Unveiling the dynamics of grid-connected converter systems: Insights into stability and synchronization
image: Team members of The Wind Power Research Center at Shanghai Jiao Tong University
Credit: All authors
As the global push for carbon neutrality intensifies, renewable energy systems face heightened demands for robust frequency and voltage support. A unique advantage of grid-following (GFL) and grid-forming (GFM) control systems lies in their complementary strengths: GFL excels in rapid power response, while GFM offers superior grid support. Combining them in heterogeneous setups enhances integration but poses synchronization challenges.
A team from Shanghai Jiao Tong University developed a frequency-domain modeling method to address small-signal instability in GFL-GFM systems. Published in the Journal of Shanghai Jiao Tong University, their study provides insights into synchronization mechanisms and stability improvements.
Background: Striving for Stable Renewable Energy Integration
Achieving carbon neutrality requires power systems to balance renewable energy integration with grid reliability. Heterogeneous GFL-GFM systems have emerged as a promising solution due to their complementary control mechanisms. However, these systems are prone to small-signal synchronization instability, a phenomenon stemming from negative damping characteristics introduced at the synchronization feedback loop.
"Feedback paths in these systems can sometimes pull system dynamics into instability, especially when dominant modes of instability reside in these loops,” explained Dr. Haoxiang Zong, lead author of the study. " Traditional frequency-domain criteria often fail under these conditions, necessitating more robust analytical approaches.”
Methods and Findings: A New Lens on Synchronization Stability
The team developed a method combining node admittance matrices and frequency-domain analysis to model GFL-GFM dynamics and identify instability sources.
The researchers demonstrated that both converter control parameters and grid conditions significantly impact synchronization stability. Negative damping in feedback paths causes instability when positive damping is insufficient, with dominant instability modes in feedback loops invalidating classical stability criteria.
"By tuning control parameters, we can mitigate negative damping effects and improve stability," said Dr. Zong. "This method provides practical guidelines for designing more resilient grid-connected systems."
Applications and Future Directions
The findings hold significant potential for renewable energy integration, particularly in guiding the design of control strategies that minimize instability risks. Future research aims to expand the method to larger, high-dimensional systems and explore interactions between multiple synchronization loops.
"Our work is a step toward ensuring renewable energy systems are not only efficient but also stable and reliable," noted Dr. Chen Zhang, corresponding author and an associate professor of the Wind Power Research Center at Shanghai Jiao Tong University.
About the Research Team
The Wind Power Research Center at Shanghai Jiao Tong University operates under two national research platforms: the National Energy Smart Grid (Shanghai) R&D Center and the National Energy Offshore Wind Power Technology Equipment R&D Center. Led by Professor Xu Cai, a Zhongda Scholar, the team has spearheaded numerous key national projects in the renewable energy domain, including wind turbine control, offshore wind power transmission technologies, and high-capacity energy storage integration.
"Our center focuses on solving practical challenges in renewable energy," said Professor Cai. "This study reflects our commitment to advancing knowledge and developing innovative solutions for a sustainable energy future."