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• 1. Aguilera, M.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
Experiences in power system multi-domain modeling and simulation with modelica & FMI: The case of gas power turbines and power systems2018In: 2018 Workshop on Modeling and Simulation of Cyber-Physical Energy Systems, MSCPES 2018 - Held as part of CPS Week, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-6, article id 8405397Conference paper (Refereed)

The turbine-governor models that are currently used in studies of power systems include over-simplifications of turbomachinery elements. Due to the growing need to support intermittent energy resources with other energy sources like gas turbines, more detailed models including an explicit representation of the physical dynamics are attractive. In this paper, the advantages of the Modelica language and the FMI standard are considered to carry out modeling and multi-domain simulation of gas turbines with power grids, which can be used to evaluate scenarios of power variability. The work gathers preliminary results of the potential that FMUs offer to promote the exchange of turbine models by manufacturers and to conduct multi-domain simulations in several tools.

• 2.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems. KTH. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
Creation of CERID: Challenge, Education, Research, Innovation, and Deployment in the context of smart MicroGrid2019In: IST-Africa 2019 Conference Proceedings / [ed] Paul Cunningham ; Miriam Cunningham, 2019Conference paper (Refereed)

The iGrid project deals with the design and implementation of a solar-powered smart microgrid to supply electric power to small rural communities. In this paper, we discuss the roadmap of the iGrid project, which forms by merging the roadmaps of KIC (knowledge and Innovation Community) and CDE (Challenge-Driven Education). We introduce and explain a five-gear chain as Challenge, Education, Research, Innovation, and Deployment, called CERID, to reach the main goals of this project. We investigate the full chain in the iGrid project, which is established between KTH Royal Institute of Technology (Sweden) and University of Dar es Salam (Tanzania). We introduce the key stakeholders and explain how CERID goals can be accomplished in higher educations and through scientific research. Challenges are discussed, some innovative ideas are introduced and deployment solutions are recommended.

• 3.
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems.
Scania Technical Centre. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems. AMO GmbH. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. RWTH Aachen University; AMO GmbH. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligenta system, Micro and Nanosystems.
Suspended Graphene Membranes with Attached Silicon Proof Masses as Piezoresistive Nanoelectromechanical Systems Accelerometers2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, no 10, p. 6788-6799Article in journal (Refereed)

Graphene is an atomically thin material that features unique electrical and mechanical properties, which makes it an extremely promising material for future nanoelectromechanical systems (NEMS). Recently, basic NEMS accelerometer functionality has been demonstrated by utilizing piezoresistive graphene ribbons with suspended silicon proof masses. However, the proposed graphene ribbons have limitations regarding mechanical robustness, manufacturing yield, and the maximum measurement current that can be applied across the ribbons. Here, we report on suspended graphene membranes that are fully clamped at their circumference and have attached silicon proof masses. We demonstrate their utility as piezoresistive NEMS accelerometers, and they are found to be more robust, have longer life span and higher manufacturing yield, can withstand higher measurement currents, and are able to suspend larger silicon proof masses, as compared to the previous graphene ribbon devices. These findings are an important step toward bringing ultraminiaturized piezoresistive graphene NEMS closer toward deployment in emerging applications such as in wearable electronics, biomedical implants, and internet of things (IoT) devices.

• 4.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits. Univ Turku, Turku, Finland..
Qassim Univ, Unaizah Coll Engn, Buraydah, Saudi Arabia.;Univ Monastir, Monastir, Tunisia.. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems. Univ Dar Es Salaam, Dar Es Salaam, Tanzania.. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems. Univ Dar Es Salaam, Dar Es Salaam, Tanzania.. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems. Univ Turku, Turku, Finland..
IoT based Appliances Identification Techniques with Fog Computing for e-Health2019In: IST-Africa 2019 Conference Proceedings / [ed] Paul Cunningham, Miriam Cunningham, IEEE , 2019Conference paper (Refereed)

To improve the living standard of urban communities and to render the healthcare services sustainable and efficient, e-health system is experiencing a paradigm shift. Patients with cognitive discrepancies can be monitored and observed through the analyses of power consumption of home appliances. This paper surveys recent trends in home-based e-health services using metered energy consumption data. It also analyses and summarizes the constant impedance, constant current and constant power (ZIP) approaches for load modelling. The analysis briefly recaptures both non-intrusive and intrusive techniques. The work reports an architecture using IoT technologies for the design of a smart-meter, and fog-computing paradigm for raw processing of energy dataset. Finally, the paper describes the implementation platform based on GirdLAB-D simulation to construct accurate models of household appliances and test the machine-learning algorithm for the detection of abnormal behaviour.

