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  • 51.
    Nikouie Harnefors, Mojgan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    ABB Corporate Research, Västerås, Sweden.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Analysis of the dc-link stability for the stacked polyphase bridges converter2015In: 2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    This paper presents an analysis of the capacitor voltage stability for a stacked polyphase bridges (SPB)

    type converter. The SPB converter comprises of several submodules which are connected in series.

    Therefore, stability of the dc-link voltage is very important to investigate. From the analysis, a corresponding

    controller and an analytical expression for stability are derived. The proposed controller and

    the associated stability condition are verified in a simulation environment and on a small experimental

    setup.

  • 52.
    Nikouie Harnefors, Mojgan
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Harnefors, Lennart
    ABB, Corporate Research, Sweden.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    DC-link stability analysis and controller design for the stacked polyphase bridges converter2017In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 32, no 2, p. 1666-1674, article id 7451258Article in journal (Refereed)
    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.

  • 53.
    Nikouie, Mojgan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Wallmark, Oskar
    Harnefors, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Torque-Ripple Minimization for Permanent-MagnetSynchronous Motors Based on Harmonic Flux Estimation2018Conference paper (Refereed)
    Abstract [en]

    This paper presents a control algorithm to reduce the torque ripple in permanent-magnet synchronous motors. This control algorithm is based on the on-line estimation of harmonic flux linkage. Together with the online estimation of the flux linkage, a proportional–integral–resonant controller is introduced to suppress the torque ripple.

  • 54.
    Nikouie, Mojgan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Zhang, Hui
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    A highly integrated electric drive system for tomorrow's EVs and HEVs2018In: Proceedings - 2017 IEEE Southern Power Electronics Conference, SPEC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-5Conference paper (Refereed)
    Abstract [en]

    This paper presents an ultra-compact integrated electric drive prototype. The prototype illustrates the integration of a fractional slot concentrated winding (FSCW) electric motor, a stacked polyphase bridges (SPB) converter, the control boards, and the water cooling plates into a common housing. This integrated prototype offers a high potential of compactness and cost reduction for electric and hybrid electric vehicles.

  • 55.
    Nikouie, Mojgan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Zhang, Hui
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Highly integratedelectric drives system for tomorrow’s EVs and HEVs2017Conference paper (Refereed)
    Abstract [en]

    This paper presents an ultra-compact integratedelectric drive prototype. The prototype illustrates the integrationof a fractional slot concentrated winding (FSCW) electric motor,a stacked polyphase bridges (SPB) converter, the control boards,and the water cooling plates into a common housing. Thisintegrated prototype offers a high potential of compactness andcost reduction for electric and hybrid electric vehicles.

  • 56.
    Norrga, Staffan
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Mayer, Anna
    Universität der Bundeswehr München.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    A Novel Inverter Topology for Compact EV and HEV Drive Systems2013In: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON 2013, IEEE , 2013, p. 6590-6595Conference paper (Refereed)
    Abstract [en]

    This paper describes a new modular inverter topol­ogy suitable for compact drive systems in electric road vehicles. The topology is based on dc-side cascading of three-phase two ­level inverter bridges, each feeding a set of three-phase windings of a motor. This topology is compared by calculation to the known modular high-frequency (MHF) converter, and is found to have similar losses and semiconductor expenditure requirements. Simulations verify the dynamic and static properties of the converter in a realistic application.

  • 57.
    Soares, Rudi
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Bessman, Alexander
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svens, Pontus
    Design Aspects of an Experimental Setup for Investigating Current Ripple Effects in Lithium-ion Battery Cells2015In: Power Electronics and Applications (EPE'15 ECCE-Europe), 2015 17th European Conference on, IEEE conference proceedings, 2015, p. 1-8Conference paper (Refereed)
    Abstract [en]

    This paper describes an experimental setup for investigating the effects of current ripple on lithium-ion battery cells. The experimental setup is designed so that twelve li-ion cells can be simultaneously tested in a controlled environment. The experimental setup allows for a wide range of current ripple in terms of frequency and amplitude. Additionally, the quantification of the current ripple effects such as the aging of li-ion cells implies that a precise measurement system has to be designed which also are discussed in the paper.

  • 58.
    Soares, Rudi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH.
    Bessman, Alexander
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Svens, Pontus
    Scania.
    An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-Ion Battery Cells2018In: Batteries-Basel, ISSN 2313-0105, Vol. 4, no 3, article id 38Article in journal (Refereed)
    Abstract [en]

    In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup’s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far.

