Impedance-Based Prediction of SSR-Generated Harmonics in Doubly-Fed Induction Generators: Preprint

Research output: Contribution to conferencePaper


Doubly-fed induction generators (DFIGs) are prone to subsynchronous resonance (SSR) with series-compensated transmission lines and experiencing SSR-generated harmonics of wide-ranging magnitudes. This paper presents a large-signal impedance-based approach for the prediction of the magnitude of SSR-generated harmonics in DFIGs. Note that the large-signal impedance of a network shows the variation in its impedance response with the magnitude of perturbation at its terminals. It is discovered in this paper that the impedance of a series-compensated transmission line starts changing with the magnitude of SSR because of the metal oxide varistor (MOV) based protection of series capacitors in the line. The changing line impedance locks the growth of SSR beyond a certain point, where the DFIG forms a limit cycle mode and emits harmonics at the SSR frequency. The discovered role of the protection of series-capacitors in SSR not only enables the prediction of the SSR-generated harmonics but it can also be used for the timely detection of an SSR event to avoid system disruption and sudden loss of a bulk generation. The large-signal impedance-based prediction of SSR-generated harmonics in DFIG-based wind and hydro generators is demonstrated using numerical simulations of a 2.5-MW, 690-V DFIG supplying to a series-compensated transmission line.
Original languageAmerican English
Number of pages8
StatePublished - 2019
Event2019 IEEE Power and Energy Society General Meeting (IEEE PES GM) - Atlanta, Georgia
Duration: 4 Aug 20198 Aug 2019


Conference2019 IEEE Power and Energy Society General Meeting (IEEE PES GM)
CityAtlanta, Georgia

Bibliographical note

See NREL/CP-5D00-76219 for paper as published in IEEE proceedings

NREL Publication Number

  • NREL/CP-5D00-72559


  • DFIG
  • doubly-fed induction generator
  • impedance analysis
  • MOV
  • series-compensated lines
  • small hydro-generators
  • SSR
  • Type III wind turbines


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