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  • 11401.
    Zhu, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Hammouri, A.
    Jordan University of Science and Technology .
    Examination of data delay and packet loss for wide-area monitoring and control systems2012In: 2012 IEEE International Energy Conference and Exhibition, ENERGYCON 2012, IEEE , 2012, p. 927-934Conference paper (Refereed)
    Abstract [en]

    Timely and synchronized phasor data at high resolutions holds a great promise for more responsible and advanced power grid operations. It is expected that the combined effort of developing new application paradigms and the supporting Information and Communication Technology (ICT) will enable the evolutionary change for future transmission grid operation. This paper addresses the design of the supporting ICT system for Wide-Area Monitoring and Control applications considering system performance. The major contribution that distinguishes this paper from previous research efforts in the same area is that this study quantifies the end-to-end data delay and the received packet rate with considerations of different levels of data concentrations. The analysis performed in this paper is not merely limited to the performance issues caused by communication networks but also provides means to view and analyze the overall data delay of the entire supporting ICT system.

  • 11402. Zhu, Kun
    et al.
    Ou, Haiyan
    Fu, Hongyan
    Remb, Edvin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Simple and Tunable Single-Bandpass Microwave Photonic Filter of Adjustable Shape2008In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, no 21-24, p. 1917-1919Article in journal (Refereed)
    Abstract [en]

    A simple and tunable single-hand pass microwave photonic filter of adjustable shape is proposed and experimentally demonstrated. The filter is based on multiple sources (spectrum-sliced by a Mach-Zehnder interferometer) and two cascaded incoherent optical structures, namely, a dispersion medium of 50-km single-mode fiber and a fiber ring delay line. In the experimental range from 1.0 to 3.8 GHz, a discretely tunable single-hand pass filter with a high Q-factor or a flat-top response is achieved by carefully matching the transfer functions of the two individual optical structures.

  • 11403. Zhu, Kun
    et al.
    Ou, Haiyan
    Ye, Chenhui
    Fu, Hongyan
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    All-optical coherence-free microwave filter with switchable passbands based on phase and intensity hybrid modulation2011In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, no 1, p. 140-143Article in journal (Refereed)
    Abstract [en]

    A simple all-optical coherence-free microwave notch filter is proposed and experimentally demonstrated. The filter with switchable passbands is based on a single-wavelength optical source and phase-intensity hybrid modulation scheme. The DC bias voltage applied to the Mach-Zehnder intensity modulator can be adjusted to switch signs of the tap coefficients, which affect the baseband response. Both lowpass and bandpass filtering responses are observed in the experiment and agree well with the simulated results.

  • 11404.
    Zhu, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Song, Ji
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Chenine, Moustafa
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Analysis of phasor data latency in wide area monitoring and control systems2010In: 2010 IEEE International Conference on Communications Workshops, ICC 2010, Capetown, 2010Conference paper (Other academic)
    Abstract [en]

    Synchronized phasor measurement based Wide Area Monitoring and Control (WAMC) system is becoming a reality within international research and development both in academia and industry. Timely and accurate data with high resolutions holds great promise for more responsible and advanced grid control and operation. Currently, most of the research focuses on the different control schemes and applications. A relatively less addressed aspect is the dependency of the WAMC system on the performance of the Information and Communication Technology (ICT) infrastructure, without whose support the projected functionalities of the WAMC systems will be not achieved. Possible delays brought by the complex data transfer and processing processes in WAMC systems are addressed in the first part of this paper. Thereafter, simulations where delayed Phasor measurements are fed to the Static Var Compensator (SVC) are conducted iteratively to detect its maximum tolerated delay. Furthermore, performance requirements for the centralized computation and control actuation are researched and analyzed based on simulation results. It also includes a study on feasibility of compensations using local signal based Power System Stablizers (PSS) in situations with much phasor data delay. The paper is concluded by suggesting ICT architecture for WAMC systems aiming to improve its robustness.

  • 11405.
    Zhu, Kun
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Yuan, Xu
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Honeth, Nicholas
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Data Volume Estimation for CIM based Information Exchange2011Conference paper (Refereed)
    Abstract [en]

    IEC 61970 and 61968, which are commonly referred as Common Information Model (CIM), are proposed to facilitate integration of EMS applications and information exchange between EMS systems with propitiatory data structures. To use communication network in an optimized manner, it is necessary to partition the potentially voluminous data into subsets given their sources, expected exchange frequency, and subscribing applications. In response to these requirements, the concept of CIM profiles is brought up by CIMug. In this paper, functions illustrating the dependency between exchange data volume and basic grid parameters for each data profile are presented. A CIM/XML/RDF file for a generally available 40 bus test system (CIM 13) and examples provided by standards are used as references. The method is validated by estimating the data sizes of similarly available 100bus and 60bus test systems that are modeled according to CIM 13 as well. The contribution of this paper is that it provides ICT system designers with a means to estimate the corresponding requirements for various CIM/XML based data exchange patterns. The estimations are performed based on commonly known grid parameters such as number of buses, branches, generators, transformers and loads together with execution frequency of particular grid planning and operation applications.

  • 11406.
    Zhu, Ning
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Song, Jun
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Cross-Order Echelle Grating Triplexer Based on Amorphous Silicon Nanowire Platform2008In: 2008 7TH INTERNATIONAL CONFERENCE ON THE OPTICAL INTERNET (COIN), NEW YORK: IEEE , 2008, p. 37-38Conference paper (Refereed)
    Abstract [en]

    We present fabrication and measurement results of an ultracompact silicon-on-insulator-based echelle-grating triplexer, which uses different diffraction orders to cover a large spectral range from 1.3 mu m to 1.5 mu m, with a footprint of 150 mu m x 200 mu m.

  • 11407.
    Zhu, Ning
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Song, Jun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, School of Electrical Engineering (EES).
    Total internal reflection type echelle grating demultiplexer based on amorphous silicon nanowire platform2008In: Proceedings of SPIE - The International Society for Optical Engineering, Hangzhou, 2008, Vol. 7134Conference paper (Refereed)
    Abstract [en]

    In this paper we present measurement results of an ultracompact echelle-grating demultiplexer based on silicon-on-insulator nanowire platform, in which we introduced a total internal reflection design of the grating facets to improve the diffraction efficiency. An average increase of the diffraction efficiency with 3.7dB is observed for the 3 channels compared to a normal design.

