A Current-Scaling Strategy for Droop-Controlled Grid-Forming Inverters in Off-Grid Systems

Samuel C. Schüler; Mateus Radke; Paulo J. D. de O. Evald; Telles B. Lazzarin

doi:10.18618/REP.e202631

Authors

Samuel C. Schüler Federal University of Pelotas
Mateus Radke Federal University of Pelotas
Paulo J. D. de O. Evald Federal University of Pelotas
Telles B. Lazzarin Federal University of Santa Catarina

DOI:

https://doi.org/10.18618/REP.e202631

Keywords:

Current limiters, Fault-ride through capability, Meta-heuristic optimization, Renewable energy

Abstract

The progressive replacement of synchronous generation by inverter-based renewable energy resources is altering the dynamical structure of modern power systems, reducing system strength due to the inertia curtailment. In this context, grid-forming inverters have emerged as a fundamental technology capable of establishing voltage and frequency in inverter-dominated grids. However, their effective deployment is intrinsically dependent on the control framework that must guarantee stability, robustness, and interoperability under complex and uncertain operating conditions. The most adopted grid-forming control strategy is droop control. This work presents a proportional scaling strategy in the inner current loop for droop-controlled grid-forming inverters, which preserves the current angle, reducing only its magnitude if a large disturbance occurs. Moreover, an innovative grid-forming controller parametrization procedure based on hybrid jellyfish search and particle swarm optimizer is also provided. This methodology avoids empirical tuning and allows incorporating system constraints in the controller tuning procedure. Hardware-in-the-loop results demonstrate high performance of the optimized droop under nominal operation, load variation, black-start, and faults.

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Author Biographies

Samuel C. Schüler, Federal University of Pelotas

He is currently pursuing a bachelor's degree in Electronic Engineering at the Federal University of Pelotas (UFPel). He is an undergraduate researcher with the Group of Intelligent Systems and Control (GSIC) at UFPel. His work focuses on the development of control solutions for renewable energy systems. His research interests include control theory, renewable energy systems, and intelligent control.

Mateus Radke, Federal University of Pelotas

He is currently pursuing a bachelor's degree in Electronic Engineering at the UFPel. He received a Technologist degree in Internet Systems in 2024 from Anhanguera Educacional. He is an undergraduate researcher with the GSIC. His research interests include power electronics, renewable energy systems, embedded systems, and software development.

Paulo J. D. de O. Evald, Federal University of Pelotas

holds a bachelor's degree in Automation Engineer (2016) and a Master's degree in Computer Engineering (2018), both from the Federal University of Rio Grande (FURG), and a PhD in Electrical Engineering (2021) from the Federal University of Santa Maria (UFSM). He was a post-doctoral researcher at Intelligent Automation and Robotics Research Group (NAUTEC/FURG) from 2022 to 2023. Currently, he is a post-doctoral researcher at the Institute of Power Electronics (INEP) at Federal University of Santa Catarina (UFSC). Since 2022, he has been a Professor at the Federal University of Pelotas (UFPel) in the Engineering Center. He is the leader of the GSIC, and a member of the Group of Power Electronics and Control (GEPOC) from UFSM, INEP/UFSC, the Brazilian Society of Power Electronics (SOBRAEP), and National Institute of Science and Technology in Power Electronics: Developing Technologies for a Sustainable Energy Transition (INCT EPTech). His main research areas are renewable energy, power electronics control applications, biomedical system control, and meta-heuristic optimization of controllers.

Telles B. Lazzarin, Federal University of Santa Catarina

holds a bachelor's degree (2004), a master's degree (2006), a doctorate (2010), and a postdoctorate (2011) in Electrical Engineering from UFSC. He was a visiting researcher at Northeastern University in Boston from 2017 to 2018. Since 2013, he has been a Professor at UFSC in the Department of Electrical and Electronic Engineering. Currently, he is Visiting Professor at Laboratoire de Génie électrique et électronique de Paris (GeePs) at France, coordinator of INCT EPTech, president of SOBRAEP, and Associate Editor of the IEEE Open Journal of Power Electronics (OJ-PEL) and the Open Journal of Power Electronics. His main research interests include switched-capacitor converters, switched-capacitor hybrid converters, single-phase rectifiers, voltage inverters, converters for small wind generators, and high-gain DC-DC converters.

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