Bachelor/Semester/Master Theses

The electrification of construction machinery, such as excavators or dump trucks, has recently been gaining popularity due to numerous technical, economical, and ecological benefits. At HPE, concepts to replace hydraulic excavators with electrical counterparts are investigated. The excavator’s battery voltage can vary substantially around its nominal value (up to ±25%). To boost this voltage up to a constant DC-link voltage for a motor drive (with energy recuperation), a highly compact and efficient bidirectional boost converter is required. In this project, you will commission a prototype system of a given boost converter design. This task includes the PCB, the magnetic components (inductors), the cooling system and the implementation of converter control & safety functions in VHDL. Thereafter, you will test the system at multiple operating points. Finally, you will make improvements to the PCB and/or the inductive components for an improved prototype system based on your findings during testing.

Simon Beck, ETL F12, beck@hpe.ee.ethz.ch

25% Control 10% Hardware Design 10% Simulation 30% Testing 25% VHDL Coding

• Interest and knowledge in power electronic systems • Interest and knowledge in hardware design Working language: English/German

Dr. Jürgen Biela

The electrification of construction machinery, such as excavators or dump trucks, has recently been gaining popularity due to numerous technical, economical, and ecological benefits. At HPE, concepts to replace hydraulic excavators with electrical counterparts are investigated. The fully electric excavator includes multiple converters to enable wireless power transfer (WPT) across all joints and a boost converter to stabilise the battery voltage. In addition, energy recuperation is possible thanks to all converters being bidirectional. In this project, you will design the essential control system to coordinate all converters and enable their safe and efficient operation. To do so, you will use the system’s communication links (both wired and wireless). Thereafter, you will implement the control & safety functions for the overall system in VHDL. Finally, you will commission and test the complete system on real hardware in our state-of-the-art laboratory.

Simon Beck, ETL F12, beck@hpe.ee.ethz.ch

20% Control 10% Simulation 20% Testing 50% VHDL Coding

• Interest and knowledge in power electronic systems and/or control and communication systems Working language: English/German

Dr. Jürgen Biela

The electrification of construction machinery, such as excavators or dump trucks, has recently been gaining popularity due to numerous technical, economical, and ecological benefits. Therefore, concepts to replace hydraulic excavators actuators with electric counterparts are investigated at HPE. To enable bidirectional power flow to such electric actuators, wireless power transmission (WPT) is employed. Thereby, the mechanical durability is increased compared to brush rings or external cables, while maintenance requirements are reduced. In this project, you will commission the prebuilt WPT converter hardware, which consists of the primary and secondary PCBs as well as the WPT transformer. After validating the basic functionality of the system (isolation, switching, V&I measurements, etc.), you will develop safety and control mechanisms in VHDL to enable the full operation of the converter. Finally, you will make adjustments to the PCBs and/or WPT transformer for an improved prototype system based on your findings during operation.

Simon Beck, ETL F12, beck@hpe.ee.ethz.ch

10% Control 10% Hardware Design 10% Simulation 35% Testing 35% VHDL Coding

• Interest and knowledge in power electronic systems • Interest and knowledge in hardware design Working language: English/German

Dr. Jürgen Biela

Hyperloop is the next evolution of rail-based transportation, combining the speed of aircraft and the efficiency of the railway industry. EuroTube is focusing on the implementation of hyperloop infrastructure, with the first step being the DemoTube test track in Dübendorf, Switzerland. In DemoTube, test vehicles will be propelled by a track mounted, long primary linear induction motor (LIM). A track mounted motor solves the problem of transferring electrical power to a vehicle within a vacuum tube and drastically reduces the weight of the vehicle. However, the long primary needs to be split into segments to ensure the efficient operation of the motor. In this master thesis, the student will investigate the strategy for the switching of the motor segments, the transient effects caused by it, possible mitigation measures (i.e. filters) and propose a hardware setup for the final configuration in the test track.

Ioannis Stavropoulos, R&D Electrical Hardware Engineer, EuroTube, Please email your CV and transcript to ioannis.stavropoulos@eurotube.org

● Literature review on induction motors, transient phenomena and filters ● Simulation of the electrical circuit and determination of the best possible switching strategy and hardware ● Optional: Proposal of electrical hardware ● Summary of the results and compilation of a written report

● Knowledge of power electronics and electrical motors ● High motivation and interest in the topic ● Able to work independently and be creative ● Experience or interest in learning circuit simulation tools

Dr. Jürgen Biela

Hyperloop is the next evolution of rail-based transportation, combining the speed of aircraft and the efficiency of the railway industry. EuroTube is focusing on the implementation of hyperloop infrastructure, with the first step being the DemoTube test track in Dübendorf, Switzerland and the next one being a 3km test track (AlphaTube) in canton Valais, Switzerland. In AlphaTube, test vehicles will be propelled by a track mounted, long primary linear electric motor. In this master thesis, the student will investigate different linear motor types and topologies for the future 3km AlphaTube vacuum transport demonstrator. The track-side (long primary) motor will be 400m long and will propel the vehicle to 900km/h, reaching a peak power of 10MW. Possible motor types of interest are the permanent magnet synchronous motor and the synchronous reluctance motor, while both double-sided and single-sided topologies can be investigated. The designs will be compared to the existing linear induction motor design of EuroTube for efficiency, cost and optimal usage of materials. The motor designs should be verified in a 2D or 3D finite element analysis software.

