Assessment, Cause Localization, and Mitigation for Small-Signal Stability Risks in Multi-Parallel Grid-Forming Converter Systems

This article addresses small-signal stability issues for multi-parallel grid-forming converter systems based on a newly developed extended passivity theory. The proposed methods provide streamlined, decentralized stability conditions that cover the full frequency range with reduced conservativeness, serving as theoretical tools and practical guidelines for assessment, cause localization, and mitigation of small-signal instability risks in such systems. Numerical examples and experimental results are provided to verify the effectiveness of the proposed methods.