  • 59.
    Soares, Rúdi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems. KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Lindbergh, Göran (Contributor)
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Svens, Pontus (Contributor)
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Analysis and Prediction of the Harmonic Content in the Battery Currentof a Commercial Hybrid-Electric BusIn: IEEE Transactions on Transportation ElectrificationArticle in journal (Refereed)
    Abstract [en]

    This paper presents a comparison of the harmoniccontent in the battery current in two, commercialhybrid electric vehicles (HEVs) (intercity passenger buses)when operated in realistic drive scenarios. These harmonicscan contribute to issues related to electromagnetic compatibilityand indirectly accelerate the aging of the battery dueto elevated cell temperatures caused by associated ohmiclosses. A key finding is that low-frequency harmonics (upto approximately 130 Hz) attributed to resolver eccentricityand non-ideal effects in the voltage-source inverter (VSI) (upto approximately 260 Hz) were significant in terms of magnitudes.Also, the variation between the two HEVs (in termsof current magnitude) were substantial for these harmonics.This is an important observation since it demonstratesthat significant, low-frequency harmonics can be presentin the battery current and that modeling and collectingexperimental data from a single corresponding vehicle maynot sufficiently represent the harmonic content in the batterycurrent for a fleet of vehicles.

  • 60.
    Soares, Rúdi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Loh, Poh Chiang (Contributor)
    Chinese University of Hong Kong.
    Integration of Magnified Alternating Current in Battery Fast Chargers based on DC-DC Converters using Transformerless Resonant Filter DesignIn: IEEE Transactions on Transportation ElectrificationArticle in journal (Refereed)
    Abstract [en]

    For safety and longevity reasons, in subzero temperatures, lithium-ion batteries can only be charged after precommissioningtheir temperature. Therefore, in such conditions fast charging depends on fast heating. Recently,the injection of AC currents into lithium-ion batteries has been reported as a technique with potential to decreaseheating time. This paper proposes a method based on a multi-objective algorithm for DC-DC converter designusing transformerless resonant filters. The method enables the DC-DC converters to produce magnified AC currentin addition to the DC current. Using the proposed design method, a topological survey of DC-DC converters withmagnified AC current capability composed of either half- or full-bridge switch arrangements is carried out. Inthe presented experimental setup, it is demonstrated that by using an LCL circuit with specific component valuesand a full-bridge switch arrangement, magnifications of up to 15.7 may be reached. Further, by matching theswitching frequency with the frequency where the LCL and the battery resonate, for the same injected AC current,the current flowing in the semiconductors and the switching frequency could be reduced. This allowed a lossreduction in the semiconductors of up to 75%, when compared with an equivalent DC-DC converter enabled toproduce a non-magnified AC current.

  • 61.
    Soares, Rúdi
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Bessman, Alexander
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svens, P.
    Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle2017In: 2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 45-50Conference paper (Refereed)
    Abstract [en]

    In this paper, the harmonic content of the battery current in a commercial hybrid vehicle (bus) is measured and analyzed for a number of different driving situations. It is found that the most prominent harmonic reaches peak magnitudes that can be higher than 10% of the maximum dc-current level with a maximum frequency less than 150 Hz. Further, it is found that this harmonic can be approximated using a fitted, simple analytical expression with reasonable agreement for all driving situations considered.

  • 62.
    Soares, Rúdi
    et al.
    KTH.
    Bessman, Alexander
    KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH.
    Svens, Pontus
    KTH.
    A Control Method for Battery Heating Using Alternating CurrentManuscript (preprint) (Other academic)
  • 63.
    Soares, Rúdi
    et al.
    KTH.
    Bessman, Alexander
    KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Svens, Pontus
    KTH.
    An Experimental Setup with Alternating Current Capability for Evaluating Large Lithium-ion Batteries CellsManuscript (preprint) (Other academic)
  • 64.
    Tolstoy, Georg
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Larsson, Björn
    ABB Machines.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Elimination of vector changes due to sector changes with DTC2014In: 2014 16th European Conference on Power Electronics and Applications, EPE-ECCE Europe 2014, IEEE , 2014, p. 6910748-Conference paper (Refereed)
    Abstract [en]

    In this paper it has been investigated if there is a possibility to reduce the switching frequency for a two-level inverter by improving the direct torque control (DTC) algorithm by adding a non-switching condition when a new sector is entered. It is believed that the DTC switching table can be improved by adding a non-switching condition when sector change occurs. This will reduce the number of switching actions by up to 12 per electrical rotation without interfering with the electrical machine performance.