  • 11408.
    Zhu, Ning
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Song, Jun
    KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Experimental demonstration of a cross-order echelle grating triplexer based on an amorphous silicon nanowire platform2009In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, no 3, p. 383-385Article in journal (Refereed)
    Abstract [en]

    We present the design, fabrication, and characterization of an ultracompact silicon-on-insulator-based echelle grating triplexer. It is based on the cross-order design, which utilizes different diffraction orders to cover a large spectral range from 1.3 to 1.5 mu m with three channels located at 1310, 1490, and 1550 nm and with a footprint of 150 mu m X 130 mu m.

  • 11409.
    Zhu, Shaoling
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Experimental Study on Low Power Wireless Sensor Network Protocols with Native IP Connectivity for BuildingA utomation2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The recent development of wired and wireless communication technologiesmake building automation the next battlefield of the Internet of Things. Multiplestandards have been drafted to accommodate the complex environmentand minimize the resource consumption of wireless sensor networks. This MasterThesis presents a thorough experimental evaluation with the latest Contikinetwork stack and TI CC2650 platform of network performance indicators,including signal coverage, round trip time, packet delivery ratio and powerconsumption. The Master Thesis also provides a comparison of the networkprotocols for low power operations, the existing operating systems for wirelesssensor networks, and the chips that operate on various network protocols. Theresults show that CC2650 is a promising competitor for future development inthe market of building automation.

  • 11410.
    Zhu, Xiaoqian
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Coordinated MIMO Precoder EvaluationBased on Measurement in IndoorEnvironment2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis, we investigate the performance of the coordinated MIMO precoders, using measured channels in indoorvenvironment. Instead of simulated radio propagationvconditions, measured channels are used to evaluate the precoder performance for real-world channels. Our measurement campaign includes several scenarios such as femtocell and “heterogeneous” networks. The study results illustrate that the precoders could reduce the interference significantly and support a high system throughput especially over high SNR where interference is dominant.

    Degree of freedom (DoF) is defined as the maximum number of data stream that could independently coordinate to be transmitted interference-free. Theoretically, the precoders could support 1 DoF per user, while DoF of uncoordinated transmission is 0 per user. Interference Alignment(IA) study arises from information theory of DoF in the interference channel (IC). Three precoding algorithms are investigated to align the interference: maximum sum rate, maxSINR and minWLI. Considering the distributed precoder methods, “maxSINR” always performs better than “minWLI”. Since it tries to maximize the user’s SINR instead of only repressing the interference as “minWLI” does. While “maximum sum rate” is not good at finding an IA like solution that scales well at high SNR. However “maximum sum rate” converges faster than “maxSINR” and “minWLI”.

    Our study about IA feasibility shows that precoding jointly over two subcarriers, using so called frequency extensions, allows 4 users to communicate interference-freeover a 2 × 2 MIMO IC. Without frequency extensions, only 3 users can communicate interference-free.

  • 11411. Zhu, Y.
    et al.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    The Box-Jenkins Steiglitz-McBride algorithm2016In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 65, p. 170-182Article in journal (Refereed)
    Abstract [en]

    An algorithm for identification of single-input single-output Box-Jenkins models is presented. It consists of four steps: firstly a high order ARX model is estimated; secondly, the input-output data is filtered with the inverse of the estimated disturbance model; thirdly, the filtered data is used in the Steiglitz-McBride method to recover the system dynamics; in the final step, the noise model is recovered by estimating an ARMA model from the residuals of the third step. The relationship to other identification methods, in particular the refined instrumental-variable method, are elaborated upon. A Monte Carlo simulation study with an oscillatory system is presented and these results are complemented with an industrial case study. The algorithm can easily be generalized to multi-input single-output models with common denominator.

  • 11412. Zhuo, S.
    et al.
    Shokri-Ghadikolaei, Hossein
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wang, Z.
    Adaptive congestion control in cognitive industrial wireless sensor networks2015In: Proceeding - 2015 IEEE International Conference on Industrial Informatics, INDIN 2015, IEEE conference proceedings, 2015, p. 900-907Conference paper (Refereed)
    Abstract [en]

    Strict quality of service requirements of industrial applications, challenged by harsh environments and huge interference especially in multi-vendor sites, demand incorporation of cognition in industrial wireless sensor networks (IWSNs). In this paper, a distributed protocol of light complexity for congestion regulation in cognitive IWSNs is proposed to improve the channel utilization while ensuring predetermined performance for specific devices, called primary devices. By sensing the congestion level of a channel with local measurements, a novel congestion control protocol is proposed by which every device decides whether it should continue operating on the channel, or vacate it in case of saturation. Such a protocol dynamically changes the congestion level based on variations of non-stationary wireless environment as well as traffic demands of the devices. The proposed protocol is implemented on STM32W108 chips that offer IEEE 802.15.4 standard communications. Experimental results confirm substantial performance enhancement compared to the original standard, while imposing almost no signaling/computational overhead. In particular, channel utilization is increased by 56% with fairness and delay guarantees. The presented results provide useful insights on low-complexity adaptive congestion control mechanism in IWSNs.

  • 11413. Zima-Bockarjova, Marija
    et al.
    Matevosyan, Julija
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Zima, Marek
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Sharing of Profit From Coordinated Operation Planning and Bidding of Hydro and Wind Power2010In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 25, no 3, p. 1663-1673Article in journal (Refereed)
    Abstract [en]

    Depending on market rules, namely congestion management and balancing management, coordination between wind and hydro producers may be mutually beneficial. In this paper we propose a new collaboration scheme and a fair and transparent method, based on the Shapley value, for splitting the extra value caused by a coordinated bidding and operation strategy. We account for uncertainties in wind forecast and energy price evolution. We demonstrate the proposed approaches on a realistic system including congested lines, wind farm and a hydro plant consisting of several reservoir stages.