• 5.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
Wearable in a Cloud2018In: 2018 IEEE/ACM INTERNATIONAL CONFERECE ON CONNECTED HEALTH: APPLICATIONS, SYSTEMS AND ENGINEERING TECHNOLOGIES (CHASE), IEEE , 2018, p. 7-8Conference paper (Refereed)

I Nowadays, health care at home becomes more and more important, there are also some product which can measure the ECG, EMG with wearable device. However, these devices are not so accurate for diagnosis because of the low sample rate and less channel on body. In this project, we design a wearable system with 8-channels AFE and use Wi-Fi module to transfer the data to cloud so that we can measure the ECG or EMG more accurate at home, almost at the same sample rate and channels at the hospital. And then the cloud is built for received the data and a real-time display can help doctor monitor the patients' condition remotely. template is essential with some standard steps.

• 6.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Space and Plasma Physics.
The Difference Between Isolated Flux Transfer Events and Flux Transfer Event Cascades2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402Article in journal (Refereed)

This flux transfer event (FTE) study is based on 984 FTEs originally identified by Wang et al. (2005, ) in Cluster data. Due to Cluster's orbit, the FTE list exclusively contains events detected at the high-latitude dayside magnetopause and low-latitude flanks. The focus of this study is on FTE separation time. The results show that FTEs appearing in cascades are mainly located at the northern dusk and southern dawn magnetopause, while isolated FTEs are equally spread over the region covered by Cluster. This difference may be explained by the different interplanetary magnetic field (IMF) conditions during which the subsets occur. For isolated FTEs, average IMF B-y is close to zero. During such conditions, FTEs are expected to form at arbitrary longitudes along an equatorial merging line. After formation, they propagate northward and southward, causing an equal distribution at higher latitudes. In contrast, FTE cascades typically occur during weakly southward IMF with a negative B-y component. Their asymmetric distribution at higher latitudes is consistent with both the component and the antiparallel merging model for nonzero B-y. In both scenarios, newly formed FTEs are expected to move to the northern dusk and southern dawn regions, as observed. Many FTE cascades appearing during northward IMF are located close to the low-latitude flanks, confirming previous reports. We discovered that such FTEs appear during large IMF values. Another new result is that 16% of all isolated FTEs appear during small IMF cone angles, suggesting that these may form as a result of magnetosheath jets impacting on the magnetopause.

• 7.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
Univ Carlos III Madrid, Dept Commun & Signal Theory, Leganes 28911, Spain.. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
Ka-Band Fully Metallic TE40 Slot Array Antenna With Glide-Symmetric Gap Waveguide Technology2019In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 67, no 10, p. 6410-6418Article in journal (Refereed)

Gap waveguide has recently been proposed as a low-loss and low-cost technology for millimeter-wave components. The main advantage of the gap waveguide technology is that the microwave components can be manufactured in two metallic pieces that are assembled together without electrical contact. The leakage through a thin air gap between the two pieces is prevented by a 2-D periodic structure offering an electromagnetic bandgap (EBG). This EBG is conventionally implemented with metallic pins. Here, we propose the usage of a holey glide-symmetric EBG structure to design a $4\times 4$ slot array antenna that is fed with a TE40 mode. The TE40 excitation is designed based on a TE10-TE20 mode converter whose performance is initially evaluated by radiation pattern measurements. The final antenna, the $4\times 4$ slot array antenna, was manufactured in aluminum by computer numerical control (CNC) milling. The antenna has a rotationally symmetric radiation pattern that could find application as a reference antenna as well as for 5G point-to-point communications.

• 8.
Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
Department of Electrical Engineering, LUT University, Lappeenranta, Finland. Department of Electrical Engineering, LUT University, Lappeenranta, Finland. Saimaa University of Applied Sciences, Lappeenranta, Finland. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
Investigation of a direct liquid cooling system ina permanent magnet synchronous machine2019In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Refereed)

A high demand for electrification of the transportsector has resulted in a need to provide compact and reliableelectric power trains where the electric machine is a key element.The cooling system has a strong impact on the specific torqueand power capability of the machine. The selection of thecooling solution should not be based on the steady-state coolingperformance only but also on the transient characteristics owingto the typical operational load nature of the propulsion system,where the load is not continuous (as it usually is in industrialapplications), but it frequently varies in time depending on thevehicle type and the driving style. This paper investigates indetail the cooling capabilities of a direct winding liquid coolingsolution and compares it with a traditional frame liquid coolingarrangement in the transient condition. As a result of thecomparison, it was found that the location of heat removal closeto the heat source makes the temperature transient time faster,which allows to apply overload operating points more frequently.

