Stability analysis of small signals under different ratios of grid-following to grid-forming converters sent via flexible DC delivery-Feng Li1, Zhijie Li2,*, Shuangmian Yang1, Jinyu Wang2 and Yibo Zhang1 1TBEA Science & Technology Investment Co., Ltd., Tianjin, 301700, China 2College of Electrical Engineering, Xi'an Jiaotong University, Xian, Shanxi, 712000, China

 Stability analysis of small signals under different ratios of grid-following to grid-forming converters sent via flexible DC delivery Feng Li1, Zhijie Li2,*, Shuangmian Yang1, Jinyu Wang2 and Yibo Zhang1 1TBEA Science & Technology Investment Co., Ltd., Tianjin, 301700, China 2College of Electrical Engineering, Xi'an Jiaotong University, Xian, Shanxi, 712000, China 

 Abstract: Under the "dual carbon" strategy, frequent wide-band grid oscillations caused by grid-following converters as the interface for renewable energy integration have become common. Existing studies suggest that the addition of grid-forming converters can address this issue, but few explain the reasons from a stability mechanism perspective. Additionally, most studies overlook the interaction between converters and sending-end converter stations. This paper first conducts sequential impedance modeling. Then, based on impedance network analysis, it examines the impact of sending-end converter stations on stability assessment. Finally, by adjusting the grid-following/grid-forming ratio, Nyquist curves under different ratios are generated to analyze the mechanism by which grid-forming converters enhance gridfollowing small-signal stability. Corresponding simulation models are also developed for validation.

LINK: https://iopscience.iop.org/article/10.1088/1742-6596/2896/1/012028

A Study on Internal Fault Simulation Methods for 345kV Autotransformers 345kV 단권변압기 내부고장 모의방법에 관한 연구 Jong-Kee Choi ․ You-Jin Lee ․ Jun-Ho Cho ․ Young-Hun Kwon ․ Ji-Hwan Park ․ Young-Hun Jang 최종기† ․ 이유진* ․ 조준호** ․ 권영훈*** ․ 박지환§ ․ 장영훈

 

SCHEMATIC DIAGRAM THREE-PHASE PHASE FAILURE DETECTOR CIRCUIT AND THREE-PHASE PHASE SEQUENCE-Simulation and Analysis Using PSpice

 

Power Transfer Stability Analysis of Grid Forming Converters-Seong-Jeon Lee ․ Joosik Kwak ․ Gyu-Sub Lee-Dept. of Electrical and Computer Engineering, Seoul National University (SNU), Seoul, Republic of Korea and Seoul National University Electric Power Research Institute (SEPRI),

 Power Transfer Stability Analysis of Grid Forming Converters SCR에 따른 그리드 포밍 인버터의 전력 전달 안정성 분석 Seong-Jeon Lee ․ Joosik Kwak ․ Gyu-Sub Lee 이성전* ․ 곽주식** ․ 이규섭†

 Abstract

 With the growth of renewable energy sources (RES) and energy storage systems (ESS), the number of distributed generators (DGs) integrated into power systems via voltage source converters (VSCs) has been increasing. VSCs are operated either in grid-following (GFL) or grid-forming (GFM) control modes. While the GFM mode offers the advantage of not requiring a phase-locked loop (PLL) for grid synchronization, it exhibits a stability issue when the grid impedance decreases. To analyze the stability concerns of GFM inverters, a PSCAD simulation-based study was conducted considering the short-circuit ratio (SCR) and the grid impedance X/R ratio (the ratio of inductive to resistive impedance). The results demonstrate that GFM inverters become more unstable as the SCR increases and the X/R ratio decreases. Key Words Grid forming converter, Short circuit ratio, Stability analysis, Voltage sourced converter, X/R Ratio † Corresponding Author : Dept. of Electrical and Computer Engineering, Seoul National University (SNU), Seoul, Republic of Korea and Seoul National University Electric Power Research Institute (SEPRI), Seoul, Republic of Korea. E-mail : lgs1106@snu.ac.kr https://orcid.org/0000-0002-6313-4685 * Dept. of Electrical and Computer Engineering, Seoul National University (SNU), Seoul, Republic of Korea. https://orcid.org/0009-0003-1996-001X ** Korea Electric Power Corporation Research Institute, Republic of Korea. Received : Oct. 30, 2024 Revised : Apr. 29, 2025 Accepted : Aug. 14, 2025 Copyright ⓒ The Korean Institute of Electrical Engineers This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ISSN 1975-8359 [Print] / ISSN 2287-4364 [Online]

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 http://journal.auric.kr/AURIC_OPEN_temp/RDOC/kiee01/kieet_202509_005.pdf

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Stability Analysis of Grid-Following and GridForming Converters Based on State-Space Modelling Xian Gao, Student Member, IEEE, Dao Zhou, Senior Member, IEEE, Amjad Anvari-Moghaddam, Senior Member, IEEE, and Frede Blaabjerg, Fellow, IEEE AAU Energy, Aalborg University, Aalborg, Denmark

 Stability Analysis of Grid-Following and GridForming Converters Based on State-Space Modelling

 Xian Gao, Student Member, IEEE, Dao Zhou, Senior Member, IEEE, Amjad Anvari-Moghaddam, Senior Member, IEEE, and Frede Blaabjerg, Fellow, IEEE AAU Energy, Aalborg University, Aalborg, Denmark

 Abstract - This paper conducts a comprehensive analysis and comparison of the control loops of the grid-following and grid-forming voltage source converters connected to the power grid. Eigenvalue trajectories are studied in order to obtain an accurate stability analysis. A timedomain simulation model of a 1.5 kW grid-connected converter is developed by using Matlab/Simulink to investigate the stability of the grid-following and gridforming control under different short-circuit ratios. The stability boundaries of the grid-following control and the grid-forming control are explored and compared with theoretical analysis. The result reveals that the gridfollowing control is better suited for a stiff power grid, while the grid-forming control is more suitable for a weak power grid. Finally, an experimental prototype is established to verify the effectiveness of the theoretical analysis.

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https://vbn.aau.dk/ws/portalfiles/portal/630238234/V13_Stability_Analysis_of_Grid-Following_and_Grid-Forming_Converters_Based_on_State-Space_Modelling.pdf