The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Numerical Impulse Response Tests to Identify Dynamic Induction-Machine Models

Anna-Kaisa Repo

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 4th of April, 2008, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9275-2)   [953 KB]
Dissertation is also available in print (ISBN 978-951-22-9274-5)

Abstract

The aim of the study is to identify dynamic models for induction machines using two-dimensional finite-element analyses. Attention is given mainly to cage-induction machines with closed rotor slots and deep rotor bars. However, cage-induction machines with semi-closed rotor slots and slip-ring machines are considered as well.

Two new applications of numerical impulse response tests are presented. The tests are performed within a time-stepping finite-element analysis. First, an impulse excitation is applied to the stator voltage and the response of the stator current is studied. Next, an impulse excitation is applied to the rotor position angle and the response of electromagnetic torque is studied. The results of the impulse tests are used to estimate parameters for small-signal models in the frequency domain. The estimation is performed by fitting the results of an impulse response test to the corresponding analytical small-signal model. The analytical models are based on the theory of electrical machines and their parameters have a physical meaning.

Based on the study, it is concluded that the skin effect in rotor bars has a significant influence on the results of the impulse response tests. In order to obtain a good fit, the skin effect has to be taken into account in the structure of the analytical model. In addition, the saturation of iron has a prominent effect. The effects of saturation can be detected as harmonics in the frequency response and in the values of parameter estimates. A model for saturation can be included in the small-signal models. In the case of this more advanced model, the parameter estimates obtain a clear physical interpretation.

The applicability of impulse response tests is based on the assumption of linear time-invariant behaviour of the system. The assumption is studied by several means. Within the tests, the amplitude, length, and initial time of the impulse excitation is varied and the results are compared. It is concluded that, in the case of normal operation points, the assumption can be made. The reasonability of the parameter estimates is evaluated by comparing the values with steady-state circuit parameters. The steady-state parameters are estimated using a time-harmonic finite-element analysis.

When the impulse is applied to the rotor position angle and the torque response is computed, the results predict negative electromagnetic damping within some frequency ranges. This phenomenon is also studied by measurements. It is observed that, within the range of predicted negative damping, self-excited torsional oscillations occur.

This thesis consists of an overview and of the following 9 publications:

  1. A.-K. Repo and A. Arkkio, Parameter estimation of induction machines using the numerical impulse method, Proceedings of the International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM 2006), Taormina, Italy, 23-26 May 2006, No. WA1-19136, 6 pages.
  2. A.-K. Repo and A. Arkkio, Numerical impulse response test to estimate circuit-model parameters for induction machines, IEE Proceedings - Electric Power Applications, volume 153, number 6, November 2006, pages 883-890. © 2006 The Institution of Engineering and Technology (IET). By permission.
  3. Anna-Kaisa Repo, Asko Niemenmaa, and Antero Arkkio, Estimating circuit models for a deep-bar induction motor using time harmonic finite element analysis, Proceedings of the 17th International Conference on Electrical Machines (ICEM 2006), Chania, Crete, Greece, 2-5 September 2006, No. 614, 6 pages. © 2006 by authors.
  4. A.-K. Repo and A. Arkkio, Numerical impulse response test to identify parametric models for closed-slot deep-bar induction motors, IET Electric Power Applications, volume 1, number 3, May 2007, pages 307-315. © 2007 The Institution of Engineering and Technology (IET). By permission.
  5. Anna-Kaisa Repo, Marko Hinkkanen, and Antero Arkkio, Parameter estimation for induction motors to study the effects of voltage, frequency and slip, Proceedings of the 12th European Conference on Power Electronics and Applications (EPE 2007), Aalborg, Denmark, 2-5 September 2007, 10 pages.
  6. Marko Hinkkanen, Anna-Kaisa Repo, Mikaela Cederholm, and Jorma Luomi, Small-signal modelling of saturated induction machines with closed or skewed rotor slots, Conference Record of the 2007 IEEE Industry Applications Conference, 42nd Industry Applications Society Annual Meeting, New Orleans, Louisiana, USA, 23-27 September 2007, pages 1200-1206.
  7. Marko Hinkkanen, Anna-Kaisa Repo, Mikaela Cederholm, and Jorma Luomi, Small-signal model for saturated deep-bar induction machines, Proceedings of the 12th European Conference on Power Electronics and Applications (EPE 2007), Aalborg, Denmark, 2-5 September 2007, 10 pages.
  8. Anna-Kaisa Repo, Paavo Rasilo, and Antero Arkkio, Dynamic electromagnetic torque model and parameter estimation for a deep-bar induction machine, IET Electric Power Applications, in press. © 2008 by authors and © 2008 The Institution of Engineering and Technology (IET). By permission.
  9. Anna-Kaisa Repo, Paavo Rasilo, Asko Niemenmaa, and Antero Arkkio, Identification of electromagnetic torque model for induction machines with numerical magnetic field solution, IEEE Transactions on Magnetics, in press. © 2008 IEEE. By permission.

Errata of publication 8

Keywords: induction machines, parameter estimation, frequency response, finite element analysis

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© 2008 Helsinki University of Technology

Last update 2011-05-26