In recent years the vehicle industries have been making much efforts to reduce the environmentalimpact by switching from the traditional combustion engine to electrification with battery driven electricvehicles. Producing electric trucks requires more batteries and operates at a higher voltage and currentthan commercial electric cars. Therefore, detection and protection from short-circuits are crucial issuesin the development of these vehicles to ensure safety. This master thesis project aims to investigatedifferent methods for current measurement, which are commercially available and used in the batteryjunction box in an electric vehicle for current monitoring and detection of overcurrent and short-circuits. A practical experimental validation is then performed to test the desaturation detection method as ashort-circuit detection method with a solid state breaker. The experimental results showed that theshort-circuit could be detected within just 7µs and the total time for the solid state breaker to detectand cut the circuit could be done within around 15µs. The discussion around the current measurementmethod came to the conclusion that the Hall sensor or the flux gate current transducer could be apossible replacement of the shunt that is currently being used in order to reduce losses as the systemoperates at higher current levels. Comparison of this method with different existing current measurement sensors is suggested to do inthe future work.

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Continuum mechanics is used to model the mechanical behaviour of concrete structures subjected to high rates of loading in defence applications. Large deformation theory is used and an isotropic elastic-plastic constitutive equation with isotropic hardening, damage and strain rate dependent loading surface. The hydrostatic pressure is governed by an equation of state. Numerical analysis is performed using the finite element method and the central difference method for the time integration. Projectile penetration is studied and it is concluded that it is not suitable to use material description of the motion of both the target and the projectile together with an erosion criterion. Instead, the material description should be used only for the projectile and the spatial description for the target. In this way the need for an erosion criterion is eliminated. Also, in the constitutive model used it is necessary to introduce a scaling of the softening phase in relation to the finite element size, in order to avoid strain localization. Drop weight testing of reinforced concrete beams are analysed, where a regularisation is introduced that renders mesh objectivity regarding fracture energy release. The resulting model can accurately reproduce results from material testing but the regularisation is not sufficient to avoid strain localization when applied to an impact loaded structure. It is finally proposed that a non-local measure of deformation could be a solution to attain convergence. The third study presents the behaviour of a concrete constitutive model in a splitting test and a simplified non-local theory applied in a tensile test. The splitting test model exhibits mesh dependency due to a singularity. In the tensile test the non-local theory is shown to give a convergent solution. The report https://www.diva-portal.org/liu/webform/form.jsp#paper0is concluded with a discussion on how to better model concrete materials.

Following continued emission of greenhouse gases climate change is increasingly becoming a greater threat to the continued well-being of people around the world. While airports contribute around 2.5% of the global greenhouse emissions it delivers the greenhouse gases higher up in the atmosphere which increases the negative effect of greenhouse gases. In response airports around Sweden are working towards implementing green airports and flights. This will be done in part by supplying the facility with green energy from local green power facilities but also in part by replacing the traditional fuel from petroleum-based flights to electrical flights. This report examines the required solar plant to support both the existing facility and the future planned electrical flights with solar energy. This report will examine the required size and configuration of the solar plant to supply necessary power with the help of the simulation tool SAM and weather data from NSRDB. This report will also investigate the current system capabilities and required changes to handle the increased load demand and power production into the facility using power flow simulations of the current system with the future loads