• 9.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
A Study on Realistic Energy Storage Systems for the Privacy of Smart Meter Readings of Residential Users2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 150262-150270Article in journal (Refereed)

The introduction of smart meters sparked concerns about privacy breach through real-time monitoring of electric power consumption. Valuable private information about occupancy, behaviour, health, religion and wealth can be extracted from the user’s power profile which urges measurements to protect the integrity of the user. One physical mitigation technique to assure privacy is explored using energy storage systems. Real energy storage technologies are limited in their energy capacities and power capabilities, which have to be appropriately sized to fulfil their role. This paper analyses and compares different energy storage technologies (li-ion, lead-acid, electric double layer capacitor and flywheel) for the protection of residential users by estimating the minimal required capacities and costs for both single and multiple user cases. The analysis is based on actual measured user data from the REDD data set. The results show that the integrity can be protected with reasonable capacities and investments ranging in the margin of market available products.

• 10.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. XaarJet ltd..
Industrial Digital Fabrication Using Inkjet Technology2019Doctoral thesis, comprehensive summary (Other academic)

The use of acoustic waves initiated by the deformation of a microchannel is one method for generating monodisperse, micrometer-sized droplets from small orifices and is employed in piezo-electric inkjet printheads. These printheads are used in both graphical printing and digital fabrication, where functionalities, such as optical, biological, electrical or mechanical, are being produced locally. The processes leading to detrimental artifacts such as satellite droplets or nozzle outages, however, are not fully understood and require profound experimentation. This thesis presents both novel techniques to study jetting for optimal droplet formation and reliability, as well as the post-processing techniques required for solution-based production of a conductive feature on low-cost polymeric substrates.

A multi-exposure imaging system using laser light pulses shorter than 50 ns and a MEMS micro-mirror enabled the imaging of the droplet formation at ten instances on the droplet's  travel towards the substrate. The technique allows for the study of droplet formation, satellite droplet break-up and secondary tail formation allowing for better control and understanding of the process.

Reliability measurement using a linescan camera was introduced to record every droplet ejected from the width of a printhead. The variations in droplet velocity and misalignment of the printhead required the use of a constant background illumination to reliably capture the droplets. The resulting low-contrast images were post-processed using statistical analysis of the graylevel distributions of both, the droplet and background pixels, and were subsequently used in a histogram matching algorithm to enable reliable identification of the threshold value required for unhindered detection of missing droplets based on the printed image. Using temporal oversampling the technique was shown to qualitatively describe droplet velocity variations introduced by the actuation of the printhead.

The conversion of inkjet-printed metallic nanoparticle inks to conductive structures was investigated with a focus on the applicability to industrial processes. Intense pulsed light (IPL) processing achieved comparable results to convective oven sintering in less than ten seconds. The dynamics of IPL sintering were found to be strongly dependent on the spectral composition of the light resonating in the processing chamber. By implementing a passive filtering concept, thermal runaway was prevented and the line conformation was optimized irrespective of the underlying substrate. Alternatively, pulse-shaping, to tailor the energy flux into the deposit and incorporate drying in the IPL process, was found to generate conductive copper features without pre-drying.

The findings were applied to applications comprising small droplet generation for nanoimprint lithography, the fabrication of conductors for blind via connections to buried LED dies as well as the hybrid generation of hyperbolic ion-trap electrodes for  mass spectrometry applications. The addition of the non-contact and high accuracy of the inkjet process enabled suitable performance that lies beyond that of conventional processes.