  • 11414. Zimmer, F.
    et al.
    Friedrichs, M.
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Mueller, M.
    Bakke, T.
    Schenk, H.
    Lakner, H.
    The integration of mono-crystalline silicon micro-mirrors on CMOS for SLM applications2008In: International Conference on Multi-Material Micro Manufacture, 2008, p. 35-38Conference paper (Other academic)
  • 11415. Zimmer, Fabian
    et al.
    Bring, Martin
    List, Matthias
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Fabrication of mono-crystalline Silicon Micro-mirror Arrays using adhesive Wafer Transfer Bonding2009In: MikroSystemTechnik KONGRESS 2009, 2009Conference paper (Other academic)
    Abstract [en]

    Spatial light modulators (SLMs) based on indivvidually addressable micro-mirrors do show an increased use in projection displays, DUV lithography and adaptive optics. Mirror planarity and deflection characteristics are important issues for these applications. Mono-crystalline silicon as mirror material offers a great possibility to combine the perfect surface with the good mechanical properties of the crystalline material. Nevertheless, the challenge is the integration of mono-crystalline silicon in a CMOS process with low temperature budget (below 450deg C) and restricted material options. Thus, standard processes like epitaxial growth or re-crystallization of poly-silicon cannot be used. We will present a CMOS-compatible approach, using adhesive wafer transfer bonding with Benzocyclobutene (BCB) of a 300nm thin silicon membrane, located on a SOI donor wafer. After the bond process, the SOI donor wafer is grinded and spin etched to remove the handle silicon and the buried oxide layer, which results in a transfer of the mono-crystalline silicon membrane to the CMOS wafer. This technology is fully compatible for integration in a CMOS process, in order to fabricate SLMs, consisting of one million indivvidually addressable mono-crystalline silicon micro-mirrors. In this paper, we present fabrication process as well as first results of SLM devices with a pixel pitch of 16 micrometer.

  • 11416. Zimmer, Fabian
    et al.
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Bakke, Thor
    Bring, Martin
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    One-Megapixel Monocrystalline-Silicon Micromirror Array on CMOS Driving Electronics Manufactured With Very Large-Scale Heterogeneous Integration2011In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 20, no 3, p. 564-572Article in journal (Refereed)
    Abstract [en]

    In this paper, we demonstrate the first high-resolution spatial-light-modulator chip with 1 million tilting micromirrors made of monocrystalline silicon on analog high-voltage complementary metal-oxide-semiconductor driving electronics. This device, as result of a feasibility study, shows good optical and excellent mechanical properties. The micromirrors exhibit excellent surface properties, with a surface roughness below 1-nm root mean square. Actuated micromirrors show no imprinting behavior and operate drift free. Very large-scale heterogeneous integration was used to fabricate the micromirror arrays. The detailed fabrication process is presented in this paper, together with a characterization of the SLM devices. Large arrays of individually controllable micromirrors are the enabling component in high-perfomance mask-writing systems and promising for high throughput deep-ultraviolet maskless lithography systems. The adoption of new materials with enhanced characteristics is critical in meeting the challenging demands with regard to surface quality and operation stability in the future. Very large-scale heterogeneous integration may enable virtually any solid-state material to be integrated together with CMOS electronics. [2010-0272]

  • 11417.
    Zimmer, Fabian
    et al.
    Fraunhofer IPMS.
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Bakke, Thor
    SINTEF, Norway.
    Bring, Martin
    Fraunhofer IPMS.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Very large scale heterogeneous system integration for 1-megapixel mono-crystalline silicon micro-mirror array on CMOS driving electronics2011In: 2011 IEEE 24th International Conference on Micro Electro Mechanical Systems (MEMS), 2011, p. 736-739Conference paper (Refereed)
    Abstract [en]

    In this paper we demonstrate the first high mirror-count 1-level spatial light modulator (SLM) chip with 1 million tilting micro-mirrors made of mono-crystalline silicon on analogue, high-voltage CMOS driving electronics. The device from a feasibility study shows good optical and excellent mechanical properties. The micro-mirrors exhibit excellent surface properties with a surface roughness below 1 nm RMS, actuated micro-mirrors show no imprinting behavior and operate drift-free. Very large scale heterogeneous system integration was used to fabricate the micro-mirror array; the process is presented in this paper together with a characterization of the fabricated device.

  • 11418. Zimmer, Fabian
    et al.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Lapisa, Martin
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Ludewig, Thomas
    Bring, Martin
    Friedrichs, Martin
    Bakke, Thor
    Schenk, H.
    van der Wijngaart, Wouter
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Fabrication of large-scale mono-crystalline silicon micro-mirror arrays using adhesive wafer transfer bonding2009In: Proceedings of SPIE - The International Society for Optical Engineering / [ed] David L. Dickensheets, Harald Schenk, Wibool Piyawattanametha, 2009, Vol. 7208, p. 720807-Conference paper (Refereed)
    Abstract [en]

    Today,spatial light modulators (SLMs) based on individually addressable micro-mirrors playan important role for use in DUV lithography and adaptiveoptics. Especially the mirror planarity and stability are important issuesfor these applications. Mono-crystalline silicon as mirror material offers agreat possibility to combine the perfect surface with the goodmechanical properties of the crystalline material. Nevertheless, the challenge isthe integration of mono-crystalline silicon in a CMOS process withlow temperature budget (below 450°C) and restricted material options. Thus,standard processes like epitaxial growth or re-crystallization of poly-silicon cannotbe used. We will present a CMOS-compatible approach, using adhesivewafer transfer bonding with Benzocyclobutene (BCB) of a 300nm thinsilicon membrane, located on a SOI-donor wafer. After the bondprocess, the SOI-donor wafer is grinded and spin etched toremove the handle silicon and the buried oxide layer, whichresults in a transfer of the mono-crystalline silicon membrane tothe CMOS wafer. This technology is fully compatible for integrationin a CMOS process, in order to fabricate SLMs, consistingof one million individually addressable mono-crystalline silicon micro-mirrors. The mirrors,presented here, have a size of 16×16 µm2. Deflection isachieved by applying a voltage between the mirrors and theunderlying electrodes of the CMOS electronics. In this paper, wewill present the fabrication process as well as first investigationsof the mirror properties.

  • 11419.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Estimation of Power System Inertia2016In: Power and Energy Society General Meeting (PESGM), 2016 17-21 July 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Information about power system inertia is of utmost importance for the Transmission System Operators (TSOs), so that it can be guaranteed that the stability of the system is not under risk. A new offline inertia estimation method is proposed in this paper. The method includes the calculation of the total power change after a disturbance in the system, based on selection of appropriate time ranges of the Rate Of Change Of Frequency(ROCOF) curve. Nordic32 test system is used for the simulations, where different disturbances, load dynamics and data processing tools are considered. Finally, a comparison of the proposed method to two methods proposed in the past takes place.

  • 11420.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Power system inertia estimation by approaching load power change after a disturbance2017In: Power & Energy Society General Meeting, 2017 IEEE, Chicago, IL, USA: Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    The substitution of conventional synchronous power plants by intermittent generation leads to reduced power system inertia. This transition deteriorates system's frequency response and necessitates the estimation of power system inertia, so that adequate power resources are preserved. An offline estimation method is proposed in this paper, which aims to estimate the power change of the loads due to voltage dependency after a disturbance. To do that, data available at the generator buses are employed. The proposed method is applied on a modified version of Nordic32 test system under twenty different scenarios, which include generator and load disconnections. Finally, a comparison with two offline methods presented in the past literature takes place and demonstrates the advantages and disadvantages of the proposed method.

