Generalized Formulation of Steady-State Equivalent Circuit Models of Grid-Forming Inverters

Author(s)

Cunha, Vinicius C. ^{[1, 2]} ; Kim, Taehyung ^[1] ; Barry, Nicholas ^[1] ; Siratarnsophon, Piyapath ^[1] ; Santoso, Surya ^[1] ; Freitas, Walmir ^[2] ; Ramasubramanian, Deepak ^[3] ; Dugan, Roger C. ^[3]

Affiliation

^[1] Univ Texas Austin, Dept Elect & Comp Engn, Austin, TX 78712 - USA

^[2] Univ Estadual Campinas, Dept Syst & Energy, BR-13083970 Campinas - Brazil

^[3] Elect Power Res Inst, Knoxville, TN 37932 - USA

• Document type: Journal article
• Source: IEEE OPEN ACCESS JOURNAL OF POWER AND ENERGY; v. 8, p. 352-364, 2021.
• Web of Science Citations: 0

Abstract

This work proposes positive- and negative-sequence equivalent circuits of grid-forming inverters for steady-state analysis. The proposed models are especially attractive for performing long-duration voltage regulation analysis and short-circuit studies involving grid-forming inverters. Our proposed equivalent circuit models are based on the inverter's voltage and current control loops in the alpha beta and dq frames. For this reason, they operate according to prescribed control functions and specified impedances (i.e., filter impedance, current limiter block, virtual admittance block, and PI/PR controller block). The equivalent circuit model accuracy is validated by comparing system steady-state voltage and current responses obtained by detailed time-domain models in PSCAD/EMTDC to those by the equivalent circuit models implemented in steady-state load flow program (e.g., OpenDSS). Two distinct control structures implemented in the alpha beta and dq frames are used for the validation. Single line-to-ground and line-to-line-to-ground faults are simulated in a small islanded microgrid as well as the IEEE 34-node test feeder. Fault impedances varying from 0 to 5 ohms are simulated. We show that the equivalent models precisely replicate the steady-state response of the detailed time-domain models. (AU)

• FAPESP's process: 16/08645-9 - Interdisciplinary research activities in electric smart grids
• Grantee: João Bosco Ribeiro do Val
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/20186-8 - Estimation of topology, line parameters and switches status in medium voltage distribution systems using smart meter measurements
• Grantee: Vinicius Carnelossi da Cunha
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 17/10476-3 - Integration of new methods into distribution management systems in the presence of distributed energy resources and smart meters
• Grantee: Vinicius Carnelossi da Cunha
• Support Opportunities: Scholarships in Brazil - Doctorate