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  • 101.
    Johansson, Niklas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Ängquist, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Designing power flow control devices using the power controller plane: An improved methodArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This paper introduces an improved method for design of Power Flow Controllers (PFC) in the power controller plane where the active power of the PFC line is plotted versus the difference in voltage angle between the PFC terminals. The power controller plane makes it possible to graphically visualize the working area of a PFC in a power grid and thus determine the grid situations which are dimensioning for the PFC. The paper extends the existing methods for design of PFC:s in the power controller plane by introducing a method to decouple the power grid- and PFC characteristics in a power system of arbitrary size. With this approach, it is possible to graphically compare and design PFC:s of different types and with different characteristics in the same plot by simple geometrical considerations. The method is intended to provide additional insight into how the power flow control capabilities of different PFC:s depend on the selected PFC characteristics and the grid conditions. Additionally, the method has the potential to simplify the process for selection and design of a PFC. The paper includes a study of the accuracy of the proposed method in two test systems of different complexity.

  • 102.
    Kolessar, Remy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    A new physics-based circuit model for 4H-SiC power diodes implemented in SABER2001Inngår i: Proc. of the Sixteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2001, APEC 2001, vol. 2,  4-8 March 2001. / [ed] IEEE, 2001, s. 989-994Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A circuit-oriented model for 4H-SiC power diodes is presented. The modeling technique used in this work was previously applied to a silicon (Si) power diode model for both turn-on and turn-off transients, and presents a good trade-off between accuracy and speed. The model is physics-based, but includes judicious approximations for fast calculation, and includes up-to-date physical models for silicon carbide, with temperature dependence. The proposed model is practically implemented in the circuit simulator SABER, using the MAST modeling language. Model performances are compared to measurements on 2.5 kV 400 A Si IGBT/SiC diode modules from ABB at various input currents.

  • 103.
    Kolessar, Remy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    An experimentally validated electro-thermal compact model for 4H-SiC power diodes2001Inngår i: Proc. of IEEE International Symposium on Industrial Electronics ISIE, 12-16 June 2001, vol. 2. / [ed] IEEE, 2001, s. 1345-1350Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The implementation of a circuit-oriented model for high-current, high-voltage 4H-SiC power diodes is presented. The compact modeling technique used presents a good trade-off between accuracy and speed for modeling of bipolar power devices, and a high flexibility for inclusion of various physical models. Implementation in the SABER circuit simulator of the model is performed using the MAST hardware description language (HDL). Up-to-date physical models for 4H-SiC semiconductor materials including thermal dependence, which are relevant for the device switching behavior are evaluated and implemented in the compact model. Simulation results using the proposed model are compared to both measurements and device simulations on 2.5 kV, 400 A Si-IGBT/4H-SiC diode modules from ABB at various circuit and temperature conditions. The model has proven to be a valuable simulation tool for investigation of future power circuit designs based on SiC technology.

  • 104.
    Kolessar, Remy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Electro-Thermal Circuit Model for the Power Diode Turn-On Process2000Inngår i: Proc. of the IEEE Nordic Workshop on Power and Industrial Electronics, Aalborg, Denmark, June 2000., 2000, s. 69-73Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a physics-based, electro-thermal model for thepower diode turn-on is presented. The model, implementedin the circuit simulator SABER, is based on an approximationof the carrier distribution in the n-base of the diode usingsecond degree polynomials, resulting in a fast but accuratecalculation method. The turn-on physics is accuratelydescribed by taking into account low injection level as well asa correct transport equation for the minority carriers. Modelperformances are compared both to device numerical simulationsand measurements and show good agreements forvarious circuit and temperature conditions, as well as for differentdevice designs.

  • 105.
    Kolessar, Remy
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Physics-Based Power Device Models in SABER - Implementation Issues2000Inngår i: Proc. of the IEEE Computer in Power Electronics, COMPEL 2000, Blacksburg, USA, August 2000. / [ed] IEEE, 2000, s. 18-22Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, the implementation issues of physics-based power device models in the SABER circuit simulator through the MAST High Description Language (HDL) are discussed. The possibility to use dynamical if-statements in the system matrix (equations section) of a MAST template is presented. By means of this implementation method, systems of differential equations for boundary value problems can be efficiently implemented and solved in SABER. To illustrate the method, the implementation of a physics-based power diode model is taken as an example. Simulation results using this model are presented to demonstrate the efficiency and numerical stability of the method.

  • 106.
    Korssell, Tomas
    et al.
    KTH.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Lindeborg, Rolf
    ITT Flygt.
    Development and Testing of a Measurement Device for Prediction of Stator Core Quality1996Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the past, and still today it has been hard to find good methods to locate and determine the magnitude of the iron losses in stator cores and from that obtain an overall quality check. In order to meet the future demands on high-effeciency motors with high power density it is essential to have a good knowledge where the stator losses are located and what size they have in specific parts of the stator. This paper presents a method to measure the stator core losses in different parts of the stator by means of a measurement device and determine the relative stator losses in the different parts. The paper gives a hint how to design an appropriate measurement device for a stator with certain dimensions. In the end of the paper results from measurements on sttator cores with different sheet qualities are presented.