  • 65.
    Tolstoy, Georg
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Larsson, B.
    Elimination of vector changes due to sector changes with DTC*2015In: EPE Journal: European Power Electronics and Drives Journal, ISSN 0939-8368, Vol. 25, no 4, p. 11-16Article in journal (Refereed)
    Abstract [en]

    In this paper it has been investigated if there is a possibility to reduce the switching frequency for a two-level inverter by improving the direct torque control (DTC) algorithm by adding a non-switching condition when a new sector is entered. It is believed that the DTC switching table can be improved by adding a non-switching condition when sector change occurs. This will reduce the number of switching actions by up to 12 per electrical rotation without interfering with the electrical machine performance.

  • 66. Wallmark, Oskar
    Control of permanent-magnet synchronous machines in automotive applications2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the design and analysis of control system structures for electric drives equipped with permanent-magnet synchronous machines (PMSMs) in automotive applications. Sensorless control, meaning vector control without a mechanical rotor position sensor, is considered and a speed and position estimator of phase-locked loop type is analyzed thoroughly. Modifications are proposed to allow for operation in the whole speed range and to improve the estimator's capacity to handle large speed estimation errors. It is shown that rotor saliency affects the estimator dynamics which may become unstable for certain parameter selections and operating conditions. Simple parameter selection rules are therefore derived in order to guarantee stability and to simplify an implementation. Of particular interest for PMSMs with small or negligible rotor saliency, an estimator, extracting position information solely from the back-electromotive force is also considered. The estimator is based on the well known "voltage model" and modifications are proposed in order to improve the estimator's performance in the low-speed range by guaranteeing synchronization at startup and allowing stable rotation reversals. The theory of loss minimization by means of control is applied to a PMSM drive intended for propulsion in a hybrid electric vehicle. Through stronger field weakening, the fundamental core losses can be reduced at the expense of increased resistive losses. The study shows, however, that the additional inverter losses, due to the addition of extra field weakening, reduce the potential to minimize the total losses considerably. A review of fault-tolerant PMSM drives is presented and control algorithms are proposed for achieving sensorless control, closed-loop field-weakening control, and maximum utilization of the available inverter voltage for a drive that, for redundancy, adopts an additional inverter leg connected to the neutral point of the machine. The impact of various electrical faults in a vehicle equipped with in-wheel motors and individual steering actuators is also investigated. Here, it is shown that vehicle stability can be maintained with only minor displacements using a closed-loop path controller and an optimal approach, recently reported in the literature, to allocate tire forces.

  • 67. Wallmark, Oskar
    On Control of Permanent-Magnet Synchronous Motors in Hybrid-Electric Vehicle Applications2004Licentiate thesis, monograph (Other academic)
  • 68.
    Wallmark, Oskar
    et al.
    Chalmers Univ Technol, Dept Energy & Environm.
    Carlson, O.
    Harnefors, L.
    Loss minimization of a PMSM drive for a hybrid electric vehicle2004Conference paper (Refereed)
  • 69.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Galic, Johann
    Prediction of dc-link current harmonics from PM-motor drives in railway applications2012In: Electrical Systems for Aircraft, Railway and Ship Propulsion (ESARS), 2012, IEEE , 2012, p. 6387397-Conference paper (Refereed)
    Abstract [en]

    Depending on the rotor magnet and stator winding configurations, the magnitude of the resulting flux-linkage harmonics in permanent-magnet (PM) motor drives can be substantial. The flux-linkage harmonics result into dc-link current harmonics that can cause the operation of certain track circuits (used to identify the presence of a train on a track section) to malfunction. Predicting the impact of flux-linkage harmonics on the dc-link current is therefore necessary since it may be an important factor to take into consideration when sizing the converter input filter. In this paper, the flux-linkage harmonics from an experimental railway traction PM motor are analyzed using two-dimensional finite element (2DFEM) simulations. Data from the 2DFEM simulations are then used to model the PM motor drive system in a real-time simulator (RTS) model. Output data from the RTS model are compared to experiments with good agreement. Additionally, the impact of resolver eccentricity, typically arising due to bearing wear, on the resulting dc-link current is investigated. A simple analytical model is presented to model resolver eccentricity. The proposed model is then used in the RTS model to analyze the resulting impact on the harmonic content of the dc-link current.

