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  • 1.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Modular multilevel converter AC motor drives with constant torque from zero to nominal speed2014In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 50, no 3, p. 1982-1993Article in journal (Refereed)
    Abstract [en]

    Modular multilevel converters are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities combined with low average switching frequencies for the semiconductor devices create an ideal combination for very high-efficiency drives. However, the large number of devices and capacitors that have to conduct the fundamental-frequency current require more complex converter control techniques than its two-level counterpart. Special care needs to be taken for starting and operation at low speeds, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages and disturb the output waveforms. In this paper, principles for converter operation with high torque in the whole speed range are investigated. Experimental results from a down-scaled 12-kVA prototype converter running a loaded motor at various speeds between standstill and the rated speed are also provided.

  • 2.
    Arshad, Waqas M.
    et al.
    KTH, School of Electrical Engineering (EES).
    Thelin, Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Bäckström, T.
    Sadarangani, Chandur
    KTH, Superseded Departments, Electrical Systems.
    Use of transverse-flux machines in a free-piston generator2004In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 40, no 4, p. 1092-1100Article in journal (Refereed)
    Abstract [en]

    This paper investigates the use of transverse-flux machines (TFMs) in a free-piston generator, an integration of a combustion engine and a linear electrical machine. For hybrid vehicles (the intended application), this integrated device has benefits in efficiency, emissions, reliability, etc. Conventional TFMs are dimensioned and their shortcomings illustrated. Several surface-mounted TFM designs are suggested. These designs, initially believed to be promising, are later discovered to be. poor during the three-dimensional finite-element method (3-D FEM) analysis. These designs suffered from a large axial pole-to-pole armature-flux leakage in the stator. This problem is solved in the proposed buried-magnets TFM variants, for which patents have been filed as well. A 5-kW proof-of-concept prototype of one such design is dimensioned that allowed the near fulfilment of 3-D FEM verifiable system demands. One phase. of this dimensioned three-phase prototype is built. Measurements on this,prototype showed that the use of short pole lengths in the machine had led to manufacturing defects. Nevertheless, the electromagnetic viability of the design could still be approximately verified.

  • 3.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Arvanitidis, Ioannis
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Physical modeling and control of dynamic foaming in an LD-converter process2001In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 37, no 4, p. 1067-1073Article in journal (Refereed)
    Abstract [en]

    This paper deals with physical modeling and control of dynamic foaming in the LD-converter process. An experimental setup consisting of a water model, digital signal processor, and PC hardware is built and shown to be useful for studying dynamic foaming. Furthermore, a foam height estimation algorithm is presented and validated through experiments. Finally, sound signals from the LD-converter and water model are compared and similarities between them are found.

  • 4.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Johansson, Andreas
    Medvedev, Alexander
    Johansson, Robert
    SSAB Tunnplåt AB.
    Model-based estimation of molten metal analysis in the LD converter: experiments at SSAB Tunnplat AB in Lulea2002In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 38, no 2, p. 565-570Article in journal (Refereed)
    Abstract [en]

    Experiences from field tests of a model-based molten metal analysis estimation system for the Linz and Donawitz converter process are reported. Experiments have been carried out during a six-month-long period on two converters at SSAB Tunnplat AB, Lulea, Sweden. The achieved results prove viability of the approach taken and indicate its high potential regarding estimation accuracy and robustness. It is also concluded that some further system development is necessary to enable modeling of additives and lance level before the system can be recommended for permanent installation

  • 5.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sensitivity analysis of an LQ optimal multivariable controller for a fine coal injection vessel2000In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 36, no 3, p. 871-876Article in journal (Refereed)
    Abstract [en]

    This paper deals with a sensitivity analysis of a linear quadratic optimal multivariable controller for a fine coal injection vessel used in the blast furnace process. The multivariable controller from a previous work is briefly presented and the closed-loop system is studied by means of a sensitivity analysis. Effects of disturbances and uncertainty on the closed-loop system are studied based on analysis of the singular values of the sensitivity and the complementary sensitivity functions, the relative gain array, and the minimized condition numbers. Finally, the sensitivity analysis is validated by the use of logged data from test operation at the coal injection plant at SSAB Tunnplat AB, Lulea, Sweden

