Unified Frequency-Domain Small-Signal Stability Analysis for Interconnected Converter Systems

During the past decades, the small-signal stability of the interconnected converters has been extensively researched, and several impedance/admittance-based criteria were reported and effectively verified. However, the equivalence and correlation among these criteria have not been clearly expounded. In this article, the internal relationship among the existing five stability criteria is first studied by modeling and stability analysis for different interconnected converters, and proving the equivalence of these stability criteria. Then, from the perspective of the application complexity, the convenience for system design, and the reliability against zero-pole cancellation risk, the optimal stability criteria for different types of interconnected converter systems are recommended. Finally, based on a cascaded system composed of boost and buck converters and a paralleled system consists of two single-phase LCL inverters, the correctness of the proposed viewpoints is demonstrated by case studies and experiments.