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  • 1.
    Abrahamsson, Lars
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Optimal PowerFlow (OPF) Model with Unified AC-DC Load Flow and Optimal Commitmentfor an AC-catenary Railway Power Supply System (RPSS) fed by aHigh Voltage DC (HVDC) transmission lineManuscript (preprint) (Other academic)
    Abstract [en]

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

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

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

  • 2.
    Alahakoon, Sanath
    KTH, Superseded Departments, Electric Power Systems.
    Digital motion control techniques for electrical drives2000Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    Digital motion control area toady is a well-established one,which is believed to be first initiated by power electronicengineers in the early seventies. Modern digital controltheory, advances in digital signal processor andmicrocontroller technology and recent developments in powerelectronic devices have made this field a very competitive one.The objective of this thesis is to present some digital motioncontrol techniques that can be applied for electrical drives.This is done by investigating two motion control problemsassociated with electrical drives; namely, precision motioncontrol and sensorless motion control.

    Application of digital motion control techniques for preciseeccentric rotor positioning of an induction machine with ActiveMagnetic Bearings (AMB) is the first application problemaddressed in the thesis. The final goal is to prepare aflexible test rig for the study of acoustic noise in standardinduction machines with rotor eccentricity. AMB control hasbeen a challenging task for the control engineers since itsinvention. Various types of control techniques - both analogand digital - have been attempted with a lot of success overthe past years. In the application area of rotating machines,the whole concept of AMB control means stabilizing the rotor ofthe machine in the exact center of the radial AMBs andmaintaining that position under magnetic disturbance forcesexerted on it by the stator under running condition. The aim ofthe first part of the thesis is to present several digitalmotion control techniques that would give the user theflexibility of moving the rotor to any arbitrary position inthe air gap and maintaining that eccentric position.

    The second part of the thesis dealt with sensorless controlof Permanent Magnet Synchronous Motors (PMSM) for high-speedapplications. Conventional PMSM drives employ a shaft-mountedencoder or a resolver to identify the rotor flux position. Itis advantageous to eliminate the shaft-mounted sensor byincorporating sensorless control schemes for PMSM drive systemsdue to many reasons. A sensorless control scheme must besufficiently robust and less computationally heavy for it to besuccessful. However, reliable performance of a sensorlesscontrol drive strategy is always an integration of many digitalmotion control techniques. Implementation of fast currentcontrol by overcoming sampling delay in the discrete system isa key issue in this respect. Suitable speed control with areliable controller anti-windup mechanism is also essential.Compensation techniques for the inverter non-idealities mustalso be incorporated to achieve better performance. In thispart of the thesis, all these aspects of a well performingsensorless control strategy for a PMSM are investigated.Frequency dependent machine parameter variation, which is asignificant practical problem against achieving the expectedperformance of these control strategies, is also addressed.

    Most of the problems addressed in the thesis are related toimplementation issues of a successful control method. Theapproach in this work is to find solutions to those applicationissues from the automatic control theory.

    Keywords:Eccentric rotor positioning, modeling,integrator anti-windup, bumpless transfer, identification,periodic disturbance cancellation, sampling delay compensation,cascaded control, speed and position estimation, compensationsfor non-idealities, parameter estimation, start-uptechnique

  • 3.
    Alahakoon, Sanath
    KTH, Superseded Departments, Electric Power Systems.
    On digital control techniques for active magnetic bearings1999Licentiate thesis, comprehensive summary (Other scientific)
  • 4.
    Amelin, Mikael
    KTH, Superseded Departments, Electric Power Systems.
    Alternative för landsbygdselektrifiering i utvecklingsländer. En fallstudie i kKasulu, Tanzania1997Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 5.
    Amelin, Mikael
    KTH, Superseded Departments, Electric Power Systems.
    Small-scale Renewable Energy Sources for Rural Electrification. Possibilities and Limitations1998Report (Other academic)
  • 6.
    Andersson, Bengta
    KTH, Superseded Departments, Electric Power Systems.
    An Optimisation Model for a Complex Small Scale Hydropwer System2003Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 7.
    Andersson, Jonas
    KTH, Superseded Departments, Electric Power Systems.
    On IT system integration: prospects and consequences of energy market deregulation1997Licentiate thesis, comprehensive summary (Other scientific)
  • 8.
    Aravand, Payman
    KTH, Superseded Departments, Electric Power Systems.
    Power Flow Calculation for Control of Power Network Data1999Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 9.
    Arnborg, Stefan
    KTH, Superseded Departments, Electric Power Systems.
    Emergency control of power systems in voltage unstable conditions1997Doctoral thesis, monograph (Other scientific)
  • 10.
    Axente, Iurie
    KTH, Superseded Departments, Electric Power Systems.
    Belastningsfördelning i kommplex form: En ny metod för analys av stabiliteten i stationära tillstånd2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 11.
    Baldursdottir, Iris
    KTH, Superseded Departments, Electric Power Systems.
    Nätvärn mot långsam spänningsinstabilitet i det Nordiska kraftsystemet2001Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 12.
    Bertling, Lina
    KTH, Superseded Departments, Electric Power Systems.
    On reliability assessment of distribution systems and reliability centred maintenance1999Licentiate thesis, monograph (Other scientific)
  • 13. Billinton, R.
    et al.
    Fotuhi-Firuzabad, M.
    Bertling, Lina M.
    KTH, Superseded Departments, Electric Power Systems.
    Bibliography on the application of probability methods in power system reliability evaluation 1996-19992001In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 16, no 4, p. 595-602Article in journal (Refereed)
    Abstract [en]