  • 70.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Galic, Johann
    Jansson, Magnus
    Mosskull, Henrik
    A robust sensorless control scheme for permanent-magnet motors in railway traction applications2012In: Electrical Systems for Aircraft, Railway and Ship Propulsion (ESARS), 2012, IEEE , 2012, p. 6387457-Conference paper (Refereed)
    Abstract [en]

    Recently, the principle of indirect self control (ISC) has been shown to be suitable also for permanent-magnetmotor drives. In this paper, which is a companion paper to [1], experimental results are presented which show that ISC isa robust and suitable control principle for permanent-magnetsynchronous motors (PMSMs) in railway traction applications, also when the rotor position is not known but estimated. For PMSMs operating with a position sensor, the proposed method enables an improved system reliability if applied as a backup operation mode in the event of a failure of the position sensor.

  • 71.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Galić, J.
    Mosskull, H.
    Sensorless control of permanent-magnet synchronous motors adopting indirect self-control2012In: IET Electric Power Applications, ISSN 1751-8660, Vol. 6, no 1, p. 12-18Article in journal (Refereed)
    Abstract [en]

    This study presents a detailed description of how sensorless control of permanent-magnet synchronous motors can be implemented when the torque and stator flux amplitude are controlled using the principle of indirect self-control (ISC). As a new contribution, it is demonstrated how carrier signal injection, used to obtain accurate speed and position estimates in the low-speed region, can be incorporated in the ISC scheme. Furthermore, the impact of saturation in the rotor structure during initial rotor position detection is also analysed. Results from finite element simulations together with experimental results (from a laboratory bench setup as well as from a test train) support the obtained results.

  • 72. Wallmark, Oskar
    et al.
    Harnefors, L.
    Carlson, O.
    An improved speed and position estimator for salient permanent-magnet synchronous motors2005In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 52, no 1, p. 255-262Article in journal (Refereed)
    Abstract [en]

    In this paper, an improved phase-locked-loop-type speed and position estimator for permanent-magnet synchronous motor (PMSM) drives is considered. Particular attention is put on salient-rotor PMSMs with fast mechanical dynamics. A method is presented, whereby significantly improved tracking is achieved. While saliency makes nominal-speed stability more difficult to guarantee (an analysis of this is presented), a benefit is that signal-injection methods can be used at low speeds for accurate position estimation, which is also included in the modified estimator.

  • 73.
    Wallmark, Oskar
    et al.
    Chalmers Univ Technol, Dept Energy & Environm.
    Harnefors, L.
    Chalmers Univ Technol, Dept Energy & Environm.
    Carlson, O.
    Chalmers Univ Technol, Dept Energy & Environm.
    Control algorithms for a fault-tolerant PMSM drive2005In: IECON 2005: THIRTY-FIRST ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, VOLS 1-3, 2005, p. 1467-1473Conference paper (Refereed)
    Abstract [en]

    This paper proposes control algorithms for a fault-tolerant permanent-magnet synchronous motor (PMSM) drive. In order to improve the reliability of the drive, an algorithm for achieving sensorless control that operates properly also in fault mode is proposed. Furthermore, it is shown how a closed-loop field-weakening controller needs to be modified in order to operate properly in fault mode. The application in mind is electric vehicle propulsion and the algorithms presented are verified with experimental results using an in-wheel PMSM. With the proposed modifications, the reliability of the drive can be increased.

  • 74.
    Wallmark, Oskar
    et al.
    Chalmers Univ Technol, Dept Energy & Environm.
    Harnefors, L.
    Dep. of Energy and Environment, Chalmers University of Technology.
    Carlson, O.
    Dep. of Energy and Environment, Chalmers University of Technology.
    Post-fault operation of fault-tolerant inverters for PMSM drives2005In: 2005 European Conference on Power Electronics and Applications, 2005, p. Article number 1665886-Conference paper (Refereed)
    Abstract [en]

    This paper considerspost-faultoperationof permanent-magnet synchronous motordrivesequipped with afault-tolerantinverter. Inpost-faultmode, the faulted phase is isolated and the neutral point is connected either to an additionalinverterleg or to the midpoint of the dc bus. Different methods of controlling the neutral point voltage are presented and compared. Furthermore,operationwithout a position sensor (i.e., sensorless control) is considered and a modification to an estimator previously reported in the literature is proposed in order to take into account the effect of the asymmetry introduced due to the isolation of the faulted phase inpost-faultmode. Simulations and experimental results are provided to support the theory and demonstrate the practical impact of the modifications proposed.

