Impedance-Based Whole-System Modeling for a Composite Grid via Embedding of Frame Dynamics

Y. Gu, Y. Li, Y. Zhu, T. C. Green

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32 Citations (SciVal)
83 Downloads (Pure)


The paper establishes a methodology to overcome the difficulty of dynamic frame alignment and system separation in impedance modeling of ac grids, and thereby enables impedance-based whole-system modeling of generator-converter composite power systems. The methodology is based on a frame-dynamics-embedding transformation via an intermediary steady frame between local and global frames, which yields a locally defined impedance model for each generator or converter that does not rely on a global frame but retains all frame dynamics. The individual impedance model can then be readily combined into a whole-system model even for meshed networks via the proposed closed-loop formulation without network separation. Compared to start-of-the-art impedance-based models, the proposed method retains both frame dynamics and scalability, and is generally applicable to various network topologies (meshed, radial, etc) and combinations of machines (generators, motors, converters, etc). The methodology is used to analyze the dynamic interaction between generators and converters in a composite grid, which yields important findings and potential solutions for unstable oscillation caused by PLL-swing coupling in low-inertia grids.
Original languageEnglish
Article number9123531
Pages (from-to)336-345
Number of pages10
JournalIEEE Transactions on Power Systems
Issue number1
Early online date23 Jun 2020
Publication statusPublished - 31 Jan 2021

Bibliographical note

Funding Information:
This work was supported by the Engineering and Physical Sciences Research Council of UK (EPSRC) under Awards EP/S000909/1. Paper no. TPWRS-00016-2020.

Publisher Copyright:
© 1969-2012 IEEE.


  • Impedance/admittance
  • dynamic modeling
  • power electronics
  • power grid
  • whole system

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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