  • 6.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Medvedev, Alexander
    Marklund, Olov
    Video monitoring of pulverized coal injection in the blast furnace2002In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 38, no 2, p. 571-576Article in journal (Refereed)
    Abstract [en]

    A novel approach to monitoring and control of the coal powder injection in a blast furnace is presented and discussed. Image analysis of video recordings is used as a means to estimate the instantaneous coal flow. Initial experiments at blast furnace number 3 of SSAB Tunnplat AB, Lulea, Sweden, are reported and firsthand results on modeling and control of a single injection line are given.

  • 7.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Electric to Mechanical Energy Conversion of Linear Ultrafast Electromechanical Actuators Based on Stroke Requirements2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 4, p. 3059-3067Article in journal (Refereed)
    Abstract [en]

    The operational efficiency of ultrafast actuators used as drives in high-voltage direct-current breakers is at best 5%. To boost their efficiency, the design of the energizing circuit is crucial. A multiphysics finite-element method model coupled with a SPICE circuit model that is able to predict the performance of the actuator with an accuracy of at least 95% has been developed and verified experimentally. Several variants of prototypes and models have been simulated, built, and tested. It was shown that one of the main problems leading to low efficiencies is the stroke of the drive. However, there is a possibility to increase the efficiency of the electric to mechanical energy conversion process of the studied Thomson coil (TC) and double-sided coil (DSC) to a maximum of 54% and 88%, respectively, if their stroke is minimized. These efficiencies are idealistic, and these were obtained with clamped armature studies. The efficiency of the actuator can be increased at the expense of increasing the complexity and the cost of the contact system by designing a switch with several series-connected contacts that is encapsulated in a medium with a high dielectric strength. Another proposed solution is to design a current pulse with a rise time that is considerably shorter than the mechanical response time of the system. Parametric variations of capacitances and charging voltages show that the TC and the DSC can achieve efficiencies up to 15% and 23%, respectively. Regardless of the chosen method, the DSC has a superior efficiency compared to a TC.

  • 8.
    Colmenares, Juan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Peftitsis, Dimosthenis
    Rabkowski, Jacek
    Sadik, Diane-Perle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Tolstoy, Georg
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    High-Efficiency 312-kVA Three-Phase Inverter Using Parallel Connection of Silicon Carbide MOSFET Power Modules2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 6, p. 4664-4676Article in journal (Refereed)
    Abstract [en]

    This paper presents the design process of a 312-kVA three-phase silicon carbide inverter using ten parallel-connected metal-oxide-semiconductor field-effect-transistor power modules in each phase leg. The design processes of the gate-drive circuits with short-circuit protection and power circuit layout are also presented. Measurements in order to evaluate the performance of the gate-drive circuits have been performed using a double-pulse setup. Moreover, electrical and thermal measurements in order to evaluate the transient performance and steady-state operation of the parallel-connected power modules are shown. Experimental results showing proper steady-state operation of the power converter are also presented. Taking into account measured data, an efficiency of approximately 99.3% at the rated power has been measured for the inverter.

  • 9.
    Cossale, Marco
    et al.
    Dipartimento Energia, Politecnico di Torino, Italy .
    Krings, Andreas
    ABB Corporate Research, Sweden .
    Soulard, Juliette
    KTH, School of Electrical Engineering (EES).
    Boglietti, Aldo
    Dipartimento Energia, Politecnico di Torino, Italy .
    Cavagnino, Andrea
    Dipartimento Energia, Politecnico di Torino, Italy .
    Practical Investigations on Cobalt–Iron Laminations for Electrical Machines2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 4, p. 2933-2939Article in journal (Refereed)
    Abstract [en]

    The adoption of high-performance soft magnetic material can be considered a possible way to respect the challenging design specifications for aerospace and automotive electrical machines. This paper presents an accurate noninvasive investigation of magnetic and energetic properties of cobalt–iron stator cores. In particular, the focus lies on the annealing processes aimed to maximize the magnetic saturation and the mechanical strength. Three cobalt–iron stator core samples coming from different annealing processes have been analyzed, both from the BH characteristics and losses viewpoints. Stator slot effects on the magnetic measurements have been investigated by finite-element method. A fringing effect correction factor to be applied on the measured BH curves is as well reported. In order to complete the experimental campaign analysis, micrographic analysis of the material structure is presented, as well as the iron losses separation coefficients.

