PhD THESIS - Abstract - ?· PhD THESIS - Abstract - ... Voltage source inverter topology. ... created…

Download PhD THESIS - Abstract - ?· PhD THESIS - Abstract - ... Voltage source inverter topology. ... created…

Post on 03-Jul-2018

213 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • FACULTY OF ELECTRICAL ENGINEERING

    Eng. Nicolae tefan PREDA

    PhD THESIS

    - Abstract -

    OPTIMIZATION AND IMPLEMENTATION OF THE DUAL FIELD ORIENTED VECTOR

    CONTROL FOR THE CAGE INDUCTION MACHINE

    PhD Supervisor, Prof. Dr. -eng. Maria IMECS

    Evaluation committee PRESIDENT: Prof.Dr.Ing Radu Ciupa Dean, Faculty of Electrical Engineering,

    Technical University of Cluj-Napoca; MEMBERS: Prof.Dr.Ing. Maria Imecs PhD Supervisor, Technical University of Cluj-Napoca; Prof.Dr.Ing. Rzvan Mgureanu Reviewer,

    Politehnica University of Bucharest; Prof.Dr.Ing. Alexandru Bitoleanu Reviewer,

    University of Craiova; Prof.Dr.Ing. IulianTudor Mircea Birou Reviewer,

    Technical University of Cluj-Napoca.

  • Chapter 1 represents the introductive part of the thesis, where the general context, the objectives and the structure of the thesis are presented. Starting from the main objective, which is the implementation of the dual field oriented vector control, and considering the general structure of an electrical drive, the drives components (motor, converter, modulation technique, vector control structure) will be modeled and simulated. For implementation and experimental tests, the models of the motor and converter will be removed and replaced with the correspondent physical ones. A second objective was aimed by this thesis, which is the energetical optimization of the dual field oriented vector control structure for large power drives.

    Therefore, the thesis is divided into 7 chapters out of which the first one is introductory and the seventh one contains conclusions, contributions and perspectives. The thesis also contains a reference list, a list of published papers and annexes.

    The 2nd chapter deals with induction machine modelling and simulation. Starting from the general equations of the asynchronous motor, a set of expressions are derived which are used for modeling in Simulink the squirrel-cage induction motor, using stator-fixed (natural) coordinates.

    Fig 1. Structure used for simulation of the induction motor.

    Validation of the model is done through simulation, by supplying the motor from a three-phase sinusoidal balanced voltage reference. The simulation is performed using the nameplate data and parameters of a real asynchronous motor from Siemens.

    Chapter 3 presents the power converter and the modulation method used to control the semiconductor devices.

    Fig. 2. Diode bridge rectifier topology. Fig. 3. Voltage source inverter topology.

  • The solution chosen for supplying the motor is an indirect static frequency converter, composed of a three-phase bridge diode rectifier and a three-phase voltage source inverter. These two form the most commonly used solution for a.c. motor supply and can be found in compact form along with integrated circuits for protection and control.

    The space-vector (or space-phasor) modulation SVM was used for controlling the switching of the inverter. Considering the topology of the chosen inverter, only 8 basic voltage vectors can be produced at the inverters output (out of which two are zero).

    Fig. 4. Basic voltage vectors produced by the VSI.

    Using space-vector modulation, a given reference voltage vector can be synthesized using two non-zero basic voltage vectors and the zero ones:

    6,1,11 =+= ++ kuuu kkkkref .

    The on-time of the active voltage vectors can be easily computed:

    = 3

    sin3 ref

    dck uV

    sin31 =+ref

    dck uV

    while the on-time of the zero vectors )(1 1870 ++=+= kk (also called free-wheeling duration), can be distributed regarding different optimization criteria. According to this distribution, several modulation methods can be obtained. In the thesis, five SVM techniques were treated:

    - the classical (simple suboptimal) SVM :

    20

    87

    ==

    - and four discontinuous (flat-top) methods:

    For Simulink modeling of the SVM methods, a series of computation steps were taken in consideration, with which the duty cycle for each inverter leg is obtained. An original is made to the reference voltage vector position determination. The method used divides the

  • voltage hexagon into sextants and sectors and uses simple comparisons to determine the vectors position, without using any trigonometric functions or look-up tables.

