Grid-Current-Feedback Active Damping for LCL Resonance in Grid-Connected Voltage-Source Converters

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This paper investigates active damping of LCL-filter resonance in a grid-connected voltage-source converter with only grid-current feedback control. Basic analysis in the s-domain shows that the proposed damping technique with a negative high-pass filter along its damping path is equivalent to adding a virtual impedance across the grid-side inductance. This added impedance is more precisely represented by a series RL branch in parallel with a negative inductance. The negative inductance helps to mitigate
phase lag caused by time delays found in a digitally controlled system. The mitigation of phase-lag, in turn, helps to shrink the region of nonminimum-phase behavior caused by negative virtual resistance inserted unintentionally by most digitally implemented active damping techniques. The presented high-pass-filtered active damping technique with a single grid-current feedback loop is thus a more effective technique, whose systematic design in the z-domain has been developed in this paper. For verification, experimental
testing has been performed with results obtained matching the theoretical expectations closely.
Original languageEnglish
JournalI E E E Transactions on Power Electronics
Issue number1
Pages (from-to)213-223
Number of pages11
Publication statusPublished - Jan 2016


  • LCL filter
  • Nonminimum phase system
  • Resonance damping
  • Virtual impedance
  • Voltage-source converter


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