A modern vehicle is controlled by a distributed network of embedded devices - Electronic Control Units. The software of these devices is updated over an easily accessible and standardised diagnostic interface. Their hardware capabilities are very low, and thereby the security implementations are fairly minimalistic. This thesis analyses the Electronic Control Units used in the heavy-duty vehicle company Scania for security vulnerabilities. First, a list of security requirements was compiled. The implementation of these requirements was verified on several Electronic Control Units by the application of software testing methods. Testing identified two potentially dangerous shortfalls: short encryption seeds used in the authentication challenge, and a lack of reliable software source verification. These vulnerabilities were validated by performing experimental attacks. A brute-force attack was performed on a device with 2-byte seeds and keys. Next, an active man-in-the-middle attack was successfuly carried out to bypass authentication and ash the Electronic Control Unit with arbitrary software. Additionally, a passive man-in-the-middle attack was performed to sniff and store software files. The final attack was a combination: a valid seed and authentication code pair was sniffed over a flashing session, followed by using the pair to gain access later. To mitigate these attacks, it is most important to use long authentication seeds and keys, and implement all security standards. Public-key cryptography may also be an alternative for authentication. Software data encryption could be considered for integrity and confidentiality. A less computation-intense solution would be adding cryptographic signatures to messages.

Silicon Carbide (SiC) is suggested as a superior material for high temperature and high power electronic applications, thanks to its excellent properties. In this thesis, design and measurements of integrated circuits in bipolar 4H-SiC aiming for high temperature power applications are reported. On the low power side, a linear voltage regulator is demonstrated followed by introduction of a general-purpose opamp, which is employed to build other circuits such as a Schmitt trigger and a relaxation oscillator. On the high power side, a monolithic drive circuit for power BJTs is designed and tested in different loading conditions including resistive, capacitive and finally together with a commercial power BJT. The aforementioned circuits have been tested in the temperature range 25 - 500 °C, and are operational in the full range. The performance of each circuit is analyzed and directions for future work is suggested. The integrated circuits of this thesis set the reference for future advances in power integrated circuits in bipolar SiC. / <p>QC 20141208</p>

<p>QC 20150512</p>

Nowadays, due to lack of a strong interconnection between electric power systems within EU, there is a concern about the restricted power exchange. On the other hand, one of the factors which results in necessity of improving the level of power exchange is development of renewable energy sources such as offshore wind farms. Multi-terminal HVDC (MTDC) systems are supposed to be one of the cost-effective ways to aggregate a huge amount of renewable energies on one side and on the other side connect it to the main AC system through a common DC network. Possibility of such connections has led to the proposition of a meshed DC grid which connects several renewable energy sources and large AC systems. In order to fully take advantages of such AC-DC systems in the realsize power systems, extensive research has to be carried out to reveal their steady state and dynamic behavior. This thesis addresses different steady state aspects of such hybrid AC-DC systems. In the first part of thesis, we develop a multi-option power flow approach for hybrid AC-DC grids. The main contribution of this approach is that only one additional state variable is added to the AC and DC variables for each slack converter to handle the slack converter losses. Doing so, all AC, DC and converter equations are solved simultaneously. This makes the power flow algorithm much simpler than the sequential approaches where one external iterative loop is assigned to compute the converter losses. Such a high number of iterative loops in the sequential approaches makes the algorithm not only complicated and time consuming, but also unreliable. In the second part of thesis, given the nonconvex nature of Power Flow Optimisation (OPF) problem, a convex OPF formulation for AC grids with embedded DC networks based on the new Line Flow Based (LFB) variablesand in the form of Second Order Cone Programming (SOCP) is developed. SOCPs are a general form of linear programming accompanied by nonlinear constraints in the form of convex cones which can be efficiently solved through Interior Point methods (IPMs). / <p>QC 20130116</p>

One barrier to sustainable development is considered to be greenhouse gas emissions and pollution caused by transport, why climate targets are set around the globe to reduce these emissions. Electric vehicles (EVs), may be a sustainable alternative to internal combustion engine vehicles since having EVs in the car park creates an opportunity to reduce greenhouse gas emissions. This is due to the efficiency of the electric motor. For EVs with rechargeable batteries the opportunity to reduce emissions is also dependent on the generation mix in the power system. EVs with the possibility to recharge the battery from the power grid are denoted plug-in electric vehicles (PEVs) or plug-inhybrid electric vehicles (PHEVs). Hybrid electric vehicles (HEVs), without external recharging possibility, are not studied, hence the abbreviation EV further covers PHEV and PEV. With an electricity-driven private vehicle fleet, the power system will experience an increased amount of variable electricity consumption that is dependent on the charging patterns of EVs. Depending on the penetration level of EVs and the charging patterns, EV integration creates new quantities in the overall load profile that may increase the load peaks. The charging patterns are stochastic since they are affected by the travel behavior of the driver and the charging opportunities which imply that the EV integration also will have an effect on the load variations. Increased load variation and load peaks may create a need for upgrades in the grid infrastructure to reduce the risk for losses, overloads or damaging of components. However, with well-designed incentives to the EV users the variable electricity consumption due to electric vehicle charging (EVC) may become a flexible load that can help the power system mitigate load variations and load peaks. The aim with this licentiate thesis is to investigate the impact of EVC on load profiles and load variations. The thesis reviews and categorizes EVC models in previous research. The thesis furthermore develops electric vehicle charging models to estimate the charging impact based on charging patterns induced by private car travel behavior. The models mainly consider uncontrolled charging (UCC) related to stochastic individual car travel behavior and induced charging needs for PHEVs. Moreover, the thesis comments on the potential of individual charging strategies (ICS) with flexible charging and external charging strategies (ECS). Three key factors are identified when considering the impact of EVC on load profiles and load variations. The key factors are: The charging moment, the charging need and the charging location. It is concluded that the level of details concerning the approach to model these key factors in EVC models will impact the estimations of the load profiles. This means that models taking into account a higher level of mobility details will be able to create a more realistic estimation of a future UCC behavior, enabling for more accurate estimates of the impact on load profiles and the potential of ICS and ECS. / <p>QC 20130116</p>