    This paper presents a bibliography of papers on the subject of power system reliability evaluation. Papers in such areas as: probabilistic load flow, probabilistic production costing, probabilistic transient stability evaluation etc. have not been included except where they specifically address power system reliability evaluation. It includes material which has been made available since the publication of six previous papers Bibliography on the Application of Probability Methods in Power System Reliability Evaluation, IEEE Transactions on Power Apparatus and Systems PAS-91, 1972, pp. 649-660, Pas-97, 1978, pp. 2235-2242, PAS-103, 1984, pp. 275-282, IEEE Transactions on Power Systems, Vol. 3, no. 4, Nov. 1988, pp. 1555-1564, Vol. 9, No. 1, Feb. 1994, pp. 41-49, and Vol. 14, no. 1, Feb. 1999, pp. 51-57.

  • 14.
    Bochkareva, Viktoria
    KTH, Superseded Departments, Electric Power Systems.
    Development planning of electricity distribution network1997Licentiate thesis, monograph (Other scientific)
  • 15.
    Bäckström, Thomas
    KTH, Superseded Departments, Electric Power Systems.
    Integrated energy transducer drive for hybrid electric vehicles2000Doctoral thesis, monograph (Other scientific)
  • 16.
    Carlsson, Anna
    KTH, Superseded Departments, Electric Power Systems.
    Simulering av frekvensomvandlare2001Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 17.
    Centeno, Eva
    KTH, Superseded Departments, Electric Power Systems.
    Dubbelmatad asynkrongenerator för vindkraft2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 18.
    Cheong, Kam-Hoong
    KTH, Superseded Departments, Electric Power Systems.
    IT strategy for electric utilities1999Doctoral thesis, comprehensive summary (Other scientific)
  • 19.
    Daugulis, Arnis
    KTH, Superseded Departments, Electric Power Systems.
    Requirements engineering in IT procurement projects at power utilities: bridging the gap between theory and practice1998Licentiate thesis, comprehensive summary (Other scientific)
  • 20.
    Derrico, Antonio
    KTH, Superseded Departments, Electric Power Systems.
    Analys av ett industriellt elnät hos Vattenfall Värme, Uppsala2002Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 21.
    Ek, Erik
    KTH, Superseded Departments, Electric Power Systems.
    Reaktiv effektkompensering i distributionsnät2002Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 22.
    Engdahl, Henrik
    KTH, Superseded Departments, Electric Power Systems.
    Simuleringsbevis för växelverkade par av egenvärden1998Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 23.
    Engström, Jörgen
    KTH, Superseded Departments, Electric Power Systems.
    On design of slotless permanent magnet machines1999Licentiate thesis, monograph (Other scientific)
  • 24.
    Falconer, Ingvar
    KTH, Superseded Departments, Electric Power Systems.
    Interconnectors and Market Power in Deregulated Electric Power Systems1999Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 25.
    Farieta, Jaime Antonio
    KTH, Superseded Departments, Electric Power Systems.
    Kortsiktig produktionsplanering1999Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 26.
    Fransson, Anders
    KTH, Superseded Departments, Electric Power Systems.
    Visning i realtid a dynamiska storheter i elkraftsystem2001Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 27.
    fält, Johan
    et al.
    KTH, Superseded Departments, Electric Power Systems.
    Katzman, Jakob
    KTH, Superseded Departments, Electric Power Systems.
    SPICA - ARISTO JÄMFÖRELSE studie av analysprogram med avseende på spånningskollaps i elektriska kraftsystem2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Safe operation of a large synchronous power system as Nordel is not an easy task.

    There are several aspects to take into consideration. This thesis focuses on the problems due to voltage collapses in a transmission system.

    The ability to foresee an upcoming collapse is vital to maintain stable operation of the grid. The grid operator at Svenska Kraftnät (SvK) uses the computer program SPICA to predict the maximum transfer limit at specified transfer sections. SPICA uses actual states from the grid to predict the transfer limitation, and a quarter later a renewed estimate is produced and so on. This means that the operator can se his transfer limits vary every fifteen minutes.

