A unified approach to modeling and stability equivalence analysis for grid-forming and grid-following converters

• Published in: Electric power systems research Vol. 235; p. 110861
• Main Authors: Yu, Changzhou, Xu, Haizhen, Chen, Chen, Sun, Meimei, Fu, Xinxin, Zhang, Xing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2024
• Subjects: Grid-connected converters; Renewable energy generation; Stability analysis; Grid-connected converters; Renewable energy generation; Stability analysis
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/j.epsr.2024.110861

•A unified small-signal model and impedance stability analysis for grid-forming (GFM) and grid-following (GFL) converters under identical topology and parameters.•Analysis of the stability and delineation of stability domains for GFM and GFL converters across varying short circuit ratios (SCRs).•Experimental validation of the stability of GFM and GFL converters under different SCRs. With the increasing penetration of renewable energy generation, the large-scale integration of grid-connected converters, serving as interfaces, has led to the characteristics of a weak grid with low strength and low inertia, resulting in insufficient stability of existing grid-following (GFL) converters. Grid-forming (GFM) converters, by emulating the characteristics of traditional synchronous machines, can operate stably in weak grids, but their introduction creates a complex operational state with mixed modes, presenting unprecedented challenges to the system. To address this, this paper first analyzes the structure and GFM/GFL control strategies of grid-connected converters; based on this, a comprehensive model framework for GFM/GFL converters is established, and the control of the converters is divided into three parts: LCL with the grid, output control, and power control, each modeled with a small-signal approach; using the established small-signal models, the stability of GFM/GFL converters under different grid short circuit ratios (SCR) is analyzed. Finally, a 20 kW test platform was constructed, and the correctness of the modeling and analysis was jointly verified using simulation frequency sweep methods and experimental time-domain stability analysis techniques.