Ioannis Stavropoulos, R&D Electrical Hardware Engineer, EuroTube, Please email your CV and transcript to ioannis.stavropoulos@eurotube.org

● Literature review on linear electric motors ● Derivation of the equivalent electrical circuit and hardware ● Finite element analysis of different motor types and topologies ● Summary of the results and compilation of a written report

● Electrical engineering student ● Knowledge of electrical motors ● High motivation and interest in the topic ● Able to work independently and be creative ● Experience or interest in learning circuit simulation and finite element analysis tools

Dr. Jürgen Biela

At Porsche, a design procedure for the optimal design of power inverters was developed while focusing on power density and efficiency. The design of the drive inverter is subject to various optimization objectives, e.g. efficiency, continuous power, installation space in the vehicle and costs. In this project, you will develop an optimization framework in order to evaluate different inverter designs and chip configurations in a 3L-TT inverter setup with varying semiconductor technologies (Si IGBT, SiC, GaN) in a multi-objective optimization procedure for a given target drive system. Generally speaking, the results will lie on a pareto front as the objectives are conflicting. An existing toolchain provides a framework which may serve as a starting basis for your models. Subsequently, the designs should be analyzed and generic recommendations should be given for different vehicle applications and classes.

krismer@lem.ee.ethz.ch, robin.lehner2@porsche.de

20 % Modelling / Implementation 40 % Optimization 40 % Analysis & Design guidelines

Experience in MATLAB using optimization algorithms

Dr. Jürgen Biela

EuroTube is focusing on the implementation of hyperloop vacuum transport infrastructure, with the first step being the DemoTube test track in Dübendorf, Switzerland and the next one being a 3km test track (AlphaTube) in canton Valais, Switzerland. AlphaTube is planned to be a 3 km long Hyperloop test track built using ½ scale concrete tubes of 2.2m. This will serve as a test and development facility, for "full-scale" technology research, with launch tests of vehicles at target speeds of 900 km/h. The top of the tube will be covered with solar panels. The aim of this master thesis is to propose a design of a DC/DC insulated converter integrated with the PV plant into the 3kV DC bus, taking into account the spatial peculiarities of a 3km long linear PV array. In a real system, voltages higher than 3kV will probably be used, so the proposed topology should be scalable to higher voltages if possible. The result of the thesis will later be integrated into an overall energy flow based model to define the AlphaTube Microgrid.

Antoine Juge, R&D Electrical Hardware Engineer, EuroTube, Please email your CV and transcript to antoine.juge@eurotube.org

● Literature review ● Study of existing topology and technical limitations from MVDC Integration and galvanic insulated DC/DC usage ● PV and converter space distribution strategy analysis, definition of the optimum converter power level ● Design of a DC/DC converter model: Topology and switch technology definition, Coil sizing and design, Capacitor sizing and design, Energy flow and losses calculation, Filter design and harmonics level definition ● Optional : Control algorithm implementation

● Electrical engineering student ● Knowledge of power electronics ● High motivation and interest in the topic ● Experience or interest in learning circuit simulation tools

Dr. Jürgen Biela

Moderne Brennstoffzellenfahrzeuge benötigen eine Druckluftversorgung, welche vorteilhaft mit Hilfe eines Turbokompressors realisiert wird. Der zugehörige Umrichter muss neben den funktionalen Spezifikationen eine geringe Baugrösse aufweisen und herausfordernden Kostenzielen gerecht werden. Um Marktanwendungen mit immer höher Ausgangsleistung der Brennstoffzelle zu unterstützen, muss auch die Umrichter-Ausgangsleistung kontinuierlich erhöht werden. Dazu sollen in dieser Arbeit verschiedene Möglichkeiten zur Erhöhung der Ausgangsleistung der vorhandenen Technologieplattform untersucht werden. Mögliche Ansätze liegen in der Parallelschaltung von mehreren Leistungshalbleitern, einer Optimierung der thermischen Anbindung der Halbleiter an die Wasserkühlung, sowie der Einsatz alternativer Modulationsverfahren, welche die Ausnutzung der Halbleiter- und Filterkomponenten verbessern. Zu Beginn dieser Masterarbeit soll daher basierend auf vorhandenen Rechenmodellen das Potential der verschiedenen Optimierungsansätze analytisch beurteilt werden. Basierend auf den theoretischen Resultaten sollen zielführende Massnahmen ausgewählt und anschliessend für die messtechnischen Überprüfung in einem Hardware-Prototyp implementiert werden. Im letzten Teil der Arbeit soll die erreichbare Leistungserhöhung durch Messungen am Prototyp verifiziert werden. Die Arbeit wird bei der ETH Spin-Off Firma CELEROTON TurboCell in Volketswil durchgeführt.