  • 11421.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Eriksson, R.
    Power system inertia estimation: Utilization of frequency and voltage response after a disturbance2018In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 161, p. 52-60Article in journal (Refereed)
    Abstract [en]

    Power system inertia is gradually being reduced due to the ongoing replacement of conventional synchronous power plants by intermittent generation. This affects the frequency response of the system and necessitates the estimation of power system inertia, so that sufficient power reserves are retained. This paper contributes with a novel disturbance-based inertia estimation method, that simultaneously estimates the power change after a disturbance. The proposed method accommodates the frequency and voltage dynamics, which significantly affect the system's power change, and hence the inertia estimation. Two separate approaches – that are also capable of standing alone – are combined, in order to accommodate the dynamics. An extended version of the Nordic32 test system is used for the application of the method, where several case studies and a comparison are investigated, so as to examine the method's accuracy and robustness.

  • 11422.
    Zografos, Dimitrios
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Paridari, Kaveh
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Estimation of power system inertia using particle swarm optimization2017In: 2017 19th International Conference on Intelligent System Application to Power Systems, ISAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 8071383Conference paper (Refereed)
    Abstract [en]

    Power system inertia is being globally reduced, due to the substitution of conventional synchronous power plants by intermittent generation. This threatens the frequency stability of the system and makes the estimation of power system inertia necessary, so that proactive measures can be imposed. A disturbance-based method is proposed in this paper, which estimates the total inertia constant of the power system. The method applies particle swarm optimization (PSO) to minimize a cost function, which is defined based on the swing equation. To do that, data available at the generator buses are employed. The proposed method is applied on the Nordic57 test system under twenty different scenarios, which include generator and load disconnections. Furthermore, a comparison with two methods presented in the literature is performed and demonstrates the higher performance of the proposed method, in the sense of the mean and the variance of the errors.

  • 11423. Zois, D. -S
    et al.
    Levorato, Marco
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mitra, U.
    Non-linear smoothers for discrete-time, finite-state Markov chains2013In: IEEE International Symposium on Information Theory: Proceedings, 2013, p. 2099-2103Conference paper (Refereed)
    Abstract [en]

    The problem of enhancing the quality of system state estimates is considered for a special class of dynamical systems. Specifically, a system characterized by a discrete-time, finite-state Markov chain state and observed via conditionally Gaussian measurements is assumed. The associated mean vectors and covariance matrices are tightly intertwined with the system state and a control input selected by a controller. Exploiting an innovations approach, finite-dimensional, non-linear approximate MMSE smoothing estimators are derived for the Markov chain system state. The resulting smoothers are driven by a control policy determined by a stochastic dynamic programming algorithm, which minimizes the MSE filtering error, and was proposed in our earlier work. An application of the smoothers derived in this paper is presented for the problem of physical activity detection in wireless body sensing networks, which illustrates the performance enhancement due to smoothing.

  • 11424.
    Zorbas, Dimitros
    et al.
    University of Piraeus.
    Douligeris, Christos
    University of Piraeus.
    Fodor, Viktoria
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Target location based sink positioning in wireless sensor networks2011In: 2011 18th International Conference on Telecommunications, ICT 2011, 2011, p. 21-26Conference paper (Refereed)
    Abstract [en]

    One of the main challenges in wireless sensor networks is to prolong the network lifetime by efficiently handling the limited battery life of the nodes. This problem becomes harder in applications where the nodes are randomly dropped in the field. In this paper we deal with the problem of the sink placement and of the network longevity, assuming a number of points in the field with known positions which must be covered by the sensors. Unlike other approaches, we consider the more realistic scenario where the coordinates of the sensors are not assumed to be known in advance and, thus, they cannot be used for the computation of the positions of the sinks. We present two solutions for the above problem; one based on the distance between the points and the second on the probability that a sensor may cover many points. We evaluate our approaches and compare them to algorithms that use the knowledge of the positions of the sensors in order to compute likely sink locations. It is shown that both proposed approaches present similar or better performance concerning network lifetime, while at the same time they significantly decrease the algorithm complexity.

  • 11425.
    Zorita, Julio
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Dynamics of small satellites with gravity gradient attitude control2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    SWIM (Space Weather using Ion Spectrometers and Magnetometers) is a CubeSat to be launched with the purpose of studying interaction between the Sun and the Earth. A magnetometer will be placed in a boom which provides gravity gradient stabilization. SWIM will be inserted in a 600 km circular orbit and it is required to maintain a LVLH (Local Vertical Local Horizontal) position. This master thesis analyses the dynamical behavior of SWIM. For doing so an attitude simulator and a mass model have been developed. Mass model has been designed according to linear stability analysis. Simulations with the mass model have been carried out from the most ideal environment to realistic orbit. As a result it has been deduced that gravity gradient stabilization propagates initial conditions which are perturbed by aerodynamic and magnetic torques. Magnetic torques could lead to uncontrolled yaw spin. Additionally the deployment of two solar panels to guarantee passive stabilization for yaw axes has been studied. Three axes stabilization and LVLH pointing can be achieved in an orbit lower than 600 km.

  • 11426. Zou, Y.
    et al.
    Hu, X.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, China.
    Lin, Z.
    Compact coplanar waveguide low-pass filter using a novel electromagnetic bandgap structure2006In: 7th International Symposium on Antennas, Propagation and EM Theory, Proceedings, 2006, p. 1039-1042Conference paper (Refereed)
    Abstract [en]

    In the present paper, a new electromagnetic bandgap (EBG) structure is proposed to design and fabricate low-pass filters on coplanar waveguide (CPW). Using the novel EBG structure, the filter prototypes exhibit sharp cutoff and low insertion loss in the passband. An equivalent lumped L-C circuit mode is introduced to describe the proposed EBG structure, which manifests an elliptic-function low-pass frequency response. Using only three units of this novel EBG cell, a compact low-pass filter device has been fabricated, which achieved sharp cutoff and deep attenuation levels on the stop band. The measured results showed consistency with the simulation using the method of momentum (MoM).

