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  • 251.
    Zdanowski, Mariusz
    et al.
    Warsaw University of Technlogy.
    Rabkowski, Jacek
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Kostov, Konstantin
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    The Role of the Parasitic Capacitance of the Inductorin Boost Converters with Normally-On SiC JFETs2012Inngår i: 2012 7th International Power Electronics and Motion Control Conference (IPEMC), IEEE conference proceedings, 2012, s. 1842-1847Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper the impact of the parasitic capacitance ofthe inductor on the performance of a fast-switching boostconverters with SiC JFETs is discussed. Two inductor designs,one conventional and another with a space between the windinglayers, are investigated and their parasitic capacitances aremeasured by different methods. The air-gap between the windinglayers reduced the inductor self-capacitance more than 8 times.The two inductors were used in a 2 kW, 100 kHz boost converterwith a normally-on SiC JFET and their performance wascompared. When the inductor with a low self-capacitance wasused, there were fewer oscillations during the switchingtransients and the losses were reduced about 16 %.

  • 252. Zhang, H.
    et al.
    Wang, X.
    Harnefors, Lennart
    ABB, Västerås, Sweden.
    Gong, H.
    Hasler, J. -P
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    SISO Transfer Functions for Stability Analysis of Grid-Connected Voltage-Source Converters2019Inngår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 55, nr 3, s. 2931-2941, artikkel-id 8640057Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 253.
    Zhang, Hongyang
    et al.
    ABB, Power Grids Div, Vasteras, Sweden..
    Harnefors, Lennart
    ABB, Corp Res, Vasteras, Sweden..
    Wang, Xiongfei
    Aalborg Univ, Dept Energy Technol, Aalborg, Denmark..
    Hasler, Jean-Philippe
    ABB, Power Grids Div, Vasteras, Sweden..
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    SISO Transfer Functions for Stability Analysis of Grid-Connected Voltage-Source Converters2018Inngår i: 2018 International Power Electronics Conference (IPEC-NIIGATA 2018 -ECCE ASIA), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 3684-3691Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Converter grid interaction is of great interest in a weak-grid condition. In this paper, an alternative multi-input multi-output closed-loop system is developed for the stability analysis of grid-connected voltage-source converters. In contrast to the conventional dq-impedance model and the eigenvalue analysis, this model eventually yields a single-input single-output transfer function. This enables to apply a single Nyquist curve for analyzing the overall system stability. The model is validated against time domain simulations and it shows excellent accuracy for predicting the system stability.

  • 254.
    Zhang, Hongyang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Ängquist, Lennart
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Norrga, Staffan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Östlund, Stefan
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Benchmark of high-power STATCOM topologies for flicker compensation2016Inngår i: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE), IEEE, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The current from an electrical arc furnace (EAF) in a steel plant is highly unsymmetrical, i.e. it comprises a large amount of negative sequence. This causes problems with the voltage stability in the capacitor submodules for a static synchronous compensator (STATCOM), when implemented using the modular multilevel converter (M2C) concept. In order to counteract the uncontrollability of the capacitor voltage, a common practice is to circulate a zero-sequence fundamental current or a direct current. The method brings the benefit of re-balancing the active power among the individual phases while it requires over-rating of the valve current or dc voltage of the STATCOM. This would in practice give a more expensive design. This paper presents a benchmark of various M2C-based STATCOM designs considering the valve overrating. The STATCOM topologies will be benchmarked with the EAF modeled for all possible combinations of positive-and negative-sequence current. The rating comparison considering the dc capacitor ripple and zero-sequence harmonic injection are discussed.

  • 255.
    Zhang, Lidong
    et al.
    ABB Power Systems.
    Harnefors, Lennart
    ABB Power Systems.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Interconnection of Two Very Weak AC Systems by VSC-HVDC Links Using Power-Synchronization Control2011Inngår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 26, nr 1, s. 344-355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, voltage-source converter (VSC) based high-voltage dc (HVDC) transmission is investigated for interconnection of two very weak ac systems. By using the recently proposed power-synchronization control, the short-circuit capacities of the ac systems are no longer the limiting factors, but rather the load angles. For the analysis of the stability, the Jacobian transfer matrix concept has been introduced. The right-half plane (RHP) transmission zero of the ac Jacobian transfer matrix moves closer to the origin with larger load angles. The paper shows that, due to the bandwidth limitation imposed by the RHP zero on the direct-voltage control of the VSC, high dc-capacitance values are needed for such applications. In addition, the paper proposes a control structure particularly designed for weak-ac-system interconnections. As an example, it is shown that the proposed control structure enables a power transmission of 0.86 p.u. from a system with the short-circuit ratio (SCR) of 1.2 to a system with an SCR of 1.0. This should be compared to previous results for VSC based HVDC using vector current control. In this case, only 0.4 p.u. power transmission can be achieved for dc link where only one of the ac systems has an SCR of 1.0.

