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Sturing van een permanent-magneet synchrone machine voor een lib.ugent.be/fulltxt/RUG01/001/418/136/RUG01-001418136... · PDF file 2010-09-08 · Abstract—This article gives an

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  • Kristof Vandemergel

    machine voor een elektrische wagen Sturing van een permanent-magneet synchrone

    Academiejaar 2008-2009 Faculteit Ingenieurswetenschappen Voorzitter: prof. dr. ir. Jan Melkebeek Vakgroep Elektrische energie, systemen en automatisering

    Master in de ingenieurswetenschappen: werktuigkunde-elektrotechniek Masterproef ingediend tot het behalen van de academische graad van

    Begeleiders: Thomas Vyncke, Steven Thielemans Promotor: prof. dr. ir. Jan Melkebeek

  • Voorwoord

    Gedurende de studiejaren aan de universiteit werd het steeds duidelijker dat de optiekeuze ”Elek-

    trische Energietechniek”mij het meest aanspreekt. Deze thesis heeft mij toegelaten vele inzichten

    en facetten, die tijdens de opleiding werden onderwezen, in de praktijk toe te passen. Het on-

    derwerp van de thesis is brandend actueel en vereist nog vele jaren grondige analyse en research.

    Ik ben dan ook dankbaar dat ik de kans kreeg een steentje bij te dragen aan het onderzoek van

    deze nieuwe technologie. Bij deze wens ik iedereen te bedanken voor de steun die ik kreeg bij

    het tot stand komen van dit eindwerk. In het bijzonder dank aan Prof. Jan Melkebeek en de

    twee hoofdbegeleiders, Thomas Vyncke en Steven Thielemans, voor het wederzijdse vertrouwen.

    Kristof Vandemergel, juni 2009

    -Strange is our situation here upon earth. Each of us comes for a short visit, not

    knowing why, yet sometimes seeming to a divine purpose. From the standpoint of

    daily life, however, there is one thing we do know: That we are here for the sake of

    others...for the countless unknown souls with whose fate we are connected by a bond

    of sympathy. Many times a day, I realize how much my outer and inner life is built

    upon the labors of people, both living and dead, and how earnestly I must exert myself

    in order to give in return as much as I have received.- Albert Einstein

    i

  • Toelating tot bruikleen

    “De auteur geeft de toelating deze scriptie voor consultatie beschikbaar te stellen en delen van de

    scriptie te kopiëren voor persoonlijk gebruik.

    Elk ander gebruik valt onder de beperkingen van het auteursrecht, in het bijzonder met betrekking

    tot de verplichting de bron uitdrukkelijk te vermelden bij het aanhalen van resultaten uit deze

    scriptie.”

    Kristof Vandemergel, juni 2009

    ii

  • Sturing van een permanent-magneet

    synchrone motor voor een elektrische

    wagen door

    Kristof Vandemergel

    Scriptie ingediend tot het behalen van de academische graad van

    Master in de ingenieurswetenschappen: werktuigkunde-elektrotechniek

    Academiejaar 2008–2009

    Promotoren: Prof. Dr. Ir. J. Melkebeek, Ir. T. Vyncke en Ir. S. Thielemans

    Scriptiebegeleiders: Ir. T. Vyncke en Ir. S. Thielemans

    Faculteit Ingenieurswetenschappen

    Universiteit Gent

    Vakgroep Elektrische energie, systemen en automatisering

    Voorzitter: Prof. Dr. Ir. J. Melkebeek

    Samenvatting

    In dit werk verdiep ik mij in verscheidene aspecten van het elektrisch rijden. De lezer krijgt een algemene cultuur over het elektrisch rijden voorgeschoteld. Deze tekst verdiept zich verder op verschillende sturingen om vertrekkend van de stand van het gaspedaal de motor aan te drijven. Twee belangrijke soorten sturingen worden naderbij beschouwd, namelijk veldoriëntatie en directe koppelcontrole. Om vergelijking mogelijk te maken spits ik mij toe op een axiale-flux motor die ik ter beschikking had gedurende het academiejaar.

    Trefwoorden

    Elektrisch rijden, axiale-flux permanent magneet motor, veldoriëntatie, directe koppelcontrole,

    simulatie

  • Control of an PMSM for electric vehicles Kristof Vandemergel

    Supervisor(s): Jan Melkebeek, Thomas Vyncke, Steven Thielemans

    Abstract—This article gives an overview of two main control strategies to drive synchronous motors: Field Oriented Control (FOC) and Direct Torque Control (DTC). In this study these two methods have been devel- oped in alternative implementations to drive a specific axial flux PMSM. The evaluation is based on the simulation results.