  • 75.
    Wallmark, Oskar
    et al.
    Chalmers Univ Technol, Dept Energy & Environm.
    Harnefors, L.
    Chalmers Univ Technol, Dept Energy & Environm.
    Carlson, O.
    Chalmers Univ Technol, Dept Energy & Environm.
    Sensorless control of PMSM drives for hybrid electric vehicles2004Conference paper (Refereed)
    Abstract [en]

    This paper considers the implementation of a speed and position estimator for a permanent-magnet synchronous machine in a hybrid-electric vehicle application. A modified variant of the estimator of phase-locked loop type, previously developed by Harnefors and Nee, is presented, in order to take into account effects of saliency and operation in the whole speed region. Furthermore, design rules for all parameter settings are given. Based on drive-cycle simulations, important operating points are chosen for evaluation, with good results, on an existing experimental setup.

  • 76. Wallmark, Oskar
    et al.
    Harnefors, Lennart
    Sensorless control of salient PMSM drives in the transition region2006In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 53, no 4, p. 1179-1187Article in journal (Refereed)
    Abstract [en]

    This paper considers speed and position estimation of salient permanent-magnet synchronous machines (PMSMs). An estimator of phase-locked loop (PLL) type is considered. Signal injection techniques are used in the zero-speed and low-speed regions, while information found in the back electromotive force (EMF) is used for higher speeds. Particular focus is put on the transition region, i.e., the speed region where the estimator switches between signal-injection and back-EMF-based methods. It is shown that the estimator may become unstable for certain setups of machine parameters and operating conditions if the transition region is determined incorrectly. To avoid this instability, design rules for how the transition region should be determined, as well as recommended selections for all parameters introduced, are given. The results of the analysis are also supported with experimental results.

  • 77.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Harnefors, Lennart
    Carlson, Ola
    Control algorithms for a fault-tolerant PMSM drive2007In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 54, no 4, p. 1973-1980Article in journal (Refereed)
    Abstract [en]

    This paper proposes control algorithms for a fault-tolerant permanent-magnet synchronous motor (PMSM) drive. In order to improve the reliability of the drive, an algorithm for achieving a sensorless control that operates properly also in fault mode is proposed. Furthermore, it is shown how a closed-loop field-weakening controller needs to be modified in order to operate properly in fault mode. Automotive applications are in mind and the algorithms presented are verified with experimental results using an in-wheel PMSM. With the proposed modifications, the reliability of the drive can be improved.

  • 78.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jonasson, O.
    Vehicles with autonomous corner modules: Control and fault handling aspects2007In:  , 2007Conference paper (Other academic)
  • 79.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2.
    Kjellqvist, Peter
    Analysis of a Low-Cost Air-Gap Winding for Permanent Magnet Synchronous Motors2009In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 24, no 4, p. 841-847Article in journal (Refereed)
    Abstract [en]

    This paper presents an analysis of a concentrated air-gap winding concept intended for low-cost, high-speed applications where the reduced winding construction cost can motivate its use. Expressions for magnet flux linkage, torque, winding inductance, and unbalanced magnetic pull are derived and compared, with good agreement, to measurements and results obtained from finite-element simulations.

  • 80.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Kjellqvist, Peter
    Meier, Florence
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Analysis of Axial Leakage in High-Speed Slotless PM Motors for Industrial Hand Tools2008In: 2008 IEEE INDUSTRY APPLICATIONS SOCIETY ANNUAL MEETING, 2008, p. 2070-2075Conference paper (Refereed)
    Abstract [en]

    This paper presents an analysis of axial leakage effects in high-speed, slotless permanent magnet (PM) motors for industrial hand-tool applications. Analytical predictions and results from a finite-element simulation model are compared to experimental results from three, series-produced PM motors. The reduction in predicted and measured flux density outside the motor's axial ends is substantial; the flux density has practically vanished only a few millimeters outside the stator lamination stack. To predict the resulting flux linkage, a simple winding model is presented where the winding is made up of a discrete number of winding layers. Using this winding model, it is verified that the reduction in flux linkage, manifested as a reduction in the back electromotive force (EMF), is dependent on the motor's axial length but also that the effect is minor for slotless PM motors with dimensions suitable for hand-tool applications. The results are also supported by no-load line-to-line voltage measurements on the three PM motors.

