Electrical Engineering

Welcome to MSc thesis presentation by Sewwandi Meegoda on
Fault Detection of HVDC Transformer Windings using Impedance Protection
Date: Friday, August 22, 2025 Time: 8:30 – 9:15 Place: Edit Room Analysen (Teams link available below)
Supervisor: Arsalan Hadaeghi, Hitachi Energy Examiner: &nbsp;Massimo Bongiorno Opponent: Nigalyadevi Kulandaivel and Diyasha Chenali Hapuarachchi
Abstract: Power transformers play a key role in high voltage direct current (HVDC) systems to overcome the limitations of conventional AC transmission and are expensive and fundamental components in power systems. Transformer winding faults are among the most prevalent issues in transformers. Since winding faults are aggravated in nature, transformer winding short circuits need to be detected at early stages. The existing transformer protection methods encounter difficulties in detecting certain winding faults in transformers, i.e., faults that occur near the neutral point or with higher fault resistance. This study investigates and develops a reliable method for transformer winding fault detection based on impedance protection by calculating the winding impedance utilizing the terminal voltage and current measurements, and comparing the impedance values under fault conditions with their steady-state condition values. A three-phase transformer was modelled in PSCAD simulation software using three multi-winding single-phase transformers to model internal faults. Turn to turn faults were simulated for different fault locations, and analyzed impedance values of each scenario using a conventional impedance protection method and Machine Learning algorithms (ML) to identify the winding faults and their location. The fault studies were conducted on a symmetric monopolar Voltage Source Converter (VSC) based HVDC system. The terminal voltage and current measurements were utilized to derive impedance values for each fault condition. The obtained voltage, current, and impedance measurements were fed to train the developed Machine Learning algorithm Models. A higher accuracy is obtained by optimizing the ML model parameters in fault detection, classification, and fault location detection.
Everyone is most welcome!
Sewwandi, Arsalan and Massimo&nbsp;
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Welcome to the Master Thesis Presentation &nbsp; Investigation of HV-LV Isolated DC-DC Converter Topologies for Automotive Applications &nbsp; By Meghana Viswanath Tuppada &nbsp; Master Thesis work conducted at Volvo Cars Corporation, Sweden, supervised by Rajiv Augustine &nbsp; Examiner: Yujing Liu Opponents: Shenzhen Liang &nbsp; Time: 09:00-10:00 &nbsp;on Friday, 22 August, 2025 Place: E2 Uno Lamm room, Department of Electric Power Engineering
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Abstract: In this work the design of isolated DC/DC converter such as phase shifted full bridge with three different secondary topologies full bridge (FB), center tapped (CT) and current doubler(CD) are discussed which are to be used in auxiliary power module (APM) to power the LV battery in an electric vehicle. The converters are designed for a full load power of 7500 W and an input voltage range of 370 V- 920 V to achieve regulated output of 15 V at an operating frequency of 100 kHz. The main work involves the design of transformer, inductor, component level loss analysis and estimation of efficiency of the converters at various loads and input voltages.
Phase shift is a modulation technique used to control the operation of the switches in the primary where all the switches in the primary operate for a fixed duty cycle of 50% but with a phase shift. The phase shift depends on the input voltage and turns ratio of the transformer. In this topology zero voltage switching (ZVS) is achieved through the leakage inductance of the transformer so turn on losses are zero but turn off losses are unavoidable. Silicon carbide (SiC) MOSFET’s are used in the primary and Silicon (Si) MOSFET’s are used in the secondary.
Several design considerations were taken into account such as paralleling of switches on the secondary, variation of on state resistance, junction temperature rise of the switches. All the converters were simulated in MATLAB/Simulink to find the currents in the components to estimate the conduction , switching losses in MOS FET’s, copper losses in transformer and inductor. The waveforms of the converters are verified theoretically and through simulations. Comparison of the converters based on the total losses and efficiency is done at the end of this work which made it evident that the PSFB-CT has a better performance at low load PSFB-CD has a better performance at high load. Further investigation comparison of topologies such as traditional half bridge and LLC can be considered. Different topology architectures involving interleaving/paralleling of the power stages or components can be considered to improve the performance.
Welcome!
Meghana &amp; Yujing&nbsp;