  • 10.
    Espin Delgado, Angela
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Camarillo-Penaranda, Juan Ramón
    Universidad de los Andes, Bogota, Colombia.
    Ramos, Gustav
    Universidad de los Andes, Bogota, Colombia.
    Characterization of Phase-Angle Jump in RadialSystems using Incremental Voltage Phasors2019In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 55, no 2, p. 1117-1125Article in journal (Refereed)
    Abstract [en]

    A methodology for characterizing the phase-angle jump associated with voltage sags in radial systems using incremental voltage quantities is presented in this paper. The incremental voltage phasor is defined as the difference between the pre-fault and the during-fault voltage phasors at the point of common coupling. The characteristics of this phasor are stated for different fault conditions as a function of system impedances. Both fault impedance and source neutral grounding impedance are considered in the analysis. Furthermore, the vector representation of phasors and impedance diagrams are employed as a graphical aid for understanding the incremental quantities behavior as a function of the system parameters. An algorithm for fault classification is also presented. Finally, the theoretical analysis is confirmed using real data provided by the Department of Energy and the Electric Power Research Institute. The results of this paper can be useful in future works for fault classification and fault location.

  • 11.
    Harnefors, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Model-Based Current Control of AC Machines Using the Internal Model Control Method1998In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 34, no 1, p. 133-141Article in journal (Refereed)
    Abstract [en]

    In this paper, the internal model control (IMC) method is applied to AC machine current control. Permanent magnet synchronous machines and induction machines are considered. The result is synchronous-frame proportional integral (PI) or PI-type controllers, the parameters (gain and integration time) of which are expressed directly in certain machine parameters and the desired closed-loop bandwidth. This simplifies the controller design procedure, eliminating or reducing the need for trial-and-error steps, and is the main purpose for using IMC.

  • 12.
    Johansson, Andreas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Medvedev, Alexander
    Detection of incipient clogging in pulverized coal injection lines2000In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 36, no 3, p. 877-883Article in journal (Refereed)
    Abstract [en]

    This paper deals with the detection of clogging in the coal injection lines of a blast furnace. A physical model is developed and augmented with a signal that represents clogging. A nonlinear observer is proposed and shown to have any predefined convergence rate. An adaptive detection threshold scheme which is robust against time-varying uncertainties is employed. Simulations and experiments with real data are carried out to illustrate the usefulness of the methods.

  • 13. Kjaer, P. C.
    et al.
    Kjellqvist, Tommy
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Delaloye, C.
    Estimation of field current in vector-controlled synchronous machine variable-speed drives employing brushless asynchronous exciters2005In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 41, no 3, p. 834-840Article in journal (Refereed)
    Abstract [en]

    In wound-rotor synchronous machine variable-speed drives, accurate information about the field winding current is paramount to obtain high dynamic and steady-state performance, such as unity power factor. When brushless excitation is employed and no direct measurement of field winding current is available, it must be estimated. This is a topic which has not received much attention in the literature, despite its importance in high-power synchronous motor drives. This paper presents two different methods for field current estimation, applied in a vector-controlled voltage-source converter-fed drive. Experimental results illustrate the steady-state accuracy and dynamic performance.

  • 14. Kjaer, Philip C.
    et al.
    Norrga, Staffan
    KTH, Superseded Departments, Electrical Systems.
    Östlund, Stefan
    KTH, Superseded Departments, Electrical Systems.
    A primary-switched line-side converter using zero-voltage switching2001In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 37, no 6, p. 1824-1831Article in journal (Refereed)
    Abstract [en]

    A new primary-switched ac/dc converter and its modulation are presented. It employs a single- or three-phase transformer, with a matrix converter (primary) and a conventional two-level converter (secondary). This allows galvanic isolation at medium-frequency zero-voltage primary commutation and five line-side voltage levels. Two distinct modulation methods are explained in detail, and it is shown how a combination of these allows optimal operation in terms of efficiency and voltage harmonics. Measured waveforms on a 30-kW prototype confirm the expected performance.