  • 107.
    Kostov, Konstantin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rabkowski, Jacek
    Warsaw University of Technology, Poland .
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Conducted EMI from SiC BJT boost converter and its dependence on the output voltage, current, and heatsink connection2013Inngår i: 2013 IEEE ECCE Asia Downunder - 5th IEEE Annual International Energy Conversion Congress and Exhibition, IEEE ECCE Asia 2013, IEEE , 2013, s. 1125-1130Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In comparison to their Silicon (Si) counterparts, the Silicon Carbide (SiC) power transistors have lower on-state resistance and higher switching speed, power and temperature ratings. These advantages make it possible to build smaller, lighter and more efficient power converters. Unfortunately, all these benefits come at the price of higher conducted and radiated electromagnetic interference (EMI). This paper investigates the conducted disturbances from a 6 kW boost converter with SiC bipolar junction transistors (BJTs). The results show that the conducted emissions at the input of the converter are approximately proportional to the output voltage, but almost independent on the load current. The effect of the heatsink on the conducted EMI was studied as well. It was found that using separate heatsinks for the diode and the BJT did not affect the level of conducted emissions significantly, but the way of connecting the heatsink does. A floating heatsink is bad from an EMI point of view, and in many cases it may not be allowed for safety reasons. When the heatsink is grounded, alone or together with the negative terminal, the common-mode noise increases the EMI measured at the positive line and decreases the EMI on the negative line. However, this appears only in the lower frequency range. At higher frequencies, connecting the heatsink in any way is better than letting it float. Therefore, the best option is to connect the heatsink to the negative line of the boost converter, and if grounding is required, it may be grounded as well. This may not be possible in systems where the negative voltage bus is at non-zero potential.

  • 108.
    Kostov, Konstantin S.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Combining diagonal connection and cancellation turn in electromagnetic interference filtering2014Inngår i: IET Power Electronics, ISSN 1755-4535, Vol. 7, nr 3, s. 559-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a new printed circuit board (PCB) implementation of the diagonal connection is proposed. The two capacitors that are connected diagonally are laid out as close as possible and in such a way that their currents have opposite directions. The new layout combines the benefits of the so-called 'cancellation turn' with the benefits of the diagonal connection, without the need for additional PCB space and components. The experimental results show that the self-resonant frequency of the diagonally connected capacitors increased by 32%. Additionally, the coupling between the diagonally connected capacitors and a capacitor on the other side of the filter was reduced by 20-25 dB.

  • 109.
    Kostov, Konstantin S.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Priecinsky, M.
    The input impedance of common mode and differential mode noise separators2013Inngår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013, 2013, s. 1688-1695Konferansepaper (Fagfellevurdert)
    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 band 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 CISPR 16 standard, do not fulfill the input impedance requirement. This leads to unreliable CM and DM measurements, and consequently, to EMI filter oversizing and design by trial-and-error.

  • 110. Kostov, Konstantin S.
    et al.
    Schroth, Sebastian
    Krismer, Florian
    Priecinsky, Martin
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Kolar, Johann W.
    The Input Impedance of Common-Mode and Differential-Mode Noise Separators2015Inngår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, nr 3, s. 2352-2360, artikkel-id 6954393Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 111.
    Kretschmar, Karsten
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    An AC Converter with a Small DC link Capacitor for a 15kW Permanent Magnet Synchronous Integral Motor1998Inngår i: Proc. of the International Conference on Power Electronics and Variable Speed Drives 1998, 1998, s. 622-625Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An AC/AC power converter designed to feed a permanent magnet synchronous motor with a rated power of 15 kW is investigated in this paper. The converter consists of a diode rectifier, a small DC link capacitor and an inverter, which is controlled by an open loop pulse width modulation system (PWM). The circuit is simulated and the simulation results are analyzed and verified by measurements. Due to the small capacitor, special emphasis is put on the analysis of the DC link voltage. The paper also includes an analytical expression of the ripple of the DC link voltage.

  • 112.
    Kretschmar, Karsten
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Analysis of the Efficiency and Suitability of Different Converter Topologies for PM Integral Motors2001Inngår i: Proc. of the Australian Universities Power Engineering Conference (AUPEC 2001), Perth, Australia, September 2001, 2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an analysis of di®erent converter types regarding their suitability for a 15kWpermanent magnet (PM) integral motor. A calculation method is proposed in order to estimatethe e±ciency of the di®erent topologies. The results of the calculations are compared with thecomplexity of the system in order to ¯nd the most suitable converter for this application.

  • 113.
    Kretschmar, Karsten
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Comparison of different Converters with Sinusoidal Line Currents suited for a 15 kW Permanent Magnet Integral Motor2000Inngår i: Proc. of the IEEE Nordic Workshop on Power and Industrial Electronics, Aalborg, Denmark, June 2000., 2000, s. 79-83Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper three different converter topologiesare compared concerning their usability for permanent magnet integral motors. In the analysis special attention is payed to the efficiency ofeach converter topology, since the volume of the converter is highly dependent on the cooling requirements. Aspects of power factor correction of the line currents are also included in this paper. Only two of the three converter topologies fulfill the EMC standards. The line-side switch-mode rectifier and the Vienna rectifier. Both have a satisfactory efficiency but the line-side switch-mode rectifier provides also a regenerative braking possibility.