    After modeling, the five SVM methods and the converter were validated through simulation. Also an harmonic analysis of the modulation techniques was performed, which was confirmed experimentally through implementation on a digital signal processor DSP.

    Chapter 4 deals with the dual-field oriented vector control of the squirrel-cage induction motor. The dual-field orientation principle came from analyzing the advantages and disadvantages of the two classical field-oriented methods (the rotor field and the stator field one):

    - rotor-field oriented control benefits from decoupled control of flux and torque through stator-current components and linear static mechanical characteristics, but the stator voltage computation is highly complex so usually closed-loop current PWM inverters are needed;

    - stator-field oriented control benefits from a simple stator voltage computation, making it applicable to open-loop voltage inverters, but decoupled control is only obtained with compensation of the stator current components and the static mechanical characteristics are nonlinear.

    The dual-field orientation claims the advantages of both methods and eliminates the disadvantages. Therefore, the flux control and generation of the stator current components is done in the rotor-field oriented frame:

    m

    rsd L

    ir

    =

    r

    e

    mp

    rsq

    m

    Lz

    Li

    r =

    3

    2

    The stator voltage components are computed in the stator-field oriented frame:

    dt

    diRu ssdssd ss

    += ssqssq sss iRu +=

    Two dual-field oriented vector control structures were taken in consideration, one with voltage compensation loop and one simplified, without voltage compensation.

    Fig. 5. Block diagram of the simulation structure for the dual-field oriented vector control for the squirrel-cage induction motor fed by a VSI.

    For identification of the orientation fields, three field computation methods were compared. Each method was modeled and simulated, and the method yielding the best results was chosen for field identification in the dual-field oriented vector control structure.

  • The complete vector control structure was modeled using SimulThe PI controller gains were tuned using SISO Design tool, for the 4 control loops (two current loops, one rotor flux loop and one speed loop), taking in consideration a few design requirements regarding bandwidth and overshoot.. For tunintransfer functions from each loop were determined and the gains were determined graphically in SISO tool.

    The two control structures were simulated, different test being run in order to compare the two structures and analyze their steady

    Chapter 5 describes the experimental setup built for implementation and testing of the dual-field vector control.

    The experimental setup can be considered of being composed of two parts: a computational and control part (consisting of a computer, a dSPACE development system and software) and a high-power part (consisting of induction converters, transducers etc.)

    Fig. 6. Block diagram of the experimental setup

    Fig. 7. Block diagram of the experimental setup

    The complete vector control structure was modeled using SimulThe PI controller gains were tuned using SISO Design tool, for the 4 control loops (two current loops, one rotor flux loop and one speed loop), taking in consideration a few design requirements regarding bandwidth and overshoot.. For tuning, each loop was described, the transfer functions from each loop were determined and the gains were determined graphically

    The two control structures were simulated, different test being run in order to compare e their steady-state and dynamic behavior.

    describes the experimental setup built for implementation and testing of the

    The experimental setup can be considered of being composed of two parts: a rol part (consisting of a computer, a dSPACE development system and power part (consisting of induction motor, load motor, power

    Fig. 6. Block diagram of the experimental setup computational

    . Block diagram of the experimental setup power part.

    The complete vector control structure was modeled using Simulink and PLECS. The PI controller gains were tuned using SISO Design tool, for the 4 control loops (two current loops, one rotor flux loop and one speed loop), taking in consideration a few design

    g, each loop was described, the transfer functions from each loop were determined and the gains were determined graphically

    The two control structures were simulated, different test being run in order to compare

    describes the experimental setup built for implementation and testing of the

    The experimental setup can be considered of being composed of two parts: a rol part (consisting of a computer, a dSPACE development system and

    motor, load motor, power

    computational part.

    part.

  • Fig. 8. View of the whole experimental setup.

    The load motor used is a surfacefor torque generation a simple vector control structure was chosen ( the constant torque ancontrol strategy).

    The dual-field oriented control for the induction machine was implemented on the experimental setup through a realprogram was structured into 5 modules and synchronizsed with the PWM generation throug

Recommended

View more >