Identification of Three-Phase Grid Impedance in the Presence of Parallel Converters

Roni Luhtala, Tuomas Messo, Tomi Roinila, Henrik Alenius, Erik de Jong, Andrew Burstein, Alejandra Fabian

Research output: Contribution to journalArticleAcademicpeer-review

17 Citations (Scopus)


Grid impedance is an important parameter which affects the control performance of grid-connected power converters. Several methods already exist for optimizing the converter control system based on knowledge of grid impedance value. Grid impedance may change rapidly due to fault or disconnection of a transmission line. Therefore, online grid identification methods have been recently proposed to have up-to-date information about the grid impedance value. This is usually done by perturbing the converter output current and measuring the response in output voltage. However, any parallel converters connected to the same interface point will cause errors, since the measured current differs from the current that is flowing through the grid interface point. This paper points out challenges and errors in grid impedance identification, caused by parallel converters and their internal control functions, such as grid-voltage support. Experimental grid-impedance measurements are shown from the power hardware-in-the-loop setup developed at DNV-GL Flexible Power Grid Lab.
Original languageEnglish
Article number2674
Issue number14
Publication statusPublished - 2019


  • DC–AC power converters
  • Grid impedance identification
  • Power hardware-in-the-loop


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