  • 11427. Zou, Y. Z.
    et al.
    He, H. J.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Analysis and optimization of an InGaAsP/InP waveguide variable optical attenuator2006In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 262, no 2, p. 188-192Article in journal (Refereed)
  • 11428. Zou, Yong-Zhuo
    et al.
    Lin, Zhi-Li
    Ling, Ti
    Yao, Jun
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A new broadband differential phase shifter fabricated using a novel CRLH structure2007In: Journal of Zhejiang University-Science A, ISSN 1673-565X, Vol. 8, no 10, p. 1568-1572Article in journal (Refereed)
  • 11429.
    Zou, Zhenhua
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Real-time communication in wireless lossy networks2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The last decades’ tremendous advances in wireless communications havebeen driven mainly by personal communications. Radio resource allocationmechanisms for optimizing key metrics, such as average throughput and delay,are by now rather well-developed. However, with the increased interest inwireless machine-to-machine communication, new challenges emerge, such asmulti-hop connectivity, lossy and bursty links, battery-powered nodes, andchanging/unknown link parameters, among others. With these challenges inmind, this thesis studies real-time communication in wireless lossy networks,and how the resulting networking primitive can be used to design networkedcontrol systems with optimal closed-loop performance.

    First, we study optimal forwarding of deadline-constrained traffic overmulti-hop networks with losses on links described by finite-state Markovchains. We consider two problems: maximizing the probability that packetsare delivered within specified deadlines; and minimizing the expected energycost with a guaranteed probability of on-time delivery. Both problems fallinto the category of Markov Decision Processes and can be studied in a generaldynamic programming framework. Particular instances with Bernoulliand Gilbert-Elliot loss models, which admit insight and efficient computations,are discussed. Moreover, a number of extensions and variations ofthe deadline-constrained forwarding problem are investigated. These extensionsinclude systems with unknown channel states and unknown link lossmodels, scenarios with multiple concurrent flows, and solutions adapted toopportunistic routing and the recent WirelessHART standard.

    Second, we show how the solution for the deadline-constrained forwardingproblem can be used in the optimal co-design of networked control systems.Specifically, we consider the joint design of packet forwarding policies andcontrollers for wireless control loops where sensor data are sent to the controllerover an unreliable and energy-constrained multi-hop wireless network.For fixed sampling rate of the sensor, the co-design problem separates into twowell-defined and independent subproblems: transmission scheduling for maximizingthe deadline-constrained reliability and optimal control under packetloss. We develop optimal and implementable solutions for these subproblemsand show that the optimally co-designed system can be efficiently found.

    Finally, we study online shortest-path routing problems in which link delaysare time-varying and modeled by random processes with initially unknownparameters. The optimal path can only be estimated by routing packetsthrough the network and observing the realized delays. The aim is to finda routing policy that minimizes the regret (the cumulative delay difference)between the path chosen by the policy and the unknown optimal path. Weformulate the problem as a combinatorial bandit optimization problem andconsider several scenarios. For each scenario, we derive the tight asymptoticlower bound on the regret that has to be satisfied by any online routing policy.These bounds help us to understand the performance improvements wecan expect when (i) taking routing decisions at each hop rather than at thesource only, and (ii) observing per-link costs rather than aggregate path costs.Efficient algorithms are proposed and evaluated against the state-of-the-art.

  • 11430.
    Zou, Zhenhua
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Real-time wireless communication with per-packet deadlines2012Licentiate thesis, monograph (Other academic)
  • 11431.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Demirel, Burak
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Minimum-energy packet forwarding policies for guaranteed LQG performance in wireless control systems2012In: 2012 IEEE 51st Annual Conference on Decision and Control (CDC), IEEE , 2012, p. 3341-3346Conference paper (Refereed)
    Abstract [en]

    This paper studies minimum-energy packet forwarding policies for communicating sensor measurements from plant to controller over an unreliable multi-hop wireless network so as to guarantee that the optimal controller achieves a prespecified closed-loop performance. For fixed sampling interval, we demonstrate that the minimal linear-quadratic control loss is monotonically decreasing in the reliability of the sensor-to-controller communication. This allows us to decompose the overall design problem into two separate tasks: finding the minimum end-to-end reliability that allows to achieve a prespecified linear-quadratic loss, and developing minimum-energy packet forwarding policies under a deadline-constrained reliability requirement. We develop optimal solutions for both subproblems and show how the co-designed system with minimum forwarding energy cost and guaranteed LQG control performance can be found by a one-dimensional search over admissible sampling periods. The paper ends with a numerical example which demonstrates the effectiveness of the proposed framework.

  • 11432.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Deadline-constrained maximum reliability packet forwarding with limited channel state information2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE Communications Society, 2013, p. 1721-1726Conference paper (Refereed)
    Abstract [en]

    This paper considers real-time packet forwarding over wireless multi-hop networks with lossy and bursty links. Our objective is to maximize the probability that individual packets reach their destination before a hard deadline. The loss processes on links are modeled by finite-state Markov chains. While the parameters of the Markov chains are assumed to be known, the instantaneous channel states are not accessible but have to be estimated from observations of successes and failures of actual packet transmissions. We formulate the forwarding problem as a partially observable Markov decision process and derive the optimal forwarding policy. A novel technique, based on maximum-volume inscribed ellipsoids, for computing approximate solutions with reduced implementation complexity is proposed. We further discuss structural properties of the value function and the optimal actions. Finally, numerical examples illustrate the power of the developed techniques.

  • 11433.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Minimum-energy packet forwarding over lossy networks under deadline and reliability constraints2012In: 10th International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt),2012, IEEE conference proceedings, 2012, p. 224-231Conference paper (Refereed)
    Abstract [en]

    This paper studies minimum-energy packet forwardingover multi-hop lossy networks under deadline andreliability constraints. We assume a routing topology in theform of a directed graph with packet loss processes on linksdescribed by finite-state Markov chains, and formulate the forwardingproblem as a finite-horizon constrained Markov decisionprocess. We show that the minimum energy forwarding policyunder hard deadline and reliability constraint can be computedusing dynamic programming, and that the optimal forwardingpolicy is a randomized policy over two history-independent anddeterministic policies. Closed-form optimal policies are derivedfor some particular scenarios. Numerical examples show thatthe transmission energy cost of achieving reliabilities close to themaximum can be significant when links are bursty. In addition,transmission power adjustments can further reduce energy cost.Finally, we develop simple heuristic policies with a good balancebetween transmission energy cost and reliability.

