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  • 1.
    A. M. Naiini, Maziar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Horizontal Slot Waveguides for Silicon Photonics Back-End Integration2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.

    The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.

    The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.

    From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.

    With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.

     

     

     

     

  • 2.
    A. Sani, Negar
    Linköping University, Department of Science and Technology, Physics and Electronics.
    M-PSK and M-QAM Modulation/Demodulation of UWB Signal Using Six-Port Correlator2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays high speed and high data rate communication are highly demanded. Consequently, wideband and high frequency transmitter and receivers should be designed. New transmitters and receivers should also have low power consumption, simple design and low manufacturing price in order to fulfill manufacturers’ requests for mass production. Having all above specifications, six-port correlator is a proper choice to be used as modulator and demodulator in transmitters and receivers.

    In this thesis the six-port correlator is introduced, modeled and simulated using Advanced Design System (ADS) software. A simple six-port transmitter/receiver system with a line of sight link is modeled and analyzed in BER, path length and noise terms. The modulation in this system is QAM, frequency is 7.5 GHz and symbol rate is 500 Msymbol/s.

    Furthermore two methods are proposed for high frequency and high symbol rate M-PSK and M-QAM modulation using six-port correlator. The 7.5 GHz modulators are modeled and simulated in ADS. Data streams generated by pseudo random bit generator with 1 GHz bandwidth are applied to modulators. Common source field effect transistors (FETs) with zero bias are used as controllable impedance termination to apply baseband data to modulator. Both modulators show good performance in M-PSK and M-QAM modulation.

  • 3.
    Aamir, Syed Ahmed
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, J Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A 500-MHz low-voltage programmable gain amplifier for HD video in 65-nm CMOS2010In: Proceedings of 28th IEEE Norchip Conference., NORCHIP'10, Tampere: www.ieee.org , 2010, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    This work describes the implementation of a 1.2-V programmable gain amplifier (PGA) for high-definition (HD) video digitizers in a 65-nm digital CMOS process. The “pseudo” switched-capacitor (SC) PGA architecture buffers the video signal, without switching, during the active video. The SC circuitry is used for setup of DC operating point during horizontal and vertical blanking periods. Additionally, it compensates for the `sync-tip' of analog video signals to an equal blanking level for increased dynamic range to the digitizer following the PGA. The operational transconductance amplifier (OTA) employed as main amplifier in the PGA is a pseudo-differential, positive-feedback input stage architecture with a common-mode feedforward (CMFF) technique. The common-mode feedback (CMFB) is provided once two OTAs are cascaded. Schematic-level simulation results show that the OTA maintains a -3-dB bandwidth of 550 MHz, while keeping the distortion HD3 at -60 dB for a 30-MHz, 850 mVpp high definition video signal. The 88 dB DC gain is distributed among four OTA stages and the overall, combined PGA achieves a signal-to-noise ratio of 63 dB. Due to only two stacked transistors, it achieves high output swing of ±0.85 V, 1240 V/μs slew rate while consuming 10.4 mW power.

  • 4.
    Aamir, Syed Ahmed
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, J Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A 1.2-V pseudo-differential OTA with common-mode feedforward in 65-nm CMOS2010In: 17th IEEE International Conference on Electronics, Circuits, and Systems., www.ieee.org , 2010, 29-32 p.Conference paper (Refereed)
    Abstract [en]

    In this work, we describe the implementation of a 1. 2-V pseudo-differential operational transconductance amplifier (OTA) with common-mode feedforward (CMFF) and inher­ent common-mode feedback (CMFB) in a 65-nm, digital CMOS process. The OTA architecture provides an inher­ent CMFB when cascaded OTA structures are utilized andthis work has studied a cascaded amplifier consisting of fourstages. Due to the low-gain using core 65-nm circuit de­vices, the overall gain must be distributed on all four stages to acquire a gain of more than 60 dB, while maintaining a-3-dB bandwidth of 200 MHz. To achieve high gain, we propose using a modified, positive-feedback, cross-coupled input differential stage. The modified OTA achieves a high output swing of ± 0.85 V due to only two stacked transistors, 88 dB DC gain and a third-order harmonic of -60 dB for 800 mVpp at 30 MHz. Further on, in a capacitive buffer configuration, we achieve a high slew rate of 1240 V/µS, -3-dB bandwidth of 509 MHz, signal-to-noise ratio of 63 dB while consuming 10.4 mW power.

  • 5.
    Abbaraju, Nanda
    Jönköping University, School of Engineering.
    Sending and Receiving Data between Mobile and Data Logger2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 6.
    Abbasi, Mahdi
    University of Gävle, Department of Technology and Built Environment.
    Characterization of a 5GHz Modular Radio Frontend for WLAN Based on IEEE 802.11p2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The number of vehicles has increased significantly in recent years, which causeshigh density in traffic and further problems like accidents and road congestions.A solution regarding to this problem is vehicle-to-vehicle communication, wherevehicles are able to communicate with their neighboring vehicles even in the absenceof a central base station, to provide safer and more efficient roads and toincrease passenger safety.The goal of this thesis is to investigate basic physical layer parameters of ainter-vehicle communication system, like emission power, spectral emission, errorvector magnitude, guard interval, ramp-up/down time, and third order interceptpoint. I also studied the intelligent transportation system’s channel layout inEurope, how the interference of other systems are working in co-channel and adjacentchannels, and some proposals to use the allocated frequency bands. On theother hand, the fundamentals of OFDM transmission and definitions of OFDMkey parameters in IEEE 802.11p are investigated.The focus of this work is on the measurement of transmitter frontend parametersof a new testbed designed and fabricated in order to be used at inter-vehiclecommunication based on IEEE 802.11p.