Welcome to MSc thesis presentation by Malte Rosengren on
Evaluation of system strength in a converter dominated power system
Date: Friday, August 22, 2025 Time: 9:30 – 10:15 Place: Edit Room Analysen <a rel="noopener" href="https://teams.microsoft.com/l/meetup-join/19%3ameeting_Y2IyMDYyNmYtMTExOC00ODEyLWIyOGUtMDQxMWUzNzE2NzMz%40thread.v2/0?context=%7b%22Tid%22%3a%2229147a65-536d-43f9-b802-e0a1b5cf9dbf%22%2c%22Oid%22%3a%22b83f7db0-c874-4f34-a5d6-3c8457773823%22%7d" target="_blank" data-anchor="?context=%7b%22Tid%22%3a%2229147a65-536d-43f9-b802-e0a1b5cf9dbf%22%2c%22Oid%22%3a%22b83f7db0-c874-4f34-a5d6-3c8457773823%22%7d">(Teams link available)</a> Meeting ID: 378 054 048 566 0 Passcode: 4nM9SV3P 
Supervisors: Fabian Hohn and Ehsan Behrouzian, Svenska kraftnät Examiner: &nbsp;Massimo Bongiorno Opponent: Parth Vaze
Abstract: The steady increase in power electronic-interfaced generation, driven by the continued growth of renewable energy sources, is altering the dynamic behavior of modern power systems. While traditional system dynamics have been dictated by the characteristics of synchronous generators, the increasing penetration of Converter-Based Resources (CBRs) is contributing to a gradual transition toward converter dominated power systems. This transition introduces new challenges to power system stability and raises questions regarding the applicability of conventional system strength metrics, particularly the Short Circuit Ratio (SCR), which has historically been used to assess grid strength.&nbsp; The aim of this thesis is to evaluate the limitations of the SCR metric in grid strength assessment for converter-dominated power systems and to assess alternative system strength metrics that may be more suitable under these changing conditions. Furthermore, the alternative system strength metrics need to be applicable during grid planning and is therefore restricted to the data available at this stage. The study was structured into three phases: (1) an initial review of the traditional grid strength metric, SCR, supported by Electromagnetic Transient (EMT) simulations; (2) initial evaluation and selection of alternative system strength metrics through comparative evaluation using small-scale case study with EMT simulations; and (3) implementation and evaluation in PSS®E-of the most promising metrics selected in (2)- followed by validation of PSS®E results through detailed EMT simulations to determine the most reliable metric for system strength assessment.&nbsp; The results indicate that traditional SCR metric consistently overestimates system strength in systems with high CBR penetration. The preliminary grid strength assessment conducted in phase 2 identified the Available Fault Level (AFL), Equivalent Short Circuit Ratio (EqSCR), and Site-Dependent Short Circuit Ratio (SDSCR) as the most appropriate alternative metrics for evaluating grid strength. While the AFL demonstrated promise in the initial small-scale review, it exhibited inconsistencies in the estimation of system strength during the validation process in phase 3. The results obtained from the EqSCR and SDSCR metrics were closely aligned. This outcome is expected, as both methods are fundamentally similar, differing primarily in the specific computational approaches they employ. For both small-scale (phase 2) and more complex system models (phase 3), the two metrics consistently identified the point of instability. System weakness and instability were observed at EqSCR values ranging from 1.1 to 1.3, and SDSCR values between 1.2 and 1.4. Given their comparable performance, EqSCR was identified as the more suitable metric due to its greater computational efficiency. Based on these findings, this thesis recommends the use of EqSCR for system strength screening in converter dominated power systems.
Everyone is most welcome!
Malte, Fabian, Ehsan and Massimo&nbsp;

