Electrical Engineering

"Electronic design of an analog equalizer for a bone conduction stethoscope"
Abstract:&nbsp; The necessity and interest of audiologists to finely tune and customize sound frequencies according to individual patient needs, has inspired us to develop and integrate an equalizer to a bone conduction stethoscope. The project designs an analog amplifier equalizer circuit that is used for volume control and frequency selection. It captures sounds from the skull bone with the help of a skin microphone hoping to provide audiologists a flexible tool that can isolate specific frequency bands for analysis, auditory experience diagnosis and troubleshooting of bone conduction hearing aids. The switching options designed on the equalizer has bandpass filters for the audiometric frequencies with the possibility to focus the listening range to both low and high frequencies and thereby encourage audiologists to select the desired ranges of inspection. The project plan was to use the electronic features to categorize audio spectrum into bass (125Hz to 1kHz), wide (125Hz to 8kHz) and treble (1-8kHz) for testing. The test is done on two subjects with the use of a skin microphone having a strategy to check one’s own voice to understand the perception of booming effect, crispness and clarity along with normal speech auditory range of bone conduction voice. The test subjects also experimented by hearing each other’s voice through the equalizer to understand the audio spectrum as mimicked in normal hearing conditions as a reference. The next steps involved attaching a hearing aid and repeating the same procedure to interpret and analyze the assistive device under study. The results showed that the auditory experience was in sync with the theoretical expectations. To conclude, the design and testing of the prototype showed that it is a promising tool for audiologists in near future. 
Examiner: Sabine Reinfeldt, E2
Supervisor: Karl-Johan Fredén Jansson, E2
Opponents: Abdulruhman Khelil &amp; Chetan Vijaykumar
Date and time: 2 May 2024, 10.00-11.00 Location: <a href="https://maps.chalmers.se/#0b75adf5-aec9-4682-ae55-9a1e0a6dcd5a">Lunnerummet, room 3311</a>
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Title: Modeling and Control of High Robustness Inductive Power Transfer System
Conducted at Chalmers, Supervised by Junfei Tang&nbsp; Examiner: Yujing Liu&nbsp; Opponent: Jin Wang  &nbsp; Time: 15:00-16:00 on Tuesday, May 7, 2024&nbsp; Place: Fredrik Lamm, Department of Electric Power Engineering&nbsp; &nbsp; Abstract: Inductive Power Transfer (IPT) presents a promising solution for electric vehicles (EVs), yet challenges persist in achieving high tolerance against coupling and load variations. To address this issue, new model and control scheme for IPT system are required. This thesis is dedicated to the modeling and control of an IPT system with a focus on misalignment and load tolerance. &nbsp; To understand the properties and performance of the IPT system, this thesis begins with an investigation into the conventional model of an IPT system with a series-series resonant tank. Using the Finite Element Method (FEM), the electromagnetic field around the magnetic coupler is studied, providing insights into the relationship between misalignment and mutual inductance. Subsequently, an equivalent circuit is constructed for the IPT system. It becomes evident that under the conventional control scheme, the system's output power and efficiency are vulnerable to misalignment variations, posing a significant obstacle in power flow management.&nbsp; &nbsp; To address this challenge, a novel digital control strategy is proposed. By synchronizing the inverter output voltage with the transmitter current, constant output power can be achieved in high coupling conditions. The control circuit is simple, as it only captures the zero crossing of the current in the transmitting coil. However, inherent propagation delays in the measurement and control circuit can lead to frequency drift and high switching losses, thereby compromising system efficiency and output power. In response, a digital control scheme with delay compensation is introduced, and the boundary of soft switching operation is investigated. It is concluded that soft switching operation can be achieved by applying the new control strategy. Experimental results reveal that within a misalignment range of 0-160mm, the system maintains nearly constant output power. A peak efficiency of 92% can be attained when soft switching is realized in the inverter. This proposed control scheme enhances the robustness of the IPT system against misalignment variations, facilitating cost-effective hardware implementation and obviating the need for dual-side communication. However, the variation of load during power transfer can still cause change in output power.&nbsp; &nbsp; Further analysis of power flow under various load conditions reveals the system's sensitivity to load variations. Leveraging the grid-connected rectifier, the DC-link voltage, crucial for the IPT system's output power, can be controlled to address the issue. Thus, the voltage controller of a three-phase Vienna rectifier is designed. Simulation results demonstrate that the rectifier has less than 1V output voltage ripple under 800V DC-link output voltage and 50kW output power, with a total harmonic distortion of input current of 2.67%. Notably, the stability of the IPT system remains unaffected by variations in the DC-link voltage. Furthermore, the proposed control strategy provides more flexibility to the charging system without requiring additional DC-DC converters. &nbsp; This thesis addresses the key challenges in IPT system design and control, offering innovative solutions to achieve robust, efficient, and adaptable EV charging systems. The proposed control schemes provide constant output power despite changes in coupling and load conditions. Therefore, the works in this thesis pave the way for the development of versatile, compact, and lightweight IPT systems.
Welcome!&nbsp; Linhua, Junfei, and Yujing&nbsp;

