Adaptive controller based on grid impedance estimation for stable operation of grid-connected inverters under weak grid conditions

Temiz H., KEYSAN O., Demirok E.

IET POWER ELECTRONICS, vol.13, no.13, pp.2692-2705, 2020 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 13 Issue: 13
  • Publication Date: 2020
  • Doi Number: 10.1049/iet-pel.2019.1411
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Aerospace Database, Communication Abstracts, Compendex, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.2692-2705
  • Middle East Technical University Affiliated: Yes


An electric grid having high impedance seen from the connection point is considered as a weak grid and it adversely affects the system stability of grid-tied voltage source inverters in renewable power devices. In this study, an adaptive controller is proposed by configuring the settling time of the phase-locked loop based on the estimated grid impedance. Pseudorandom binary sequence injection and Fourier techniques are carried out for grid impedance estimation. Impedance-based stability analysis is performed for a predetermined steady-state operation point. The proposed method is verified by a 300-kVA inverter prototype for wide-range grid impedance varying from 0.3 to 3 mH.