Christoph Gammeter, Celeroton AG, christoph.gammeter@celeroton.com

20 % Theory 40 % Implementation 40 % Testing

- Vorlesungen «Leistungselektronik», «Design of Power Electronic Systems» und/oder «Power Electronics I/II» - Hardware Testerfahrung Working language: English/German

Dr. Jürgen Biela

At HPE, model predictive control (MPC) is investigated as an alternative control method for power electronic systems since converters with MPC can achieve a fast dynamic behavior and incorporate system constraints. The challenging part is that for implementing MPC an optimisation problem has to be solved with limited resources in embedded systems within every sampling interval in real-time, which is typically very short in power electronic systems (range of a few μs). In this project, you will develop a toolbox for enabling a rapid realtime implementation of MPC based on implemented quadratic program (QP) solvers using the Intel high-level-synthesis (HLS) compiler. The toolbox will execute an optimization routine to compare the performance considering hardware resource constraints and verify the implementation through FPGA-in-the-loop experiments.

Min Jeong, ETL F14, jeong@hpe.ee.ethz.ch

30% Coding 50% Implementation 20% Simulation

• Interest/basic knowledge in coding and FPGA Working language: English

Dr. Jürgen Biela

The electrification of construction machinery, such as excavators or dump trucks, has recently been gaining popularity due to numerous technical, economical, and ecological benefits. At HPE, concepts to replace hydraulic excavators with electrical counterparts are investigated. The excavator’s battery voltage can vary substantially around its nominal value (up to ±25%). To boost this voltage up to a constant DC-link voltage for a motor drive (with energy recuperation), a highly compact and efficient bidirectional boost converter is required. In this project, you will commission a prototype system of a given boost converter design. This task includes the PCB, the magnetic components (inductors), the cooling system and the implementation of converter control & safety functions in VHDL. Thereafter, you will test the system at multiple operating points. Finally, you will make improvements to the PCB and/or the inductive components for an improved prototype system based on your findings during testing.

Simon Beck, ETL F12, beck@hpe.ee.ethz.ch

25% Control 10% Hardware Design 10% Simulation 30% Testing 25% VHDL Coding

Interest and knowledge in power electronic systems, Interest and knowledge in hardware design, Working language: English/German

Dr. Jürgen Biela

At HPE, a three-phase three-level inverter system is currently investigated for driving a permanent magnet synchronous motor (PMSM) in electric vehicles. In order to control the motor, various control strategies are possible, such as V/f control, field-oriented control (FOC), or direct torque control (DTC). Also, for the inverter circuit, various PWM modulation schemes such as three-level space vector modulation (SVM) are known. As an example, the figure above shows a three-level neutral point clamped (NPC) inverter topology and the three-level SVM scheme. In this project, you will first study different modulation schemes and motor control concepts by means of a literature review. After selecting a modulation and control concept, you will implement it for a given PMSM, first in simulations and then in an FPGA/microcontroller. In the end, if time permits, you will validate the implementation in a prototype system.

Ruida Zhang, ETL G12, zhang@hpe.ee.ethz.ch

20% Coding 20% Control 30% Simulation 30% Theory

• Interest/knowledge in power electronic systems and control • Interest/knowledge in electric motors Working language: English

Dr. Jürgen Biela

At HPE, research is performed on Plasma Pulse Geo Drilling (PPGD) as a potential alternative to traditional mechanical drilling methods for harnessing geothermal energy in large depths (up to 10 km). The PPGD technology is based on applying fast high voltage (several hundreds of kV) electrical discharges to rocks. These discharges create plasma channels inside the rock that effectively fragment the rock. The high voltage discharges are generated with a pulse generator, which requires suitable high voltage switches. A promising type of switch for the generator is the pseudo-spark gap, known for its extended lifetime. In this project, you will design a pseudo-spark gap based on design given in literature and evaluate its performance through FEM simulations. At the end of the project, you will present a potential design solution. If conducted as a master’s thesis, a prototype could also be developed and tested.