  • 7.
    ABBASI, MUHAMMAD MOHSIN
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Solving Sudoku by Sparse Signal Processing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sudoku is a discrete constraints satisfaction problem which is modeled as an underdetermined linear

    system. This report focuses on applying some new signal processing approaches to solve sudoku and

    comparisons to some of the existing approaches are implemented. As our goal is not meant for

    sudoku only in the long term, we applied approximate solvers using optimization theory methods. A

    Semi Definite Relaxation (SDR) convex optimization approach was developed for solving sudoku. The

    idea of Iterative Adaptive Algorithm for Amplitude and Phase Estimation (IAA-APES) from array

    processing is also being used for sudoku to utilize the sparsity of the sudoku solution as is the case in

    sensing applications. LIKES and SPICE were also tested on sudoku and their results are compared with

    l1-norm minimization, weighted l1-norm, and sinkhorn balancing. SPICE and l1-norm are equivalent

    in terms of accuracy, while SPICE is slower than l1-norm. LIKES and weighted l1-norm are equivalent

    and better than SPICE and l1-norm in accuracy. SDR proved to be best when the sudoku solutions are

    unique; however the computational complexity is worst for SDR. The accuracy for IAA-APES is

    somewhere between SPICE and LIKES and its computation speed is faster than both.

  • 8.
    Abbasi, Muneeb Mehmood
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Jabbar, Mohammad Abdul
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Design and Performance Analysis of Low-Noise Amplifier with Band-Pass Filter for 2.4-2.5 GHz2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Low power wireless electronics is becoming more popular due to durability, portability and small dimension. Especially, electronic devices in instruments, scientific and medical (ISM) band is convenient from the spectrum regulations and technology availability point of view. In the communication engineering society, to make a robust transceiver is always a matter of challenges for the better performance.

    However, in this thesis work, a new approach of design and performance analysis of Low-Noise Amplifier with Band-Pass filter is performed at 2.45 GHz under the communication electronics research group of Institute of Science and Technology (ITN). Band-Pass Filtered Low-Noise Amplifier is designed with lumped components and transmission lines. Performances of different designs are compared with respect to noise figure, gain, input and output reflection coefficient. In the design process, a single stage LNA is designed with amplifier, ATF-58143. Maximally flat band-pass (BPF) filters were designed with lumped components and distributed elements. Afterwards, BPF is integrated with the LNA at the front side of LNA to get a compact Band-Pass Filtered Low-Noise Amplifier with good performance.

    Advanced Design System (ADS) tool was used for design and simulation, and each design was tuned to get the optimum value for noise figure, gain and input reflection coefficient. LNA stand-alone gives acceptable value of noise figure and gain but the bandwidth was too wide compared to specification. Band-Pass Filtered Low-Noise Amplifier with lumped components gives also considerable values of noise and gain. But the gain was not so flat and the bandwidth was also wide. Then, Band-Pass Filtered Low-Noise Amplifier was designed with transmission lines where the optimum value of noise figure and gain was found. The gain was almost flat over the whole band, i.e., 2.4-2.5 GHz compared to LNA stand-alone and Band-Pass Filtered Low-Noise Amplifier designed with lumped components. It is observed that deviations of results from schematic to layout level are considerable, i.e., electromagnetic simulation is needed to predict the Band-Pass Filtered Low-Noise Amplifier performance.

    Prototype of LNA, Band-Pass Filtered Low-Noise Amplifier with lumped and transmission lines are made at ITN’s PCB laboratory. Due to unavailability of exact values of Murata components and for some other technical reasons, the measured values of Band-Pass Filtered Low-Noise Amplifier with lumped components and transmission lines are deviated compared to predicted values from simulation.

  • 9.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Inam, Rafia
    Ericsson AB, Kista, Sweden.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Survey on Testing for Cyber Physical System2015In: Testing Software and Systems: 27th IFIP WG 6.1 International Conference, ICTSS 2015, Sharjah and Dubai, United Arab Emirates, November 23-25, 2015, Proceedings, 2015, 194-207 p.Conference paper (Refereed)
    Abstract [en]

    Cyber Physical Systems (CPS) bridge the cyber-world of computing and communications with the physical world and require development of secure and reliable software. It asserts a big challenge not only on testing and verifying the correctness of all physical and cyber components of such big systems, but also on integration of these components. This paper develops a categorization of multiple levels of testing required to test CPS and makes a comparison of these levels with the levels of software testing based on the V-model. It presents a detailed state-of-the-art survey on the testing approaches performed on the CPS. Further, it provides challenges in CPS testing.