  • 256. Zhang, Lidong
    et al.
    Harnefors, Lennart
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Modeling and Control of VSC-HVDC Links Connected to Island Systems2011Inngår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 26, nr 2, s. 783-793Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recently proposed power-synchronization control for grid-connected voltage-source converters (VSCs) has been shown to be a feasible solution for high-voltage direct-current (HVDC) transmission connected to high-impedance weak ac systems. In this paper, power-synchronization control is investigated for VSC-HVDC links connected to another type of weak ac system, i.e., low-inertia or island systems. As an example, a linear model of a typical island system feeding by a VSC-HVDC link, including a synchronous generator, an induction motor, and some passive loads, is developed for tuning the control parameters of the VSC-HVDC link. Time simulations in PSCAD/EMTDC demonstrate that VSC-HVDC systems using power-synchronization control are flexible for various network conditions, such as large-ac-system connection, island systems, or passive networks. The time simulations also show that power-synchronization control can seamlessly handle transitions between operation modes, as well as ride through ac-system faults in all network conditions.

  • 257.
    Zhang, Lidong
    et al.
    ABB power Systems, Ludvika.
    Harnefors, Lennart
    ABB Power Systems, Ludvika.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Modelling and control of VSC-HVDC connected to island systems2010Inngår i: IEEE Power and Energy Society General Meeting, IEEE , 2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The recently proposed power-synchronization control for grid-connected voltage-source converters (VSCs) has been shown to be a feasible solution for high-voltage dc (HVDC) transmission connected to high-impedance weak ac systems. In this paper, power-synchronization control is investigated for VSC-HVDC connected to another type of weak ac system, i.e., low-inertia or island systems. As an example, a linear model of a typical island system feeding by a VSC-HVDC link, including a synchronous generator, an induction motor and some passive loads, is developed for tuning the control parameters of the VSCHVDC. Time simulations in PSCAD/EMTDC demonstrate that VSC-HVDC using power-synchronization control is flexible for various network conditions, such as large-ac-system connection, island systems, or passive networks. The time simulations also show that power-synchronization control can seamlessly handle transitions between the operation modes, as well as ride through ac-system faults in all network conditions.

  • 258. Zhang, Lidong
    et al.
    Harnefors, Lennart
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik.
    Power-Synchronization Control of Grid-Connected Voltage-Source Converters2010Inngår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 25, nr 2, s. 809-820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, a novel control method of grid-connected voltage-source converters (VSCs) is proposed. The method can be generally applied for all grid-connected VSCs but may be of most importance in high-voltage dc (HVDC) applications. Different from the previous control methods, the proposed method utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine. By using this type of power-synchronization control, the VSC avoids the instability caused by a standard phase-locked loop in a weak ac-system connection. Moreover, a VSC terminal can give the weak ac system strong voltage support, just like a normal synchronous machine does. The control method is verified by both analytical models and time simulations.

  • 259.
    Zhang, Lidong
    et al.
    ABB Power Systems, Ludvika.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Multivariable feedback design of VSC-HVDC connected to weak ac systems2009Inngår i: 2009 IEEE Bucharest PowerTech / [ed] IEEE, IEEE , 2009, s. 764-771Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Power-synchronization control is particularly applicable to voltage-source converters based high-voltage direct-current (HVDC) transmission connected to weak ac systems. In this paper, the multivariable feedback design aspect of the power-synchronization control is investigated by two design approaches: internal model control (IMC) and Hinfin control. The paper shows that both of the methods can meet the design requirements and show good robustness with different model uncertainties and load disturbances. The advantage of the IMC approach is that it provides a transparent framework for control-system design and tuning. The algorithm used for the IMC design in this paper is simple, yet it achieves similar or even better performance and robustness compared to the more advanced optimization-based Hinfin controller.