Joao Martins Junior, ETL G12, martins@hpe.ee.ethz.ch

30% Hardware Design 30% Implementation 10% Modelling 30% Simulation

• Knowledge in FEM simulations; • Knowledge in high voltage engineering. Working language: English

Dr. Jürgen Biela

At HPE, high efficiency power converters based on Wide Band Gap (WBG) semiconductor devices are developed. The WBG devices can operate at higher switching frequencies, enabling a reduced filter volume and an increased power density. However, parasitics resulting from the PCB layout induce overvoltage and overcurrent stresses on these devices. To minimize these effects, accurate parasitics models are crucial, these are usually obtained with FEM simulations. In this project, you will first get into the topic of FEM simulation and then get familiar with an existing work flow for parasitics extraction using Ansys Q3D Extractor, which is often used for parasitics analysis. Existing hardware designs will serve as an analysis example. As a next step, you will investigate different layouts to minimize especially gate loop parasitics in order to achieve the best possible current distribution between paralleled devices. In case of a master’s thesis, you will validate your simulation results by hardware measurement.

Maxwell Guerne-Kieferndorf, Ruida Zhang and Bharadwaj Raghuraman, ETL F13, gmaxwell@ethz.ch

20% Implementation 20% Modelling 50% Simulation 10% Theory

• Interest in power electronic systems • Interest in FEM simulations Working language: English/German

Dr. Jürgen Biela

Particle accelerators, such as the LHC at CERN, the SLS 2.0 at PSI, or the PETRA IV at DESY, require kicker systems to inject or extract particle bunches into or out of the particle beam. These kicker systems are driven by high-voltage pulses. For new synchrotrons like the SLS 2.0, the duration of these pulses must be in the nanosecond range to meet the strict timing requirements. This is impossible to achieve with normal semiconductor devices like MOSFETs. Therefore, pulse generators based on special diodes (drift step recovery diodes, DSRDs) with ultra-fast turn-off behavior are currently being investigated at HPE. To utilize these diodes as opening switches in pulse generators, they must be driven in a distinct manner. In this thesis, you will evaluate a possible circuit topology for driving these diodes. This requires modelling and simulating the circuit and its components with tools like LTspice, MATLAB, and COMSOL/Ansys. If time permits, a hardware can be designed, implemented, and tested.

Tobias Wagner, ETL F17, wagner@hpe.ee.ethz.ch

30% Coding 40% Simulation 30% Theory

• Interest/knowledge in power electronics • Interest in modeling and simulating components and circuits Working language: English/German

Dr. Jürgen Biela

The high blocking voltages of the latest wide-bandgap semiconductors have enabled power electronic converter systems to operate within the medium voltage range. A core component of these systems is the medium-frequency transformer (MFT), which provides the necessary galvanic isolation. To insulate the medium voltage side from the low voltage side, a significant fraction of the MFT’s overall volume is consumed by the insulation. Therefore, designing an optimal MFT also necessitates optimising its insulation system. This is where your work will be crucial. In this project, you will implement an optimisation routine in MATLAB that integrates state-ofthe- art insulation models, which are currently developed at HPE. Your optimisation results will uncover previously unutilised potential in MFT design by addressing limitations caused by the absence of insulation modelling. As a master’s thesis student, you will also have the opportunity to build and experimentally test the optimised transformer, bringing your design from theory to practical validation.

Bastian Korthauer, ETL G12, korthauer@hpe.ee.ethz.ch

50% Coding 15% Hardware Design 5% Implementation 15% Testing 15% Theory

• Interest in power electronics • Interest in high voltage engineering • Interest in code optimisation Working language: English/German

Dr. Jürgen Biela

Particle accelerators, such as the LHC at CERN, the SLS 2.0 at PSI, or the PETRA IV at DESY, require kicker systems to inject or extract particle bunches into or out of the particle beam. These kicker systems are driven by high-voltage pulses. For new synchrotrons like the SLS 2.0, the duration of these pulses must be in the nanosecond range, with rise and fall times in the subnanosecond range to meet the timing requirements. These requirements are impossible to achieve with normal semiconductor devices like MOSFETs and IGBTs. One possible approach is the use of pulse generators based on SiC JFETs as opening switches. To increase the switching speed, they are operated with gate boosting. In this thesis, you will analyze and implement a circuit topology to operate SiC JFETs with gate boosting. You will simulate the circuit with e.g. LTspice and design the hardware with Altium Designer. Furthermore, the JFETs must be characterized in the lab. Finally, you will evaluate the suitability of the JFETs for nanosecond pulse generators.

Tobias Wagner, ETL F17, wagner@hpe.ee.ethz.ch

20% Coding 30% Hardware Design 30% Simulation 20% Testing

• Interest in non-standard power electronic systems • Interest and knowledge in hardware design (Altium Designer) Working language: English/German

Dr. Jürgen Biela

Particle accelerators, such as the LHC at CERN, the SLS 2.0 at PSI, or the PETRA IV at DESY, require kicker systems to inject or extract particle bunches into or out of the particle beam. These kicker systems are driven by high-voltage pulses. For new synchrotrons like the SLS 2.0, the duration of these pulses must be in the nanosecond range, with rise and fall times in the subnanosecond range to meet the timing requirements. These requirements are impossible to achieve with normal semiconductor devices like MOSFETs and IGBTs. Therefore, pulse generators based on diodes with ultra-fast turn-off behavior are currently being investigated at HPE. Your task in this thesis will be to analyze and implement a circuit topology to assess the suitability of off-the-shelf diodes for nanosecond pulse generators. You will simulate the circuit (e.g. with LTspice), design a PCB with Altium Designer, and program a microcontroller or a FPGA. Finally, you will evaluate various diodes.