Microwave materials have been widely used in a variety of applications ranging from communication devices to military satellite services, and the study of materials properties at microwave frequencies and the development of functional microwave materials have always been among the most active areas in solid-state physics, materials science, and electrical and electronic engineering. In recent years, the increasing requirements for the development of high speed, high frequency circuits and systems require complete understanding of the properties of materials function at microwave frequencies. Ferroelectric materials usually have high dielectric constants, and their dielectric properties are temperature and electric field dependent. The change in permittivity as a function of electric field is the key to a wide range of applications. Ferroelectric materials can be used in fabrication capacitors for electronic industry because of their high dielectric constants, and this is important in the trend toward miniaturization and high functionality of electronic products. The simple tunable passive component based on ferroelectric films is a varactor which can be made as a planar structure, and electrically tunable microwave integrated circuits using ferroelectric thin films can be developed. Therefore, it is very important to characterize the dielectric constant and tunability of ferroelectric thin films. This thesis shows experimental results for growth, crystalline properties and microwave characterization of Na0.5K0.5NbO3 (NKN), AgTa0.5Nb0.5O3 (ATN), Ba0.5Sr0.5TiO3 (BST) as well as AgTaO3 (ATO), AgNbO3 (ANO) thin films. The films were grown by Pulsed Laser Deposition (PLD) and rf-magnetron sputtering of a stoichiometric, high density, ceramic NKN, ATN, BST target onto single crystal LaAlO3(LAO), Al2O3 (sapphire), and Nd:YAlO3, and amorphous glass substrates. By x-ray diffractometry, NKN, ATN, BST films on LAO substrates were found to grow epitaxially, whereas films on r-cut sapphire substrates were found to be preferentially (00l) oriented. Coplanar waveguide interdigital capacitor (CPWIDC) structures were fabricated by standard photolithography processing and metal lift-off technique. Microwave properties of the NKN/Sapphire and ATN/Sapphire with CPW structures were characterized using on-wafer microwave measurement technique. Measurement setup is composed of network analyzer, probe station, and microwave G-S-G probes. External electric field through the connection between network analyzer and power supply was applied to measure voltage tunability. Measured S-parameter were used for the calculation of capacitance, loss tanδ, tunability and K-factor. The NKN films interdigital capacitors with 2 μm finger gap on Nd:YAlO3 showed superior performance compared to ATN in the microwave range from 1 to 40 GHz. Within this range, the voltage tunability (40V, 200 kV/cm) was about 29%, loss tangent ∼ 0.13, K-factor = tunability/tanδ from 152% @ 10GHz to 46% @ 40GHz. The microwave performance of ATN film CPWIDC with 2 μm finger gap on sapphire substrate in the microwave range from 1 to 40 GHz showed that frequency dispersion is about 4.3%, voltage tunability was 4.7% @ 20GHz and 200 kV/cm, loss tangent ∼ 0.068 @ 20GHz, K-factor = tunability/tanδ is ranged from 124% @ 10GHz to 35% @ 40GHz. The BST films CPWIDC with 2μmfinger gap on Al2O3 substrate showed frequency dispersion of capacitance in the microwave range from 1 to 40 GHz about 17%, voltage tunability = 1 - C(40V)/C(0) ∼ 22.2%, loss tangent ∼ 0.137 @ 20GHz, and K-factor = tunability/tanδ from 281% @ 10GHz to 95% @ 40GHz. / QC 20101207

Electricity providers has a growing interest in moving towards Renewable Energy Sources (RES) for power generation due to their attractive features. This has caused phasing out of coal, oil and nuclear power plants which use large synchronous generators for power production. These large rotational masses provide inertia to the electricity grid which compensate the sudden frequency instabilities of the grid. Therefore, lowering the system inertia opens up to frequency instabilities in the electricity grid.  As a solution for the lower system inertia, the concept of Fast Frequency Reserve (FFR) has been introduced. The timeframe of primary generation reserves can be too slow in case of a sudden frequency instability. Amongst the energy sources that can be used for FFR, this thesis work explores the possibility of a Battery Energy Storage System (BESS) to be used in FFR. To accomplish this objective, a total BESS system including power electronic converters for integration to the grid is designed in this work. The software of choice for simulation is Matlab/Simulink.  This work uses a hybrid battery model proposed by previous research which is a combination of runtime model and Thevenin model. A bidirectional Buck-Boost converter integrated with a current controller has been used as the DC-DC converter. An outer voltage control loop integrated with the inverter dq current controller has been used to connect the BESS to the gird. The function of each subsystem is observed to verify their functionality. The hybrid battery model is tested by comparing results with the battery model available in Simulink. Finally, power delivery to grid under FFR activation requirements is observed.  Results show that the hybrid battery model is a good approximation to represent a real battery cell in electrical grid applications. The simulation time can be reduced by replacing the series battery cell configuration used in this work with the Simulink battery model. The power delivery to the grid shows BESS is a reliable energy resource that can be used for FFR.