  • 11434.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Online shortest path routing: The value of information2014Conference paper (Refereed)
    Abstract [en]

    This paper studies online shortest path routing over dynamic multi-hop networks. Link costs or delays are time-varying and modelled by independent and identically distributed random processes, whose parameters are initially unknown. The parameters, and hence the optimal path, can only be estimated by routing packets through the network and observing the realized delays. Our aim is to find a routing policy that minimizes the regret (the cumulative delay difference) between the path chosen by the policy and the unknown optimal path. We formulate the problem as a combinatorial bandit optimization problem and consider several scenarios that differ in where routing decisions are made and in the information available when making the decision. For each scenario, we derive the tight asymptotic lower bound on the regret that has to be satisfied by any online routing policy. These bounds help us to understand the performance improvements we can expect when (i) taking routing decisions at each hop rather than at the source only, and (ii) observing per-link costs rather than aggregate path costs. In particular, we show that (i) is of no use while (ii) can have a spectacular impact. Efficient algorithms are proposed and evaluated against the state-of-the a

     

  • 11435.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Soldati, Pablo
    KTH, School of Electrical Engineering (EES).
    Zhang, Haibo
    KTH, School of Electrical Engineering (EES).
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Delay-constrained maximum reliability routing over lossy links2010In: Proceedings of the IEEE Conference on Decision and Control, IEEE , 2010, p. 973-978Conference paper (Refereed)
    Abstract [en]

    This paper studies the problem of joint routing and transmission scheduling for reliable real-time communication over lossy networks. We impose a strict latency bound on the packet delivery from source to destination and develop transmission scheduling policies that maximize the probability that the packet is delivered within the specified deadline. A solution to this problem allows to characterize the set of achievable latencies and packet loss probabilities for a given network. We develop dynamic programming-based solutions for deadline-constrained maximum reliability routing under Bernoulli and Gilbert-Elliot packet loss models. Particular instances of the problem that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.

  • 11436.
    Zou, Zhenhua
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Soldati, Pablo
    Huawei Technologies Sweden AB.
    Zhang, Haibo
    University of Otago, New Zealand.
    Johansson, Mikael
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Energy-efficient deadline-constrained maximum reliability forwarding in lossy networks2012In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 11, no 10, p. 3474-3483Article in journal (Refereed)
    Abstract [en]

    This paper studies the problem of optimal forwarding for reliable and energy-efficient real-time communication over multi-hop wireless lossy networks. We impose a strict per-packet latency bound and develop forwarding policies that maximize the probability that the packet is delivered within the specified deadline minus a transmission energy cost. A solution to this problem allows to characterize the set of achievable latency-reliability pairs and to trace out the Pareto frontier between achievable deadline-constrained reliability and transmission energy cost. We develop dynamic programming-based solutions under a finite-state Markov channel model. Particular instances with Bernoulli and Gilbert-Elliot loss models that admit numerically efficient solutions are discussed and our results are demonstrated on several examples.

  • 11437. Zu, L.
    et al.
    Ji, Y.
    Wang, Liping
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Zhong, L.
    Liu, F.
    Wang, P.
    Xu, J.
    Joint optimization in multi-user MIMO-OFDMA relay-enhanced cellular networks2011In: 2011 IEEE Wireless Communications and Networking Conferenc, 2011, p. 13-18Conference paper (Refereed)
    Abstract [en]

    MIMO, OFDMA and cooperative relaying are the key technologies in future wireless communication systems. However, under the usage of these technologies, resource allocation becomes a more crucial and challenging task. In multi-user MIMO-OFDMA relay-enhanced cellular networks, we formulate the optimal instantaneous resource allocation problem including user group selection, path selection, power allocation, and subchannel scheduling to maximize system capacity. We first propose a low-complex resource allocation algorithm named CP-CP under constant uniform power allocation and then use a water-filling method named CP-AP to allocate power among transmitting antennas. Moreover, we solve the original optimization problem efficiently by using the Jensen's inequality and propose a modified iterative water-filling algorithm named AP-CP. Based on AP-CP, the AP-AP algorithm is proposed to allocate power adaptively not only among subchannels but also among multiple transmitting. Finally, we compare the performance of the four schemes. Our results show that allocating power among subchannels is more effective than among transmitting antennas if the average signal-to-noise radio of users is low, and vice versa. Furthermore, the AP-AP algorithm achieves the highest throughout especially for users near the cell edge.

  • 11438. Zuin, M.
    et al.
    Dal Bello, S.
    Marrelli, L.
    Puiatti, M. E.
    Agostinetti, P.
    Agostini, M.
    Antoni, V.
    Auriemma, F.
    Barbisan, M.
    Barbui, T.
    Baruzzo, M.
    Belli, F.
    Bettini, P.
    Bigi, M.
    Bilel, R.
    Boldrin, M.
    Bolzonella, T.
    Bonfiglio, D.
    Brombin, M.
    Buffa, A.
    Bustreo, C.
    Canton, A.
    Cappello, S.
    Carraro, L.
    Cavazzana, R.
    Cester, D.
    Chacon, L.
    Chitarin, G.
    Cooper, W. A.
    Cordaro, L.
    Palma, M. Dalla
    Deambrosis, S.
    Delogu, R.
    De Lorenzi, A.
    De Masi, G.
    Dong, J. Q.
    Escande, D. F.
    Fassina, A.
    Felici, F.
    Ferro, A.
    Finotti, C.
    Franz, P.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Gaio, E.
    Ghezzi, F.
    Giudicotti, L.
    Gnesotto, F.
    Gobbin, M.
    Gonzalez, W. A.
    Grando, L.
    Guo, S. C.
    Hanson, J. D.
    Hirshman, S. P.
    Innocente, P.
    Jackson, J. L.
    Kiyama, S.
    Komm, M.
    Kudlacek, O.
    Laguardia, L.
    Li, C.
    Liu, B.
    Liu, S. F.
    Liu, Y. Q.
    Lopez-Bruna, D.
    Lorenzini, R.
    Luce, T. C.
    Luchetta, A.
    Maistrello, A.
    Manduchi, G.
    Mansfield, D. K.
    Marchiori, G.
    Marconato, N.
    Marcuzzi, D.
    Martin, P.
    Martines, E.
    Martini, S.
    Mazzitelli, G.
    McCormack, O.
    Miorin, E.
    Momo, B.
    Moresco, M.
    Narushima, Y.
    Okabayashi, M.
    Paccagnella, R.
    Patel, N.
    Pavei, M.
    Peruzzo, S.
    Pilan, N.
    Pigatto, L.
    Piovan, R.
    Piovesan, P.
    Piron, C.
    Piron, L.
    Predebon, I.
    Pucella, G.
    Rea, C.
    Recchia, M.
    Rizzolo, A.
    Rostagni, G.
    Ruset, C.
    Sajo-Bohus, L.
    Sakakita, H.
    Sanchez, R.
    Sarff, J. S.
    Sattin, F.
    Scarin, P.
    Schmitz, O.
    Schneider, W.
    Siragusa, M.
    Sonato, P.
    Spada, E.
    Spagnolo, S.
    Spolaore, M.
    Spong, D. A.
    Spizzo, G.
    Stevanato, L.
    Suzuki, Y.
    Taliercio, C.
    Terranova, D.
    Tudisco, O.
    Urso, G.
    Valente, M.
    Valisa, M.
    Vallar, M.
    Veranda, M.
    Vianello, N.
    Villone, F.
    Vincenzi, P.
    Visona, N.
    White, R. B.
    Xanthopoulos, P.
    Xu, X. Y.
    Yanovskiy, V.
    Zamengo, A.
    Zanca, P.
    Zaniol, B.
    Zanotto, L.
    Zhang, Y.
    Zilli, E.
    Overview of the RFX-mod fusion science activity2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102012Article in journal (Refereed)
    Abstract [en]