Tobias Wagner, ETL F17, wagner@hpe.ee.ethz.ch

20% Coding 40% Hardware Design 20% Simulation 20% Testing

• Interest in power electronics and semiconductor devices • Interest and knowledge in hardware design (Altium Designer) Working language: English/German

Dr. Jürgen Biela

Multilevel inverters are increasingly considered for propulsion systems of electric vehicles with high-voltage batteries due to their lower harmonic current ripple, reduced dv/dt stress on the insulation system, and the ability to use relatively low-voltage semiconductor switches. However, these benefits come with added complexities, such as unequal loss distribution among the switches and the need to balance, for example, flying capacitors highlighted in the figure. These challenges can be further aggravated during transient operation of the propulsion system. At HPE, for example, 4-level inverter topologies based on GaN HEMTs for electric vehicle applications are investigated. In this project, you will model a 4-level inverter topology in MATLAB/Simulink and analyze the loss distribution and capacitor balancing dynamics of the inverter during transient operation of the electric propulsion system. Additionally, you will investigate methods to balance the flying capacitors during transient operation.

Bharadwaj Raghuraman, ETL F14, braghuraman@ethz.ch

20% Control 60% Modelling 20% Theory

• Interest and knowledge in power electronic systems • Knowledge in MATLAB/ Simulink programming Working language: English

Dr. Jürgen Biela

GaN high-electron-mobility transistors (HEMTs) are increasingly popular in power electronic systems due to their advantages over Si/SiC devices. However, GaN HEMTs exhibit a dynamic behavior in on-state resistance, where the Rds,on immediately after switching on is higher than its DC value. Also, it has been found that the value of Rds,on is dependent on multiple factors, including the switching condition (hard or soft). The figure above shows an exemplary circuit to measure the Rds,on under hard or soft switching conditions. At HPE, a GaN HEMT is investigated for an inverter system, where accurate measurements of its dynamic Rds,on behavior are crucial for loss modeling and system optimization. In this project, you will design a setup for dynamic Rds,on measurements, covering clamping circuit design, PCB layout, and FPGA code implementation. In case of a master thesis, you will validate the setup and measure the characteristics of the device.

Ruida Zhang, ETL G12, zhang@hpe.ee.ethz.ch

10% Coding 55% Hardware Design 15% Simulation 20% Theory

• Interest/knowledge in design of power electronic systems Working language: English

Dr. Jürgen Biela

There are several core losses models, which are commonly used for the magnetic components’ design in power electronic converters. However, measurements remain essential for benchmarking these models. At HPE, various experimental setups exist to measure core losses under different conditions (sinusoidal and non-sinusoidal waveform, temperature, and frequency) for validating the loss models. In this project you will start by reviewing different experimental methods for loss measurements, considering the pros and cons and assessing the uncertainty of the measurement techniques. Based on the currently implemented two-winding method (as depicted in the figure), inductive and capacitive compensation methods will be compared in order to improve measurement accuracy. As a last step, you will design, build and commission an experimental setup together with the development of the necessary algorithms for the experimental measurements.

Marco Cotti and Miguel Astudillo, cotti@hpe.ee.ethz.ch

30% Coding 30% Hardware Design 20% Implementation 20% Testing

• Interest and knowledge in power electronic system • Interest and knowledge in electrical measurements Working language: English

Dr. Jürgen Biela

At HPE, an inverter for EVs based on GaN HEMTs is currently investigated. For optimising the design of the inverter, switching loss models have been developed, which require not only datasheet information, but also device-specific parameters so that device tolerances can be included. Parasitics such as packaging inductances need to be measured with a vector network analyser (VNA), and incomplete curves in the datasheet need to be characterised using a power device analyser (PDA). In this project, you will first get into the topic by understanding the key parameters of GaN HEMTs in the datasheet and the working principles of VNA and PDA. Then, you will design PCBs which are used as connectors between the device under test and the corresponding equipment. In the end, you will conduct the measurements (using VNA and PDA) and post-process the results. If time permits, you will also integrate the measurement results into the loss models.

