Rethinking Current Controller Design for PLL-Synchronized VSCs in Weak Grids

Hong Gong, Xiongfei Wang, Lennart Harnefors

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14 Citations (Scopus)
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This article revisits the design of the current controller for grid-connected voltage-source converters (VSCs), considering the dynamic impacts of the phase-locked loop (PLL), weak grids, and of voltage feedforward (VFF) control. First, a single-input single-output transfer-function-based model is proposed to characterize the interactions of control loops. It is analytically found that the proportional gain of the current controller essentially aggravates the instability effect of PLL in weak grids, while the cutoff frequency of the low-pass filter used with the VFF loop has a nonmonotonic relationship with the PLL-induced instability. Then, based on these findings, a guideline for redesigning the current controller of PLL-synchronized VSCs is developed, which enables a codesign of the current controller and VFF controller. Finally, simulation and experimental results confirm the validity of theoretical analyses.
Original languageEnglish
JournalIEEE Transactions on Power Electronics
Issue number2
Pages (from-to)1369-1381
Number of pages13
Publication statusPublished - 1 Feb 2022

Bibliographical note

Publisher Copyright:


  • Converters
  • current controller
  • Impedance
  • Phase locked loops
  • phase-locked loop
  • Power conversion
  • Power system stability
  • Synchronization
  • Voltage control
  • voltage feedforward control
  • voltage-source converters
  • Weak grids


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