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Senast publicerade

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    Design of HV to LV DC/DC converter using resonant topology
    (2026) Gouse Vaddinakatti, Sareena
    The increasing demand for high-voltage electric vehicle architectures requires efficient power converters. Additionally, the increasing adoption of 800 V battery architectures alongside conventional 400 V systems has increased the requirements placed on the high-voltage to low-voltage (HV-LV) DC-DC converter. Hence, a wider variation in battery voltage requires converters with a wide input-voltage range while maintaining high efficiency, compact size, and low voltage stress on the components. This thesis presents the design and evaluation of a 9 kW isolated HV-LV DC-DC converter based on a Stacked Half-Bridge (SHB) LLC resonant topology, designed to operate over an input-voltage range of 330–950 V while providing a regulated low-voltage output. The proposed converter uses the LLC resonant tank together with the SHB structure to achieve the required wide voltage-gain range. The large variation in input voltage would otherwise require a conventional LLC converter to operate over a wide gain range, potentially increasing the required operating frequency range or requiring additional conversion stages. The SHB structure provides an additional voltage gain, allowing the required conversion ratio to be achieved over the 330–950 V input range. At the same time, the LLC resonant tank enables soft-switching operation, while the SHB structure reduces the voltage stress across the primary-side switches. The converter design includes the development of the LLC resonant tank, highfrequency transformer, resonant inductor, modulation strategy, and control structure. First Harmonic Approximation (FHA) was employed for resonant tank design, and detailed loss models were implemented in MATLAB/Simulink to evaluate converter performance under practical operating conditions. Several capacitor-voltage balancing techniques were investigated, and an interleaved PWM modulation strategy was selected due to its improved balancing performance. Simulation results demonstrate that the proposed converter achieves the required voltage conversion over the specified operating range while maintaining capacitorvoltage balance and high efficiency. A maximum efficiency of 97.2% was obtained under nominal operating conditions. From the results, it can be concluded that the SHB LLC converter is a promising solution for wide-input-voltage automotive DC-DC conversion applications. It offers high efficiency, reduced component stress and increased voltage gain range of the converter.
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    Sputtered Titanium Nitride Catalysts on Sulfur Hosts and Current Collectors for Lithium–Sulfur Batteries
    (2026) Rosvall, Hugo
    Lithium–sulfur batteries (LSBs) offer high theoretical capacities (1675 mAh g−1) and are a strong prospect for next-generation energy storage, but their performance is heavily limited by the polysulfide shuttle effect and slow redox kinetics. In this study, ultrathin layers of titanium nitride (TiN) were deposited by physical vapor deposition (PVD) onto multi-walled carbon nanotubes (MWCNTs) and aluminum current collectors to evaluate their effectiveness as a catalytic coating. The cells fab ricated with TiN-coated current collectors delivered superior discharge capacities of 1261.8 and 920.3 mAh g−1 at 0.1 and 0.5 C, respectively, significantly outperforming the reference cells (1010.1 and 770.8 mAh g−1), indicating enhanced interfacial con ductivity and sulfur utilization. Modification of the MWCNT sulfur host material with TiN coatings also improved electrochemical performance, with TiN@MWCNT cathodes showing increased initial discharge capacities of 1088.9 mAh g−1 for a ∼3 nm TiN layer and 1183.1 mAh g−1 for a ∼6 nm layer at 0.1 C, compared to the uncoated MWCNT reference (1010.1 mAh g−1 ), and consistently delivering higher capacities throughout extended cycling. An initial voltage decay was observed only in the TiN-modified MWCNT electrodes, after which the voltage profiles gradually stabilized over subsequent cycles, indicating an activation period associated with the TiN@MWCNT architecture. While PVD proved effective for both the planar aluminum current collector and the nanoscale MWCNT host, the fabrication of uniform TiN coatings was considerably more straightforward on the flat current col lector surface, suggesting that nanotube–based architectures warrant further study using PVD-optimized or alternative coating strategies. Overall, the results highlight TiN as a promising interfacial modifier for LSBs.