With recent advances in power electronic technology, High-Voltage Direct Current (HVDC) transmission system has become an alternative for transmitting power especially over long distances. Multi-Terminal HVDC (MTDC) systems are proposed as HVDC systems with more than two terminals. These systems can be geographically wide. While in AC grids, frequency is a global variable, in MTDC systems, DC voltage can be considered as its dual. However, unlike frequency, DC voltage can not be equal across the MTDC system. Control of DC voltage in MTDC systems is one of the important challenges in MTDC systems. Since the dynamic of MTDC system is very fast, DC voltage control methods cannot rely only on remote information. Therefore, they can work based on either local information or a combination of local and remote information. In this thesis, first, the MTDC system is modeled. One of the models presented in this thesis considers only the DC grid, and effects of the AC grids are modeled with DC current sources, while in the other one, the connections of the DC grid to the AC grids are also considered. Next, the proposed methods in the literature for controlling the DC voltage are described and in addition to these methods, some control methods are proposed to control the DC voltage in MTDC system. These control methods include two groups. The first group (such as Multi-Agent Control methods) uses remote and local information, while the second group (such as Sliding Mode Control and H¥ control) uses local information.The proposed multi-agent control uses local information for immediate response, while uses remote information for a better fast response. Application of Multi-Agent Control systems leads to equal deviation of DC voltages from their reference values. Using remote information leads to better results comparing to the case only local information is used. Moreover, the proposed methods can also work in the absence of remote information. When AC grid is considered in the modeling, the MTDC system has anon-linear dynamic. Sliding Mode Control, a non-linear control method with high disturbance rejection capability, which is non-sensitive to the parameter variations, is applied to the MTDC system. It controls the DC voltage very fast and with small or without overshoot. Afterward, a static state feedback H¥ control is applied to the system which minimizes the voltage deviation after a disturbance and keeps the injected power of the terminals within the limits. Finally, some case studies are presented and the effectiveness of the proposed methods are shown. All simulations have been done in MATLAB and SIMULINK. / <p>QC 20140911</p>

No description available.

No description available.

Heavy metals are metallic elements with a density of at least 5 g/cm^3. Some heavy metals exist in nature and within organisms naturally, but many heavy metals are poisonous at low concentrations and the amount of heavy metals in nature has increased because of human activity, both in water and on land. X-ray fluorescence is a suitable method to measure heavy metals. X-ray fluorescence, or XRF as its abbreviated, is a measurement method that uses fluorescent x-ray radiation from elements to identify and quantify. Mitt University in Sundsvall has an x-ray lab that has a portable x-ray fluorescence instrument that has been used to conduct measurements. The samples have been sea water and bottom sediment from three different areas in Gävlebukten. One of the areas had multiple big industries nearby, one was next to the city and one on the countryside. This work shows that usage of a portable XRF instrument to measure heavy metals in sediment produces a good result. Multiple metals were detected and one sample contained mercury in a high concentration. Measurements of sea water had too low signal to noise ratio to show any presence of heavy metals in all but one sample. This assumes to be because of waters interaction with x-ray radiation in combination with the low concentration of the metals and that a too short measurement time was used.

A multi-agent system is composed of interconnected subsystems, or agents. In control of multi-agent systems, the aim is to obtain a coordinated behavior of the overall system through local interactions among the agents. Communication among the agents often occurs over a wireless medium with finite capacity. In this thesis, we investigate multiagent control systems where inter-agent communication is modelled by discrete events triggered by state conditions. In the first part, we consider event-triggered pinning control for a network of agents with nonlinear dynamics and time-varying topologies. Pinning control is a strategy to steer the behavior of a multi-agent system in a desired manner by controlling only a small fraction of the agents. We express the controllability of the network in terms of an average value of the network connectivity over time, and we show that all the agents can be driven to a desired reference trajectory. In the second part, we propose a control algorithm for multi-agent systems where inter-agent communication is substituted with a shared remote repository hosted on a cloud. Communication between each agent and the cloud is modelled as a sequence of events scheduled recursively by the agent. We quantify the connectivity of the network and we show that it is possible to synchronize the multi-agent system to the same state trajectory, while guaranteeing that two consecutive cloud accesses by the same agent are separated by a finite time interval. In the third part, we propose a family of distributed algorithms for coverage and inspection tasks for a network of mobile sensors with asymmetric footprints. We develop an abstract model of the environment under inspection and define a measure of the coverage attained by the sensor network. We show that the sensor network attains nondecreasing coverage, and we characterize the equilibrium configurations. The results presented in the thesis are corroborated by simulations or experiments. / <p>QC 20160909</p>