  • 10.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Fallah, Ali
    Amirkabir University of Technology, Tehran, Iran.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gholamhosseini, Hamid
    Auckland University of Technology, Auckland, New Zealand.
    A Novel Approach for Removing ECG Interferences from Surface EMG signals Using a Combined ANFIS and Wavelet2015In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 26, 52-59 p.Article in journal (Refereed)
    Abstract [en]

    In recent years, the removal of electrocardiogram (ECG) interferences from electromyogram (EMG) signals has been given large consideration. Where the quality of EMG signal is of interest, it is important to remove ECG interferences from EMG signals. In this paper, an efficient method based on a combination of adaptive neuro-fuzzy inference system (ANFIS) and wavelet transform is proposed to effectively eliminate ECG interferences from surface EMG signals. The proposed approach is compared with other common methods such as high-pass filter, artificial neural network, adaptive noise canceller, wavelet transform, subtraction method and ANFIS. It is found that the performance of the proposed ANFIS-wavelet method is superior to the other methods with the signal to noise ratio and relative error of 14.97 dB and 0.02 respectively and a significantly higher correlation coefficient (p < 0.05).

  • 11.
    Abboud, Mohamad Moulham
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Simulation of 3ph induction motor in Matlab with Direct and Soft starting methods.2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Asynchronous machines are considered nowadays the most commonly used electrical machines, which are mainly used as electrical induction motors. Starting the induction motor is the most important and dangerous step. The theory behind this project is based on representing the real motor by a set of equations and values in Matlab using the subsystem feature, forming a corresponding idealistic motor in a way where all the physical effects are similar. The motor is started under different loads in two methods: Direct and Soft starting. Each method is studied and discussed using supporting simulation of currents, torque, speed, efficiency and power factor curves.

  • 12.
    Abboud, Mohamad Moulham
    Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energy Science.
    Simulation of 3ph induction motor in Matlab with VVVF starting method2016Independent thesis Advanced level (degree of Master (One Year)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Nowadays, three-phase induction motors are widely used on industrial and other types of processes. Therefore, accurate knowledge of an induction motor performance is very essential to have an idea of its operation conditions. This study is a sequel of a previous one, where Direct and Soft starting methods of three-phase motors has been simulated and compared. As in the previous study, the theory behind this one is based on representing the real motor by aset of equations and values in Matlab, forming a corresponding idealistic motor in a way where all the physical effects are similar. The motor is started under three different frequencies in the VVVF method using supporting simulation of the current, torque, speed,efficiency and power factor curves. The results of the three starting methods are then discussed and compared.

  • 13. Abd Elghany, M. A.
    et al.
    El-Moursy, M. A.
    Korzec, D.
    Ismail, Mohammed
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits. Ohio State University, United States .
    High throughput architecture for OCTAGON network on chip2009In: 2009 16th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2009, IEEE , 2009, 101-104 p.Conference paper (Refereed)
    Abstract [en]

    High Throughput Octagon architecture to achieve high performance Networks on Chip (NoC) is proposed. The architecture increase. The throughput oy the network by 17% while preservin. The average latency. The area of High Throughput OCTAGON switch is decreased by 18% as compared to OCTAGON switch. The total metal resources required to implement High Throughput OCTAGON design is increased by 8% as compared to the total metal resources required to implement OCTAGON design. The extra power consumption required to achiev. The proposed architecture is 2% oy the total power consumption oy the OCTAGON architecture.

  • 14.
    Abdi Kelishami, Alireza
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Secure Privacy-Friendly Instant Messaging (IM) for Guidepal2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is fascinating, and yet often neglected, that a user’s privacy can be invaded notonly by the absence of security measures and mechanisms, but also by improperor inadequate usage of security services and mechanisms. When designingsecure systems, we must consider what services are needed and what is not.The work in this thesis revolves around privacy-friendly instant messaging (IM)systems. In such a system, an inadequate usage of security measures leads tohaving IM servers being able to intercept or gather users’ private conversations.An improper usage of security measures could bring about non-repudiationwhich is desirable when signing contracts, but unwelcome in IM and privateconversations.We will look into requirements of the desired IM system, study the currentstate-of-the-art solutions, deploy an IM server, and briefly extend an existingmodern privacy-friendly IM protocol and an open source mobile application tomeet our security and privacy requirements. This extended IM application iscalled Guidepal-IM and is available as open source1The thesis work is introduced and carried out at Guidepal, a startup companyin Stockholm. It is therefore supervised partly at Guidepal and partly at KTH.Since Guidepal is also looking into possibilities of integrating an IM featureto its current social media apps, our contribution would also briefly extend tostudying the limitations and recommendations for Guidepal’s social media appto help user privacy preservation.

  • 15.
    Abdollahi Sani, Negar
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Xin
    Acreo Swedish ICT AB, Sweden.
    Granberg, Hjalmar
    INNVENTIA AB, Sweden.
    Andersson Ersman, Peter
    Acreo Swedish ICT AB, Sweden.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Dyreklev, Peter
    Acreo Swedish ICT AB, Sweden.
    Engquist, Isak
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Göran
    Acreo Swedish ICT AB, Sweden.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Flexible Lamination-Fabricated Ultra-High Frequency Diodes Based on Self-Supporting Semiconducting Composite Film of Silicon Micro-Particles and Nano-Fibrillated Cellulose2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 28921Article in journal (Refereed)
    Abstract [en]