    Our task in this project is to validate the accuracy of the limitations obtained by SPICA. The validation process was carried out as a comparison with another power system analyser, ARISTO. The latter program simulates transient stability as a function of time, and is a versatile tool in many aspects. Another objective of this project is to develop the two programs as we discover disparity.

    Our investigations carried out in the CIGRÉ Nordic 32 test system show that, the method of repeatedly updated load flows can in some extent be used to predict the limit of stable operation, in a transfer limiting point of view. Repeatedly investigations show that the prediction seems to be more accurate, the closer the actual point of operation, is to the physical transfer limit.

    Further investigations with ARISTO as a guide, we discovered that this behaviour depended on the way to express the reactance in the generator model, which in case of a net failure causes SPICA to produce a value some few percent too high.

    During the process we also discovered a couple of improvements of the software involved, which were immediately implemented by the system administrator. The continuous upgrades have led to an iterative process of the analysis. The project also involved production of a tool for converting network-databases between ARISTO-SPICA, This has been made by ordinary staff at SvK by our requirements.

  • 28.
    Ghandari, Mehrdad
    KTH, Superseded Departments, Electric Power Systems.
    Control of power oscillations in transmission systems using controllable series devices1997Licentiate thesis, monograph (Other scientific)
  • 29.
    Ghandhari, Mehrdad
    KTH, Superseded Departments, Electric Power Systems.
    Control Lyapunov Functions: A Control Strategy for Damping of Power Oscillations in Large Power Systems2000Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    In the present climate of deregulation and privatisation, theutilities are often separated into generation, transmission anddistribution companies so as to help promote economic efficiencyand encourage competition. Also, environmental concerns,right-of-way and cost problems have delayed the construction ofboth generation facilities and new transmission lines while thedemand for electric power has continued to grow, which must bemet by increased loading of available lines. A consequence isthat power system damping is often reduced which leads to a poordamping of electromechanical power oscillations and/or impairmentof transient stability. The aim of this thesis is to examine theability of Controllable Series Devices (CSDs), such as

    Unified Power Flow Controller (UPFC)

     

    Controllable Series Capacitor (CSC)

     

    Quadrature Boosting Transformer (QBT)

     

    for improving transient stability and damping ofelectromechanical oscillations in a power system.

    For these devices, a general model is used in power systemanalysis. This model is referred to as injection model which isvalid for load flow and angle stability analysis. The model isalso helpful for understanding the impact of the CSDs on powersystem stability.

    A control strategy for damping of electromechanical poweroscillations is also derived based on Lyapunov theory. Lyapunovtheory deals with dynamical systems without input. For thisreason, it has traditionally been applied only to closed-loopcontrol systems, that is, systems for which the input has beeneliminated through the substitution of a predetermined feedbackcontrol. However, in this thesis, Lyapunov function candidatesare used in feedback design itself by making the Lyapunovderivative negative when choosing the control. This controlstrategy is called Control Lyapunov Function (CLF) for systemswith control input.

  • 30.
    Ghans Miller, Michelle
    KTH, Superseded Departments, Electric Power Systems.
    Tillförlitlighetsanalys av öeverförningssystem med användande1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 31.
    Grigoriou, Alexandra
    KTH, Superseded Departments, Electric Power Systems.
    An Optimisation Model for a Complex Small Scale Hydropower System2003Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 32.
    Gustafsson, Kjell
    KTH, Superseded Departments, Electric Power Systems.
    Likströmmar i elkraftsystem2000Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 33.
    Gustafsson, Roger
    KTH, Superseded Departments, Electric Power Systems.
    Modellering och simulering av vattenkraftverk med komplexa vattenvägar1998Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 34.
    Gwangombe, Florence
    KTH, Superseded Departments, Electric Power Systems.
    Studium av elkvaliten i ett distributionssystem i Tanzania1999Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 35.
    Haglind, Magnus
    KTH, Superseded Departments, Electric Power Systems.
    Achieving business supporting IT-systems: strategies for power utilities on a deregulated market1998Licentiate thesis, monograph (Other scientific)
  • 36.
    Harnefors, Lennart
    KTH, Superseded Departments, Electric Power Systems.
    On analysis, control and estimation of variable-speed drives1997Doctoral thesis, monograph (Other scientific)
  • 37.
    Hassani Gaghighi, Ziaedin
    KTH, Superseded Departments, Electric Power Systems.
    Stabilitetskreteria och urfasfallsskydd för generatorer1999Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 38.
    He, Ying
    KTH, Superseded Departments, Electric Power Systems.
    Modelling and evaluating automation effect on reliability of distribution systems1999Licentiate thesis, monograph (Other scientific)
  • 39.
    Hedayaty, Mohammad Ali
    KTH, Superseded Departments, Electric Power Systems.
    Jämförelse mellan statiska och dynamiska metoder för breäkning av felströmmar2000Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 40.
    Hedenstrand, Linda
    KTH, Superseded Departments, Electric Power Systems.
    Analys av styrbara seriekondensatorer med hjälp av energi-funktioner1998Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
  • 41.
    Helgeson, Anders
    KTH, Superseded Departments, Electric Power Systems.
    Analysis of dielectric response measurement methods and dielectric properties of resin-rich insulation during processing2000Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    The dielectric diagnostic methods ofpolarisation/depolarisation currents and recovery voltage,which are time domain methods, and capacitance and tandmeasurements at different frequencies, which is a frequencydomain method, have been studied here. In the first part of thethesis, these measurement methods are analysed and evaluated.Three different types of insulation systems are included in theevaluation, oil/paper ("high" loss), resin-rich mica tape("medium" loss) and cross-linked polyethylene, XLPE, ("low"loss). These three systems have different dielectric responsein both shape and magnitude. Conclusions are made regardingchoice of measurement method depending on the dielectricresponse of the insulation material. Examples are also given ofhow to estimate conductivity and the dielectric responsefunction in the time domain from measurements with a finitecharging period.