  • 114. Krismer, Florian
    et al.
    Schroth, Sebastian
    Ertl, Hans
    Kostov, Konstantin Stoychev
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Kolar, Johann Walter
    Analysis and Practical Relevance of CM/DM EMI Noise Separator Characteristics2017Inngår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 32, nr 4, s. 3112-3127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work investigates sources of measurement errors that result for common mode/differential mode (CM/DM) separators in a practical measurement environment, with a particular focus on the recently presented input impedance criterion for CM/DM separators, derives the respective analytical expressions, and employs a detailed analytical model to verify the obtained findings. Furthermore, a method is derived, which determines the worst-case measurement error by reason of cross coupling for given measured DM and CM output voltage components. Based on an example, this work illustrates how the obtained expressions can be advantageously used in a computer program to automatically decide whether a particular spectral measurement component represents a useful measurement result or if it is strongly affected by cross coupling (CM to DM and DM to CM). Finally, the paper presents the realization and accompanying experimental results of an active CM/DM separator, which allows for low realization effort and features competitive separation capabilities (DMTR/CMRR > 50 dB and CMTR/DMRR > 42 dB for frequencies up to 10 MHz).

  • 115.
    Lefevre, Louis
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Soulard, Juliette
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Design procedure for Line-Start Permanent Magnet Motors2000Inngår i: Proc. of the IEEE Nordic Workshop on Power and Industrial Electronics, Aalborg, Denmark, June 2000., 2000Konferansepaper (Fagfellevurdert)
  • 116.
    Leksell, Mats
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Harnefors, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Machine Design Considerations for Sensorless Control of PM Motors1998Inngår i: Proc. of the International Conference on Electrical Machines 1998, 1998Konferansepaper (Fagfellevurdert)
  • 117.
    Lim, Jang-Kwon
    et al.
    Acreo, Kista.
    Bakowski, Mietek
    Acreo, Kista.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Design and gate drive considerations for epitaxial 1.2 kV buried grid N-on and N-off JFETs for operation at 250°C2010Inngår i: SILICON CARBIDE AND RELATED MATERIALS 2009, PTS 1 AND 2, STAFA-ZURICH: TRANS TECH PUBLICATIONS LTD , 2010, Vol. 645/648, s. 961-964Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The main problem when the conventional PSpice JFET model is used to simulate a vertical short-channel buried-grid JFET is caused by the constant values of Threshold Voltage (VTO) and Transconductance (BETA). This paper presents a new model for the vertical short-channel buried-grid 1200V JFET, where both VTO and BETA vary with respect to the Drain-Source voltage. Simulation data from Medici have been analyzed in order to extract the analytical equations for VTO and BETA. Also other PSpice parameters are extracted from these data. The proposed circuit model has been simulated in Matlab by optimizing the same algorithm that PSpice uses. A variety of results are shown and discussed in this paper.

  • 118.
    Lim, Jang-Kwon
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Bakowski, Mietek
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Analysis and Experimental Verification of the Influence of Fabrication Process Tolerances and Circuit Parasitics on Transient Current Sharing of Parallel-Connected SiC JFETs2014Inngår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 29, nr 5, s. 2180-2191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Operation of parallel-connected 4H-SiC vertical junction field effect transistors (VJFETs) from SemiSouth is modeled using numerical simulations and experimentally verified. The unbalanced current waveforms of parallel-connected VJFETs are investigated with respect to the spread in the critical parameters of the device structure and to the influence of the parasitic inductances in the measurement circuit. The device structures are reconstructed based on scanning electron microscopy (SEM) analysis, electrical characterization, and device simulations. The doping concentration and profile depth of a p-grid formed by angular implantation are studied as main contributors that influence the variation of the on-state characteristics, and the threshold voltage of the experimental devices. It has been shown elsewhere that similar differences in p-grid also lead to differences in gate-source breakdown voltage. The switching performance of the parallel-connected JFETs is measured using single and double gate drivers in a double-pulse test and compared with simulations. The switched current and voltage waveforms from measurements are reproduced in simulation by introducing the parasitics. From the analysis, it is found that reasonable differences in doping levels and profiles of the p-grid give rise to significant differences in device parameters. However, even with these parameter differences and circuit asymmetries, it is possible to successfully operate parallel-connected VJFETs of this type.