    Low cost and flexible devices such as wearable electronics, e-labels and distributed sensors will make the future "internet of things" viable. To power and communicate with such systems, high frequency rectifiers are crucial components. We present a simple method to manufacture flexible diodes, operating at GHz frequencies, based on self-adhesive composite films of silicon micro-particles (Si-mu Ps) and glycerol dispersed in nanofibrillated cellulose (NFC). NFC, Si-mu Ps and glycerol are mixed in a water suspension, forming a self-supporting nanocellulose-silicon composite film after drying. This film is cut and laminated between a flexible pre-patterned Al bottom electrode and a conductive Ni-coated carbon tape top contact. A Schottky junction is established between the Al electrode and the Si-mu Ps. The resulting flexible diodes show current levels on the order of mA for an area of 2 mm(2), a current rectification ratio up to 4 x 10(3) between 1 and 2 V bias and a cut-off frequency of 1.8 GHz. Energy harvesting experiments have been demonstrated using resistors as the load at 900 MHz and 1.8 GHz. The diode stack can be delaminated away from the Al electrode and then later on be transferred and reconfigured to another substrate. This provides us with reconfigurable GHz-operating diode circuits.

  • 16.
    Abdulhadi, Sami
    Karlstad University, Faculty of Technology and Science.
    ARM i inbyggt system: med prototyp2009Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Embedded systems has become more and more common in today's society. The embedded systems are included in almost everything today, from various vehicles to children's toys.

    Today's technology means that yesterday's solutions can be realised on a fraction of the area. More and more become surface mounted with smaller and more complex circuits. This is not always an advantage for the developers when assembling and soldering prototype circuit boards become a more difficult and/or an expensive process.

    The goal is to create an embedded system with an ARM-processor. The system will consist of USB-OTG, ethernet, various memory like FRAM and microSD and a display with touchscreen for user interface. The project includes everything from choice of components to test and verification with program code.

    The time was too short to include all the parts that was planned. The result of the project was a prototype card and two small program sequences, one that blinks the two light diodes on the card and one that writes a picture on the display.

    This embedded system is intended for evaluating ARM-processors by Mikrododakt AB.

  • 17.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Ostovar, Ahmad
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A Direct Method for 3D Hand Pose Recovery2014In: 22nd International Conference on Pattern Recognition, 2014, 345-350 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel approach for performing intuitive 3D gesture-based interaction using depth data acquired by Kinect. Unlike current depth-based systems that focus only on classical gesture recognition problem, we also consider 3D gesture pose estimation for creating immersive gestural interaction. In this paper, we formulate gesture-based interaction system as a combination of two separate problems, gesture recognition and gesture pose estimation. We focus on the second problem and propose a direct method for recovering hand motion parameters. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Our experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation. This application is intended to explore the system capabilities in real-time biomedical applications. Eventually, system usability test is conducted to evaluate the learnability, user experience and interaction quality in 3D interaction in comparison to 2D touch-screen interaction.

  • 18.
    Abid, Fahim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Intermodulation due to interaction of photovoltaic inverter and electric vehicle at supraharmonic range2016In: 2016 17th International Conference on Harmonics and Quality of Power, Piscataway. NJ, 2016, 685-690 p., 7783471Conference paper (Refereed)
    Abstract [en]

    Advent of power electronic switching is introducing more and more non-linear loads in the low voltage grid. Besides harmonic current generation in the frequency range below 2 kHz, these non-linear loads are also responsible for current emission in the range of 2 kHz to 150 kHz, commonly known as supraharmonic emission. Supraharmonic currents mainly flow between nearby appliances and heavily influence the overall emission of neighboring devices. This paper presents an analysis of supraharmonic interaction between a photovoltaic inverter and an electric vehicle. It has been noticed that intermodulation distortion arises as a result of interaction between different switching frequencies used by the devices. Later, additional household equipment were added to photovoltaic and electric vehicle to observe their effect on intermodulation distortion. All the measurements were conducted in a controlled laboratory environment imitating a domestic customer.

  • 19.
    Abidin, Aysajan
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding.
    New Universal Hash Functions2012In: Lecture Notes in Computer Science, Vol. 7242 / [ed] Frederik Armknecht and Stefan Lucks, Springer Berlin Heidelberg , 2012, 99-108 p.Conference paper (Refereed)
    Abstract [en]

    Universal hash functions are important building blocks for unconditionally secure message authentication codes. In this paper, we present a new construction of a class of Almost Strongly Universal hash functions with much smaller description (or key) length than the Wegman-Carter construction. Unlike some other constructions, our new construction has a very short key length and a security parameter that is independent of the message length, which makes it suitable for authentication in practical applications such as Quantum Cryptography.

  • 20.
    Abrahamson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of the dimensioning factors of the railway power supply system2007In: Computational Methods and Experimental Measurements XIII, WIT Press, 2007, Vol. 46, 85-95 p.Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast - in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the and and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 21.
    Abrahamsson, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Hedlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kamf, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Bernhoff, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings2014In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, Vol. 61, no 6, 3012-3021 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.