  • 260.
    Zhang, Lidong
    et al.
    ABB Power Systems, Ludvika.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES).
    Harnefors, Lennart
    KTH, Skolan för elektro- och systemteknik (EES).
    Analysis of Stability Limitations of a VSC-HVDC Link Using Power-Synchronization Control2011Inngår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 26, nr 3, s. 1326-1337Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, the stability limitations are analyzed for a voltage-source converter (VSC) based high-voltage direct-current (HVDC) link using power-synchronization control for two feasible operation modes: alternating-voltage control and reactive-power control. As a comparison, the analysis has been done by the phasor approach and the space-vector approach. While the phasor approach is straightforward to apply and gives intuitive analytical results, the space-vector approach reflects more dynamic insights of the system. This is achieved by using a unified dynamic modeling of both the ac system and the VSC by means of a new introduced modeling approach Jacobian transfer matrices. This approach shows that non-minimum-phase phenomena due to competing effects between alternating voltages and currents following phase-angle changes impose a fundamental limitation on the achievable bandwidth of the VSC-HVDC link. At moderate voltage levels, a VSC-HVDC link operating in alternating-voltage control mode is able to achieve higher bandwidth than in reactive-power control mode since the right-half plane (RHP) zero is located further from the origin in the former mode.

  • 261.
    Zhang, Yafan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling. Jönköping University, Sweden.
    Belov, Ilja
    Bakowski, Mietek
    Lim, Jang-Kwon
    Leisner, Peter
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Investigation of a Finned Baseplate Material and Thickness Variation for Thermal Performance of a SiC Power Module2014Inngår i: 2014 15th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2014, IEEE Computer Society, 2014, artikkel-id 6813817Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A simplified transient computational fluid dynamics model of an automotive three-phase double-side liquid cooled silicon carbide power inverter, including pin-fin baseplates, has been developed and qualified for parametric studies. Effective heat transfer coefficients have been extracted from the detailed pin-fin baseplate model for two coolant volume flow rates 2 l/min and 6 l/min, at the coolant temperature 105 degrees C. The inverter model includes temperature dependent heat losses of SiC transistors and diodes, calculated for two driving cycles. Baseplate materials such as copper, aluminum-silicon carbide metal matrix composite, aluminium alloy 6061 as well as virtual materials have been evaluated in the parametric studies. Thermal conductivity, specific heat and density have been varied as well as thickness of the finned baseplates (1 to 3 mm). A trade-off between temperature of SiC chips and baseplate weight has been investigated by means of Pareto optimization. The main results of the parametric studies include a weak dependence (1 to 3 degrees C) of the chip temperature on baseplate thickness. Furthermore, switching e.g. between copper and AlSiC results in 5 to 8 degrees C increase of the chip temperature, at 65 to 70 % baseplate weight reduction.

  • 262.
    Zhang, Yafan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling. Acreo Swedish ICT AB.
    Belov, Ilja
    Jönköpng University.
    Sarius, Niklas G.
    Sp Technical Research Institute of Sweden.
    Bakowski, Mietek
    Acreo Swedish ICT AB.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leisner, Peter
    Sp Technical Research Institute of Sweden.
    Thermal evaluation of a liquid/air cooled integrated power inverter for hybrid vehicle applications2013Inngår i: 2013 14th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2013, New York: IEEE , 2013, s. 6529944-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A thermal design of an integrated double-side cooled SiC 50kW-1200V-200A power inverter for hybrid electric vehicle applications has been proposed to enable cooling in two different automotive operating environments: under-hood and controlled temperature environment of passenger compartment. The power inverter is integrated with air/liquid cooled cold plates equipped with finned channels. Concept evaluation and CFD model calibration have been performed on a simplified thermal prototype. Computational experiments on the detailed model of the inverter, including packaging materials, have been performed for automotive industry defined application scenarios, including two extreme and one typical driving cycles. For the studied application scenarios the case temperature of the SiC transistors and diodes have been found to be below 210°C. The maximum steady-state temperature of the DC-link capacitor has been below 127 °C for the worst-case scenario including liquid cooling, and up to 140 °C for the worst-case scenario with air-cooling.