  • 119.
    Lim, Jang-Kwon
    et al.
    Acreo.
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Bakowski, Mietek
    Acreo.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Modeling of the impact of parameter spread on the switching performance of parallel-connected SiC VJFETs2013Inngår i: Materials Science Forum, Trans Tech Publications Inc., 2013, s. 1098-1102Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Operation of parallel-connected 4H-SiC VJFETs from SemiSouth was measured and modeled using numerical simulations. The unbalanced current waveforms in parallel-connected VJFETs were related to spread in the critical parameters of the device structure and to the influence of the parasitic inductances in the measurement circuit. The physical device structure was reconstructed based on SEM analysis, electrical characterization, and device simulations. The two hypothetical critical design parameters that were studied with respect to spread were the p-gate doping profile (Case 1) and the emitter doping (Case 2). Variation in both parameters could be related to variation in the emitter breakdown voltage, the on-state characteristics, and the threshold voltage of the experimental devices. The switching performance of the parallel-connected JFETs was measured using a single gate driver in a double pulse test and compared with simulations. In both investigated cases a very good agreement between measurements and simulations was obtained. The modeling of the transient performance relies on good reproduction of transfer characteristics and circuit parasitics.

  • 120.
    Lim, Jang-Kwon
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik. Acreo Swedish ICT AB, Sweden.
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES).
    Sadik, Diane-Perle
    KTH, Skolan för elektro- och systemteknik (EES).
    Bakowski, M.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Evaluation of buried grid JBS diodes2014Inngår i: 15th International Conference on Silicon Carbide and Related Materials, ICSCRM 2013, Trans Tech Publications Inc., 2014, s. 804-807Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The 4H-SiC Schottky barrier diodes for high temperature operation over 200 °C have been developed using buried grids formed by implantation. Compared to a conventional JBS-type SBD with surface grid (SG), JBS-type SBD with buried grid (BG) has significantly reduced leakage current at reverse bias due to a better field shielding of the Schottky contact. By introducing the BG technology, the 1.7 kV diodes with an anode area 0.0024 cm2 (1 A) and 0.024 cm2 (10 A) were successfully fabricated, encapsulated in TO220 packages, and electrically evaluated. Two types of buried grid arrangement with different grid spacing dimensions were investigated. The measured IV characteristics were compared with simulation. The best fit was obtained with an active area of approximately 60% and 70% of the anode area in large and small devices, respectively. The measured values of the device capacitances were 1000 pF in large devices and 100 pF in small devices at zero bias. The capacitance values are proportional to the device area. The recovery behavior of big devices was measured in a double pulse tester and simulated. The recovery charge, Qc, was 18 nC and 24 nC in simulation and measurement, respectively. The fabricated BG JBS-type SBDs have a smaller maximum reverse recovery current compared to the commercial devices. No influence of the different grid spacing on the recovery charge was observed.

  • 121.
    Lim, Jang-Kwon
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling. Acreo Swedish ICT AB, Sweden.
    Reshanov, Sergey
    Kaplan, W.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Zhang, A.
    Hjort, T.
    Schöner, A.
    Bakowski, M.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Temperature-Dependent Characteristics of 4H-SiC Buried Grid JBS Diodes2015Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 821/823, s. 600-603Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    4H-SiC Schottky Barrier Diodes (SBD) have been developed using p-type buried grids (BGs) formed by Al implantation. In order to reduce on-state resistance and improve forward conduction, the doping concentration of the channel region between the buried grids was increased. The fabricated diodes were encapsulated with TO-254 packages and electrically evaluated. Experimental forward and reverse characteristics were measured in the temperature range from 25 °C to 250 °C. On bare die level, the forward voltage drop was reduced from 5.36 V to 3.90 V at 20 A as the channel doping concentration was increased, which introduced a low channel resistance. By the encapsulation in TO-254 package, the forward voltage drop was decreased approximately 10% due to a lower contact resistance. The on-state resistance of the identical device measured on bare die and in TO-254 package increased with increasing temperature due to the decreased electron mobility in the drift region resulting in higher resistance. The incremental contact resistances of the bare dies were larger than in the packaged devices. One key issue associated with conventional Junction Barrier Schottky (JBS) diodes is a high leakage current at high temperature operation over 200 °C. The developed Buried Grid JBS (BG JBS) diode has significantly reduced leakage current due to a better field shielding at the Schottky contact. The leakage current of the packaged BG JBS diodes is compared to pure SBD and commercial JBS diodes.

  • 122.
    Lim, Jang-Kwon
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Tolstoy, Georg
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Bakowski, Mietek
    Acreo, Kista.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Comparison of total losses of 1.2 kV SiC JFET and BJT in DC-DC converter including gate driver2011Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 679/680, s. 649-652Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 1.2 kV SiC JFET and BJT devices have been investigated and compared with respect to total losses including the gate driver losses in a DC-DC converter configuration. The buried grid, Normally-on JFET devices with threshold voltage of -50 V and -10V are compared to BJT devices with ideal semiconductor and passivating insulator interface and an interface with surface recombination velocity of 4.5·104 cm/s yielding agreement to the reported experimental current gain values. The conduction losses of both types of devices are independent of the switching frequency while the switching losses are proportional to the switching frequency. The driver losses are proportional to the switching frequency in the JFET case but to a large extent independent of the switching frequency in the BJT case. The passivation of the emitter junction modeled here by surface recombination velocity has a significant impact on conduction losses and gate driver losses in the investigated BJT devices.