  • 22.
    Abrahamsson, Lars
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Railway Power Supply Models and Methods for Long-term Investment Analysis2008Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    The aim of the project is to suggest an investment planning programwhere the welfare of the society is to be maximized. In order to beable to decide on a wise investment plan, one needs to know theconsequences of different choices of power system configurations.Therefore the impacts of different future traffic demands are ofinterest for a railway power system owner.Since investments are supposed to last a long time, their futureusage has to be considered. Moreover, the lead times of investmentscan be of considerable duration lengths. Because of the uncertaintyof the future, deterministic case studies might not be suitable andthen a large number of outcomes are to be studied, probable outcomesas well as outcomes with a high level of impact.In order to be able to make a valid long-term investment analysis ofthe railway power supply system, one needs to use proper railwaypower supply models and methods. The aim of this thesis is topresent a stable modeling and methodological basis for the cominginvestment planning phase of this PhD research project. The focus isset on studying the consequences of a railway power supply systemwhich is too weak.The thesis contains an overview of models of some electrical andmechanical relations important for electric traction systems. Someof these models are further developed, and some are modified forimproved computational properties. A flexible electric tractionsystem simulator based on the above mentioned models has beendeveloped and the applied methods and resulting abilities arepresented.The main scientific contribution of this thesis is that a fast andapproximative neural network model, which calculates some importantaggregated results of the interaction between the railway powersystem and the train traffic, has been developed. This approximativemodel was developed in order to reduce computation times. Reductionof computation times is very important when a huge number ofoutcomes are studied. A complete simulation of a train power systemin operation takes a long time, often not less than about a tenth ofthe simulated traffic time. The neural network is trained with someselected aggregated results extracted from a wide set of railwayoperation simulation cases. The choices of network inputs andoutputs are motivated in the thesis. The performance of thesimulator as well as the approximator are visualized in casestudies.

  • 23.
    Abrahamsson, Lars
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal Railroad Power Supply System Operation and Design: Detailed system studies, and aggregated investment models2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Railway power supply systems (RPSSs) differ mainly from public power systems from that the loads are moving. These moving loads are motoring trains. Trains can also be regenerating when braking and are then power sources. These loads consume comparatively much power, causing substantial voltage drops, not rarely so big that the loads are reduced. By practical reasons most RPSSs are single-phase AC or DC. Three-phase public grid power is either converted into single-phase for feeding the railway or the RPSS is compartmentalized into separate sections fed individually from alternating phase-pairs of the public grid. The latter is done in order not to overload any public grid phase unnecessarily much.

    This thesis summarizes various ways of optimally operating or designing the railway power supply system. The thesis focuses on converter-fed railways for the reasons that they are more controllable, and also has a higher potential for the future. This is also motivated in a literature-reviewing based paper arguing for the converter usage potential. Moreover, converters of some kind have to be used when the RPSS uses DC or different AC frequency than the public grid.

    The optimal operation part of this thesis is mainly about the optimal power flow controls and unit commitments of railway converter stations in HVDC-fed RPSSs. The models are easily generalized to different feeding, and they cope with regenerative braking. This part considers MINLP (mixed integer nonlinear programming) problems, and the main part of the problem is non-convex nonlinear. The concept is presented in one paper. The subject of how to model the problem formulations have been treated fully in one paper.

    The thesis also includes a conference article and a manuscript for an idea including the entire electric train driving strategy in an optimization problem considering power system and mechanical couplings over time. The latter concept is a generalized TPSS (Train Power Systems Simulator), aiming for more detailed studies, whereas TPSS is mainly for dimensioning studies. The above optimal power flow models may be implemented in the entire electric train driving strategy model.

    The optimal design part of this thesis includes two aggregation models for describing reduction in train traffic performance. The first one presented in a journal, and the second one, adapted more useful with different simulation results was presented at a conference. It also includes an early model for optimal railway power converter placements.

    The conclusions to be made are that the potential for energy savings by better operation of the railway power system is great. Another conclusion is that investment planning models for railway power systems have a high development potential. RPSS planning models are computationally more attractive, when aggregating power system and train traffic details.

  • 24.
    Abrahamsson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Optimal drift och dimensionering avbanmatningssystem: Slutrapport Elektraprojekt2016Report (Other academic)
  • 25.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Kjellqvist, Tommy
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    HVDC Feeder Solution for Electric Railways2012In: IET Power Electronics, ISSN 1755-4543Article in journal (Refereed)
    Abstract [en]

    The railway power supply systems in many sparsely populated countries are relatively weak. Weak railway power supply systems causes problems with power quality, voltage drops, and high transmission losses.

    For AC railway power supply systems with a different frequency than the public grid, high-voltage AC (HVAC) transmission lines are common, connected to the catenary by transformers.

    In this paper an alternative design based on an HVDC feeder is suggested. The HVDC feeder is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at public frequency. The converter stations between the public grid and the HVDC feeder can be sparsely distributed, in the range of 100 km or more, whereas the converters connecting the HVDC feeder to the catenary are distributed with a much closer spacing. Their ratings can be lower than substation transformers or electro-mechanical converters, since the power flow can be fully controlled.

    Despite a relatively low power rating, the proposed converters can be highly efficient due to the use of medium frequency technology. The HVDC-based feeding system results in lower material usage, lower losses and higher controllability compared to present solutions.

    Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 26.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Kjellqvist, Tommy
    Elekt Konsult AB, Kraftelektronik, Sweden.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    High-voltage DC-feeder solution for electric railways2012In: IET Power Electronics, ISSN 1755-4543, Vol. 5, no 9, 1776-1784 p.Article in journal (Refereed)
    Abstract [en]

    For AC railway power supply systems with a different frequency than the public grid, high-voltage AC transmission lines are common, connected to the catenary by transformers. This study suggests an alternative design based on an high-voltage DC (HVDC)-feeder, which is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at a public-grid frequency. The converter stations between the public grid and the HVDCfeeder can be sparsely distributed, not denser than on 100 km distances, whereas the converters connecting the HVDC-feeder to the catenary are distributed denser. Their ratings can be lower than present-day substation transformers or converters, since the power flows can be fully controlled. Despite a relatively low-power rating, the proposed converters can be highly efficient because of the use of medium frequency technology. The proposed feeding system results in lower material usage, lower losses and higher controllability compared with the present solutions. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared with conventional systems, especially for cases with weak feeding, and when there are substantial amounts of regeneration from the trains.

