Multi-physical modeling of the graphite electrode within a lithium-ion battery: Study of heterogeneities and aging mechanisms Nicolas Dufour

 SUMMARY

The negative electrode of lithium-ion batteries is commonly made of graphite. Although having an interesting specific capacity, aging, intercalation kinetics and lithium transport both in the active material and the electrode porosities limit its optimal and homogeneous operation. In this thesis work, the mechanisms behind these limits are explained using a multi-physics model of the porous electrode type. A sensitivity study of the model parameters showed the importance of the parameters related to intercalation kinetics and lithium transport in solid and liquid phases. The exploitation of the model, validated experimentally, shows that, during the operation of the electrode, the appearances of lithiation heterogeneity are correlated with the particular shape of the equilibrium potential of graphite with respect to its lithiation rate. The modeling of the particle size distribution greatly amplifies these heterogeneities and significantly degrades the overall performance of the electrode. As a first approach, an operando measurement of the distribution of lithiation states confirms the heterogeneous aspect of the electrode operation. Data on the cycling and calendar performances of graphite-NMC cells have allowed the construction of different electrode aging models. The growth of the passivation layer (SEI) can alone explain the loss of cyclable lithium. The SEI heterogeneities obtained by the model are negligible in the current state. The capacity gains and sudden losses are explained respectively by SEI dissolution and lithium-plating formation mechanisms.

VIEW FULL THESIS: https://theses.hal.science/tel-02148211v1/document

100kW, 10kHz Medium Frequency Transformer Design Optimization and Experimental Verification Marko Mogorovic, Student Member, IEEE, Drazen Dujic, Senior Member, IEEE

 100kW, 10kHz Medium Frequency Transformer Design Optimization and Experimental Verification Marko Mogorovic, Student Member, IEEE, Drazen Dujic, Senior Member, IEEE 

 Abstract—This paper describes a novel, model based, design optimization methodology for high-power medium frequency transformers for medium-voltage high-power electronic applications, namely emerging solid state transformers. Presented procedure enables the designer to interactively select the most optimal design in a simple and intuitive way, while inherently offering flexibility in terms of various design alternatives, depending on the component availability. The core of the design algorithm is explained in detail together with all of the relevant modeling and technical challenges associated with realization of a prototype. A 100 kW, 10 kHz medium frequency transformer prototype has been designed according to the presented algorithm, practically realized and thoroughly tested in order to verify the theoretical design.

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 https://infoscience.epfl.ch/entities/publication/7d2c7186-c374-4bda-a35a-88cd849f908c

Conversores CC-CC com Elevado Ganho Estático Baseados na Associação e na Integração dos Conversores Boost Modificado e SEPIC-André M. Senderski Universidade Tecnológica Federal do Paraná Francisco J. Viglus Universidade Tecnológica Federal do Paraná Mário L. da Silva Martins Universidade Federal de Santa Maria Carlos Henrique Illa Font Universidade Tecnológica Federal do Paraná

 

Conversores CC-CC com Elevado Ganho Estático Baseados na Associação e na Integração dos Conversores Boost Modificado e SEPIC

André M. Senderski Universidade Tecnológica Federal do Paraná

 Francisco J. Viglus Universidade Tecnológica Federal do Paraná 

 Mário L. da Silva Martins Universidade Federal de Santa Maria 

 Carlos Henrique Illa Font Universidade Tecnológica Federal do Paraná 

 ABSTRACT 

This paper presents a study of two non-isolated DC-DC converter topologies with high static gain, basedon the association and integration of modified Boost and SEPIC converters. The associated topology usestwo controlled switches, while the integrated one employs only one. When performing the integration, theswitching cell known asR2P2is obtained. The proposed converters achieve high voltage gains ,making them suitable for applications where a reduced number of components is desirable, commonconnection between input and output, simplifying the control and command circuit. The paper presentsthe details of the derivation of the topologies and the operating principle including the topological stagesand main waveforms, in addition to the comparative analysis with similar converters previously proposedin the literature. To validate the analyses, two prototypes with a nominal power of 200 W, dimensionedto operate with an input voltage of 26 V and an output voltage of 260 V are presented. The convertersoperate at a switching frequency of 50 kHz, with an efficiency of 93.4 % for the associated converter and89.2 % for the integrated converter at rated power.

VIEW FULL ARTICLE: https://journal.sobraep.org.br/index.php/rep/article/view/1031/923

Thermoelectric Characterization of IGBT Power Modules: An Approach by Static and Dynamic Methods-Deivid F. de Souza1,∗, Diego S. Greff11Federal University of Santa Catarina, PPGESE, Joinville, SC, Brazil

 

Eletronica de Potencia, Rio de Janeiro, v. 30, e202510, 2025 Thermoelectric Characterization of IGBT Power Modules: An Approach by Static and Dynamic Methods-Deivid F. de Souza1,∗, Diego S. Greff11Federal University of Santa Catarina, PPGESE, Joinville, SC, Brazil

 ABSTRACTThis study evaluates IGBT modules with a focus on efficiently measuring their thermalimpedance, a critical factor in reliability assessments. The research employs the Thermo Electric SensitiveParameter method to measure the Virtual Junction Temperature and obtain the Thermal Impedancecurve. These experimental results are compared with datasheet values, using power modules without abaseplate. Two methodologies, dynamic and static, are utilized, both demonstrating consistent performancein evaluating thermal characteristics. The study also addresses the importance of accounting for non-linearity in thermal conductance due to temperature dependency, which is essential for accurate thermalcharacterization. Additionally, it explores the potential for measuring the Thermal Impedance betweenJunction and Case in power modules without a baseplate, offering a comprehensive understanding ofthermal performance.

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A Review of Boost Converter Analysis and Design in Aerospace Applications-E. Mattos, A. M. S. S. Andrade, G. V. Hollweg, J. R. Pinheiro and M. L. S. Martins

 Abstract— Often, for simplicity, it is adopted for boost converter inductor and capacitor design the inductor current variation (Δ IL), defining it as an output current percentage. However, this kind of methodology does not guarantee the inductor and capacitor minimum values that assure the converter working on continuous mode operation, discontinuous mode operation, or when it is desired to operate the converter at the boundary between these modes. The aim of this paper is to present a theoretical study of the no-losses boost converter. The principle of operation and static analysis are developed in detail for operation on the following modes: continuous mode operation, discontinuous current mode operation and at the boundary between these modes. During this analysis, all four variables (input and output currents and voltages) are considered as design choices for independent variables that determine the boundary between continuous and discontinuous modes. In addition, a design methodology is presented to illustrate the theoretical procedures, which guarantee the inductor and capacitor minimum values according to the desired operation mode. Finally, the simulation results proof the theoretical analysis.

VIEW FULL PAPER: https://www.ufsm.br/app/uploads/sites/737/2019/08/23_-_A_REVIEW_OF_BOOST_CONVERTER_ANALYSIS_AND_DESIGN_IN_AEROSPACE_APPLICATIONS.pdf