Medium-Frequency Transformer Scaling Laws:  Derivation, Verif ication, and Critical Analysis

Guillod, Thomas; Kolar, Johann W.

doi:10.24295/cpsstpea.2020.00003

Cited by 28 publications

(12 citation statements)

References 27 publications

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“…Therefore, the concept of connecting magnetically the cells to compose the entire MTB DC-DC converter with MWT leads to benefits that can be demonstrated, using the 2WT in a conventional modular approach (i.e 2WT-based topologies), as reference. Thus, as a FOM, the area product A p of a MWT [44], [45] [cf. (1)] can be used for deriving a scaling law, relating the volume of the MWT with the number of cells N cells,pri for any architecture (symmetrical or asymmetrical) [cf.…”

Section: B Power Densitymentioning

confidence: 99%

A Comprehensive Assessment of Multiwinding Transformer-Based DC–DC Converters

Pereira

Hoffmann

Zhu

et al. 2021

IEEE Trans. Power Electron.

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Multiwinding-Transfomer-based (MTB) DC-DC converter did emerge in the last 25 years as an interesting possibility to connect several energy systems and/or to offer higher power density because of the reduction of transformer core material and reduction of power converter stages. MTB DC-DC converters can be considered as an interesting compromise between non-modular and a modular DC-DC converter since they are themselves modular in the construction. This eventually leads to some fault-tolerant possibilities since the multiwinding transformer (MWT) connects multiples ports and if one of them is not working anymore and it can be isolated, the others might still continue operating. Unfortunately, it is exactly the MWT that creates most of the technical challenges of this class of DC-DC converters because of the cross-coupling effects among the cells which make especially the resonant-topology very challenging to be designed. This paper reviews the history of the MTB DC-DC and then provides a classification of them, comparing them with Figure of Merits (FOM) and focusing on which is the maximum possible number of windings and which are the most suited magnetic core types. The problems coming from cross-coupling and the possible fault-tolerant operation are analysed with the help of simulation and experimental results.

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Section: B Power Densitymentioning

confidence: 99%

A Comprehensive Assessment of Multiwinding Transformer-Based DC–DC Converters

Pereira

Hoffmann

Zhu

et al. 2021

IEEE Trans. Power Electron.

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“…The use of the HF transformers imposes challenges on the scalability of the isolated matrix inverters. The limiting factors are core losses (losses from eddy current and magnetic losses), high-frequency losses (skin and proximity effects and winding losses in the high current application), parasitic resonances (usually between the capacitance and leakage inductance of the transformer, but the topology has some influence on it) [143]. Depending on the operating switching frequency, the impact of the total transformer losses in the total power loss will be different.…”

Section: Isolation Transformermentioning

confidence: 99%

Review of Isolated Matrix Inverters: Topologies, Modulation Methods and Applications

et al. 2020

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This paper presents a review of isolated matrix inverters. The study contributes to creating a point of reference for a comprehensive classification of existing solutions. Over 30 topologies were reviewed, and the main advantages and disadvantages discussed. Applications of isolated matrix inverters are summarized in a tabular form to demonstrate their flexibility for different power and voltage levels achieved due to the presence of a transformer. These inverters have been proposed for the uninterruptible power supplies, high and low-voltage/power photovoltaic systems, low-power fuel cell, different low- and high-voltage battery and/or electric vehicle chargers, audio amplifiers. The fully controlled switches on both terminals of these converters typically can provide the bidirectional power transfer capability, which is also addressed for most of the topologies, but requires some modification in their modulation strategy. Average efficiency of today’s isolated matrix inverters is comparable with the two-stage power converters; however, they can provide higher reliability and lower cost.

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“…With this, the selected designs cover wide ranges of frequency (150 kHz to 700 kHz) 10 and ripple, cf. Fig.…”

Section: Experimental Verificationmentioning

confidence: 99%

“…This is further improved in [8], where the impact of the High-Frequency (HF) copper losses is also considered. A more systematic and detailed approach is presented in [9], [10]. However, these considerations are not directly applicable to inductors, since critical key design parameters differ.…”

Section: Introductionmentioning

confidence: 99%

Minimum Loss Operation and Optimal Design of High-Frequency Inductors for Defined Core and Litz Wire

Papamanolis

Guillod

Krismer

et al. 2020

IEEE Open J. Power Electron.

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This paper studies the loss-optimal design of a power inductor employed in a 2 kW, 400 V input DC-DC converter. The design of an inductor is subject to a large number of design parameters and the implications of the different design parameters on the losses are often not clearly traceable in a full optimization, e.g., different current ripple amplitudes can lead to designs with similar losses, as larger ripple amplitudes lead to increased AC core and winding losses but lower DC losses in the winding due to lower inductance values and/or numbers of turns. In an effort to achieve a comprehensible description of the implications of the key design parameters (switching frequency, current ripple, number of turns) on the losses, the remaining parameters, e.g., core (E55/28/21 N87) and type of conductor (litz wire), are considered to be given. In a first step, the investigation is based on a simplified analytical model, which is refined in a step-by-step manner, e.g., to consider core saturation. In a second step, the implications of further critical aspects on the losses, e.g., temperatures of core and coil, are examined using a comprehensive semi-numerical model. Surprisingly, the evaluation of the losses calculated in the fr domain reveals that nearly minimum inductor losses are obtained for a current ripple that is inversely proportional to the frequency, i.e., for a constant inductance, within a wide frequency range, from 200 kHz to 1 MHz. Furthermore, the investigation reveals a decrease of the losses for increasing frequencies up to 375 kHz, e.g., from 4.32 W at 80 kHz (r = 110 %) to 2.37 W at 375 kHz (r = 18 %). The detailed analysis related to these results enables the compilation of a simple two-equations guide for the design of an inductor that achieves close to minimum losses. In a next step, interesting trade-offs are identified based on a study of the design space diversity, e.g., with respect to low cost and increased partial-load efficiency. The findings of this work are experimentally verified, i.e., the losses of three different inductors are measured with an accurate calorimetric method and at four different frequencies, ranging from 150 kHz to 700 kHz.

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Medium-Frequency Transformer Scaling Laws: Derivation, Verif ication, and Critical Analysis

Cited by 28 publications

References 27 publications

A Comprehensive Assessment of Multiwinding Transformer-Based DC–DC Converters

A Comprehensive Assessment of Multiwinding Transformer-Based DC–DC Converters

Review of Isolated Matrix Inverters: Topologies, Modulation Methods and Applications

Minimum Loss Operation and Optimal Design of High-Frequency Inductors for Defined Core and Litz Wire

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