Current Limiting Control With Enhanced Dynamics of Grid-Forming Converters During Fault Conditions

• Published in: IEEE journal of emerging and selected topics in power electronics Vol. 8; no. 2; pp. 1062 - 1073
• Main Authors: Taul, Mads Graungaard, Wang, Xiongfei, Davari, Pooya, Blaabjerg, Frede
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.06.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Circuits; Computer simulation; Constraining; Converters; Current limitation; Electric potential; fault ride-through; Frequency control; grid connection; grid forming control; Impedance; Limiting; Power system stability; Short circuits; Synchronization; Synchronous machines; Voltage; Voltage control; voltage-source converter
• ISSN: 2168-6777; 2168-6785
• DOI: 10.1109/JESTPE.2019.2931477

With an increasing capacity in the converter-based generation to the modern power system, a growing demand for such systems to be more grid-friendly has emerged. Consequently, grid-forming converters have been proposed as a promising solution as they are compatible with the conventional synchronous-machine-based power system. However, most research focuses on the grid-forming control during normal operating conditions without considering the fundamental distinction between a grid-forming converter and a synchronous machine when considering its short-circuit capability. The current limitation of grid-forming converters during fault conditions is not well described in the available literature and present solutions often aim to switch the control structure to a grid-following structure during the fault. Yet, for a future converter-based power system with no or little integration of synchronous machines, the converters need to preserve their voltage-mode characteristics and be robust toward weak-grid conditions. To address this issue, this article discusses the fundamental issue of grid-forming converter control during grid fault conditions and proposes a fault-mode controller which keeps the voltage-mode characteristics of the grid-forming structure while simultaneously limiting the converter currents to an admissible value. The proposed method is evaluated in a detailed simulation model and verified through an experimental test setup.