  • 15. Kostov, Konstantin S.
    et al.
    Schroth, Sebastian
    Krismer, Florian
    Priecinsky, Martin
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Kolar, Johann W.
    The Input Impedance of Common-Mode and Differential-Mode Noise Separators2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 3, p. 2352-2360, article id 6954393Article in journal (Refereed)
    Abstract [en]

    This paper discusses the.-networks and other circuits designed to separate the conducted electromagnetic interference (EMI) into its common mode (CM) and differential mode (DM) components. The input impedances of CM/DM separators must be 50 Omega resistive in the measurement frequency range, and they must be independent of the values of the noise signals and noise source impedances. The conditions for achieving such input impedances are derived. It is shown that many of the proposed separators, including the.-network suggested in the International Special Committee on Radio Interference (CISPR) 16-1-2 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements and, consequently, to the oversizing of EMI filters and design by trial and error.

  • 16.
    Kostov, Konstantin Stoychev
    et al.
    RISE, Swedish ICT, Acreo.
    Schroth, Sebastian
    ETH Zurich, Switzerland.
    Krismer, Florian
    ETH Zurich, Switzerland.
    Priecinsky, Martin
    Bel Power Solutions, Slovakia.
    Nee, Hans-Peter
    KTH Royal Institute of Technology, Sweden.
    Kolar, Johann W.
    ETH Zurich, Switzerland.
    The Input Impedance of Common-Mode Differential-Mode Noise Separators2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 3, p. 2352-2360, article id 6954393Article in journal (Refereed)
    Abstract [en]

    This paper discusses the Δ-networks and other circuits designed to separate the conducted electromagnetic interference (EMI) into its common mode (CM) and differential mode (DM) components. The input impedances of CM/DM separators must be 50 Ω resistive in the measurement frequency range, and they must be independent of the values of the noise signals and noise source impedances. The conditions for achieving such input impedances are derived. It is shown that many of the proposed separators, including the Δ-network suggested in the International Special Committee on Radio Interference (CISPR) 16-1-2 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements and, consequently, to the oversizing of EMI filters and design by trial and error.

  • 17.
    Krings, Andreas
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nategh, Shafigh
    SmartMotor AS, Rolls-Royce Group, Norway .
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Soulard, Juliette
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Influence of the Welding Process on the Performance of Slotless PM Motors With SiFe and NiFe Stator Laminations2014In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 50, no 1, p. 296-306Article in journal (Refereed)
    Abstract [en]

    The influence of the welding process during the manufacturing of small slotless permanent-magnet synchronous machines (PMSMs) is studied in this paper. The focus lies on the change of the magnetic properties in high-quality silicon-iron (SiFe) and nickel-iron (NiFe) electrical steel sheets with thicknesses of 0.1 and 0.2 mm. It is shown that the welding process changes the magnetic material properties significantly and increases the specific iron losses. Experimental results are provided for magnetic flux densities up to 1.5 T and frequencies from quasi-static to 200 Hz. The obtained measurement data is afterward used in finite-element method (FEM) simulations to investigate the influence of the magnetic property changes on the motor performance, particularly with regard to stator core losses.

  • 18.
    Krings, Andreas
    et al.
    ABB AB Corporate Research, Sweden .
    Soulard, Juliette
    ABB AB Corporate Research, Sweden .
    Wallmark, Oskar
    ABB AB Corporate Research, Sweden .
    PWM Influence on the Iron Losses and Characteristics of a Slot-less Permanent Magnet Motor with SiFe and NiFe Stator Cores2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 2, article id 6891228Article in journal (Refereed)
    Abstract [en]

    This paper investigates the influence of switching frequency and modulation index combined with welding on the iron losses in thin silicon-iron and nickel-iron lamination sheets of a small slot-less permanent magnet synchronous machine. First, measurements are conducted on welded and non-welded stator ring cores for switching frequencies between 1 kHz and 20 kHz and modulation indices of 0.4, 0.7, and 0.9, keeping constant fundamental flux density peak values. This is possible by changing the DC link voltage of the inverter. The obtained measurement data is afterwards used in finite element method (FEM) simulations to investigate the inverter influence on the performance of the permanent magnet synchronous machine.