  • 263.
    Zhang, Yafan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik. RISE Acreo AB, Sweden.
    Hammam, Tag
    Belov, Ilja
    Sjögren, Torsten
    Bakowski, Mietek
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Thermomechanical Analysis and Characterization of a Press-Pack Structure for SiC Power Module Packaging Applications2017Inngår i: IEEE Transactions on Components, Packaging, and Manufacturing Technology, ISSN 2156-3950, E-ISSN 2156-3985, Vol. 7, nr 7, s. 1089-1100Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents an experimental methodology for the characterization of thermomechanical displacement and friction properties in a free-floating press-pack structure, and evaluation of the tensile stress on the semiconductor die through simulation of different mechanical and thermal loading conditions. The press-pack structure consists of a single silver-metallized (1 μm) silicon carbide die (400 μm) in contact with rhodium-coated (0.4 μm) molybdenum square plates. The thermomechanical displacements in the press-pack structure have been obtained using the digital image correlation technique, and the mean random error has been $± $0.1 μm, which is approximately 10 ppm of the measured length (10.5 mm). The developed experimental method has led to an analytical estimation of friction coefficients on the interfaces' silicon carbide-molybdenum and molybdenum-copper. The results demonstrate that the thin silver layer behaves as a solid film lubricant. A 2-D finite-element model representing the experimental setup has been implemented. The difference in displacement between measurement and simulation is less than 8%. Furthermore, the coinfluence of the design parameters on the thermomechanical performance of the stacked structure has been analyzed through simulations. Finally, design guidelines to reduce the tensile stress on the silicon carbide die have been proposed regarding free-floating press-pack power electronics packaging.

  • 264.
    Zhang, Yafan
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik. Department of Netlab, RISE Acreo AB, Kista, Sweden.
    Nee, Hans-Peter
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elkraftteknik.
    Hammam, Tag
    Belov, Ilja
    Ranstad, Per
    Bakowski, Mietek
    Multiphysics Characterization of a Novel SiC Power Module2019Inngår i: IEEE transactions on components, packaging, and manufacturing technology. Part A (Print), ISSN 1070-9886, E-ISSN 1558-3678, Vol. 9, nr 3, s. 489-501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a novel power module concept specially designed for highly reliable silicon carbide (SiC) power devices for medium- and high-power applications. The concept consists of two clamped structures: 1) a press-pack power stage accommodating SiC power switch dies and 2) perpendicularly clamped press-pack heatsinks, in which the heatsinks are in contact with electrically insulated case plates of the power stage. The concept enables bondless package with symmetric double-sided cooling of the dies and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. The concept has been evaluated in a first demonstrator (half-bridge configuration with 10 paralleled SiC dies in each position). The experimental methodologies, setups, and procedures have been presented. The commutation loop inductance is approximately 9 nH at 78 kHz. The junction-to-case thermal resistance is approximately 0.028 K/W. Furthermore, a simplified 3-D finite-element thermomechanical model representing the center unit of the demonstrator has been established for the purpose of future optimization. The accuracy of the simulated temperatures is within 4% compared to the measurements. Finally, a 3-D thermomechanical stress distribution map has been obtained for the simplified model of the demonstrator.

  • 265.
    Zhang, Yafan
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik. RISE Acreo AB, Sweden.
    Neumaier, K.
    Zschieschang, O.
    Weis, G.
    Schmid, G.
    Bakowski, M.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Simulation-driven development of a novel SiC embedded power module design concept2017Inngår i: 2017 18th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikkel-id 7926252Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Silicon carbide embedded power modules enable a compact and cost competitive packaging solution for high-switching frequency and high-temperature operation applications. Power module packaging technologies span several engineering domains. At the early design stage, simulation-driven development is necessary to shorten the design period and reduce the design cost. This paper presents a novel design concept of a three-phase embedded power module (1200 V, 20 A, 55 mm × 36 mm × 0.808 mm) including silicon carbide metal-oxide-semiconductor field-effect transistor and antiparallel diode dies. Based on the E/CAD design data different layer built-up designs have been tested against thermal, mechanical, and electrical behavior. The obtained simulation data then have been evaluated against a commercial available power module (Motion Smart Power Module SMP33) which utilizes over mold direct bonded copper substrates with soldered semiconductor dies and bond wire contacts. Compared to the conventional module, the loop conductive interconnection parasitic inductance and resistance of the design concept (Vdc+ to Vdc-) reduces approximately by 88 % and 72 %, respectively. The average junction to case thermal resistance has been improved by approximately more than 10 % even though the total package size reduces by approximately 88 %. Furthermore, the contours of deformation and stresses have been investigated for the design concept in the thermomechanical simulation.