  • 27.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Schütte, Thorsten
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Use of converters for feeding of AC railways for all frequencies2012In: Energy for Sustainable Development, ISSN 0973-0826, Vol. 16, no 3, 368-378 p.Article in journal (Refereed)
    Abstract [en]

    Railways are the most energy-efficient land-based mode of transport, and electrification is the most energy-efficient way to power the trains. There are many existing solutions to supply the trains with electricity. Regardless of which particular technology is chosen, it is beneficial to interconnect the public power grids to grids supplying power to the railways. This paper shows that the most efficient, flexible, and gentle-for-the-public-grid way of doing that is through power electronic-based power converters. Converters offer great benefits regardless of whether the overhead contact lines are of DC-type or AC type, and regardless of the AC grid frequency. This paper presents neither new theory nor new experimental results. Based on already available information, this paper presents logical arguments leading to this conclusion from collected facts. Over time what used to be advanced and high-cost equipment earlier can nowadays be purchased at reasonable cost. It is obvious that for most electrically-fed railways, the use of modern power converters is attractive. Where the individual trains are high consumers of energy, the railway gradients are substantial, and the public grids feeding the railway are weak, the use of converters would be technically desirable, if not necessary for electrification.It is expected that more high-speed railways will be built, and more existing railways will be electrified in the foreseeable future. This paper could provide some insights to infrastructure owners and decision makers in railway administrations about value additions that converter-fed electric railways would provide.

  • 28.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast Estimation of Relations Between Aggregated Train Power System Data and Traffic Performance2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 1, 16-29 p.Article in journal (Refereed)
    Abstract [en]

    Transports via rail are increasing, and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system (RPSS). Future railway power demands are not known. The more distant the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding (some minutes, each) full simulations of electric railway power systems less attractive and simplifications more so. The aim, and main contribution, of this paper is to propose a fast approximator that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. This approximator approach has not previously been encountered in the literature. In the numerical example of this paper, the approximator inputs are the power system configuration; the distance between a connection from contact line to the public grid, to another connection, or to the end of the contact line; the average values and the standard deviations of the inclinations of the railway; the average number of trains; and their average velocity for that distance. The output is the maximal attainable average velocity of an added train for the described railway power system section. The approximator facilitates studies of many future railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 29.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2009In: Australian Journal of Electrical and Electronic Engineering, ISSN 1448-837X, Vol. 6, no 3, 311-318 p.Article in journal (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the railway power supply system (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time-demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on neural networks (NN) is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modelling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 30.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Traction Power System Capacity Limitations at Various Traffic Levels2011In: WCRR, World Congress on Railway Research, 2011Conference paper (Refereed)
    Abstract [en]

    The aim, and main contribution, of this paper is to propose a fine-tuned fast approximator, based on neural networks, that uses aggregated traction system information as inputs and outputs. This approximator can be used as an investment planning constraint in the optimization. It considers that there is a limit on the intensity of the train traffic, depending on the strength of the power system. In the numerical examples of this paper, the approximator inputs are the power system configuration, the distance between a connection from contact line to the public grid to another connection, and the average number of trains for that distance. The output is the maximal attainable average velocity of trains of a specific kind for the by the inputs described railway power system section. An alternative output – the traveling time is also presented. The main emphasis of this paper is on the example section, since the contribution of this paper is mainly to show on the improved simplicity and reality compliance. The applicative contribution is twofold, an improved TPSA as a planning/decision making program constraint, whereas it also can be used as a scientifically developed rule of thumb for a planner active in the field. The aim is not primarily to show that the idea works, or to motivate the principal idea, since that is done earlier. The approximator facilitates studies of many railway power system loading scenarios, combined with different power system configurations, for investment planning analysis. The approximator is based on neural networks. An additional value of the approximator is that it provides an understanding of the relations between power system configuration and train traffic performance.

  • 31.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An SOS2-based moving trains,fixed nodes, railway power system simulator2012In: WIT Transactions on the Built Environment, WIT Press, 2012, 813-823 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents and proposes an optimization model for railway power supply system simulations. It includes detailed power systems modeling train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a xed number of stationary power system nodes. The proposed model uses SOS2 (special ordered sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impact of the number of power system nodes along the contact line and the discretized time step length impacts on model accuracy and computation times are investigated. The program is implemented in GAMS (General Algebraic Modeling System). Experiences from various solver choices are also presented. The train traveling times are minimized in the example. Other studies could, e.g. consider energy consumption minimization. The numerical example is representative for a Swedish non-centralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

  • 32.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast calculation of some important dimensioning factors of the railway power supply system2007Conference paper (Refereed)
    Abstract [en]

