Examensarbeten för masterexamen


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    Loss verification of Li-ion battery cells from thermal flow measurements
    (2023) Mandeya, Andrew; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn; Istaq, Ahmed
    Abstract This master’s thesis focuses on heat generation in Lithium-ion battery cells a crucial aspect affecting their performance, lifespan, and overall safety. A custommade isothermal heat conduction calorimeter, integrated with heat flow sensors (Peltier elements), was used to measure heat flow from the lithium-ion cells. Initial experiments involved calibration and sensitivity testing using a 1.25 W resistor mat. Further heat generation experiments were conducted on lab-scale 0.25 mAh LiFePo4/Graphite cells and an 850 mAh lithium-polymer commercial pouch cell. These cells underwent electrochemical characterization tests, including formation cycles and electrochemical impedance spectroscopy (EIS), under various charge/discharge rates and temperatures. The calorimeter displayed reasonable sensitivity up to 6 mW, but higher noise levels were detected below this. Heat generation experiments were unsuccessful on the lab cells due to low dissipation of heat. However, measurements from the commercial cell agreed with established literature. The experimental results found that both irreversible (from internal cell impedance) and reversible (from electrochemical reactions) heat generation contribute to overall heat generation. Irreversible heat generation showed exothermic behaviour, especially during high current rates (especially in discharges direction), while reversible heat displayed both endothermic and exothermic behaviour and was more dominant at lower current rates (and is dependent on the state-of-charge). Interestingly, it was found that at low current rates endothermic behaviour was prominent for low state-of-charge levels while charging. Ambient temperatures significantly affected irreversible heat contributions due to resistance changes, but they did not notably impact reversible heat.
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    Optimized Pulse Pattern Control Strategy Investigation on Signal Level Hardware in the Loop
    (2023) Zou, Chenye; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn; George, Shino; Ingelström, Pär
    Abstract Electric vehicles (EVs) are gaining popularity worldwide due to their low cost of use and sustainability. Key components of the EV drivetrain include an inverter and a permanent magnet synchronous machine (PMSM). To better improve their efficiency, optimized pulse pattern (OPP) can be used. However, simulating OPP together with the inverter and motor takes a lot of time because of high computational complexity. This thesis project utilizes a hardware in the loop (HiL) platform to accelerate the simulation. The PMSM and inverter models are running on a fieldprogrammable gate array (FPGA) separately from the controller model to ensure a high sampling rate while the whole system is still running in real time. Then OPP is evaluated with this platform in comparison with the conventional space vector pulse width modulation (SVPWM). The result shows a significant advantage of OPP in reducing inverter switching losses. Finally, the limitation and operating range of the OPP is also discussed in this thesis report.
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    Development of an Energy Management System for Smart Buildings in Order to Minimize Energy Cost and to Provide Flexibility
    (2023) Stumpf, Katharina Serena; Chalmers tekniska högskola / Institutionen för elektroteknik; Steen, David; Vogt, Damian
    Abstract: The demand for Energy Management Systems (EMSs) has grown significantly in the context of modern sustainable living. This thesis addresses this demand by developing and evaluating an innovative EMS within the HSB Living Lab. The primary goal of the developed EMS is to minimize operation cost of the building by optimal scheduling of devices and maximizing revenue from providing flexibility. The thesis commences with an introduction to the growing significance of energy management in the face of increasing energy demand and the urgency of sustainable energy utilization. It delves into the background of EMS, highlighting its potential to integrate renewable sources and controllable loads for efficient energy utilization. The research methodology involves the design and implementation of an EMS tailored for the HSB Living Lab environment. The system orchestrates Battery Energy Storage (BES), Electric Vehicles (EVs), and controllable loads to balance energy supply and demand as well as the heating provided by the combination of a Heat Pump (HP), district heating and a Hot Water Tank (HWT). Real-world data collected from the living lab contributes to the evaluation of the system’s performance. Results underscore the effectiveness of the EMS in achieving energy optimization objectives. Case studies on different days demonstrate the system’s adaptability to diverse conditions and its ability to harness renewable energy sources as well as the influence of the HP on the providing of flexibility. On the summer day, a cost reduction of 56.13 % is achieved with the provision of flexibility and still 15.51 % without. The sensitivity analysis performed shows the impact of compensation on the amount of flexibility provided. In conclusion, the developed EMS stands as a testament to the potential of smart technologies in revolutionizing energy management. By seamlessly integrating various energy resources and optimizing their consumption, the system reduces costs, increases energy efficiency, provides flexibility to the Distribution System Operator (DSO) and contributes to sustainability goals. This thesis contributes valuable insights into energy management and offers a practical blueprint for similar deployments in diverse settings.
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    Versatile and Optimized Gear Selection Strategy
    (2023) Lindohf, Lindohf; Nordlander Hurtig, Oskar; Chalmers tekniska högskola / Institutionen för elektroteknik; Wik, Torsten
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    Channel state information prediction with limited UE feedback in 5G NR - Analyzing existing and enhanced codebooks
    (2023) Edby, Joakim; Puppin Romano, Thiago; Chalmers tekniska högskola / Institutionen för elektroteknik; Svensson, Tommy