  • 266.
    Ängquist, Lennart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Antonopoulos, Antonios
    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.
    Arm-current-based control of modular multilevel converters2013Inngår i: 2013 15th European Conference on Power Electronics and Applications, EPE 2013, IEEE , 2013, s. 6631999-Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 267.
    Ängquist, Lennart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Antonopoulos, Antonios
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Siemaszko, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Ilves, Kalle
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Vasiladiotis, Michail
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Nee, Hans-Peter
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Open-Loop Control of Modular Multilevel Converters Using Estimation of Stored Energy2011Inngår i: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 47, nr 6, s. 2516-2524Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 268.
    Ängquist, Lennart
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska maskiner och effektelektronik (stängd 20110930).
    Haider, Arif
    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).
    Jiang, Hongbo
    Trafikverket, Borlänge, Sweden.
    Open-loop approach to control a Modular Multilevel Frequency Converter2011Inngår i: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011) / [ed] EPE Association, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

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

  • 269.
    Ållebrand, Björn
    et al.
    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.
    Comparison of Commutation Transients of Inverters with Silicon Carbide JFETs with and without Body Diodes2004Inngår i: Proceedings of the Nordic Workshop on Power and Industrial Electronics (NORpie), 2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An inverter could be built by using silcon carbide power switches only. This can be done by using SiC JFETs which can conduct current in both directions. An interesting question is how an inverter using SiC JFETs with a body diode compares with an inverter using SiC JFETs without body diodes. This will be discussed in this paper.

  • 270.
    Ållebrand, Björn
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Design of a Gate Drive Circuit For use with SiC JFETs2002Inngår i: Proceedings of the Nordic Workshop on Power and Industrial Electronics, NORpie 2002, 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper desccribes how a gate drive can be designed for use with SiC JFETs. The gate drive is supposed to be used in an experimental set-up, which means that the design is not adapted to production constraints. The gate drive circuit can be divvided into four parts: power stage, negative voltage protection, short-circuit protection, and logic unit, which all are desccribed.

  • 271.
    Ållebrand, Björn
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Minimizing oscillations in the Diode-Less SiC JFET Inverter Bridge2002Inngår i: Proceedings of the Nordic Workshop on Power and Industrial Electronics, NORpie 2002, 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This article desccribes how the oscillations in the Diode-less SiC JFET Inverter Bridge can be minimized. Different ways of minimizing the oscillations are investigated and simulation results are presented showing how these oscillations are reduced. The cause of the oscillations are given a thorough review.

  • 272.
    Ållebrand, Björn
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner, Elektrotekniska system.
    On the choice of blanking times at turn-on and turn-off for the diode-less SiC JFET inverter bridge2001Inngår i: Proceedings of the European Conference on Power Electronics and Applications (EPE) 2001, 2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This article desccribes the choice of blanking times at turn-on and turn-off for the diode-less SiC JFET inverter bridge. It is also discussed if auxiliary capacitors should be used or not and which capacitance should be used in different cases.

  • 273.
    Ållebrand, Björn
    et al.
    KTH, Tidigare Institutioner, Elektrotekniska system.
    Nee, Hans-Peter
    KTH, Tidigare Institutioner, Elektrotekniska system.
    On the possibility to use SiC JFETs in Power Electronic circuits2001Inngår i: Proceedings of the European Conference on Power Electronics and Applications (EPE) 2001, 2001Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This article desccribes a proposed bridge circuit without anti-parallel diodes and results from preliminary computer simulations of the proposed circuit. There is a discussion of the normally-on property of the JFET and interviews with industry representatives are presented with their opinions on the SiC JFET.

3456 251 - 273 of 273
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