Ruida Zhang, ETL G12, zhang@hpe.ee.ethz.ch

30% Hardware Design 50% Testing 20% Theory

• Interest/knowledge in power electronics and power semiconductors Working language: English

Dr. Jürgen Biela

Various magnetic materials as ferrites,iron powder, and electrical steel are used, for example, in the design of power electronic converters. In this project the focus is on powder cores, a material composed of magnetic particles homogeneously distributed within a non-magnetic binder. When the magnetic flux through the material varies with time, eddy currents are induced. Due to the insulation between the particles, these currents remain confined within the individual particles. By expressing the magnetic flux of the induced field and the magnetic voltage drop along the series of particles and binder, it is possible to evaluate the material’s magnetic permeability. A model that treats particles as cylinders has already been implemented to describe the material’s magnetic permeability over frequency. In this thesis, you will consider different geometries such as spheres and ellipsoids in order to increase the accuracy of the loss models, and you will adapt the existing model accordingly. Additionally, you will conduct a comparison between the models in terms of computational performance and accuracy.

Marco Cotti, ETL F11, cotti@hpe.ee.ethz.ch

50% Coding 30% Modelling 20% Theory

• Interest in power electronic systems and material science • Interest and knowledge in Electromagnetics Working language: English

Dr. Jürgen Biela

At HPE, an OnBoard Charger (OBC) for EVs with a battery voltage >800V is currently designed. To properly design the OBC, knowledge about the battery system behavior is required. Usually, an equivalent circuit model of the battery is sufficient. A further interesting characteristic of the battery is the influence of the charger current ripple on the battery lifetime. In this project, you will do an extensive literature review on the modelling of batteries. Your results from this investigation can then be used to determine if high-frequency ripple in the battery current has a significant influence on the battery’s lifetime. Based on this, you will determine the filtering requirements for the output voltage/current of the OBC. If higher current ripple is acceptable, a more compact OBC design can potentially be achieved. In the second part of the project, you will consider electrical and thermal models of the EV battery and use these to simulate the battery behavior over its lifetime, which will contribute to the design of the OBC control system.

Maxwell Guerne-Kieferndorf, ETL F13, gmaxwell@ethz.ch

40% Modelling 10% Simulation 50% Theory

• Interest in electric vehicle battery systems • Independent and structured work Working language: English/German

Dr. Jürgen Biela

At HPE, a highly efficient and compact 11kW OnBoard Charger (OBC) for EVs with a battery voltage >800V is currently designed. The OBC is based on GaN semiconductor devices, facilitating high switching speeds and therefore higher power density and efficiency. In this project, you will first get familiar with the control structure (grid currents & battery voltage) of the OBC system. An example controller structure for a 3ϕ AC/DC converter is shown in the figure above. This is an important part of the OBC system. You will start by reviewing different control and modulation schemes for OBCs. Then you will implement simulations of a suitable control scheme. As a next step, you will investigate the load behavior and include this in the simulation. Thereafter, you will design the full control system according to the dynamic performance requirements of the OBC and implement it on an FPGA/Microcontroller. Finally, you will validate your controller with the software ModelSim, which enables a realistic simulation of the VHDL code.

Maxwell Guerne-Kieferndorf, ETL F13, gmaxwell@ethz.ch

10% Coding 30% Control 20% Modelling 20% Simulation 20% VHDL Coding

• Interest in power electronic systems • Interest in control • Basic knowledge on FPGAs Working language: English/German

Dr. Jürgen Biela

At HPE, electric vehicles (EV) with a battery voltage >800V are investigated in order to exploit benefits in terms of overall cost reduction, power density, efficiency, material use and decreased charging time. There, GaN power semiconductors are also useful for achieving a high power density and efficiency due to their fast switching speeds and low switching losses. However, due to their lower blocking voltage of around 600V, multi-level converter topologies must be used. Your task in this project is to evaluate different multi-level bridge leg topologies in terms of losses and implementation effort. By performing simulations with the circuit simulator PLECS, first conclusions about the general behavior of the circuits can be made. There, the control requirements can be determined and implemented as well. In a final step, you will design prototype bridge legs, with a strong focus on the layout of switching cells for minimal parasitics. In case of an MA, the bridge legs can also be assembled, commissioned and loss measurements can be performed.

Maxwell Guerne-Kieferndorf, ETL F13, gmaxwell@ethz.ch

40% Hardware Design 40% Simulation 20% Testing

• Interest and knowledge in power electronic systems • Ideally hardware experience (especially for SA) Working language: English/German

Dr. Jürgen Biela

Magnetic materials are fundamental to both electrical machines and electronic power converters. Magnetic cores are present in virtually all devices that use electrical energy today. For an optimised component design, it is necessary to model the losses that will occur in the core during operation. For parametrising the models, a power electronic converter capable of generating suitable excitations needed to characterise magnetic losses has been built at HPE. In this thesis, you will design, implement, and test the control and protections of the power electronic converter. Based on an existing first implementation, you will design the control of the excitation current generated by a variable frequency and voltage inverter (up to 1MHz and up to 800V) to comply with imposed requirements, validated with the help of simulation tools. The code for the generation of the control signals is implemented using VHDL, and the general control of the measurement setup is implemented in LabVIEW.