Title: Breathing Monitoring with RFID Sensing-Tag Antenna Design and Signal Processing Students: Zichen Ma and Jiaqi Wu Date and time: August 22, 2025, 10:00-11:00 Place: E2 Room 3340 Blå rummet Examiner: Xuezhi Zeng
Abstract: Real-time monitoring of respiratory function plays an essential role in both clinical diagnosis and pulmonary rehabilitation. In this work, we proposed a novel respiratory monitoring solution based on ultra-high frequency (UHF) radio-frequency identification (RFID) technology for local measurement of breathing at multiple locations simultaneously. A respiratory monitoring system was built using commercial RFID devices, and a signal processing algorithm was developed to extract respiratory features. The results demonstrate high accuracy in both respiratory rate and temporal pattern compared with a reference piezoelectric (PZT) respiratory belt. Moreover, two compact tag antennas were designed and optimized to operate on the human body. Two different methods, stencil printing and copper tape engraving, were used for tag antenna fabrication, with advantages and challenges analyzed. &nbsp;Overall, our study suggests that RFID technology holds a big potential for non-invasive and localized respiratory monitoring.
Welcome! Zichen, Jiaqqi and Xuezhi

Welcome to MSc thesis presentation&nbsp;
Title: Shaping Rewards with Temporal Information to Guide Reinforcement Learning Student name: Linus Lundgren Date: 2025-08-25 Time: 10:00-11.00 Room: 3340 Examiner: Karinne Ramirez Amaro Opponents: Linus Haraldsson and Jacob Bredin
Abstract:&nbsp; Most previous reinforcement learning (RL) methods that use pretrained Vision-Language Models (VLMs) to compute additional rewards only take the current state the system into account. This is a problem because any information emerging from the sequential nature of the problem (i.e. temporal information) is therefore disregarded. This thesis explored how temporal information can be incorporated into VLM-RL methods, by first distinguishing between fixed and adaptive temporal information. Fixed temporal information describes the system's progression through time, but doesn't capture the current change in the system as adaptive temporal information does. Positional and directional rewards were defined to take advantage of fixed and adaptive temporal information respectively, along with new supervised finetuning methods. Positional rewards are similar to previous methods in that they represent the value of the current state of the system, but potential improvements are made in this thesis by incorporating fixed temporal information in the reward computation. Then directional rewards were developed to take advantage of adaptive temporal information, to instead model the value of the current change in the system, along with new supervised objectives for finetuning the directional reward VLMs. The new positional rewards performed slightly better than previous VLM-RL methods, while a significant improvement was observed when directional rewards were also added.
Welcome! Linus and Karinne

Title: Data-driven analysis of ACC car-following time gaps for different driving contexts
Students: Yusheng Yang &amp; Ruohan Li Supervisor: Jie Zhu Volvo Cars, Fangting Zhou Chalmers, ACE Colleagues from Volvo Cars: Viktor Wänerlöv, Pengcheng Wu Examiner: Balazs Kulcsar, E2
Date: 2025. August 27, 10-11 am Place: E2 Room 5430 Femman
Abstract: Adaptive Cruise Control (ACC) is a key component of the Advanced Driver Assistance System which automatically adjusts the vehicle speed to maintain a safe distance from vehicles ahead. While velocity is the dominant factor for ACC time gap control to keep a safe distance, other relevant factors, such as infrastructure, other road users, traffic density, lead vehicle type, and environmental conditions, influence human driving behavior. In this project, we adopt a data-driven approach to analyze and quantify the influence of these factors on time gap control. We also identify and construct critical scenarios to study the combined impacts of multiple factors. We filter steady car-following driving state on the highway, and apply permutation importance to evaluate the relevance of various factors. In addition, we compare the distribution difference and calculate the confidence interval for the time gap across different traffic groups. We use a Hidden Markov Model (HMM) to cluster different states of cut-in behavior and apply a smoothing filter for sensor fusion data. These methods provide insights into human driving behavior under diverse scenarios. As a result, we propose adaptive time gap recommendations for varying driving conditions to improve user experience.
Welcome! Yusheng, Ruohan and Balazs&nbsp;