  • 123.
    Lim, Jang-Kwon
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling. Acreo Swedish ICT AB, Sweden.
    Östlund, L.
    Wang, Q.
    Kaplan, W.
    Reshanov, S. A.
    Schöner, A.
    Bakowski, M.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    A theoretical and experimental comparison of 4H- and 6H-SiC MSM UV photodetectors2012Inngår i: Silicon Carbide and Related Materials 2011, Trans Tech Publications Inc., 2012, Vol. 717-720, s. 1207-1210Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper reports on fabrication and modeling of 4H- and 6H-SiC metal-semiconductor-metal (MSM) photodetectors (PDs). MSM PDs have been fabricated on 4H-SiC and 6H-SiC epitaxial layers, and their performance analyzed by MEDICI simulation and measurements. The simulations were also used to optimize the sensitivity by varying the width and spacing of the interdigitated electrodes. The fabricated PDs with 2 ÎŒm wide metal electrodes and 3 ÎŒm spacing between the electrodes exhibited, under UV illumination, a peak current to dark current ratio of 10 5 and 10 4 in 4H-SiC and 6H-SiC, respectively. The measured spectral responsivity of 6H-SiC PDs was higher compared to that of 4H-SiC PDs, with a cutoff at 407 nm compared to 384 nm in 4H-SiC PDs. Also the peak responsivity occurred at a shorter wavelength in 6H material. A high rejection ratio between the photocurrent and dark current was found in both cases. These experimental results were in agreement with simulation.

  • 124.
    Lindahl, Martin
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. Bombardier Transportat, Vasteras, Sweden.
    Velander, Erik
    Bombardier Transportat, Vasteras, Sweden..
    Johansson, Mikael H.
    Bombardier Transportat, Vasteras, Sweden..
    Blomberg, Anders
    Bombardier Transportat, Vasteras, Sweden..
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Silicon Carbide MOSFET Traction Inverter Operated in the Stockholm Metro System Demonstrating Customer Values2018Inngår i: 2018 IEEE VEHICLE POWER AND PROPULSION CONFERENCE (VPPC), IEEE , 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    For the first time results are reported in literature of a successful field test using a silicon carbide (SiC) metal-oxide semi-conductor field-effect transistor (MOSFET) traction inverter operated in the field. The metro train has been operated over a period of 3 months on the Green Line in the Stockholm metro system. Increased traction converter power density with a volume reduction of 51 % as well as a weight reduction of 22 % have been achieved. Lower power losses allow the use of car motion cooling. From complementing measurements in the laboratory of silicon and SiC in the same power device package with varying switching frequencies considerably lower SiC temperatures can be reported.

  • 125.
    Meier, Stephan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Kjellqvist, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Design Considerations for Medium-Frequency Power Transformers in Offshore Wind Farms2009Inngår i: 2009 13th European Conference on Power Electronics and Applications, EPE '09, IEEE , 2009, s. 757-768Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a recently proposed converter system for offshore wind farms, single-phase medium-fire (MF) transformers replace the conventional three-phase line-frequency transformers that convert the electricity from the wind turbine generators to high voltage. MF operation allows a reduction of the transformer size and weight, thus leading to a compact and efficient design, which minimizes the installation and maintenance costs, This paper presents design considerations for dry-type single-phase MF power transformers in offshore wind farms. Recent transformer problems in large wind turbines have shown that a thorough and careful magnetic, electric, and thermal design is required to ensure the reliability and performance of the transformers. As a result, a suitable design for a 3 MW wind turbine transformer is proposed.

  • 126.
    Meier, Stephan
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Norrga, Staffan
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Hans-Peter, Nee
    KTH, Tidigare Institutioner, Elektrotekniska system.
    New topology for more efficient AC/DC converters for future offshore wind farms2004Inngår i: Proceedings of the 4th Nordic Workshop on Power and Industrial Electronics, Norpie ’04, Trondheim, Norway, June 2004, 2004, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The concept of a novel soft-switching AC/DC converteris applied for use in future offshore wind farms. A voltagesource converter with capacitive snubbers and cycloconverters,connected via a medium frequency AC bus, promises substantialbenefits. This paper presents this new topology and describes itsprinciple of operation. Furthermore, a comparison with state-ofthe-art adjustable speed generators reveals the potential of thisnew concept.

  • 127.
    Meier, Stephan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Control Strategies for Mutually Commutated Converter Systems without Cycloconverter Turn-off Capability2008Inngår i: EEE POWER ELECTRONICS SPECIALISTS CONFERENCE RECORDS, 2008, s. 1344-1350Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mutually commutated converter systems consisting of a voltage source converter and a cycloconverter connected by a medium-frequency transformer allow bidirectional AC/DC conversion as well as voltage transformation and isolation by the transformer. However, such converter systems require an extra power conversion stage compared to conventional converter systems, which may result in low system efficiency despite the soft-switching commutation scheme. In order to reduce the power losses in the cycloconverter, it is desirable to utilize fast thyristors instead of IGBTs. As a consequence, the cycloconverter valves lack turn-off capability because a thyristor can not be turned off by its gate. This paper describes and evaluates the most common control strategies in order to control a thyristor-based cycloconverter in a mutually commutated converter system. The behaviour of the cycloconverter depends strongly on the chosen control strategy when one of the output currents approaches zero, which may inherently affect the harmonic properties of the output voltages and currents. Experimental results from a 20 kVA prototype show that it is possible to successfully operate a mutually commutated converter system without turn-off capability.