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    Power Quality Issues with Modern Appliances
    (2026) Herold, Fuentes Diaz
    This master thesis investigates and analyzes the topic "Power quality problems with modern appliances." The investigation examines the power consumption patterns, power factor, and harmonic distortions found in a wide range of modern household lighting and devices, utilizing two power quality analyzers: Entes MPR-47SE and Unipower Unilyzer 900. Significant variations in power quality measures were observed in the experimental data, with an emphasis on the disruptive effect of harmonic distortions emitted by modern appliances such as LED bulbs and electronics; while the impact of a single appliance is marginal, the large-scale aggregation of these modern loads injects substantial cumulative harmonic distortions into the network. This collective behavior compromises the power quality and dependability of low-voltage distribution systems by overloading neutral conductors and causing premature thermal aging of distribution transformers. As a result, the study underlines the necessity to develop solutions for reducing harmonic distortions and improving power quality in residential settings. The findings reveal that while the widespread adoption of energy efficient appliances like LEDs and small electronics reduces overall consumption, it introduces severe current Total Harmonic Distortion (THD), particularly third and fifth odd harmonics, which can trigger neutral overloads, accelerate transformer degradation, and increase distribution network losses. Future research should focus on designing integrated, real-time adaptive filtering strategies through collaborative efforts among academia, industry, and regulatory bodies, with the goal of standardizing harmonic signatures and protecting grid reliability while aligning consumer device efficiency with network stability.
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    Liquid biopsy-based T-cell receptor profiling in lung cancer patients undergoing immunotherapy
    (2026) Glavenius, Alma
    Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, and immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway have significantly improved patient outcomes. However, only a subset of patients respond to treatment, highlighting the need for predictive biomarkers. The T-cell receptor (TCR) repertoire reflects the adaptive immune response and has emerged as a promising candidate biomarker for immunotherapy response. The aim of this study was to investigate whether the characteristics of the peripheral blood TCR repertoire are associated with response to anti-PD-1/PD-L1 therapy in NSCLC patients. A total of 96 longitudinal blood samples from n=18 NSCLC patients undergoing anti-PD-1/PD-L1 treatment were analysed using TCR-beta sequencing with the SiMSen-seq method. Following quality control and bioinformatic processing with a molecular identifier groups-based error correction (MIGEC) pipeline, repertoire diversity was evaluated using the number of unique clonotypes, the D50 index, and the Shannon diversity index. In addition, clonal expansion patterns were assessed by tracking highly variable clonotypes over time. Responders consistently exhibited higher TCR repertoire diversity than non-responders. At the pre-treatment baseline, responders showed a 55% higher median number of unique clonotypes, as well as higher median D50 and Shannon index values. Across all time points, responders maintained a more diverse repertoire, with a 33% higher median number of clonotypes, an 8 percentage points higher D50 index, and a 9% higher Shannon index compared with non-responders. Analysis of individual clonotype expansion revealed highly heterogeneous patterns and no clear distinction between responders and non-responders. These findings suggest that overall TCR repertoire diversity is associated with improved response to anti-PD-1/PD-L1 therapy in NSCLC, whereas monitoring individual clonotypes alone appears to be insufficient as a predictive biomarker. Larger studies are required to validate these observations and assess the clinical utility of TCR repertoire profiling in immunotherapy response prediction. Keywords: Non-small cell lung cancer, T-cell receptor repertoire, TCR-beta
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    Design och utveckling av en ergonomisk lagervagn for hantering av restflaskor i butiksmiljö
    (2026) Johansson, Markus; Mladan, Lea; Norin, Hampus; Rudmo, Fabian; Thrybom, Maja; Wester, Dan
    The shelves at Systembolaget are fronted to create a uniform and brand-neutral impression every day. This results in cardboard boxes containing wine bottles being opened and stocked on shelves, even when not all bottles fit, leading to leftover items, so-called slattar. Today, there is a lack of a standardized solution to handle the leftover bottles in an efficient and ergonomic way. Today, shopping carts are used, but they are not adapted for this purpose. This involves high physical strain, a poor overview of the leftover bottles, and inefficient workflows. The purpose of this bachelor’s thesis was to develop, design, and construct a working prototype that solved the problems the staff at Systembolaget experienced today. The project was carried out through an iterative design process where the user was the focus. Initial observations and data from a previous work formed the basis for a requirement specifica tion. Through concept generation, various evaluation methods, ergonomic analyzes, structural strength calculations, and CAD, a final concept was developed and manufactured in full scale. The result is a cart specifically designed for the handling of leftover bottles. It offers a good overview of the bottles and is adapted for good ergonomics during use, as well as a larger capacity than current carts. The construction of the cart consists primarily of steel. Even though more time is required to fully evaluate the cart, the conclusion has been drawn that the prototype offers a good overview of the leftover bottles. The cart can be rolled and maneuvered at full load. Thus, the solution fulfills the main requirements