    This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped reversed-field pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from 4 down to 1.2 values). The full range of magnetic configurations in between the two, the so-called ultra-low q ones, has been explored, with the aim of studying specific physical issues common to all equilibria, such as, for example, the density limit phenomenon. The powerful RFX-mod feedback control system has been exploited for MHD control, which allowed us to extend the range of experimental parameters, as well as to induce specific magnetic perturbations for the study of 3D effects. In particular, transport, edge and isotope effects in 3D equilibria have been investigated, along with runaway mitigations through induced magnetic perturbations. The first transitions to an improved confinement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modification of the edge electric field through a polarized electrode. The experiments are supported by intense modeling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modifications to the RFX-mod device, which will enable further contributions to the solution of key issues in the roadmap to ITER and DEMO, are also briefly presented.

  • 11439.
    Zurita Ares, Benigno
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Park, Pan Gun
    KTH, School of Electrical Engineering (EES).
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Speranzon, Alberto
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On power control for wireless sensor networks: System model, middleware component and experimental evaluation2015In: 2007 European Control Conference, ECC 2007, 2015, p. 4293-4300Conference paper (Refereed)
    Abstract [en]

    In this paper, we investigate strategies for radio power control for wireless sensor networks that guarantee a desired packet error probability. Efcient power control algorithms are of major concern for these networks, not only because the power consumption can be signicantly decreased but also because the interference can be reduced, allowing for higher throughput. An analytical model of the Received Signal Strength Indicator (RSSI), which is link quality metric, is proposed. The model relates the RSSI to the Signal to Interference plus Noise Ratio (SINR), and thus provides a connection between the powers and the packet error probability. Two power control mechanisms are studied: a Multiplicative-Increase Additive-Decrease (MIAD) power control described by a Markov chain, and a power control based on the average packet error rate. A component-based software implementation using the Contiki operating system is provided for both the power control mechanisms. Experimental results are reported for a test-bed with Telos motes.

  • 11440.
    Zuxing, Li
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Assessment of Privacy in Distributed Detection Problems2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As a promising technology, wireless sensor networks have a wide range of applications. However, the development of wireless sensor networks is stillin face of multiple challenges. Among these challenges, the privacy issue is acritical parameter involved in providing secure and reliable services and attracts much attention from researchers and engineers. In the last decade, alarge number of privacy solutions for wireless sensor networks have been proposed. However, most of them are taken as additional secure functionality blocks rather than being integrated in the original sensor network designs.

    In this thesis project, we will focus on the privacy assessment of a parallel distributed detection network, which represents a simplied physical-layer of wireless sensor networks. The security threat is assumed to come from a passive eavesdropper. Four privacy leakage criteria are proposed to evaluate the privacy issue of the distributed detection network in dierent scenarios. As references, the privacy leakages are evaluated by dierent criteria when the distributed detection system is optimized in the perspectives of Bayesian detection theory and information theory without considering the presence of the eavesdropper. Then, we propose the corresponding privacy-concerned distributed detection systems. Comparisons to the optimal detection systems are performed and they reveal the trade-off between privacy leakage suppression and detection performance degradation.

  • 11441. Zvolensky, T.
    et al.
    Chicherin, Dmitry
    Department of Radio Science and Engineering, SMARAD Centre of Excellence, Aalto University.
    Räisäinen, Antti
    Department of Radio Science and Engineering, SMARAD Centre of Excellence, Aalto University.
    Simovski, C.
    Sterner, Mikael
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Hakojarvi, H.
    Leaky-wave antenna at 77 GHz2011In: Proceedings of the 41st European Microwave Conference, 2011, p. 1039-1042Conference paper (Refereed)
    Abstract [en]

    Microelectromechanical (MEMS) technology is being used for many purposes in reconfigurable devices due to its advantages compared to other technologies, e.g., varactors. In this paper MEMS are suggested to be used for the development of leaky-wave antenna for 77 GHz. Antenna comprises a right-left handed transmission line, where a microstrip is used as the right handed transmission line. The left handed loading comprises series reconfigurable MEMS capacitors and shunt narrow strip inductors. Analytical design, simulation and measurement of a planar leaky-wave antenna structure are carried out and compared.

  • 11442.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Electrical Engineering (EES).
    Quantum optics with nanowires (Conference Presentation)2017In: QUANTUM DOTS AND NANOSTRUCTURES: GROWTH, CHARACTERIZATION, AND MODELING XIV / [ed] Huffaker, DL Eisele, H, SPIE-INT SOC OPTICAL ENGINEERING , 2017, article id UNSP 101140IConference paper (Refereed)
  • 11443. Álvarez, Jesús
    et al.
    Sola, Laura
    Cretich, Marina
    Swann, Marcus J.
    Gylfason, Kristinn B.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Volden, Tormod
    Chiari, Marcella
    Hill, Daniel
    Real time optical immunosensing with flow-through porous alumina membranes2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 202, p. 834-839Article in journal (Refereed)
    Abstract [en]

    Through the presentation of analytical data from bioassay experiments, measured by polarimetry, we demonstrate for the first time a real time immunoassay within a free standing macroporous alumina membrane. The 200 nm nominal pore diameter of the membrane enables flow-through, thereby providing an ideal fluidic platform for the targeted delivery of analytes to bioreceptors immobilized on the pore walls, enabling fast sensing response times and the use of small sample volumes (<100 μL). For the immunoassay, the pore walls were first coated with the functional copolymer, copoly(DMA-NAS) using a novel coupling process, before immobilization of the allergen protein, β-lactoglobulin, by spotting. The immuno-assay then proceeded with the binding of the primary and secondary antibody cognates, rabbit anti-β-lactoglobulin and anti-rabbit IgG respectively. Through the use of streptavidin coated quantum dots as refractive index signal enhancers, a noise floor for individual measurements of 3.7 ng/mL (25 pM) was obtained, with an overall statistical, or formal assay LOD of 33.7 ng/mL (225 pM), for total assay time below 1 h.

