Litz wire homogenization by finite elements and model-order reduction

• Daniel Klis ^[1] ; Stefan Burgard ^[1] ; Ortwin Farle ^[1] ; Romanus Dyczij-Edlinger ^[1]
  1. [1] Saarland University

     Saarland University

     Regionalverband Saarbrücken, Alemania

     
• Localización: Compel: International journal for computation and mathematics in electrical and electronic engineering, ISSN 0332-1649, Vol. 34, Nº 5 (Special Issue: IGTE 2014), 2015, págs. 1418-1432
• Idioma: inglés
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• Resumen

  • Purpose – The purpose of this paper is to determine the broadband frequency response of the impedance matrix of wireless power transfer (WPT) systems comprising litz wire coils.

    Design/methodology/approach – A finite-element (FE)-based method is proposed which treats the microstructure of litz wires by an auxiliary cell problem. In the macroscopic model, litz wires are represented by a block with a homogeneous, artificial material whose properties are derived from the cell problem. As the frequency characteristics of the material closely resemble a Debye relaxation, it is possible to convert the macroscopic model to polynomial form, which enables the application of model reduction techniques of moment-matching type.

    Findings – FE-based model-order reduction using litz wire homogenization provides an efficient approach to the broadband analysis of WPT systems. The error of the reduced-order model (ROM) is comparable to that of the underlying original model and can be controlled by varying the ROM dimension.

    Research limitations/implications – Since the present model does not account for displacement currents, the operating frequency of the system must lie well below its first self-resonance frequency.

    Practical implications – The proposed method is well-suited for the computer-aided design of WPT systems. It outperforms traditional FE analysis in computational efficiency.

    Originality/value – The presented homogenization method employs a new formulation for the cell problem which combines the benefits of several existing approaches. Its incorporation into an order-reduction method enables the fast computation of broadband frequency sweeps.