    Because of environmental and economical reasons, in Sweden and the rest of Europe, both personal and goods transports on railway are increasing. Therefore great railway infrastructure investments are expected to come. An important part of this infrastructure is the railway power supply system. Exactly how much, when and where the traffic will increase is not known for sure. This means investment planning for an uncertain future. The more uncertain parameters, such as traffic density and weight of trains, and the further future considered, the greater the inevitable amount of cases that have to be considered. When doing simulations concerning a tremendous amount of cases, each part of the simulation model has to be computationally fast – in real life this means approximations. The two most important issues to estimate given a certain power system configuration, when planning for an electric traction system, are the energy consumption of the grid and the train delays that a too weak system would cause. In this paper, some modeling suggestions of the energy consumption and the maximal train velocities are presented. Two linear models, and one nonlinear model are presented and compared. The comparisons regard both computer speed and representability. The independent variables of these models are a selection of parameters describing the power system, i.e.: power system technology used on each section, and traffic intensity.

  • 33.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Railway power supply investment decisions considering the voltage drops: Assuming the future traffic to be known2009In: 2009 15th International Conference on Intelligent System Applications to Power Systems, ISAP '09, 2009Conference paper (Other academic)
    Abstract [en]

    Transports on rail are increasing and major railway infrastructure investments are expected. An important part of this infrastructure is the railway power supply system. The future railway power demands are naturally not known for certain. The more distant the uncertain future is, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. Therefore a fast approximator that uses aggregated railway power supply system information has been developed. In particular the approximator studies the impacts of voltage drops on the traffic flow. The weaker the power system and the heavier the traffic, the greater the voltage drops. And the greater the voltage drops, the more limited the maximal attainable tractive force on the locomotives. That approximator is in this paper used as a constraint in the embryo of a railway power supply system investment planning program, where investment decisions are assumed to be realized immediately, and there is no preexisting power supply system to consider. The traffic forecasts are in this first approach assumed to be perfect. This stepwise creation of the planning program makes evaluating it easier. The basic investment planning model presented here constitutes the foundation for further improvements.

  • 34.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Operation simulation of traction systems2008In: COMPUTERS IN RAILWAYS XI, 2008, Vol. 103, 283-292 p.Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Rc-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 35.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Fast estimation of the relation between aggregated train power system information and the power and energy converted2008In: 2008 Australasian Universities Power Engineering Conference, AUPEC 2008, IEEE conference proceedings, 2008, 1-6 p.Conference paper (Refereed)
    Abstract [en]

    Transports on rail are increasing and major investments in the railway infrastructure, including the Railway Power Supply System (RPSS), are expected. The future railway power demands are naturally not known for certain. The more remote the uncertain future, the greater the number of scenarios that have to be considered. Large numbers of scenarios make time demanding simulations unattractive. The aim of this paper is to present a fast approximator that uses aggregated RPSS information. Since the electrical and mechanical relations governing an RPSS are quite intricate, an approximator based on Neural Networks (NN), is applied. This paper presents a design suggestion for an NN estimating the power and energy flows through each converter station, given RPSS data and levels of train traffic. Even if the future usage of the NN is investment planning, the modeling of such an approximator has a value in itself concerning the understanding of the relations between RPSS and train traffic.

  • 36.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Basic modeling for electric traction systems under uncertainty2006In: PROCEEDINGS OF THE 41ST INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, VOLS 1 AND 2, NEW YORK: IEEE , 2006, 252-256 p.Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is initially to present a basic modeling of the railway traction system. This model includes the basic technologies used today. The voltage dependencies of the maximal possible power consumption as well as the maximal velocity of the common Re-locomotives are included. The latter is very crucial for the studies of time table sensitivity, which is of our immediate interest. Moreover, a method is presented, that estimates the expected train delay time for a given feeding technology. The reference timetable assumes the same train and surrounding conditions, but no voltage drops. In the numerical example where the developed model is applied to a realistic test system, a set of possible amounts of railway traffic are treated as uncertainties. Mainly, the contributions of this paper are three: compiling and connecting already accepted models, the development of a method for numerical calculations using this model compilation, and an example to apply this model on.

  • 37.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Schütte, Thorsten
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model2013In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, Vol. 30, 23-40 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation overtime. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.

  • 38.
    Abrahamsson, Lars
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission lineManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency.

    A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses.

    Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 39.
    Abrahamsson, Lars
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission line2012Article in journal (Refereed)
    Abstract [en]

    In this paper an alternative railway power systems design based on an HVDC feeder is studied. The HVDC feeder is connected to the catenary by converters. Such an HVDC line is also appropriate for DC-fed railways and AC-fed railways working at public frequency. A unit commitment optimal power flow model has been developed and is applied on a test system. In this paper, the model is presented in detail. The model, in the form of an MINLP program, uses unified AC-DC power flow to minimize the entire railway power system losses. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.

  • 40.
    Abrahamsson, Sebastian
    et al.
    Linköping University, Department of Electrical Engineering.
    Råbe, Markus
    Linköping University, Department of Electrical Engineering.
    An FPGA implementation of a modulator for digital terrestrial television according to the DTMB standard2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increasing data rates in digital television networks increase the demands on data capacity of the current transmission channels. Through new standards, the capacity of exisiting channels is increased with new methods of error correction coding and modulation.

    This thesis presents the design and implementation of a modulator for transmission of digital terrestrial television according to the Chinese DTMB standard.

    The system is written in VHDL and is intended for implementation on an FPGA.