Miguel Astudillo, astudillo@hpe.ee.ethz.ch

10% Coding 30% Control 30% Implementation 10% Simulation 20% VHDL Coding

• Interest and knowledge in power electronic systems. • Interest and knowledge in control engineering. Working language: English

Dr. Jürgen Biela

Magnetic materials are a key part of both electrical machines and power electronic converters, present in almost all devices that use electrical energy nowadays. At HPE, various models of magnetic components were developed, particularly physics-based loss models for magnetic cores. Therefore, an accurate characterisation of materials is essential for advancing these models. In this thesis, you will characterise the electromagnetic properties of magnetic materials used in power electronics, including ferrites, laminated materials, and iron powder. The main focus is the development, analysis, and design of an experimental setup to measure the permittivity and conductivity of the core material. You will begin with a review of the state of the art to define the necessary accuracy and parameter ranges. Subsequently, you will design the required custom measuring fixtures, which will supplement the commercial instruments already available in the laboratory.

Miguel Astudillo and Marco Cotti, astudillo@hpe.ee.ethz.ch

30% Hardware Design 20% Modelling 30% Simulation 20% Theory

• Interest and knowledge in power electronic systems. • Interest in materials science and electromagnetism. Working language: English

Dr. Jürgen Biela

Magnetic materials are critical parts of electrical machines and power electronic converters. During the design of the magnetic devices, the power losses and the maximum temperature are among the most important design criteria, However, only the surface temperature is accessible via direct measurements. Thus, thermal models for magnetic components are needed to predict the internal hot spot. In this thesis, you will analyse how power losses and ambient conditions affect the temperature distribution in magnetic cores, with a special focus on transients and anisotropy. You will use simulation tools and theoretical models for the theoretical analysis, performing a sensitivity analysis of the ambient conditions and limit cases. In the next step, you will carry out the measurements, including the design of the necessary characterisation setup. As a final goal, your thesis will serve as a validation of the thermal aspects for global loss models in magnetic cores.

Miguel Astudillo and Marco Cotti, astudillo@hpe.ee.ethz.ch

30% Coding 10% Hardware Design 30% Simulation 30% Theory

• Interest and knowledge in power electronic systems. • Interest in materials science and heat transfer. Working language: English

Dr. Jürgen Biela

The design of power electronic systems is typically performend with optimisation procedures, where analytical models of the system and its components are required. One important "component" of the power electronic converter systems is the switching cell (i.e. bridge leg + DC-link capacitor). At HPE, various switching cell configurations are investigated to minimize the converter losses and volume. A switching cell design consists of the semiconductor devices, the gate drivers, the DC-link capacitors, and the heat sink. The arrangement of those components has significant impact on the electro-thermal performance of the converter. In this project, you will implement a Matlab tool for the design procedure of the switching cell using object-oriented programming. Therefore, you will first familiarise yourself with object-oriented programming in Matlab and the existing HPE modelling framework. You will then analyse the current implementation of the switching cell design procedure and adapt it to the HPE modelling framework.

G. Papadopoulos, ETL F13, papadopoulos@hpe.ee.ethz.ch

40% Coding 40% Implementation 10% Modelling 10% Theory

• Experience in Matlab • Basic knowledge of objectoriented techniques is a plus but not mandatory Working language: English

Dr. Jürgen Biela

The design of power electronic systems is typically performed with optimisation procedures, where analytical models of the system and its components are used. One important "component" of power electronic converter systems is the switching cell (i.e. bridge leg + DC-link capacitor). At HPE, various switching cell configurations are investigated to optimise and simplify the design of power electronics converter systems. One of the major components of a switching cell is the heat-sink. The performance of the heat sink/cooling system has a significant impact on the efficiency and power density of the converter. In this project, you will develop an analytical thermal model of the switching cell and implement the 3D representation in the X3D format based on a software tool developed in Matlab. Finally, you will intergrate the switching cell model into a converter system and evaluate the temperature distribution using FEM simualation. The final goal is to automate the process of performing thermal simulations of different converter arrangements.

G. Papadopoulos, ETL F13, papadopoulos@hpe.ee.ethz.ch

30% Coding 40% Modelling 20% Simulation 10% Theory

• Interest and knowledge in power electronic systems • Interest/knowledge in thermal modeling Working language: English

Dr. Jürgen Biela

At HPE, research is performed on Plasma Pulse Geo Drilling (PPGD) as a potential alternative to traditional mechanical drilling for harnessing geothermal energy in large depths (up to 10 km). PPGD technology is based on applying high voltage (several hundreds of kV) electrical discharges to rocks. These discharges create a plasma channel inside the rock that effectively fragments the rock. A high voltage pulse generator must be positioned near the drilling electrodes for applying those discharges to the rock. Therefore, the generator must be compact to fit inside the drilling hole. A Marx generator is a possible interesting option for ruling the pulse generator. In this project, you will use FEM simulations to model the components of Marx generator in order to avoid unwanted high electrical fields which may cause electrical failures. Furthermore you will design customised inductors for the equipment. Finally, you will present a possible optimised design for the application.

