Seamless Transition of Critical Infrastructures Using Droop Controlled Grid-Forming Inverters

Soham Chakraborty, Sourav Patel, Govind Saraswat, Atif Maqsood, Murti Salapaka

Research output: Contribution to journalArticlepeer-review

3 Scopus Citations


Seamless recovery of power to critical infrastructures, after grid failure, is a crucial need arising in scenarios that are increasingly becoming more frequent. This article proposes a seamless transition strategy using a single and unified mode-dependent droop controlled grid-forming inverters. The control strategy achieves the following objectives: 1) regulates the output active and reactive power by the droop-controlled inverters to a desired value while operating in on-grid mode; 2) seamless transition and recovery of power injections into the load after grid failure by inverters that operates in grid-forming mode all the time; 3) requires only a single bit of information on the grid/network status for the mode transition. A framework for assessing the stability of the system and to guide the choice of parameters for controllers is developed using control-oriented modeling. A controller hardware-in-the-loop-based real-time simulation study on a test system based on the realistic electrical network of a commercial-scale medical center is conducted for initial prototyping of the control strategy. A hardware experiment is conducted with two 3-..phi.., 480 -V, 125-kVA grid-forming inverters, a 3-..phi.., 480-V, 270-kVA grid simulator, a physical grid switch, and a physical load bank. The experimental data establishes the effectiveness of the always grid-forming operation and control of inverters in meeting power delivery objectives when on-grid and off-grid under various kinds of loads and scenarios while minimizing transients during transitions. Furthermore, performance comparison with existing strategies showcases the advantage of the proposed strategy.
Original languageAmerican English
Pages (from-to)1535-1546
Number of pages12
JournalIEEE Transactions on Industrial Electronics
Issue number2
StatePublished - 2024

NREL Publication Number

  • NREL/JA-5D00-83151


  • droop control
  • emergency power supply system
  • parallel inverter systems
  • small-signal stability


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