TY - JOUR A1 - Hein, Thiemo A1 - Oeser, David A1 - Ziegler, Andreas A1 - Montesinos-Miracle, Daniel A1 - Ackva, Ansgar T1 - Aging Determination of Series-Connected Lithium-Ion Cells Independent of Module Design JF - Batteries N2 - In this work, a battery consisting of eight commercial NMC/graphite cells connected in series was cycled to 60% of its initial capacity. During the test, special care was taken to ensure that the results were not influenced by either the module assembly or the module design. For this purpose, the cells were virtually connected in a laboratory environment with the help of the test device as if they were operated together in a battery. Extrinsic influences that affect cell aging were thus reduced to a minimum. Differential Voltage Analysis (DVA), Electrochemical Impedance Spectrum (EIS), and relaxation measurements were performed to analyze the aging behavior of each cell. The results show that despite a theoretically perfect module design, Cell-to-Cell Variations (CtCV) occurred during aging. The shifting Depth of Discharge (DoD) values among the cells further amplify CtCV. Lithium plating was also observed in the faster aging cells after cyclic aging, suggesting that this aging effect contributes significantly to the development of CtCV. After the aging test, the battery was equipped with an active balancing system that maximizes capacity utilization. More important, the balancing charges which are calculated iteratively within the used balancing algorithm show a strong correlation to the pure capacity losses and thus provide a new way to determine the capacity values of each cell individually without disassembling the battery. Y1 - 2023 U6 - https://doi.org/10.3390/batteries9030172 VL - 9 IS - 3 ER - TY - JOUR A1 - Holder, Marvin A1 - Eberspächer, Mark A1 - Waldschmidt, Christian T1 - A hybrid algorithm to process millimeter wave images with prism-shaped aperture JF - Advances in Radio Science N2 - To process images of a prism-shaped aperture in a radar imaging context, a hybrid algorithm is derived. This hybrid algorithm combines the benefits of backprojection and the Omega-K algorithm in terms of computational performance and flexibility. As a demonstration for an application of this algorithm, a 3D inspection system based on millimeter wave imaging is introduced. The system scans through the object, while it is passing on a conveyor belt. It comprises a curved antenna layout, which is able to synthesize the prism-shaped aperture. This aperture is shown to have superior resolution capabilities compared to a planar aperture. Some potential pitfalls when implementing the hybrid algorithm are assessed. Approximation formulae to estimate the achievable resolution are derived. The introduced algorithm is analyzed regarding its point spread function and compared to backprojection with the help of numerical simulations to demonstrate its potential. Y1 - 2025 U6 - https://doi.org/10.5194/ars-23-101-2025 SN - 1684-9973 VL - 25 IS - 23 SP - 101 EP - 111 PB - Copernicus GmbH ER - TY - JOUR A1 - Yükselen, Emir A1 - Rahimpour, Ebrahim T1 - An improvement in the design process of sustainable peak power rating transformer for solar utility JF - International Journal of Electrical Power & Energy Systems N2 - The transformer industry faces critical challenges, such as maintaining reliable production while meeting rising sustainability requirements. This paper introduces a significant advancement in the design and optimization of a transformer dedicated to a photovoltaic power plant, which exhibits a unique loading cycle distinct from standard power and distribution transformers. The main aim is to minimize the carbon footprint by enhancing the design process to improve operational performance, efficiency, and functional reliability. Such upgrades are essential for transitioning to a zero-emission electricity system and developing green energy projects. In this paper, a transformer has been studied using a combination of electrical design and 3D finite element method simulation to evaluate various design parameters. An optimization study has been conducted using an innovative multi-objective genetic algorithm utilizing a cost function that factors in size and material costs to identify the most efficient and cost-effective design solutions. The proposed design method was then validated through thermal model simulations and experimental tests based on the photovoltaic load cycle. A comparison of critical thermal parameters directly affecting the transformer’s lifetime and reliability was also drawn. The results were consistent with the expected outcomes, confirming the effectiveness and reliability of the proposed design methodology. KW - Transformer KW - Photovoltaic KW - Finite element method KW - Optimization KW - Genetic algorithm Y1 - 2025 U6 - https://doi.org/https://doi.org/10.1016/j.ijepes.2025.110928 SN - 0142-0615 VL - 170 SP - 1 EP - 13 PB - Elsevier BV ER - TY - JOUR A1 - Abouhosseini-Darzi, Mohammad A1 - Mirzaie, Mohammad A1 - Shayegani Akmal, Amir Abbas A1 - Rahimpour, Ebrahim T1 - Calculation and Analysis of the Electric Field of the OIP Bushings under Internal Humidity and Surface Polluted Conditions using FEM JF - Iranian Journal of Electrical and Electronic Engineering N2 - Bushings are one of the most important components of electrical equipment such as power transformers, reactors, capacitors. Most of the installed bushings have Oil-Immersed Paper (OIP) insulation structure. Bushing failure is caused by various reasons such as poor manufacturing process, overloading and also poor installation process, but moisture ingress is one of the main reasons of OIP bushing defect during its operation. In this paper, the electric field distribution of OIP bushings in multiple situations are simulated and effects of moisture distribution are analyzed. The simulations are stablished in polluted and clean surfaces of the studied bushing and done by COMSOL Multiphysics Software. The results show that non-uniform moisture distribution has a significant effect on electric fields of OIP insulation. This effect strongly increases with increasing the pollution on the external insulator of the bushing. © 2025, Iran University of Science and Technology. All rights reserved. KW - Finite Element Method (FEM) KW - Moisture KW - OIP Bushing KW - Pollution KW - Transformer Y1 - 2025 U6 - https://doi.org/10.22068/IJEEE.21.3.3360 VL - 21 IS - 3 SP - 1 EP - 11 ER - TY - JOUR A1 - Gustavsen, B. A1 - Rahimpour, Ebrahim T1 - High-Frequency Transformer and Reactor Models for Network Studies JF - Electra Y1 - 2023 IS - 328 SP - 1 EP - 13 ER -