Title: Grid Capacity Analysis for Cold Ironing: A Study of Ports and Maritime Vessels 15th of May at 13.00-14.00 in Fredrik Lamm room Opponent: Sima Soltanipour Examinator: Jimmy Ehnberg
This thesis examines the limitations of short-circuit capacity within electrical grids during ship-to-shore power transfers. Utilizing power system analysis software, the study investigates short-circuit scenarios under various conditions, including transient events and potential faults on both the vessel and shore-based installations.&nbsp; The research identifies key factors influencing short-circuit risk in SP systems. These include:
• Voltage stability: Maintaining voltage levels during load transfer between shipboard and shoreside power sources is crucial. Adjustments to transformer tap settings play a vital role in ensuring voltage stability.&nbsp;
• Load sharing: Parallel synchronization methods require careful consideration of combined short-circuit contributions from shipboard generators and shoreside grids to mitigate potential fault currents.&nbsp;
• Worst-case scenarios: Assessing scenarios with unknown shoreside grid parameters is critical. The study highlights the potential for higher short-circuit currents during critical events like large load startups.&nbsp;
This research emphasizes the importance of effective risk management for safe and reliable ship-to-shore power transfers. By evaluating short-circuit capacity limitations and implementing appropriate mitigation measures, such as system upgrades or operational adjustments, the overall safety and reliability of these power transfers can be significantly enhanced.
Welcome! Saman, Tohid and Jimmy

Enhancing Battery Life in the Finnish FCR-N Market: Evaluating the Potential of Flywheel Technology Date: 21st of May Room: Analysen Opponent: Arthur Vankeirsbilck
Abstract: The integration of flywheel technology with battery energy storage systems (BESS) presents a promising strategy to improve both the operational lifetime and economic viability of energy storage solutions for providing ancillary services. In this study, Mixed Integer Linear Programming (MILP) optimisation modelling is employed to investigate the benefits of combining batteries with flywheels in the context of grid frequency regulation (FCR-N market) while considering battery degradation and varying ratios of flywheel to battery capacity. The results reveal that battery degradation has little impact on the optimal dispatch of a hybrid system. highlighting the robustness of the flywheel-battery combination in mitigating battery wear during ancillary services provision. The findings demonstrate that integrating flywheels into battery systems can significantly extend the operational lifetime of the battery. Specifically, a hybrid system with a flywheel-to-battery capacity ratio of 0.2 is recommended and exhibits a notable 2.7-fold extension of battery lifetime. Moreover, the incorporation of flywheels unlocks diverse business opportunities that are not feasible with standalone battery systems, enhancing the overall economic value of the energy storage assets.
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Douwe and Jimmy

Wind power design for high capacity factors A techno-economic analysis of specific power reduction and wind-solar hybrid plants
Date: 21 of May at 11:00 Room: EDIT-room 3364
Opponent: Matilda Karlsson Examinator: Ola Carlson
Abstract: Wind power production is the fastest growing electricity producing technology in Sweden today. One of its challenges is its intermittent nature and rather low capacity factor. Therefore, this thesis investigate the effects of increasing the wind power capacity factor beyond values of 0.5. Alternatives for hourly production estimates for a single turbine, based on historical data, have been proposed, analysed, and validated.&nbsp; Two studies have been conducted. The first increases the capacity factor by decreasing the specific power, while the second consists of complementing a wind turbine with solar power. The work has analysed the consequences by these design changes on both costs and production, and the results are continuous functions of LCOE, value factor, and profit with respect to an increased capacity factor. From this, conclusions are drawn regarding the feasibility of the proposed design changes.
Most welcome!&nbsp; Emma Albinsson and Ola Carlson

"Pre-flight Mission Simulation Model for Estimating State-of-Energy(SoE) in Hybrid Aircraft"
Abstract: &nbsp; Accurate estimation of state-of-energy (SoE) is critical for the safe and efficient operation of aircraft. The multiple energy sources available in hybrid-electric aircraft make the SoE estimation a highly complex challenge. To address this, a pre-flight mission simulation model for estimating SoE has been developed and validated for hybrid-electric aircraft. This model serves two primary purposes: first, it aids in developing aircraft functions for mission planning in hybrid-electric aircraft; second, it can be used as an analysis tool for developing energy management strategies in hybrid-electric aircraft. The simulation model includes detailed models such as a mission planner, weather model, supervisory controller, aircraft model, both conventional fuel driven and electric propulsion system models and battery models. The methodology for developing and validating this simulation model is described and simulation results for hybrid-electric aircraft mission are presented.&nbsp;
Examiner: Anders Grauers, E2
Opponents: Halime Selimoglu and Bharathi Subramaniam Muthuramalingam
Date and time: 4 June 2024, 15.00-16.00 Location: &nbsp;<span style="font-size: 10.5pt; line-height: 107%; font-family: 'Lato',sans-serif; mso-bidi-font-family: 'Times New Roman'; mso-bidi-theme-font: minor-bidi; color: black; mso-color-alt: windowtext; background: #F9F9FA; font-weight: normal;"><a href="https://maps.chalmers.se/#ff20a7f0-3b89-11ea-b363-0d727521c5d9">Femman, E2 Room 5430</a>
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Presentation of master thesis

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Presentation of master thesis

Electrical Engineering

2 May 2024

10.00-11.00: Greeshma Ajayakumar, MPCOM and Raakesh Thiyagarajan, MPBME

7 May 2024

15:00-16:00 Linhua Lai, MPEPO

15 May 2024

13.00-14.00 Saman Chashm and Fassa Tohid Haddadi, MPEPO

21 May 2024

10.00-11.00 Douwe van Alderwerelt van Rosenburgh, Master’s Programme in Innovative Sustainable Energy Engineering (ISEE)

11.00-12.00 Emma Albinsson, MPSES

4 June 2024

15.00-16.00: W A Volanka Stepson, MPSYS and Nilantha Dadallage, MPSYS