  • 11444.
    Ängquist, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Antonopoulos, Antonios
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Arm-current-based control of modular multilevel converters2013In: 2013 15th European Conference on Power Electronics and Applications, EPE 2013, IEEE , 2013, p. 6631999-Conference paper (Refereed)
    Abstract [en]

    Inner control of a Modular Multilevel Converter (M2C) based on direct tolerance-band modulation of the arm currents has been studied. This approach is attractive because it allows low switching frequency, directly provides the desired arm-current waveform and enables fast protective actions at the same time as the complexity of the over-all control system is reduced. Issues related to common-mode voltage are discussed and supporting PSCAD simulations are presented together with some results from experiments with a reduced-power prototype converter.

  • 11445.
    Ängquist, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Antonopoulos, Antonios
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Siemaszko, Daniel
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Vasiladiotis, Michail
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Open-Loop Control of Modular Multilevel Converters Using Estimation of Stored Energy2011In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 47, no 6, p. 2516-2524Article in journal (Refereed)
    Abstract [en]

    The internal control of a modular multilevel converter aims to equalize and stabilize the submodule capacitor voltages independent of the loading conditions. It has been shown that a submodule selection mechanism, included in the modulator, can provide voltage sharing inside the converter arm. Several procedures for controlling the total stored energy in each converter arm exist. A new approach is described in this paper. It is based on estimation of the stored energy in the arms by combining the converter electromotive force reference, the measured alternating output current, and the known direct voltage. No feedback controllers are used. Experimental verification on a three-phase 10 kVA prototype is presented along with the description of the new procedure.

  • 11446.
    Ängquist, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Bongiorno, Massimo
    Dept. of Energy and Environment, Chalmers University of Technology, Sweden.
    Auto-normalizing Phase-Locked Loop for Grid-connected Converters2009In: 2009 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION, VOLS 1-6, NEW YORK: IEEE , 2009, p. 2430-2437Conference paper (Refereed)
    Abstract [en]

    A proper synchronization algorithm is a key issue for modern grid-connected power electronic devices, especially in case of weak networks. This paper deals with a novel Phase-Locked Loop (PLL) algorithm for power electronic devices. The proposed algorithm, here named Auto-normalizing PLL (AN-PLL), is able to deal with both amplitude and phase-angle changes in the measured grid voltage. Thus, the proposed concept provides a PLL control performance that is independent on the control signal amplitude. Advantages of the AN-PLL over the conventional PLL approach are highlighted. Experimental results are used to validate the dynamic performance of the proposed synchronization system.

  • 11447.
    Ängquist, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Haider, Arif
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Jiang, Hongbo
    Trafikverket, Borlänge, Sweden.
    Open-loop approach to control a Modular Multilevel Frequency Converter2011In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011) / [ed] EPE Association, 2011Conference paper (Refereed)
    Abstract [en]

    Frequency converters are required to supply power from the public three-phase network to railways using 16.7 Hz single-phase in their rolling stock. The emerging Modular Multilevel Converter (M2C) technology offers the possibility to make such power conversion in one step using Modular Multilevel Frequency Converters (MMFC) with full-bridge sub-modules. A detailed study of the modulation and control of such converters is presented in this paper. The voltage inserted by each arm of the MMFC is a mixture of the three-phase 50 Hz voltage and the single phase 16.7 Hz voltage. It is important that the voltage reference given to the modulator will be carefully reproduced by the converter because any deviation can introduce undesired frequency components from the single-phase side to the three-phase side and vice versa. The fact that the low frequency, single-phase load causes low-frequency ripple in the total capacitor voltage complicates the problem to generate the correct modulation pattern. In this paper it is proposed to solve that difficulty by estimating the instaneous total capacitor voltages in each arm and provide that information to the modulator. It is shown that such estimations can be performed using measured currents on the single- and three-phase sides. Stable single-phase voltage, symmetrical undistorted three-phase currents and stable converter capacitor voltages are achieved under varying loading conditions. Models in Matlab/Simulink (continuous) and EMTDC/PSCAD (discrete sub-modules) have been developed in this study.

  • 11448.
    Ängskog, Per
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap.
    Avsiktliga elektromagnetiska störningar: Det osynliga hotet2014In: Electronics and the Environment, ISSN 1095-2020, Vol. 1, p. 16-17Article in journal (Other academic)
    Abstract [sv]

    I vårt moderna samhälle blir vi alltmer beroende av olika elektroniska kommunikations- och styrsystem, något som redan har upptäckts av kriminella, som utnyttjat svagheter i systemen för att begå brott. Detta är ett nytt scenario vi måste acceptera och lära oss hantera.

  • 11449.
    Ängskog, Per
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap.
    EMP-symposium 8-9 maj 2014 i Oslo2014In: Electronic Environment, Vol. 2, p. 22-23Article in journal (Other (popular science, discussion, etc.))
  • 11450.
    Ängskog, Per
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Högskolan i Gävle.
    Bäckström, Mats
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. SAAB Aeronautics, SAAB AB.
    Vallhagen, Bengt
    SAAB Aeronautics, SAAB AB.
    High Power Microwave Effects on Coated Window Panes2015In: Asia Electromagnetics Conference (ASIAEM) 2015, 2015Conference paper (Refereed)
    Abstract [en]

    Today window panes are usually coated with at least one metal or metal oxide layer to prevent heat energy of the light spectrum from propagating to the other side. This has given problems regarding radio propagation through windows, which might be utilized as a part of a buildings IEMI protection. This paper reports the results from measurements of the shielding effectiveness of a selection of modern window panes before and after irradiation with high power electromagnetic waves. The shielding effectiveness measurements are made in a nested reverberation chamber covering the range 1 – 18 GHz; both before and after high power irradiation at 1.3 GHz. The results show that the shielding effectiveness of window panes may be severely impaired due to thermal stress effects on the coatings during the irradiation, depending of the type of coating.

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