    Furthermore, relations between time domain and frequencydomain and the possibilities of Fourier transforming data fromone domain to the other are discussed. Fourier transforming isdone with a spline approximation technique, the Hamonapproximation and by fitting base functions that have analyticFourier transforms to measured data. These techniques arereviewed with special attention to the problem of estimatingdata outside the measurement window.

    The second part of the thesis includes studies of the changeof dielectric properties during the manufacturing stage of acomposite insulation used in high voltage rotating machines.The insulation consists of a resin-rich mica tape with wovenglass or polyester film (PET) as carrier material. The aim wasto improve the quality of the composite insulation byoptimising the heat and pressure cycle used in theproduction.

    A test cell has been designed and built to be able toprocess simple parallel plate samples under conditions similarto the factory process. With a maximum heating rate of 9°C/min and a maximum cooling rate of 20° C/min arbitrarytemperature paths could be programmed. All samples wereprocessed under static pressure in the MPa range.

    The chemical reaction during curing of the resin-rich micatape was studied with differential scanning calorimetry (DSC).A simple reaction rate model was fit to the DSC measurementsmaking it possible to calculate the degree of curing during anarbitrary temperature path.

    The change of dielectric response with time during curingunder different temperature paths and at a constant pressurewas monitored. Both laboratory experiments and factorymeasurements have been made and based on these measurements asimple network model is proposed to explain the measureddielectric response in terms of material structure and degreeof curing.

    Keywords: Dielectric response, diagnostic methods, Hamon,Fourier transform, rotating-machine, insulation, resin-rich,mica tape, curing, process, monitoring, differential scanningcalorimetry (DSC), network model.

  • 42.
    Helgeson, Anders
    KTH, Superseded Departments, Electric Power Systems.
    Dielectric properties of machine insulation studied with dielectric response1997Licentiate thesis, monograph (Other scientific)
  • 43.
    Herbig, Arnim
    KTH, Superseded Departments, Electric Power Systems.
    On load flow control in electric power systems2000Doctoral thesis, monograph (Other scientific)
  • 44.
    Hersoug, Ellef
    KTH, Superseded Departments, Electric Power Systems.
    Alternative för landsbygdselektrifiering i utvecklingsländer. En fallstudie i Kasulu, Tanzania1997Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 45.
    Hillberg, Emil
    KTH, Superseded Departments, Electric Power Systems.
    Detaljerad beskrivning av de synkronmaskinmodeller som används i Simpow2002Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 46.
    Holmgren, Björn
    KTH, Superseded Departments, Electric Power Systems.
    Dielectric response, breakdown strength and water tree content of medium voltage XLPE cables1997Licentiate thesis, monograph (Other scientific)
  • 47.
    Jalal, Mona
    KTH, Superseded Departments, Electric Power Systems.
    Modeling of power systems in PSCAD-EMTDC for analyzes of power swings2004Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 48.
    Ji, Song
    KTH, Superseded Departments, Electric Power Systems.
    Frekvensskanning av HVDC2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 49.
    Jiang, Hongbo
    KTH, Superseded Departments, Electric Power Systems.
    Multiterminal HVDC system with forced commutated voltage source converters1997Licentiate thesis, monograph (Other scientific)
  • 50.
    Jiang, Ying
    KTH, Superseded Departments, Electric Power Systems.
    Active and reactive power control for transmission system with voltage souce converters1997Doctoral thesis, monograph (Other scientific)
123 1 - 50 of 145
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