  • 19.
    Millinger, Jonas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Soulard, Juliette
    KTH.
    High Frequency Characterization of Losses in FullyAssembled Stators of Slotless PM Motors2018In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367Article in journal (Refereed)
    Abstract [en]

    Abstract—The recent emerge of wide band-gap (WBG) powertransistors enables higher switching frequencies in electricalmotor drives. Their full utilization from a system point ofview requires quantification of the corresponding time-harmonicmotor losses. As an initial step, this paper presents a uniquestudy of stator losses for three different commercially availablenon-oriented silicon-iron (SiFe) steel grades (with laminationthicknesses 0.1, 0.2 and 0.3 mm). The investigations cover awide frequency range (10-100 kHz) at different levels of DC-bias(up to 1.6 T). Iron losses are identified from measurements onfully assembled stators, deploying a novel technique. By utilizingfully assembled stators, no additional samples are required.Manufacturing influence is inherently incorporated. Results showthat measured iron losses are twice as high at 10 kHz comparedto Epstein test results, which emphasizes the need to incorporatemanufacturing influence on iron losses at high frequencies. Thelevel of DC-bias is also observed to have a significant impacton iron losses (up to 30 %). Even though thinner laminationsare known for reducing iron losses, the reduction is much lowerthan anticipated in the studied frequency range due to skin effect.Using 0.1 mm lamination gauge instead of 0.3 mm reduces lossesby 50 % at 10 kHz, while the same substitution at 100 kHz onlyreduces losses by 30 %. Future work includes loss separation incomplete converter-fed machines.

  • 20. Nee, Hans-Peter
    et al.
    Lefevre, L.
    Thelin, P.
    Soulard, Juliette
    KTH, Superseded Departments, Electrical Systems.
    Determination of d and q reactances of permanent-magnet synchronous motors without measurements of the rotor position2000In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 36, no 5, p. 1330-1335Article in journal (Refereed)
    Abstract [en]

    The interest in permanent-magnet synchronous motors:(PMSMs) is increasing in a wide area of applications. Since most PMSMs will operate without a shaft sensor in the future, valuable: information for experimental determination of machine parameters will be lost,In this paper, therefore, a method is presented where the induced EMF and the d-axis reactance are determined in a no-load test and the q-axis reactance is determined in a load test. The load angle delta is determined from the load test by means of a new analytical method. In this way, no separate measurement of the load angle is required. The method is especially suitable for line-start PMSMs which normally operate with negative d-axis current and, therefore, are not saturated in the d-axis flux paths. Moreover, the method is very simple to carry out for any laboratory technician, since the only tests that have to be made are standard tests which are made on standard induction motors on a regular basis.

  • 21.
    Norrga, Staffan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Meier, Stephan
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Östlund, Stefan
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    A three-phase soft-switched isolated AC/DC converter without auxiliary circuit2008In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 44, no 3, p. 836-844Article in journal (Refereed)
    Abstract [en]

    This paper describes an ac/dc converter system consisting of a voltage-source converter (VSC) with purely capacitive snubbers and a two-phase by three-phase cycloconverter, connected via a medium-frequency (MF) transformer. By alternately commutating the two converters, it is possible to achieve beneficial switching conditions for all semiconductor devices. A commutation and modulation algorithm is described, which allows for pulsewidth-modulation control of the output voltage while maintaining soft switching. Low-load operation of the converter is a potential difficulty because the load current may be insufficient for recharging the snubber capacitors of the VSC. However, if the cycloconverter is used to momentarily short circuit the transformer, a quasi-resonant commutation mode of the VSC can be achieved, making a fast and soft commutation of the VSC down to zero load possible, without an auxiliary circuit. Furthermore, the design and operation of a 40-kVA prototype converter system are described. The experimental results from the prototype clearly show the practical feasibility of the studied concept.