    Keywords— Axial flux PMSM, Field Oriented Control, Direct Torque Control, Simulation

    I. I NTRODUCTION

    RESEARCHERS and automobile companies believe that thecar of the future will be electrically driven and in my opin- ion the energy resource for that electric vehicle (EV) will be a battery pack. The most important driver to leave the use of anin- ternal combustion engine, is reducing the impact of human kind on its natural environment and reducing the growing shortages of fuel resources.

    First EVs consisted of a single electric motor with a physical drive line, transmission gears and a differential to the wheels. New concepts of motor designs experiment with multi motor systems to drive each wheel individually to overcome most of the mechanical losses associated with the drive train. The motor is called a wheelmotor or hub-in motor[1].

    PMSMs are extremely suitable to directly drive the wheel without the use of transmission. They combine compactness, low weigth and high efficiency. Axial flux PMSMs have a higher proportion power to weight then radial flux PMSMs and their shape suites better for mounting into the wheel. Furthermore an increasing number of poles is wanted in raising the torque and in allowing lower rotation speed. These proporties plead for using axial flux PMSMs.

    In this abstract, we will first briefly investigate the motor char- acteristics of the sample motor, provided by the Universityof Ghent, in order to assign numerical values to the parametersof the PMSM model. These will be used in the subsequent section to simulate FOC and DTC. Two different types of FOC will be evaluated and compared to each other. The influence of mea- surement faults is a topic that deserves our attention. Finally in this article the classic DTC is compared to different adapted DTCs based on Space Vector Modulation (SVM-DTC).

    II. M ODELING THE AXIAL FLUX PMSM

    This study is limited to the control of a sinusoid PMSM. The main difference between the radial and the axial flux PMSM is the direction of the flux and the current. The basic principles for modeling the radial flux PMSM are valid for both systems and lead to the same mathematical expressions and PMSM model. The absence of saliency between the direct and the quadratic axes in Surface mounted PMSM (SPMSM), makes it possible to use the complex time diagram. In steady-state the diagram consist of a back-emf in series with a stator resistance and induc- tance. To obtain their numerical values, a DC motor drives the

    axial flux machine at constant speed. By measuring the voltage and the current at the machine terminals under different loading conditions, the following values are found (Table I).

    Flux linkage Ψ̂ 8,5072 mVs Stator resistance Rs 5,6 mΩ Stator inductance Ls 46,76µH

    TABLE I

    NUMERICAL VALUES OF THE MOTOR PARAMETERS OF THE AXIAL FLUX

    PMSM.

    III. C ONTROL OF THE AXIAL FLUX PMSM

    In this section two important control principles are imple- mented to control the axial flux PMSM mentioned above.

    A. Field Oriented Control

    Field orientation controls the current along the q-axis in aro- tor reference frame (dq). This control experiences some advan- tages as mentioned in [2]. Transformation of the current to a (dq)-frame is necessary and is the reason why an position mea- surement or estimation is inevitable. Two different practical im- plementations will be discussed furthermore:id = 0-control andψ = 0-control. The first one controls both current compo- nentsid andiq separately.id is kept zero, whileiq is propor- tional to the wanted torque (Eq. 1).ψ = 0-control is particular case of angle control. The angle between the current and the q-axisψ is kept zero. The amplitude of the current vector is like iq proportional to the torque.

    T = 3

    2 Npψ

    magniq = 3

    2 Npψ

    magn|i| cosψ (1)

    These two control methods are simulated thoroughly. In steady state (Figure 1) both methods produce the wanted torque when averaged over the simulated time. The frequency at which the VSI can switch between the upper and the lower mosfet is limited here by 20kHz. Due to this limitation, the current rises and falls within a switching period. The ripple in the current can be found in the torque. Further examination shows that the torque ripple is independent of the desired torque and varies with the speed according to a quadratic relation. The explanation lies in the fact that the stator resistance and inductance are very small for this particular motor and herefore the current or torque doesn’t influence the switching signals for the VSI. The ampli- tude of the ripple isn’t constant along the outline of the motor, but is instead modulated with a frequency three times higher then the electrical frequency. In the frequency spectrum wefind two spikes in the neighbourghood of the switching frequency:

  • fs − 3 · fe andfs + 3 · fe wherefs andfe denote respectively the switching frequency and the electrical frequency.

    Simulation time t (ms)

    E le

    ct ro

    m a

    g n

    e tic

    to rq

    u eT

    e (N

    m ) id = 0-controlψ = 0-control

    0 0, 2 0, 4 0, 6 0, 8 1, 0 1, 2 1, 4 4, 35

    4, 4

    4, 45

    4, 5

    4, 55

    4, 6

    4, 65

    4, 7

    4, 75

    4, 8

    4, 85

    Fig. 1. Steady state torque ripple in nominal circumstances

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