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    Modeling and Simulation of Soft Switching in Traction Inverter
    (2023) Lu, Kuang; Gandla, Lakshmi Priya; Chalmers tekniska högskola / Institutionen för elektroteknik; Lundberg, Stefan
    In this thesis, two soft switching inverter topologies the Active Clamped Resonant DC Link Inverter (ACRDCLI) and theAuxiliary Resonant Commutated Pole Inverter (ARCPI) are designed. Their performance is compared with the Hard Switched Inverter (HSI) in simulations. In order to ensure the balance of the soft switching resonant circuit and to achieve a certain reference current, the parame ters of the circuit components are selected according to the references and modified appropriately. The load is modelled as a Permanent Magnet Synchronous Machine (PMSM) equivalent circuit and the parameters are taken from the Finite Element Method (FEM) data based on a fixed operating point. The total power losses in the switches are calculated based on the loss profile in Piecewise Linear Electrical Circuit Simulation (PLECS). Hysteresis current control and Space Vector Pulse Width Modulation (SVPWM) are used to control the current of the ACRDCLI and the ARCPI respectively. Two different state machines have also been designed to ensure the proper operation of the two soft switching topologies. The same control method is used for two HSIs as a control group to have a fair comparison. By simulating each topology under the similar conditions it can be concluded that each topology can output similar power and the total losses in two soft switching topologies are reduced by 18% compared to HSI, especially in switching losses by 98% at 33 kHz switching frequency. Due to the circuit complexity and poor Total Harmonic Distortion (THD) perfor mance of the ACRDCLI only the ARCPI is further analysed for different switching frequencies and current operating points. At high switching frequency of 80 kHz the THD value for the ARCPI is 0.286 % and for the HSI the THD is 0.366 %. With increasing switching frequency the THD for the ARCPI is smaller than the HSI and the ACRDCLI. The ARCPI gives the maximum efficiency of 97.57 % at 25 kHz switching frequency. Compared to the HSI there is an efficiency improvement of 1.71 % with the ARCPI at high switching frequency.
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    Analysis of Multi-level Inverters for Electric Vehicle Application
    (2023) Seshadri, Manoj Krishna; Kanipakam, Vishal; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn
    Abstract Traditional two-level inverters are used for electric vehicles on the market today. But, in recent years there is a growing interest in multi-level inverters to be used as the propulsion inverter in electric vehicles. So, this thesis work analyzes the performance of a multi-level inverter of different topologies as a traction inverter and a comparison is made with a traditional two-level inverter. Using a multi-level inverter, multiple levels of the output voltage can be obtained which helps in the reduction of losses and also THD. The implementation and analysis of this work are mostly carried out in PLECS software where different topologies of the multi-level inverter are modeled, simulated and the comparison between the different topologies is made in various aspects such as losses, THD, and also the DC link ripple from the capacitors. The thermal analysis is also done as the inverter models are designed considering the thermal properties of the power module. Finally, a comparison of the different topologies is made using two different switches. One uses the SiC switch and the other uses the GaN switch. In this thesis, a two-level inverter and a multi-level inverter of three levels are in vestigated. In a multi-level inverter, four different topologies (i.e., Neutral point clamped inverter, T-type neutral point clamped inverter, Flying capacitor inverter, and Cascaded H-bridge inverter) are modeled, simulated, and analyzed. Two differ ent switching strategies (i.e., Sine wave PWM and Space vector PWM) are imple mented for the inverter models. But for the multi-level inverter models, phase-shifted sine wave PWM is used. As the number of levels increases, the complexity of the modulation technique, cost, and size of the inverter increases. So, when it comes to selecting an inverter, it is a trade-off between all the above parameters.
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    Semi-empirical ageing model development of Traction battery
    (2023) Gao, Yidan; Lei, Huijia; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn
    Abstract In this thesis work a semi-empirical model for lithium-ion battery calendar ageing and cycling ageing behaviour was built based on several ageing factors. For the calendar ageing, the factors include State of Charge (SOC), temperature and storage time. For the cycling ageing, the factors include Full Equivalent Cycles (FEC), temperature, Depth of Discharge (DOD), C-rate and middle-SOC. More than six groups of independent research data and two different chemistry of lithium-ion batteries, Lithium Nickel-Manganese-Cobalt Oxide (NMC) are included (NMC111 and NMC442). The developed ageing model can be used for several different type of cells. The primary tool for data analysis and modelling is Matlab. This thesis investigates the relations of ageing factors and their influence on the degradation of batteries in the final model. Then the obtained model was validated and managed to be fitted for three different batteries’ ageing data with minor adjustments. An ageing model was acquired with separated calendar ageing and cycling ageing. The RMSE of each data sets is from 1.5-1.9 which is considered good to use for prediction. Besides, the stressed factors of the ageing model have been studied in order to provide input parameters for the required applications in a BMS. The research shows that the storage time has an important influence on the calendar ageing process. The storage temperature is more important than the storage SOC. Regarding cycling ageing, the FEC plays an important role in the ageing process.The cycling temperature and the SOC window are more important than the C-rate.
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    Low voltage electric system modeling and simulation
    (2023) Bhuyan, Mohammed Fazlur Rahman; Likhan, Sadia Sultana; Chalmers tekniska högskola / Institutionen för elektroteknik; Liu, Yujing; Liu, Yujing
    Abstract The automotive vehicle production industry has become a huge business nowadays. The vehicle market is intense and the competition is hard. Every supplier wants to give their best product and maintenance solution to the vast amount of customers who are eagerly waiting for upgrade versions and new inventions of vehicles. So, a lot of research has been going on in the vehicle industry to provide a comfortable driving and travelling experience to the end user. These research works generally comprise a lot of experi ments that require a good amount of time and money. In order to make the experiments faster, easier, and cost-effective it is a good idea to use a soft ware based model. With this software model, the initial feasibility test can be done, and then the finally passed model from the feasibility test can be developed for further practical improvement. So, in this way combination of both the software and practical model will ultimately speed up the research work and make the process more easier and cost-effective. The goal of this thesis report is to develop a software-based model for industrial and marine vehicles. In this thesis report, the low voltage auxiliary power transmission system of a basic marine vehicle (mainly used for cruise) is investigated. Such a vehicle generally contains an alternator, a battery, and loads (lights, air con ditioning system, driving control system, emergency system, etc.) The main parts of an auxiliary system like the alternator and battery are thoroughly investigated to develop an equivalent model of them that can be applicable in MATLAB SIMULINK software. After developing the model for each part they interlinked with each other. Then finally the results are compared with the practical output.
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    A Channel Estimation Between a Base Station, Intelligent Reflecting Surface, and a User Equipment
    (2023) Saltykova, Ekaterina; Chalmers tekniska högskola / Institutionen för elektroteknik; Monti, Paolo