  • 22.
    Nøland, Jonas Kristiansen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Evestedt, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Pérez-Loya, J. José
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Abrahamsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Lundin, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator2017In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 53, no 3, p. 2016-2027Article in journal (Refereed)
    Abstract [en]

    Generally, PM machines are used as PMG pre-exciters in 3-stage brushless excitations systems. This paperpresents the design, characterization and prototyping of a rotatingbrushless PM exciter used in a proposed 2-stage excitation systemfor a synchronous generator. The proposed design reduces thenumber of components compared with conventional systems.A comparison with the state-of-the-art conventional excitationsystems is given. The design of a fast-response, or high initialresponse, brushless exciter requires active rectification on therotating frame, replacing the non-controllable diode bridge. Theobjective was to construct an exciter with the capability of a50 Aoutput field current as well as a high value of the available ceilingvoltage and ceiling current. The final exciter was constructed to befitted into an in-house synchronous generator test setup. A finiteelement model of the exciter was validated with experimentalmeasurements. The exciter prototype is also compared with analternative armature design with non-overlapping single-layerconcentrated windings but with the same main dimensions.The paper includes a general design procedure suitable foroptimization of PM brushless exciters that fulfill the requirementsof their synchronous generators and the grid.

  • 23.
    Rabkowski, Jacek
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Peftitsis, Dimosthenis
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Design Steps Toward a 40-kVA SiC JFET Inverter With Natural-Convection Cooling and an Efficiency Exceeding 99.5%2013In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 49, no 4, p. 1589-1598Article in journal (Refereed)
    Abstract [en]

    This paper describes the concept, design, construction, and experimental investigation of a 40-kVA inverter with silicon carbide junction field-effect transistors (JFETs). The inverter was designed to reach an efficiency exceeding 99.5%. The size of the heat sink is significantly reduced in comparison to silicon insulated-gate bipolar transistor designs, and the high efficiency makes it possible to use free-convection cooling. This could potentially increase reliability compared with solutions with fans. A very low conduction loss has been achieved by parallel connecting ten 85-m Omega normally-ON JFETs in each switch position. A special gate-drive solution was applied, forcing the transistors to switch very fast (approximately 10 kV/mu s), resulting in very low switching losses. As output power is almost equal to input power, special effort was done to precisely determine the amount of semiconductor power losses via comparative thermal measurements. A detailed analysis of the measurements shows that the efficiency of the inverter is close to 99.7% at 40 kVA.

  • 24.
    Salomonsson, Daniel
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Sannino, Ambra
    Power Technologies Division, ABB Corporate Research.
    An adaptive control system for a dc microgrid for data centers2008In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 44, no 6, p. 1910-1917Article in journal (Refereed)
    Abstract [en]

    In this paper, an adaptive control system for a dc microgrid for data centers is proposed. Data centers call for electric power with high availability, and a possibility to reduce the electric losses and, consequently, the need for cooling. High reliability can be achieved by using local energy sources, and by using a dc power system, the number of conversion steps, and therefore also the losses, can be reduced. The dc microgrid can also supply closely located sensitive ac loads during outages in the ac grid. The proposed dc microgrid can be operated in eight different operation modes described here, resulting in 23 transitions. The control system coordinates the operation of converters, sources, and switches used in the dc microgrid. The control system is tested in the simulation software package PSCAD/EMTDC, and the results of the most interesting transitions are presented. The results show that it is possible to use the proposed dc microgrid to supply sensitive electronic loads and also, during ac-grid outages, supply closely located sensitive ac loads. To reduce the current transients experienced by grid-connected ac/dc converters, fast grid-outage detection and fast switches are required.

