectiveness in analyzing and suppressing destabilizing interactions between the converter and the grid.