Empirical Evaluation of GPS Clock Accuracy for Isochronous Droop-Based Inverters: Preprint

Tobin Meyers, Barry Mather

Research output: Contribution to conferencePaper


Grid-forming inverters rely upon an internal reference to regulate the grid’s voltage and frequency. Without a reliable reference, issues such as loss of synchronism, frequency instability, and unequal power sharing can occur. One proposed internal phase reference for grid-forming inverters is generated by the controller’s clock, but this is affected by nonidealities in the crystal oscillator leading to time drift in the phase reference. To improve the controller’s clock accuracy, the Global Positioning System (GPS) can be used to calibrate the internal clock. Previously, GPS-based clock calibration was explored theoretically and various methods were developed for mitigating frequency/phase drift at the power system level. This paper experimentally validates the direct performance of GPS time-calibration at the controller level and justifies its use in maintaining an accurate phase reference for droop-based grid-forming inverters.
Original languageAmerican English
Number of pages9
StatePublished - 2021
EventIEEE Energy Conversion Congress and Exposition (ECCE 2021) -
Duration: 10 Oct 202114 Oct 2021


ConferenceIEEE Energy Conversion Congress and Exposition (ECCE 2021)

Bibliographical note

See NREL/CP-5D00-82055 for paper as published in proceedings

NREL Publication Number

  • NREL/CP-5D00-77573


  • clock drift
  • decentralized
  • droop
  • GPS
  • grid forming inverter
  • stability
  • synchronization


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