  • 25. Shimizu, Kazuo
    et al.
    Sugiyama, Takeki
    Liyanage Samaratunge, Manisha Nishamani
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kanamori, Masaki
    Application of Microplasma for NOx Removal2009In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 45, no 4, p. 1506-1512Article in journal (Refereed)
    Abstract [en]

    In this paper, microplasma is investigated, which occurs between the narrow gap of the electrodes covered with dielectric materials. The discharge gap is set on the order of micrometers by changing a spacer from 0 to 100 mu m. In this paper, the characteristics of microplasma, such as discharge voltages, discharge currents, and discharge power that is obtained with the help of Lissajous figures, and the relationships between these electric characteristics are presented. The characteristics of ozone generation by a microplasma electrode are investigated. Treatment by microplasma for the simulated exhaust gas, which contains NOx and C3H8 as a role of HC and CO, is estimated experimentally. In the absence of O-2, the exhaust gas is decomposed by nitrogen atomic species in particular. In the presence of O-2, it is decomposed by nitrogen atomic species and oxidized by ozone. By-product analysis of treated gases is carried out by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. When HC, NOx, and N-2 are included in the simulated exhaust gas, HCN, N2O, and CH4 are confirmed as by-products of the microplasma treatment.

  • 26. Tuovinen, T.
    et al.
    Hinkkanen, M.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Luomi, J.
    Comparison of a reduced-order observer and a full-order observer for sensorless synchronous motor drives2012In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 48, no 6, p. 1959-1967Article in journal (Refereed)
    Abstract [en]

    Two back-electromotive-force-based position observers are compared for motion-sensorless synchronous motor drives: the reduced-order observer and the adaptive full-order observer. A stabilizing gain is proposed for the adaptive full-order observer, which guarantees the local stability of the closed-loop system, if the motor parameters are known. Equations for the steady-state position error and for the linearized estimation-error dynamics under erroneous parameters are derived, and the robustness of the two observers against parameter errors is analyzed and compared. The observers are experimentally evaluated using a 6.7-kW synchronous reluctance motor drive in low-speed operation and under parameter errors. The gain selection of the reduced-order observer is easier, but the adaptive full-order observer can be made more robust against parameter variations and noise.

  • 27.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2. KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Kjellqvist, Peter
    Meier, Florence
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2. KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Analysis of Axial Leakage in High-Speed Slotless PM Motors for Industrial Hand Tools2009In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 45, no 5, p. 1815-1820Article in journal (Refereed)
    Abstract [en]

    This paper presents an analysis of axial-leakage effects in high-speed slotless permanent-magnet (PM) motors for industrial hand-tool applications. Analytical predictions based on a 2-D model and results from a 3-D finite-element (3DFEM) simulation model are compared with experimental results from three series-produced PM motors. The reduction in flux density (resulting from 3DFEM simulations and measurements) outside the motor's axial ends is substantial; the flux density has practically vanished only a few millimeters outside the stator lamination stack. To predict the resulting flux linkage, a simple winding model is presented where the winding is made up of a discrete number of winding layers. Using this winding model, it is verified that the reduction in flux linkage, manifested as a reduction in the back electromotive force, is not only dependent on the motor's axial length but also that the effect is minor for slotless PM motors with dimensions suitable for hand-tool applications. The results are also supported by no-load line-to-line voltage measurements on the three PM motors.

  • 28. Zhang, H.
    et al.
    Wang, X.
    Harnefors, Lennart
    ABB, Västerås, Sweden.
    Gong, H.
    Hasler, J. -P
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    SISO Transfer Functions for Stability Analysis of Grid-Connected Voltage-Source Converters2019In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 55, no 3, p. 2931-2941, article id 8640057Article in journal (Refereed)
    Abstract [en]

    Converter-grid interaction is of great interest in a weak-grid condition. This paper presents a single-input-single-output (SISO) open-loop transfer function for the stability analysis of grid-connected voltage-source converters. Differing from the conventional input impedance method and the eigenvalue analysis, an alternative multi-input-multi-output closed-loop system is developed in the paper and it eventually yields an SISO open-loop transfer function. This enables the application of a single Nyquist curve for analyzing the overall system stability. The model is validated against time-domain simulations as well as experimental results showing excellent accuracy for predicting the system stability.

  • 29.
    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.

  • 30.
    Östlund, Stefan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Brokemper, Michael
    Sensorless Rotor Position Detection from Zero to Ratted Speed for an Integrated PM Synchronous Motor Drive1996In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 32, no 5, p. 1158-1165Article in journal (Refereed)
1 - 30 of 30
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