  • 128.
    Meier, Stephan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Modulation strategies for a mutually commutated converter system in wind farms2007Inngår i: 2007 European Conference on Power Electronics and Applications, EPE, 2007, s. 1221-1230Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A novel mutually commutated converter (MCC) system consisting of a voltage source converter (VSC) and a cycloconverter connected by a medium-frequency (MF) transformer is adapted for the power collection and conversion in large wind farms. Different modulation strategies based on space vectors are described and evaluated with regard to the very restrictive constraints on the modulation and commutation of the thyristor valves in the cycloconverter. This paper shows that a feasible and effective modulation strategy can be found in order to provide the desired reference voltage vector during every single modulation interval and under all operating conditions. The proposed current clamping control strategy is based on stopping the gate pulses of the conducting thyristor valve during a certain dead-time whenever the current in the corresponding phase leg becomes zero.

  • 129.
    Meier, Stephan
    et al.
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    Norrga, Staffan
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner                               , Elektrotekniska system.
    New topology for more efficent converters for future offshore wind farms2004Inngår i: Proceedings of the Nordic Workshop on Power and Industrial Electronics, Norpie '04, 2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The concept of a novel soft-switching AC/DC converteris applied for use in future offshore wind farms. A voltagesource converter with capacitive snubbers and cycloconverters,connected via a medium frequency AC bus, promises substantialbenefits. This paper presents this new topology and describes its principle of operation. Furthermore, a comparison with state-ofthe-art adjustable speed generators reveals the potential of this new concept.

  • 130.
    Meier, Stephan
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Norrga, Staffan
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner, Elektrotekniska system.
    New Voltage Source Converter Topology for HVDC Grid Connection of Offshore Wind Farms2004Inngår i: Proceedings of the 11th International Power Electronics and Motion Control Conference, EPEPEMC ’04, Riga, Latvia, September 2004, 2004, s. 1-7Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Large offshore wind farms are recently emerging aspromising alternative power sources. Long distances betweenoffshore generation and onshore distribution grid demand new solutions for their connection to the AC network. HVDC systems based on voltage source converters (VSC) are a promisingalternative to conventional AC transmission above a certain cablelength. This paper presents a new VSC transmission topology for HVDC grid connection of offshore wind farms.

  • 131.
    Modeer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    High-Voltage Tapped-Inductor Buck Converter Utilizing an Autonomous High-Side Switch2015Inngår i: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 62, nr 5, s. 2868-2878Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A high-voltage tapped-inductor buck converter utilizing a novel autonomous high-voltage valve is presented in this paper. Its application as auxiliary power supply for high-power cascaded-converter submodules is discussed, followed by a presentation of the most challenging problems in designing a low-power high-voltage step-down converter. The TI-buck converter topology is analyzed, which together with the novel autonomous high-voltage valve overcomes most of the problems. Analytical expressions describing the operation as well as circuit simulations are presented. Finally, an experimental evaluation of a 3-kV 70-W prototype converter utilizing the proposed autonomous high-voltage valve with series-connected super-junction MOSFETs is presented.

  • 132.
    Modeer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Implementation and testing of high-power IGCT-based cascaded-converter cells2014Inngår i: Proc. Energy Conversion Congress and Exposition (ECCE), 2014 IEEE, IEEE , 2014, s. 5355-5359Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the design and implementation of cascaded-converters cells based on integrated gate-commutated thyristor (IGCT) half-bridges. The cell design is presented together with a discussion of means to supply gate drive power and as well as the cooling of the cell components. Also, the operation of the cells in a high-power resonant test circuit is presented.

  • 133.
    Modeer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Resonant Test Circuit for High-Power Cascaded Converter Submodules2013Inngår i: Proc. European Conference on Power Electronics and Applications (EPE), 2013., IEEE , 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a test circuit and methodology suitable for testing high-power half-bridge submodules such as would be used in cascaded converters for high-voltage dc converters. The circuit utilizes a series resonant tank and two half-bridge submodules with voltage and impedance cancellation in order to minimize hardware requirements.

  • 134.
    Modéer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Loss comparison of different sub-module implementations for modular multilevel converters in HVDC applications2011Inngår i: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011) / [ed] EPE Association, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a loss calculation and comparison between different submodule topologies and semiconductor choices for a Modular Multilevel Converter in a 1.1GW, ±320kV HVDC application.

  • 135.
    Modéer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    High-voltage tapped-inductor buck converter auxiliary power supply for cascaded converter submodules2012Inngår i: 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012, IEEE , 2012, s. 19-25Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper firstly presents a discussion of the requirements for an auxiliary power supply for high-power modular multilevel converter submodules. Next, some of the most challenging problems in designing a low power high voltage step-down converter are presented. Further, a suitable topology, the tapped-inductor buck converter, that overcomes most of the problems is analyzed. Both analytical expressions describing the operation and circuit simulations are presented. Finally, an experimental evaluation of a 3 kV, 100W prototype converter utilizing an autonomous high-voltage switch is presented.

