Power-synchronization control for ultra-weak AC networks: comprehensive stability and dynamic performance assessment

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Abstract

Power-synchronization control (PSC) is emerging as a promising control strategy to improve the stability and performance of voltage-source converters (VSCs) in ultra-weak AC grids. However, evaluation of this method to date has investigated performance only at single controller operating points rather than applying a holistic approach to simultaneously vary multiple controller gains. This paper develops a new methodology, based on small-signal model eigenvalue analysis, which achieves a comprehensive analysis of PSC-VSC stability. The maximum achievable active power transfer of PSC is established across a broad range of controller tunings. In addition, the impacts of two-way and three-way coupling between the power-synchronization control, AC voltage control and high-pass current filter gains are quantified. A new stable tuning region is introduced, which represents the controller parameter space for stable operation. It is shown that PSC can achieve rated power transfer into an AC grid (short circuit ratio (SCR)=1) at multiple controller operating points, but dynamic performance varies significantly within this region. The stability boundary and dynamic performance are validated experimentally using a control hardware-in-the-loop and real-time digital simulator (RTDS) setup. The robustness of PSC to SCR changes is also highly tuning-dependent. The practical recommendations arising from this work are a set of controller gains that provide stability and good dynamic performance at high power transfer for ultra-weak grid-connected VSCs employing PSC.
Original languageEnglish
Pages (from-to)441-450
Number of pages10
JournalIEEE Open Journal of the Industrial Electronics Society
Volume2
DOIs
Publication statusPublished - 12 Aug 2021

Keywords

  • power-synchronization control
  • VSC
  • weak grids
  • small signal analysis

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