  • 81.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2. KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Kjellqvist, Peter
    Meier, Florence
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2. KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Analysis of Axial Leakage in High-Speed Slotless PM Motors for Industrial Hand Tools2009In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 45, no 5, p. 1815-1820Article in journal (Refereed)
    Abstract [en]

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

  • 82.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lundberg, S.
    Bongiorno, M.
    Input Admittance Expressions for Field-Oriented Controlled Salient PMSM Drives2012In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 27, no 3, p. 1514-1520Article in journal (Refereed)
    Abstract [en]

    This paper presents analytical expressions for the converter input admittance in field-oriented controlled permanentmagnet synchronous motor (PMSM) drives. The effect of rotorsaliency is taken into consideration and the derived admittance expressions are valid for maximum-torque-per-ampere as well ashigh-speed (field weakening) operation. Experimental results illustrate the validity of the derived admittance expressions. The presented work can be used to predict dc-link voltage instabilities inPMSM drives in, e.g., railway traction, aerospace and automotive applications.

  • 83.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Nikouei Harnefors, Mojgan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    DC-link and machine design considerationsfor resonant controllers adopted in automotive PMSM drivesIn: Article in journal (Refereed)
  • 84.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Nybacka, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Malmquist, Daniel
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Burman, Magnus
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Wennhage, Per
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Géoren, Peter
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Design and implementation of an experimental research and concept demonstration vehicle2014In: 2014 IEEE Vehicle Power and Propulsion Conference, VPPC 2014, IEEE conference proceedings, 2014Conference paper (Refereed)
    Abstract [en]

    This paper introduces the Research Concept Vehicle (RCV), an experimental research and demonstration vehicle developed at KTH Royal Institute of Technology. The vehicle is intended as a platform to implement, validate, and demonstrate research results from different research projects carried out at KTH. In its first generation, the RCV is a pure electric vehicle where each wheel is equipped with an in-wheel motor and individual steering and camber actuators. This high level of over actuation allows for a wide range of experimental evaluation in several fields of research, which is listed in this paper. Results from initial experimental test drives are also included.

  • 85.
    Wanner, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Edrén, Johannes
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Jonasson, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Fault-Tolerant Control of Electric Vehicles with In-Wheel Motors through Tyre-Force Allocation2012In: Proceedings of the 11th International Symposium on Advanced Vehicle Control, Seoul: Japan Society of Mechanical Engineers (JSAE) , 2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a fault handling strategy for electric vehicles with in-wheel motors. The ap-plied control algorithm is based on tyre-force allocation. One complex tyre-force allocation meth-od, which requires non-linear optimization, as well as a simpler tyre force allocation method are developed and applied. A comparison between them is conducted and evaluated against a standard reference vehicle with an Electronic Stability Control (ESC) algorithm. The faults in consideration are electrical faults that can arise in in-wheel motors of permanent-magnet type. The results show for both tyre-force allocation methods an improved re-allocation after a severe fault and thus re-sults in an improved state trajectory recovery. Thereby the proposed fault handling strategy be-comes an important component to improve system dependability and secure vehicle safety.

  • 86.
    Wanner, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jonasson, Mats
    Volvo Cars AB.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Stensson Trigell, Annika
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Control allocation strategies for an electric vehicle with a wheel hub motor failure2015In: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, Vol. 10, no 3, p. 263-287Article in journal (Refereed)
    Abstract [en]

    Three fault-tolerant control strategies for electric vehicles with wheel hub motors are presented and compared, which are all based on the control allocation principle. The main objective is to maintain the directional stability of the vehicle in case of a component failure during high speed manoeuvres. Two simplified strategies that are suited for on-board implementation are derived and compared to an optimal control allocation strategy and a reference vehicle with a basic electronic stability control system. The occurring faults are considered to be in the electric high-voltage system that can arise in wheel hub motors. All three control allocation strategies show improved re-allocation of traction forces after a severe fault, and hence an improved directional stability. However, the performance of both simplified algorithms shows limitations in case of force demands outside the capabilities of the respective actuator. This work shows that vehicle safety is increased by the proposed fault-tolerant control strategies.

  • 87.
    Zanuso, Giovanni
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Fodor, Viktória
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Peretti, Luca
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Networked electric drives in the Industry 4.02018Conference paper (Refereed)
    Abstract [en]

    Industrial automation has been recently challenged by new initiatives such as Industry 4.0, which promises higher connectivity between the devices in an industrial plant. The goal of this work is to discuss how electric drives, widely employed in industry, could benefit from this increased connectivity. Specific applications, such as condition monitoring and multi drive systems, are considered to show the advantages of the industrial network presence, combined with the introduction of new data driven methods. Moreover, the status of industrial communication technologies is depicted, and their suitability for condition monitoring and multi-drive systems applications is described.

