Improved grid impedance compensation for phase-locked loop to stabilize the very-weak-grid connection of VSI's
- Li, Chuanyue
- Liu, Wei
- Liang, Jun
- Ding, Xiaolin
- Cipcigan, Liana M.
DOIAbstract
Voltage source inverters (VSIs) with vector control based on phase-locked loop (PLL) suffer instability when connecting to a very weak AC grid (short circuit ratio (SCR)<1.3). The conventional grid impedance compensation for the PLL by virtually reducing the grid impedance can stabilize this connection. However, the analysis in this paper indicates that its stabilization effectiveness is sensitive to grid impedance variance and, indeed, overcompensation causes the PLL instability. Therefore, in this paper, an improved grid impedance compensation for the PLL is proposed to achieve the same stabilization for very-weak-grid connection and possess a good tolerance of grid impedance variance and overcompensation. A comprehensive Small-signal mod...
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