Title: Road Friction Aware Adaptive Cruise Control via Robust Nonlinear Model Predictive Control Presenters: Mubina Crnic and Sotiris Koutsoftas Opponents: Asija Boracic Examiner: &nbsp;Nikolce Murgovski Time: Thursday, 2025-08-28, 10:00 Room: E2 Room 7430 Landahlsrummet, Hörsalsvägen 9, 7th floor Zoom link: <a rel="noopener" href="https://chalmers.zoom.us/j/66585117727" target="_blank">https://chalmers.zoom.us/j/66585117727</a>&nbsp;
Abstract: Road friction is a fundamental factor affecting vehicle safety, especially under adverse weather conditions such as rain, snow or ice. Reduced road grip increases stopping distances and the likelihood of loss of control, contributing to a significant number of traffic accidents each year. While modern Advanced Driver Assistance Systems (ADAS) are designed to enhance driving safety, many systems still lack the ability to adapt their behaviour in real time to varying road friction levels, limiting their effectiveness in low-friction or rapidly changing weather conditions. This thesis addresses this limitation by developing a friction-aware, curvature-adaptive adaptive cruise control framework based on a Robust Nonlinear Model Predictive Control formulation. The controller anticipates road curvature and spatially-varying friction by incorporating predicted profiles into the optimization problem. To account for uncertainty, both friction and lead vehicle behaviour are modeled stochastically, friction bounds widen along the prediction horizon using a beta-distributed sampling while the lead vehicle’s acceleration varies randomly within feasible physical limits. These variations are reflected in dynamic safety constraints that adapt to evolving conditions ahead of the ego vehicle.
Welcome! Mobina, Sotiris and Nikolce

Welcome to the master thesis presentation &nbsp;&nbsp; Test Methodology for Residential Stationary Battery Energy Storage Systems &nbsp; by Khentsane Mgiba&nbsp;
Friday, August 29, 14.15 Fredrik Lamms room, Chalmers Electric Power Engineering division &nbsp;&nbsp; Opponent: Entong Liu Examiner: Torbjörn Thiringer
Abstract&nbsp; In this work, a compressed test sequence is proposed to characterize and assess the annual performance of a stationary battery energy storage system integrated with a residential solar PV system, within a shorter testing duration. The approach followed consists of studying annual system profiles (load demand and irradiance profiles) obtained from historical measurements, through which four representative days that best reflect the system’s annual operational patterns were systematically selected. &nbsp;The dimensioning aspect for the battery energy storage system, PV and power electronic converter systems, along with their relationship between the energy and power capacities of the battery, was studied through a market survey. The criteria utilized in the selection of the representative days assess the relative error between sums and averages values of the annual and representative day system profiles. These representative days serve as the basis for the compressed test sequence. To evaluate the performance of the system, the relevant performance metrics were evaluated. These include conversion efficiencies based on the energy flow path in the system, battery storage capacity, and round-trip efficiency. The results of the market survey indicated that a typical energy-to-power ratio ranging between 2–3.5 kWh/kWp, with an average battery size of around 5–10 kWh for SBESS coupled with a PV system in residential applications. The survey also highlighted that the size of the SBESS is influenced not only by the size of the PV system, but also by the power electronics converter (PEC) capacity and the system topology connection applied in the system. Through the utilization of flow duration curves, the results show how closely the selected representative days align with the annual system profiles. For load demand, the relative errors between the daily and annual averages and sums were 0.1\% and 1.6\%, respectively. The irradiance profile showed slightly higher deviations, with relative errors of 3.0\% for averages and 4.7\% for sums between daily and annual values, respectively. This highlights the impact of transitional boundaries between seasons, where the largest deviations in seasonal profiles are observed. The proposed test sequence followed a 4-day sequence, with two additional days reserved for reconditioning and rebalancing the battery's state of charge (SOC). The Battery Management System (BMS) of the SBESS regulates the battery energy flow based on the selected representative day profiles. In this way, the test sequence allows the battery to be cycled according to the load demand and the PV throughput, following the self-consumption and self-sufficiency control strategy commonly used in residential applications. &nbsp;
Welcome!
Khentsane och Torbjörn