  • 41.
    Abro, Mehwish
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Modelling the exfoliation of graphite for production of graphene2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of my thesis is to make a theoretical model of data obtained from liquid-phase exfoliation of graphene. The production of graphene in the liquid phase exfoliation is a cost efficient method One part of this work is devotedto learn the method of production of graphene by the shear mixing technique from the graphite and to estimate some important parameters which are crucial for the process. Other part of my work is based on studying the liquid-phase exfoliation mechanism of graphene through ultrasonication technique. This method is time consuming as compared to shearmixing.

  • 42. Accoto, Nadia
    et al.
    Rydén, Tobias
    Lund University.
    Secchi, Paolo
    Bayesian Hidden Markov Models for Performance-Based Regulation of Continuity of Electricity Supply2010In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 0885-8877, Vol. 25, no 3, 1236-1249 p.Article in journal (Refereed)
    Abstract [en]

    A fundamental aspect in the regulation of the continuity of electricity supply is the identification of faults that could be caused by an exceptional event and, therefore, that are outside the utility control and responsibility. Different methods have been proposed during the years: the interpretation of the observed faults as a signal of an underlying system naturally leads to the analysis of the problem by means of a hidden Markov model. Thesemodels, in fact, are widely used for introducing dependence in data and/or for modeling observed phenomena depending on hidden processes. The application of this method shows that the model is able to identify exceptional events; moreover, the study of the estimated model parameters gives rise to reality-linked considerations.

  • 43.
    Ackeby, Susanne
    et al.
    STRI AB.
    Ohlsson, Lars
    Falbygdens Energi AB.
    Etherden, Nicholas
    STRI.
    Regulatory Aspects of Energy Storage in Sweden2013Conference paper (Refereed)
    Abstract [en]

    This paper highlights the possibilities and limitations of investing in energy storage for use at distribution level under the existing regulatory framework in Sweden. The paper further gives a brief overview of possible applications and ownership models for energy storage in a distribution grid. It was concluded that it is allowed for a network operator to own an energy-storage installation; there are however restrictions in the use of the installation for trade in electricity. A general observation from the study was that there are uncertainties in the interpretation of the laws and regulations due to the complete absence of experience in the use of grid-size energy storage.

  • 44.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Overview of government and market driven programs for the promotion of renewable power generation2001In: Renewable energy, ISSN 0960-1481, Vol. 22, no 1-3, 197-204 p.Article in journal (Refereed)
  • 45.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Andersson, G.
    Söder, Lennart
    KTH, Superseded Departments.
    Distributed generation: a definition2001In: Electric power systems research, ISSN 0378-7796, Vol. 57, no 3, 195-204 p.Article in journal (Refereed)
  • 46.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Andersson, Göran
    Söder, Lennart
    KTH, Superseded Departments.
    Electricity market regulations and their impact on distributed generation2000In: Electric Utility Deregulation and Restructuring and Power Technologies, 2000. Proceedings. DRPT 2000. International Conference on, 2000, 608-613 p.Conference paper (Refereed)
    Abstract [en]

    Distributed generation (DG) has attracted a lot of attention recently and might become more important in future power generation systems. As different definitions are used worldwide, the paper briefly discusses the definition of DG. The future development of DG, however, will, to a not insignificant part, depend on the legal framework. As the legal framework can vary significantly for different competitive electricity markets, this paper briefly identifies and analyses some variations in the regulatory approaches, e.g. for power exchanges, balance services and ancillary services, in different countries. It also illustrates the influence of market regulations on the development of distributed power generation. Based on this analysis, it can be concluded that regulatory aspects might decisively influence the development of distributed power generation

  • 47.
    Ackermann, Thomas
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Centeno-Lopez, Eva
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Grid Issues for Electricity Production Based on Renewable Energy Sources in Spain, Portugal, Germany, and United Kingdom2008Book (Other academic)
  • 48.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    Wind energy technology and current status: a review2000In: Renewable & sustainable energy reviews, ISSN 1364-0321, Vol. 4, no 4, 315-374 p.Article, review/survey (Refereed)
  • 49.
    Ackermann, Thomas
    et al.
    KTH, Superseded Departments.
    Söder, Lennart
    KTH, Superseded Departments.
    An overview of wind energy-status 20022002In: Renewable & sustainable energy reviews, ISSN 1364-0321, Vol. 6, no 1-2, 67-128 p.Article, review/survey (Refereed)
  • 50.
    Adis, Kurtalic
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    Linkfire2011Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Planen var att konstruera en PCI-Express-till-PCI brygga för fyra MoCA radiokort. Problem uppstod då det visade sig att PLC8112 inte kunde hantera fyra PCI samtidigt som var utlovat från tillverkaren av bryggan. För att lösa problemet fick PCI6152 läggas till i designen. Det är en PCI-till-PCI brygga som också ska klara att hantera upp till fyra PCI enligt tillverkaren. Fyra MoCA radiokort förbrukar mycket ström. Två spänningsregulatorer lades till i designen för att kunna leverera de strömmar som krävs. För att säkerställa att radiokorten som ansluts till Linkfire inte blir för varma så placeras en temperatursensor under ett radiokort. Temperatursensorn har endast av/på lägen och till den ansluts två fläktar, därmed så betraktas dem som en fläkt då de inte är individuellt styrda.

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