"Power systems are regarded as the most complex man-made systems. This complexity can be attributed to the substantial number of buses within the system and the numerous rapidly changing, highly nonlinear dynamics of the CIGs. However, this is not an advantage; rather, it is the fundamental cause of system instability. Given the artificial nature of the system, it would seem advisable to conduct a simpler system. How can we reduce complexity and enhance system safety and reliability? A fundamental approach involves decoupling and reducing system order. For instance, DC asynchronous interconnection employs the flexible controllability of power electronics to isolate grid dynamics." says Prof. Yong Min, a researcher at the State Key Laboratory of Power System Operation and Control at Tsinghua University.
They published their study on 27 October, 2025, in iEnergy.
A novel concept to design the GFM
In the study, the research group proposed a novel concept for the design of grid-forming (GFM) control. A GFM converter should, within its capability limits, strive to control itself as a constant voltage source without introducing control dynamics. Regulation should only be performed to ensure device safety when the capability limits are exceeded. This control approach can significantly reduce the dynamics within the system and the dynamic interactions among devices, thereby enhancing the system's safety. "The dynamics of SGs leads to both rotor angle stability issues and frequency stability issues. However, they are dominated by physical processes and can hardly be reduced. The dynamics of CIGs are dominated by control processes and can be reduced with proper control strategies. The prevailing approaches for emulating SGs inherit these stability issues and introduce additional new converter-driven stability issues. Thus, we believe these strategies are not suited for future CIG-dominated systems." says Zhenyu Lei, a Ph.D candidate specializing in power system dynamics.
Transforming the power system from a complex dynamic system into a static system.
Following the idea to controlling CIGs as constant voltage sources, a corresponding GFM control strategy, named FF-GFM control, is proposed. With the proposed strategy, the system's frequency and synchronization dynamics are significantly reduced, to the point where it becomes a static system. The system frequency is almost always fixed at its rated value. Only static safety issues determined by the power-flow equations exist; no stability issues related to dynamic processes are present. Moreover, it should be noted that the CIGs equipped with the proposed control strategy are compatible with existing power sources, such as SGs and grid-following CIGs, which is crucial for the gradual implementation of the proposed framework within existing power systems. "It is our contention that our work offers a superior solution for 100% renewable power systems." says Prof. Lei Chen.
The above research is published in iEnergy, which is a fully open access journal published by Tsinghua University Press. iEnergy publishes peer-reviewed high-quality research representing important advances of significance to emerging power systems. At its discretion, Tsinghua University Press will pay the open access fee for all published papers from 2022 to 2026.
About iEnergy
iEnergy is a quarterly journal launched on March 2022. It has published 4 volumes (13 issues). Authors come from 21 countries, including China, the United States, Australia, etc., and world's top universities and research institutes, including University of Nebraska Lincoln, Columbia University, Imperial College of Science and Technology, Tsinghua University, etc. 12 published articles are written by academicians from various countries. The published papers have also attracted an overwhelming response and have been cited by 179 journals, including top journals in the field of power and energy like Nature Materials, Advanced Materials, Joule, Energy Environmental Science, etc., from 45 countries.
iEnergy publishes original research on exploring all aspects of power and energy, including any kind of technologies and applications from power generation, transmission, distribution, to conversion, utilization, and storage. iEnergy provides a platform for delivering cutting-edge advancements of sciences and technologies for the future-generation power and energy systems. It has been indexed by ESCI (Impact factor 5.1), Ei Compendex, Scopus (CiteScoreTracker 2024 7.4), Inspec, CAS, and DOAJ.