Welcome to the Master thesis presentation
Title: Optimizing Grid-Connected PV-Battery Systems Using MPC-Based Reinforcement Learning with Degradation Awareness
Authors: Ida Hägeryd and Stjepana Sever Examiner: Torsten Wik
Time: 16:15 Friday August 29 Place: Lunnerummet (E2 Room 3311)
Abstract:&nbsp; This thesis presents a degradation-aware Model Predictive Control–based Reinforcement Learning (MPC-RL) framework for optimal energy management in residential grid-connected photovoltaic (PV) battery systems. The goal is to minimize total operating costs while accounting for battery degradation, grid price variability, and forecast uncertainty. The MPC formulation incorporates a parametrized stage cost that includes grid energy costs, battery wear, and state-of-charge (SoC) penalty window, with parameters tuned using a Q-learning algorithm. Gaussian Process Regression (GPR) is used to forecast the net residual power (PV production minus demand) based on temporal and historical features, enabling a realistic simulation environment and improved MPC decision-making. The proposed method is benchmarked against a baseline non-parametrized MPC controller, purely RL-based strategies from literature, and a simple Gaussian residual model. Results show that while the proposed MPC-RL approach does not outperform all RL benchmarks in short-term simulations, it achieves competitive performance with reduced degradation and improved constraint handling. GPR-based residual forecasts outperform the Gaussian baseline, reducing total monthly costs by up to 84 euros compared to the random-sampling approach, and closely tracking actual residual trends. These findings suggest that MPC-RL with GPR prediction offers a promising and degradation-conscious approach for residential microgrid energy management.
Welcome! Ida, Stjepana and Torsten

BSc thesis presentation: Step Response of a Dipole Antenna Towards Switched-mode Antennas Students: &nbsp;Simon Brask &amp; Benjamin Asteberg When: den 29 augusti 2025 14:00-15:00 Where: E2 Room 3315 Eliasson Examiner: Rob Maaskant
Abstract Communication technologies are rapidly evolving and increasingly dependent on high data throughput. Optimizing the way signals are transmitted and received is essential to meet the demands regarding energy consumption. Optimally designed active antennas serve as the primary means to significantly reduce power loss to enhance data rates. One promising development in this field is the use of switched-mode antennas, which incorporate active and/or passive reconfigurable components such as PIN diodes, MEMS switches, varactors, or RF switches to dynamically adjust terminal voltage/current behavior. These antennas have the potential to decrease power consumption and reduce operational costs. However, they are still under active research and are not deployed in a widespread manner, primarily due to technical challenges that arise when adding nonlinear switching elements. This thesis investigates the step response of a dipole antenna as a foundational study towards the development of switched-mode antennas. To this end, the voltage-current transients at the antenna terminals are modeled through an equivalent RLC circuit. Additionally, the radiation from a short dipole antenna is modeled/approximated by the field from a dipole point source. Using this antenna model we analyze the terminal transient voltage and current, as well as the radiated field, under a single step-function excitation. The transient response is obtained through a Laplace and Fourier analysis. The transient behavior of this approximate antenna model is validated through MATLAB, LTSpice, and the electromagnetic simulation software CST, all resulting in a qualitatively similar damped sinusoidal port current characteristic with a natural resonance frequency of about 78 MHz. Furthermore, a switched-mode antenna is a nonlinear system generating higher-order harmonics for the terminal voltage/current as well as the radiated fields. The frequency domain analysis correctly predicts these higher-order harmonics. This work provides a simplified yet robust framework for understanding the input current-voltage and radiated field dynamics of dipole antennas in switch-mode operational scenarios, offering a stepping stone for future studies on real-time reconfigurable antenna systems. Furthermore, the circuit could be simulated over a longer period with alternating switching time (e.g. pulse width modulation).
Welcome! Simon, Benjamin and Rob

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Presentation of master thesis

Master thesis presentations at Electrical Engineering

22 August, 2025

08.30-09.15 Sewwandi Meegoda, MPEPO

09.00-10.00 Meghana Viswanath Tuppada, MPEPO

09.30-10.30 Malte Rosengren, MPEPO

10.00-11.00 Zichen Ma & Jiaqi Wu, MPICT and MPMED

25 August, 2025

10.00-11.00 Linus Lundgren, MPDSC

27 August, 2025

10.00-11.00 Yusheng Yang & Ruohan Li, MPICT and MPALG

28 August, 2025

10.00-11.00 Mubina Crnic & Sotiris Koutsoftas, MPSYS

29 August, 2025

14.15-15.15 Khentsane Mgiba, MPEPO

16.15-17.15 Ida Hägeryd & Stjepana Sever, MPSYS

14.00-15.00 Simon Brask & Benjamin Asteberg, MPICT and MPEPO