Implantable biomedical wireless sensors provide monitoring of vital health signs such as oxygen, temperature and intraocular pressure and may help to analyse and detect diseases in humans and animals. However, one of the design challenges of implantable devices is providing a safe and reliable energy source. Replaceable batteries are one of the most common methods for powering up implantable devices and have been used in e.g.cardiac pacemakers for decades. However, the need for a regular battery replacement may require surgical incisions. Multiple studies have been done on energy harvesting from ambient energy sources to provide the required power for the operation of the implantable sensor and thus reducing the need for battery replacement. In this work, a circuit-level radio frequency (RF) energy harvesting system has been designed and simulated in 65 nm CMOS process technology. The system consists of an AC-DC converter, a DC-DC converter, a Ring oscillator, a Buffer, and a Voltage sensor with comparators, dividers and a reference generator. The rectifier operates at a frequency of 900 MHz and offers a power conversion efficiency (PCE) of 71%. The doubler works at 50 MHz with a voltage conversion efficiency (VCE) of 98%. Additionally, the Voltage sensor monitors the voltage level of the energy-storing unit, that in this project is intended to be an mm-size rechargeable battery. If the voltage level is equal to or higher than a threshold value, Vref, the harvesting system will be in discharging mode. Similarly, if the voltage level is below Vref, then the system will be in charging mode.

Energy harvesting can be used to consume the potential power of the surrounding environment. This harvesting can be done in different ways, some common energy harvesting modalities are vibrations, heat differences, solar power, and RF energy. In this Master Thesis, these different methods for harvesting energy are studied and the one that is the most suitable for an environment inside an embankment dam is further explored. If some energy harvesting modalities can operate well in that environment then it might be possible to monitor the embankment dam from the inside. The hope is to create an energy harvesting platform equipped with some suitable sensors which can be placed inside an embankment dam and collect data for a longer duration of time. Considering how an embankment dam is structured, it was concluded that the best possible energy harvesting method is wireless ultra-high frequency radio signals. An RF energy harvesting platform was created and tested, both in a laboratory and buried underground, mimicking the environment inside an embankment dam. These tests were measured and the results showed some promise that it is possible to use this energy harvesting method to power a sensor platform underground.

Since 2003, when the first batch of academic Cubesats was launched, 463 of these satellites havereached orbit. The issues faced in the early years were documented and since then the marketof Commercial off-the-shelf components, launch brokers and other auxiliary companies hassky-rocketed. Despite of the popularization of this educational satellites, or perhaps becauseof it, the rate of failures in this type of Cubesats kept constant over the years.The first part of this thesis explores the issues associated with development of academiccubesats found in literature, as well as the good practices and recommendations given by theteams. The studied works are divided in periods in order to examine possible trends in thetypes of issues and good practices reported.The document continues with an introduction to new paradigms and methodologies for ProjectManagement and Systems Engineering, paying special attention to Agile methodologies andMBSE and how they are, or could be applied, to academic Cubesat projects to mitigate thecommon issues and implement good practices.The use case of Cubesat for Radiation Environment Monitoring Experiment, the project wherethe author did his Master’s internship, is used to introduce the Time and Space Partitioningarchitecture in embedded systems, a very interesting approach that provides more reliabilitythan usual approaches and some project management benefits.Finally the use case of APTAS, another academic Cubesat project where the author wasinvolved, is used to illustrate how the issues and good practices mentioned in the first sectionaffect projects. This is achieved by extracting metrics about student engagement, turnoverratios and a thorough examination of the internal resources of the project.

The UnoSat Platform is a software and 3D structure platform built with Arduino Uno boardsthat allows easier implementation of a satellite project in a 1-n unit CubeSat format. It isdesigned to improve and speed up development of balloon - nanosat projects of the M2 TSImaster. It provides a 3D-printable Lego based structure that can be extended by stackingmultiple pieces on top of each other. The structure parts allow to quickly increase thenumber of Arduinos and add shields on top of already integrated Arduinos. Because ofthis, the structure allows for easy prototyping, and printed pieces can be reused in futureprojects. The platform also provides a communication system that is very efficient andreduces the possibilities of programming mistakes when implementing communication. Itallows serializing and parsing data into and from a binary format, provides protection againsttransmission errors via cyclic redundancy checksum and allows dynamically sized messagepayloads. Additionally, it supports one way or both ways communication not only between agroundstation and an embedded device, but also between two embedded devices. The codeon the embedded device is generated specifically for a communication configuration, whichmakes it very efficient in terms of processing and memory usage on the embedded device.