  • 88.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Evaluation of Modular Integrated Electric Drive Concepts for Automotive Traction Applications2017In: IEEE Transactions on Transportation ElectrificationArticle in journal (Other academic)
    Abstract [en]

    In order to achieve compactness and realize a certain level of fault tolerance in integrated motor drives, a number of integrated modular motor drive concepts have been proposed in recent years. In this paper, converter topology candidates suitable for an IMMD are considered with particular focus on the stacked polyphase bridges cconverter; the parallel-connected polyphase bridges converter, and the modular high frequency converter. A comparative evaluation of the studied topologies is presented and discussed in terms of machine design aspects, power losses, capacitor energy storage requirements, costs, and cell redundancy using the conventional two-level three-phase drive system as reference.

  • 89.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Evaluation of winding arrangements in electric machinery for modular electric drives2016In: 2016 IEEE 8th International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016, IEEE conference proceedings, 2016, p. 2820-2825Conference paper (Refereed)
    Abstract [en]

    This paper considers different winding connection configurations for a modular electric drive based on series/ parallel connected polyphase bridges converter. Suitable stator winding connection configurations are identified to adapt to the converter topologies considered. Particular focus is put on the post-fault performance. Selected winding layouts are evaluated using 2D-FEM simulations.

  • 90.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    An iterative FEA-based approach for the design of fault-tolerant IPM-FSCW machines2015In: 2015 17TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'15 ECCE-EUROPE), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    This paper presents an iterative finite-element analysis (FEA) approach for the design of integrated electric drives comprising of interior permanent magnet fractional-slot concentrated winding (IPM-FSCW) machines and the stacked poly-phase bridges (SPB) converter. Particular focus is put on fault tolerance to handle a shorted converter submodule and the level of fault tolerance versus compactness (torque density) and power factor is quantified in the form of a case study considering a 30 kW, 2000 rpm machine.

  • 91.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    On fault tolerance for IPM-FSCW machines adopting a modular converter2014In: 2014 17th International Conference on Electrical Machines and Systems, ICEMS 2014, 2014, p. 1633-1638Conference paper (Refereed)
    Abstract [en]

    This paper investigates the fault-tolerant capability of a number of 30 kW permanent magnet (PM) machines with fractional-slot concentrated windings (FSCWs) when connected to two types of modular type converters recently proposed in the literature. Due to the strong PM rotor magnetization when using NdFeB-type magnets, the resulting short-circuit currents during a converter submodule short-circuit was found to be larger than the rated current which, potentially, may cause the machine to overheat. Reducing the PM rotor magnetization will reduce the short-circuit current but also affect the constant power speed range (CPSR). The results further highlight the importance of a tailored design specification when designing FSCW PM machines in automotive applications.

  • 92.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Mojgan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Machine design considerations for an MHF/SPB-converter based electric drive2014In: 2014 The 40th Annual Conference of the IEEE Industrial Electronics Society, IECON 2014, 2014, p. 3849-3854Conference paper (Refereed)
    Abstract [en]

    This paper identifies suitable phase/slot/pole combinationsfor fractional-slot concentrated winding (FSCW)permanent-magnet machines when forming an integrated electricdrive together with a modular high frequency (MHF) converteror a stacked polyphase bridge (SPB) converter.

  • 93.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Haghbin, S.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Lundmark, S.
    Carlson, O.
    Transient modeling of an integrated charger for a plug-in hybrid electric vehicle2011In: Proceedings of the 2011 14th European Conference on Power Electronics and Applications, EPE 2011, IEEE conference proceedings, 2011, p. 1-10Conference paper (Refereed)
    Abstract [en]

    This paper considers a permanent magnet assisted synchronous reluctance (PMSynRel) machine for an integrated charger application for use in a plug-in hybrid electric vehicle (PHEV). The integrated charger functionality means that the machine is also used when the battery is charged from the electrical grid. A finite element model (FEM) is presented from which a transient model of the complete system is derived. The resulting model can be used for simulating and tuning the algorithms needed to synchronize the machine to the electrical grid and controlling the charging process.