Joao Martins Junior, ETL G12, martins@hpe.ee.ethz.ch

30% Hardware Design 30% Modelling 10% Simulation 30% Theory

• Knowledge in FEM simulations; • Knowledge in Matlab; • Knowledge in high voltage engineering. Working language: English

Dr. Jürgen Biela

At HPE, research is performed on Plasma Pulse Geo Drilling (PPGD) as a potential alternative to traditional mechanical drilling for harnessing geothermal energy in large depths (up to 10 km). PPGD technology is based on applying high voltage (several hundreds of kV) electrical discharges to rocks. These discharges create a plasma channel inside the rock that effectively fragments the rock. A high voltage pulse generator must be positioned near the drilling electrodes for applying those discharges to the rock. Therefore, the generator must be compact to fit inside the drilling hole. A Tesla transformer is a possible interesting option for generating the required high voltage pulses. In this project, you will use analytical as well as FEM models to optimise a Tesla transformer to meet the size and efficacy constraints of the project. At the end, you will present a possible design solution. In case of a master thesis, a virtual prototype can be designed.

Joao Martins Junior, ETL G12, martins@hpe.ee.ethz.ch

20% Hardware Design 40% Modelling 10% Simulation 30% Theory

• Knowledge in Matlab; • Knowledge in high voltage engineering. Working language: English

Dr. Jürgen Biela

Due to the advances in the technology of wide-band gap switching devices unprecedented switching speeds can be achieved in power electronic converters. However, the fast switching can cause significant oscillations in the transformer’s winding structure, which can negatively impact its overall performance and insulation lifetime. At HPE, these internal overvoltages are modelled, which helps designing reliable transformers. As part of this project, you will design a medium frequency transformer (MFT) with an improved overvoltage behaviour. You will start by familiarising with a state of the art overvoltage model by investigating different design strategies that reduce the MFT’s voltage oscillations. Next, you will design and build (only MA) a suitable MFT prototype. Once, the MFT is constructed you will verify the design through performing a series of measurements and by comparison to an existing benchmark-design. This is a unique opportunity to gain hands-on experience in an exciting and rapidly advancing field. Good results are likely to be published.

Bastian Korthauer, ETL G12, korthauer@hpe.ee.ethz.ch

50% Coding 15% Hardware Design 5% Implementation 15% Testing 15% Theory

• Interest in power electronics • Interest in code optimisation Working language: English/German

Dr. Jürgen Biela

At HPE, various basic switching cell configurations are investigated to optimise the design of power electronics converter systems. A switching cell design consists of the semiconductor devices, the gate drivers, the DC-link capacitors, and the heat sink. The arrangement of those components has significant impact on the electrical and thermal performance of the converter. In this project, you will design PCBs for a few different half-bridge switching cell configurations. The PCB design will be performed in Altium and evaluated in terms of parasitics. Eventually, you will build and test the designed switching cell as well as measure the switching losses. In case of a master thesis, a comparison of the different arrangements will follow in order to examine the trade-off between efficiency and power density.

G. Papadopoulos, ETL F13, papadopoulos@hpe.ee.ethz.ch

40% Hardware Design 20% Simulation 30% Testing 10% Theory

• Interest and knowledge in power electronic systems • Interest/knowledge in PCB design and testing Working language: English

Dr. Jürgen Biela

Increasing the efficiency of electric powertrains, and hence the range of an electric vehicle, is a crucial aspect for mass adoption of electric vehicles. The main loss component in electric powertrains are the high-frequency iron losses in the electric motor, so targeting this component will yield the most benefit. The iron losses can be reduced, for example, by having a near-sinusoidal flux density variation through the use of multilevel inverters. At HPE, for example, 4-level inverter topologies with different modulation strategies and their impact on high-frequency losses are investigated. Modulation strategies can be implemented either through carrier or space vector based approaches. In this project, you will analyze both of these approaches in MATLAB simulation environment and also implement them on a DSP/ FPGA controller. Additionally, you will also do a comparison of these methods based on implementation effort, computational time, and memory allocation.

Bharadwaj Raghuraman, ETL F14, braghuraman@ethz.ch

10% Control 40% Implementation 40% Simulation 10% Theory

• Interest and knowledge in power electronic systems • Interest/knowledge in VHDL programming Working language: English

Dr. Jürgen Biela