• 11.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. XaarJet ltd..
Xaar plc.
Quantitative Assessment of Inkjet Reliability under Industrial Conditions: Measuring All Drops during Extended High‐Duty Printing2018In: Handbook of Industrial Inkjet Printing / [ed] Werner Zapka, Weinheim: Wiley-VCH Verlagsgesellschaft, 2018, p. 445-458Chapter in book (Refereed)

Reliability is one of the key challenges in inkjet technology. Nozzles perform unreliably for a number of reasons, such as drying, clogging through air‐ and inkborne contaminants, ingestion of air, or nozzle plate flooding. To extract quantitative information about the number of missing droplets from the acquired images, suitable algorithms need to be applied. To identify the presence of the droplet, a value derived from the characteristics of the area of interest needs to be compared with the threshold value. The Line Scan approach for the measurement of reliability offers a convenient way to assess reliability of a printhead in a laboratory environment providing quantitative and statistical data about location, duration, and time of misfire events. With the knowledge of the printhead frequency and the hypothetical print resolution applied in the printing experiments, the length of such tic marks as a number of subsequent missing droplets can be calculated.

• 12.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. IIT Delhi, India. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. IIT Delhi, India. Uppsala University, Sweden. Inland University of Norway.
Approximate Computing Applied to Bacterial Genome Identification using Self-Organizing Maps2019In: 2019 IEEE Computer Society Annual Symposium on VLSI (ISVLSI), IEEE Computer Society, 2019, p. 560-567, article id 8839522Conference paper (Refereed)

In this paper we explore the design space of a self-organizing map (SOM) used for rapid and accurate identification of bacterial genomes. This is an important health care problem because even in Europe, 70% of prescriptions for antibiotics is wrong. The SOM is trained on Next Generation Sequencing (NGS) data and is able to identify the exact strain of bacteria. This is in contrast to conventional methods that require genome assembly to identify the bacterial strain. SOM has been implemented as an synchoros VLSI design and shown to have 3-4 orders better computational efficiency compared to GPUs. To further lower the energy consumption, we exploit the robustness of SOM by successively lowering the resolution to gain further improvements in efficiency and lower the implementation cost without substantially sacrificing the accuracy. We do an in depth analysis of the reduction in resolution vs. loss in accuracy as the basis for designing a system with the lowest cost and acceptable accuracy using NGS data from samples containing multiple bacteria from the labs of one of the co-authors. The objective of this method is to design a bacterial recognition system for battery operated clinical use where the area, power and performance are of critical importance. We demonstrate that with 39% loss in accuracy in 12 bits and 1% in 16 bit representation can yield significant savings in energy and area.

• 13.
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
Power System Inertia Estimation and Frequency Response Assessment2019Doctoral thesis, monograph (Other academic)

Power plant emissions constitute a major source of environmental pollution. This renders the gradual replacement of such power plants by renewable energy sources imperative. Changes in the quota between conventional generation and renewable energy sources introduce challenges that the modern power systems have to encounter. For example, conventional power plants are replaced by wind turbines and photovoltaics, which do not contribute to system's inertia. As a result, power system inertia decreases and frequency stability becomes a concern. Frequency stability is affected by the amount of power system inertia, along with the response of controllable frequency reserves and the amount of power imbalance. Therefore, the estimation of power system inertia, as well as the frequency response assessment is necessitated, so that appropriate actions can be taken to ensure frequency stability.

The first part of this thesis focuses on power system inertia estimation. Four disturbance based inertia estimation methods are proposed. The methods accommodate the frequency and/or voltage variations that arise after a disturbance and estimate both the total inertia constant and the total power imbalance of the system. This is achieved by considering suitable functions that can approximate the voltage and frequency dependency of the loads, as well as the response from the governors. The proposed methods are applied on frequency responses from simulations of a test system under several different scenarios. The performance of the methods under lack of certain data is investigated, in order to examine if they can be employed under realistic conditions. An extensive analysis is performed, which enables the selection of the most appropriate method, depending on the information that is available.

The second part of the thesis deals with frequency response assessment. First, the use of simplified dynamic equivalent models is examined. The parameters of either governor or frequency response models of the system are identified and validated by employing historic events. Data are obtained from events from the power systems of Sweden and Texas. After the identification, the frequency response model of the system can be simulated to assess frequency stability. Secondly, the thesis examines methods that deal solely with the prediction of frequency nadir. The examined methods either use neural networks or linear regression. The accuracy of the methods, as well as the uncertainty that is introduced by system non-linearities, are assessed through simulations.

By proposing methods for estimating power system inertia and frequency response, this thesis attempts to provide additional solutions to the challenges that modern power systems have to face. It offers supplementary tools to increase the system awareness, in order to take appropriate actions in case of frequency events.

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