  • 94.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lasson, Anders
    Volvo Cars AB.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Off-Vehicle Evaluation of Active Oscillation Damping Schemes2014In: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, Vol. 2, no 2, p. 264-271Article in journal (Refereed)
    Abstract [en]

    Torsional drivetrain oscillations are a well-known problem in electrical or hybrid electric drivetrains and may greatly influence the driving comfort. An experimental testing setup that can be used to design and evaluate active oscillation damping schemes is proposed in this paper. Instead of an in-vehicle test, the drivetrain transmission is emulated from mathematic models, executed by a servo drive which is connected to the physical electrical drive system. The proposed setup functions as a hardware-in-the-loop simulator and can be easily adjusted to simulate any drive trains without additional cost.

  • 95.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Torque dynamics in sensorless PMSM drives2012In: Electrical Machines (ICEM), 2012 XXth International Conference on, IEEE , 2012, p. 2273-2278Conference paper (Refereed)
    Abstract [en]

    In automotive drivetrains used in hybrid electric vehicles, the transmission connecting the electric machine(s) and the combustion engine often introduce non linear phenomena such as gear play and backlash. These non-ideal effects can result in drivetrain oscillations which, in turn, can be mitigated by a controller manipulating the torque reference of the electric machine. If a permanent-magnet synchronous machine (PMSM) is operated without using a position sensor (sensorless), the resulting torque dynamics (from the torque reference to the shaft torque) is different compared to the situation when the rotor position is known. Hence, it is desirable to know the torque dynamics for PMSMs operating sensorless when the drivetrain torque oscillation controller is tuned. This paper presents a number of models, evaluated using simulations, describing the torque dynamics of PMSM drives with and without the use of a position sensor.

  • 96.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Analysis of a deeply saturated sensorless PMSynRel drive for an automotive application2011In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011), IEEE conference proceedings, 2011, p. 1-10Conference paper (Refereed)
    Abstract [en]

    This paper presents an method of mapping feasible region for a sensorless control PMSynRel drive using the resulting position error signal. Thanks to the rotor anisotropy, the rotor position can be detected at low speeds by means of injecting high frequency voltage, either a pulsating voltage vector in the estimated synchronous frame or a rotating vector in the stator frame, on top of the fundamental excitation. However, the resulting position error signal is degraded and distorted by magnetic saturation (including crosssaturation) and spatial inductance harmonics. Therefore, the feasible region is used to find the stable operating points. Instead of mapping the inductances, which is time consuming, position error signal is used to map the feasible sensorless control region. A prediction method of the maximum position estimation error is also presented by taking the spatial inductance harmonics into account. After that, some techniques are presented to compensate the cross-saturation and slot harmonic effects in order to improve the sensorless control quality. Additionally, it is shown how saturation in the rotor bridges affects the initial polarity detection required during startup.

  • 97.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Damping of Torsional Drive-Train Oscillationsusing a Position Sensorless PMSynRel DriveIn: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Other academic)
  • 98.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Low-Speed Sensorless Control With Reduced Copper Losses for Saturated PMSynRel Machines2013In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, no 4, p. 841-848Article in journal (Refereed)
    Abstract [en]

    Permanent-magnet-assisted synchronous reluctance (PMSynRel) machines are generally well suited for sensorless operation at all speeds since the rotor topology possesses a magnetic saliency. However, magnetic saturation can result in a vanishing differential saliency which renders sensorless control at certain operating points difficult (or even impossible) at low speed. In this paper, an optimization procedure, based on results from finite-element (FEM)-based simulations, is proposed. As output, current reference trajectories are obtained in which copper losses are kept at minimum, while the capability for sensorless control is still maintained. The results from the FEM-based simulations are in good agreement with the corresponding experimental results. For the experimental prototype in consideration, the torque limit when operating sensorless at low speed is increased substantially from below 45% to around 95% of its rated value with only slightly increased copper losses. Additionally, the impact of position-dependent harmonics on the magnetic cross saturation (affecting the steady-state position estimation error) is found to be substantial. This highlights that this spatial variation should be taken into consideration for accurate prediction of performance during sensorless operation even if the winding of the machine is of the conventional distributed type.

  • 99.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lasson, Anders
    Off-Vehicle Evaluation of Active Oscillation Damping Schemes2013In: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Torsional drivetrains oscillations is a well known problem in electrical or hybrid electric drivetrains which may greatly influence the driving comfort. An experimental testing setup that can be used to design and evaluate active oscillation damping schemes is proposed in this paper. Instead of in-vehicle test, the drivetrain transmission is emulated from mathematic models, executed by a servo drive which is connected to the physical electrical drive system. The proposed setup functions as a hardware-in-the-loop simulator and can be easily adjusted to simulate any drivetrains without additional cost.

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