  • 136.
    Modéer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Loss comparison of different sub-module implementations for modular multilevel converters in HVDC applications2012Inngår i: EPE Journal: European Power Electronics and Drives Journal, ISSN 0939-8368, Vol. 22, nr 3, s. 32-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a loss calculation and comparison between different submodule topologies and semiconductor choices for a Modular Multilevel Converter in a 1.1 GW, ± 320 kV HVDC application. Accordingly, a detailed analysis of the losses for three different M2C implementations using both insulated gate bipolar transistors (IGBTs) and integrated gatecommutated thyristors (IGCTs) is presented. The losses for six different submodule realizations are shown in a loss breakdown in Fig. 7. It shows that the very low conduction loss of the IGCT is to some degree offset by higher switching losses and extra turn-on snubber losses but that the IGCT implementations provide significantly lower losses than their IGBT counterparts. The loss break-down also shows that clamp-double submodules and full-bridge submodules suffer from approximately 25% and 50% additional losses respectively as compared to the half-bridge case. An experimental verification of the loss calculations has been performed using a down-scaled M2C prototype. The results show a very good agreement between calculations and measured losses.

  • 137.
    Modéer, Tomas
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Zdanowski, Mariusz
    Warsaw University of Technology.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Design and evaluation of tapped inductors for high-voltage auxiliary power supplies for modular multilevel converters2012Inngår i: 15th International Power Electronics and Motion Control Conference and Exposition, EPE-PEMC 2012 ECCE Europe, IEEE , 2012, s. DS1b.231-DS1b.235Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Tapped-inductor buck converters can provide large step-down ratios at high efficiency and are well suited in auxiliary power supplies for modular multilevel converter cells supplying gate drive units etc. In this paper the design and testing of three low-leakage tapped inductors for use in a 3kV, 100W buck converter is described.

  • 138.
    Monge, Mauro
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Johansson, Nicklas
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Ängquist, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Adaptive control for power oscillation damping by means of a Thyristor Controlled Series Capacitor (TCSC)2008Inngår i: 2008 PROCEEDINGS OF THE 43RD INTERNATIONAL UNIVERSITIES POWER ENGINEERING CONFERENCE, NEW YORK: IEEE , 2008, s. 37-41Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes an adaptive method for control of a TCSC device for power oscillation damping. The aim is to mitigate power oscillations in power systems with one dominating oscillation mode. To design the controller, a simple generic model of the power system with only a few variables is used. Initially, a fixed-parameter controller which is based on a pole-placement technique is designed. The controller is then implemented in a digital simulator and tested in a four-machine power system. The fixed-parameter controller performs well in most cases but in some contingencies, a performance decay is seen. To improve the controller performance, an adaptive control design has been investigated. The investigated controller is a Self-Tuning Regulator and a Recursive Least-Squares method is used to estimate the system model parameters. An open-loop controller for transient stability improvement and a closed-loop PI-controller for power flow control are also presented. The adaptive controller has been validated with good results by means of simulations of a number of contingencies in different operating conditions of the four-machine system.

  • 139.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rotor Slot Design of Inverter-Fed Induction Motors1995Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The most dramatic improvements in inverter-fed induction motors are achieved by the change of rotor slot geometry, which can reduce the harmonic winding losses of the rotor to a minimum. Based on an immense number of finite-element calculations, optimal values of different geometrical dimensions of the rotor slot with a U-shaped bridge have been determined. The slot can be designed step by step according to simple analytical expressions for any inverter-fed induction motor, regardless of power rating or speed. The basic principles of the loss mechanisms are explained qualitatively to support the results from the numerical calculations.

  • 140.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    The Interaction of Pair Harmonics of Inverter-Fed Induction Motors with Iron Bridges in the Rotor1994Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A quasi linear harmonic model for inverter-fed induction motors is presented and verified by measurements and finite element analysis. The model is capable of describing the load dependence of the harmonic currents and powers of induction motors with iron bridges in the rotor. Effects like negative input powers for harmonics can be calculated by means of analytical expressions.

  • 141.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Gustavson, Fredrik
    KTH.
    On the Choice of Diameter-Length Ratio, Slot-Tooth Ratio and Pole Number of Variable Speed Induction Motor Drives1996Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The diameter-length ratio, slot-tooth ratio and the pole number can principally be chosen freely when designing a special induction motor for inverter supply. This paper deals with general aspects on these design parameters. Special attention is paid to motors requiring a high pull-out torque, such as traction motors. It is found that a traction motor should normally be an "iron motor". Moreover, it is found that the potential to increase the pull-out torque when making a slim motor is due to secondary effects like reduced end-turns. Finally, it is found that a design with four poles is seldom far from the optimal pole number. For high-speed drives two-pole motors are sometimes better and for traction drives six-pole motors are sometimes preferable.

