Journal: Electrical Engineering

Abbreviation

Electr Eng

Publisher

Springer

Journal Volumes

ISSN

1432-0487
0948-7921

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2016 - 201952020 - 20221
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Publications 1 - 6 of 6
  • Magnetic Equivalent Circuit of MF Transformers: Modeling and Parameter Uncertainties
    Item type: Journal Article
    Guillod, Thomas; Krismer, Florian; Kolar, Johann W. (2018)
    Electrical Engineering
    Medium-frequency (MF) transformers are extensively used in power electronic converters. Accordingly, accurate models of such devices are required, especially for the magnetic equivalent circuit. Literature documents many different methods to calculate the magnetizing and leakage inductances of transformers, where, however, few comparisons exist between the methods. Furthermore, the impact of underlying hypotheses and parameter uncertainties is usually neglected. This paper analyzes nine different models, ranging from simple analytical expressions to 3D detailed numerical simulations. The accuracy of the different methods is assessed by means of Monte Carlo simulations and linearized statistical models. The experimental results, conducted with a 100kHz/20kW MF transformer employed in a 400V DC distribution system isolation, are in agreement with the simulations (below 14% inaccuracy for all the considered methods). It is concluded that, considering typical tolerances, analytical models are accurate enough for most applications and that the tolerance analysis can be conducted with linearized models.
  • Analysis and Performance Evaluation of a Three-phase Sparse Neutral Point Clamped Converter for Industrial Variable Speed Drives
    Item type: Journal Article
    Cittanti, Davide; Guacci, Mattia; Miric, Spasoje; et al. (2022)
    Electrical Engineering
    This paper analyzes the operation and characterizes the performance of a three-phase three-level (3-L) Sparse Neutral Point Clamped converter (SNPCC) for industrial variable speed drives (VSDs). The operating principle of the SNPCC, which advantageously employs a lower number of power transistors than a conventional 3-L inverter, is described in detail, focusing on the AC-side differential-mode and common-mode voltage formation and on the DC-side mid-point current generation processes. The degrees of freedom in the SNPCC modulation scheme are defined and several switching sequences are investigated. Afterwards, the stresses on the active and passive components (e.g. semiconductor losses, machine phase current ripple, DC-link capacitor RMS current, etc.) are calculated by analytical and/or numerical means, enabling a straightforward performance comparison among the identified switching sequences. The most suited modulation strategy for VSD applications is then selected and a chip area sizing procedure, aimed at minimizing the total semiconductor chip size, is applied to a 800V 7.5kW three-phase system. The performance limits of the designed SNPCC are evaluated and finally compared to the ones of conventional 2-L and 3-L solutions, highlighting the promising cost/performance trade-off of the analyzed topology.
  • What a MES(s)! A bibliometric analysis of the evolution of research on multi-energy systems
    Item type: Journal Article
    Balakrishnan, Divya; Haney, Aoife B.; Meuer, Johannes (2016)
    Electrical Engineering
    Multi-energy systems combine different energy vectors (e.g. electricity, heat, cooling) and operate at different levels (e.g. building, district, and region). Although in theory, multi-energy systems should allow for lower carbon impacts compared to systems in which single energy vectors are considered individually, implementation of multi-energy systems is often difficult due to the number of technologies and actors involved and the complexity of their interactions. In this article, we conduct a bibliometric analysis based on over 20,000 articles from the Web of Science to investigate how knowledge on two important multi-energy systems, Microgrids and Smart Grids, has developed. Our findings identify areas that have been under-researched to date, offer a means of transferring learning between different multi-energy systems and provide practical guidance for the implementation of multi-energy systems.
  • Systematic higher order nonlinear analysis of power systems operating under perturbation conditions
    Item type: Journal Article
    Rodriguez-Villalón, Osvaldo; Medina, Aurelio (2017)
    Electrical Engineering
    In this paper, the modal series method is revisited and an extension on the method to include higher order terms is proposed. This proposal is based on the introduction of the multidimensional Laplace transform and association of variables theorems to deduce the analytical closed-form solution when it is applied to the analysis of a nonlinear power system model. The method is systematic and can incorporate higher order terms to the modal analysis to determine nonlinear modal interaction. When the power system is operating under stressed conditions, such as an increase in load demand, it results very important to consider the oscillations due to its nonlinear nature. Thus, the method is carefully exemplified with the application to the synchronous machine-infinite busbar power system operating under stress conditions. The oscillations produced during changes in its operation are analyzed as well as the nonlinear interaction through nonlinear indices and nonlinear participation factors. The time domain responses are compared between linear approximation, modal series, normal forms method and the direct numerical full solution of the nonlinear power system model.
  • Unified Power Flow Analysis of String Current Diverters
    Item type: Journal Article
    Kasper, Matthias; Bortis, Dominik; Kolar, Johann W. (2018)
    Electrical Engineering
  • Electromagnetic Field Patterns and Energy Flux of Efficiency Optimal Inductive Power Transfer Systems
    Item type: Journal Article
    Bosshard, Roman; Guillod, Thomas; Kolar, Johann W. (2017)
    Electrical Engineering
    The design of contactless power supplies with inductive power transfer (IPT) is still a challenge even though such systems have become more and more established for various applications. This article presents an intuitive, educational introduction to IPT system design for practicing engineers who are new to the field. While following the path of the energy through the IPT system, the contactless power transfer is explained with a circuit-oriented approach, extended by an analysis of the field patterns and the energy flux across the air gap. Finite element method simulation results for the Poynting vector are shown to illustrate the power transfer process. Finally, a minimization of the reactive power demand of the IPT coils is performed, from which the general requirements for an efficiency optimal design of the IPT system can be intuitively understood.
Publications 1 - 6 of 6