Medium-frequency power transformer using GOES for a three-phase dual active bridge

Kauder, Tobias; Belgrand, Thierry; Lemaître, Régis; Thul, Andreas; Hameyer, Kay

doi:10.1016/j.jmmm.2020.166672

Cited by 10 publications

(3 citation statements)

References 11 publications

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“…Silicon steels are typically used in high power applications with an operating frequency of approximately 1 kHz [13,15,16], due to high peak flux density, and magnetic materials for power conversion have been thoroughly surveyed and summarized by the authors of [14]. Silicon steels are typically used in high power applications with an operating frequency of approximately 1 kHz [13,15,16], due to high peak flux density, and low material cost. Ribbon-wound amorphous cores are employed at operating frequencies below 10 kHz [17], due to a lower core loss than silicon steels.…”

Section: Introductionmentioning

confidence: 99%

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

et al. 2021

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This article reports an investigation into ferrite and nanocrystalline materials for the medium-frequency transformer of a dual active bridge DC-DC converter, which plays a key role in the converter’s efficiency and power density. E65 MnZn ferrite cores and toroidal and cut nanocrystalline cores are selected for the construction of 20-kHz transformers. Transformer performance is evaluated with a 1.1-kW (42–54 V)/400 V dual active bridge DC-DC converter with single-phase shift and extended phase shift modulations. The experimental results indicate that the toroidal nanocrystalline transformer had the best performance with an efficiency range of 98.5–99.2% and power density of 12 W/cm3, whereas the cut-core nanocrystalline transformer had an efficiency range of 98.4–99.1% with a power density of 9 W/cm3, and the ferrite transformer had an efficiency range of 97.6–98.8% with a power density of 6 W/cm3. A small mismatch in the circuit parameters is found to cause saturation in the nanocrystalline toroidal core, due to its high permeability. The analytical and experimental results suggest that cut nanocrystalline cores are suitable for the dual active bridge DC-DC converter transformers with switching frequencies up to 100 kHz.

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Section: Introductionmentioning

confidence: 99%

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

et al. 2021

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“…This core technology is suitable for slightly lower frequencies and higher peak flux densities. Papers [38,39] present a 30 kVA-3 kHz single-phase transformer and a 200 kVA three-phase one operating at 1 kHz with GOES cores. The material crystalline structure is very stable; the material takes the benefits from a long industrial experience that demonstrates a very long-life expectancy [40].…”

Section: Introductionmentioning

confidence: 99%

Design of High-Power Solid-State Transformers with Grain-Oriented Electrical Steel Cores

et al. 2022

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The paper proposes a simple structure of high−power solid−state transformers (SSTs) able to control the energy flow in critical lines of the medium−voltage (20 kV) distribution grid. With an increasing number of renewable intermittent sources connected at the nodes of the meshed distribution grid and a reduced number of nodes connected to large power plants, the distribution grid stability is more and more difficult to achieve. Control of the energy flow in critical lines can improve the stability of the distribution grid. This control can be provided by the proposed high−power SSTs operating a 20 kV with powers over 10 MW. This function is difficult to achieve with standard SST technologies that operate at high frequencies. These devices are made with expensive magnetic materials (amorphous or nanocrystalline cores) and a limited power by SST cells. The required total power is reached by assembling many SST cells. On the other hand, existing SST designs are mainly aimed at reducing the equipment’s size and it is difficult to design small objects able to operate at high voltages. The authors propose to use cores made with grain−oriented electrical steel (GOES) thin strips assembled in wound cores. Experimental results obtained, with GOES wound cores, show that the core losses are lower for a square voltage than for a sine one. This counterintuitive result is explained with an analytical calculus of eddy currents and confirmed by a non−linear time−stepping simulation. Therefore, simple converter structures, operating with rectangular voltages and low switching losses, are the best solutions. Experimental results also show that the core losses decrease with temperature. Consequently, high−power SST cells can be made with transformers whose GOES cores are hotter than coils for reducing core losses and keeping copper losses at low levels. The paper proposes an appropriate transformer mechanical structure that avoids any contact between the hot GOES wound core and the winding, with a specific cooling system and thermal insulation of the hot GOES wound core. The proposed design makes it possible to build SST cells over 1MW and full SSTs over 10 MW at moderate costs.

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“…Medium frequency transformer, MFTs, are fundamental to the development of newly advanced DC-DC converters [1][2][3][4]. These converters are becoming key player in building Smart-Grid environments [5], in interfacing renewable energy to medium power grids [6][7][8][9], in constructing the emerging solid-state transformer technology [5,10], and in electric vehicles, as shown in Figure 1.…”

Section: Introduction 1motivation and Incitementmentioning

confidence: 99%

Ferrites and Nanocrystalline Alloys Applied to DC–DC Converters for Renewable Energies

et al. 2022

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The medium frequency transformer (MFT) with nanocrystalline alloys is quintessential in new DC–DC converters involved in various front-end applications. The center piece to achieve high-performance, efficient MFTs is the core. There are various options of core materials; however, no deep information is available about which material characteristics and design procedure combo are best to get high performance MFTs while operating at maximal power density. To provide new insights about interrelation between the selection of the core material with the compliance technical specifications, differently to other proposals, this research work aims to design and build, with the same methodology, two MFT prototypes at 20 kHz, with nanocrystalline and ferrite cores, to highlight power density, and overall performance and cost, as matching design criteria. As the experimental results show, a nanocrystalline core has the highest power density (36.91 kW/L), designed at 0.8 T to obtain low losses at 20 kHz, achieving an efficiency of 99.7%. The power density in the ferrite MFT is 56.4% lower than in the nanocrystalline MFT. However, regarding construction cost, the ferrite MFT is 46% lower, providing this a trend towards low-cost DC–DC converters. Finally, high power density in MFTs increases the power density of power DC–DC converters, which have relevant applications in fuel cell-supplied systems, renewable energies, electric vehicles, and solid-state transformers.

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Medium-frequency power transformer using GOES for a three-phase dual active bridge

Cited by 10 publications

References 11 publications

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

Performance Comparison of Ferrite and Nanocrystalline Cores for Medium-Frequency Transformer of Dual Active Bridge DC-DC Converter

Design of High-Power Solid-State Transformers with Grain-Oriented Electrical Steel Cores

Ferrites and Nanocrystalline Alloys Applied to DC–DC Converters for Renewable Energies

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