  • 142.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Kolar, Johann W.
    Friedrichs, Peter
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Special Issue on Wide Bandgap Power Devices and Their Applications, 20142014Inngår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 29, nr 5, s. 2153-2154Artikkel i tidsskrift (Fagfellevurdert)
  • 143. Nee, Hans-Peter
    et al.
    Lefevre, L.
    Thelin, P.
    Soulard, Juliette
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Determination of d and q reactances of permanent-magnet synchronous motors without measurements of the rotor position2000Inngår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 36, nr 5, s. 1330-1335Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 144.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nipp, Eckart
    KTH.
    A contribution to the Calculation of Harmonic Iron Losses of Inverter-fed Induction Motors1994Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper describes a method to calculate harmonic hysteresis and eddy-current losses of inverter-fed induction motors. Perticularly a general method for determination of hysteresis losses is presented. Finally harmonic loss calculations of an inverter-fed induction motor are compared to measurements.

  • 145.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rabkowski, Jacek
    Warsaw University of Technology.
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Multi-chip circuit designs for silicon carbide power electronics2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As the chip sizes of commercially available silicon carbide power transistors will remain smaller than for silicon counterpartsin the next five to ten years, multi-chip circuit designs will be necessary in order to reach power levels exceeding10 kW. In the present paper, therefore, experiences from parallel connected discrete devices, multi-chip modules,and parallel-connected multi-chip modules are presented. It is concluded that new multi-chip circuit designs are necessaryif the high switching speeds of silicon carbide power transistors should be exploited. In the opinion of the authors,each chip must be contacted by means of individual current paths, and internal bus bars conducting the whole current ofthe module must be avoided.

  • 146.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Peftitsis, Dimosthenis
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Tolstoy, Georg
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Colmenares, Juan
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Sadik, Diane
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Bakowski, Mietek
    Acreo Swedish ICT AB, Sweden.
    Lim, Jang-Kwon
    Acreo AB, Kista.
    Antonopoulos, Antonios
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Ängquist, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Zdanowski, Mariusz
    Warsaw University of Technology.
    High-Efficiency Power Conversion Using Silicon Carbide Power Electronics2013Inngår i: Proc. of International Conference on silicon carbide and related materials (ICSCRM) 2013, Miyazaki, Japan, Sept. 29–Oct. 4, 2013, Trans Tech Publications Inc., 2013, s. 1083-1088Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The message of this paper is that the silicon carbide power transistors of today are good enough to design converters with efficiencies and switching speeds beyond comparison with corresponding technology in silicon. This is the time to act. Only in the highest power range the devices are missing. Another important step towards high powers is to find new solutions for multi-chip circuit designs that are adapted to the high possible switching speeds of unipolar silicon carbide power transistors.

  • 147.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Sadarangani, Chandur
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    The influence of load and rotor slot design on harmonic losses of inverter-fed induction motors1993Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a study of the influence of iron bridges in induction motor rotor slots on both the fundamental and harmonic components is presented. A suitable model for the fundamental component is shown. A theory to explain the erratic load dependence of pair harmonics is presented. The test inverter and the measurement equipment is described and the experimental verification of the harmonic theory is described.

  • 148.
    Nee, Hans-Peter
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Sadarangani, Chandur
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    The Steady-State Torque Equation of Induction Motors with U-Shaped Iron Bridges in the Rotor Slots1996Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a modified torque equation for inverter-fed induction motors with U-shaped iron bridges in the rotor is presented. The equation is derived from a modified equivalent circuit with a contsnt bridge voltage introduced in the rotor circuit. A simplified method to estimate the pull-out torque is also presented. This method can be used in conjunction with the conventional equivalent circuit.

  • 149.
    Nikouei Harnefors, Mojgan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES).
    Harnefors, Lennart
    KTH, Skolan för elektro- och systemteknik (EES).
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Operation Under Fault Conditions of the Stacked Polyphase Bridges Converter2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The stacked polyphase bridges converter consists of several submodules that, on the input dc side, all are connected in series. Whereas controller designs presented in previous studies have been found promising for realizing equal voltage sharing between submodules, the survival and stability under fault conditions have not been studied. This paper presents a control strategy that enables survival of the converter after the occurrence of a sudden short circuit of a single transistor switch. The results are verified by simulations.

  • 150.
    Nikouie Harnefors, Mojgan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Jin, Lebing
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Harnefors, Lennart
    ABB, Corporate Research, Sweden.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    DC-link stability analysis and controller design for the stacked polyphase bridges converter2017Inngår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 32, nr 2, s. 1666-1674, artikkel-id 7451258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The stacked polyphase bridges (SPB) converter consists of several submodules that all are connected in series to a voltage source. The total dc-link voltage should split in a balanced way among the submodules. This does not always occur inherently. This paper presents an analysis of the capacitor voltage stability for the SPB converter. From the analysis, criteria for stability are derived and three alternatives of a suitable balancing controller are designed. The proposed controller alternatives and their associated stability properties are verified on an experimental setup and by simulation.

123456 101 - 150 of 273
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