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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Low-Frequency Signal-Injection Method for Speed Sensorless Vector Control of Induction Motors

Veli-Matti Leppänen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S3 at Helsinki University of Technology (Espoo, Finland) on the 17th of December, 2003, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6851-5)   [649 KB]
Dissertation is also available in print (ISBN 951-22-6842-6)

Abstract

A new method for the speed sensorless vector control of induction motors at low speeds is presented. The method overcomes the well-known low-speed limitations of conventional methods based on an ideal motor model, yet without relying on a more detailed motor model or parasitic effects. To overcome the low-speed limitations, the ideal motor model is augmented with mechanical dynamics. The response of the electromechanical system to a low-frequency ac current signal injected into the stator winding depends on the direction of the signal relative to the rotor flux direction. Based on this dependency, a new algorithm for rotor flux angle estimation, applicable when the total moment of inertia is not too high, is developed. The estimation method tolerates any low-speed operation point, including zero stator frequency, which is validated by simulations and experiments. The robustness of the method against errors in motor parameter estimates is shown both theoretically and experimentally. The algorithm is also combined with a full-order flux observer, yielding fast dynamics in addition to steady-state stability at low speeds.

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

  1. Leppänen V.-M. and Luomi J., 2001. Estimating the back-EMF of an induction motor. Proceedings of the 9th European Conference on Power Electronics and Applications (EPE 2001). Graz, Austria, 27-29 August 2001, on CD-ROM.
  2. Leppänen V.-M. and Luomi J., 2002. Effect of equation of motion on low-frequency impedance of induction motors – an approach for rotor flux angle estimation. Proceedings of the 10th Power Electronics and Motion Control Conference (EPE-PEMC 2002). Cavtat & Dubrovnik, Croatia, 9-11 September 2002, on CD-ROM.
  3. Leppänen V.-M. and Luomi J., 2002. A tracking controller for a speed sensorless induction machine drive. Proceedings of the 2002 Nordic Workshop on Power and Industrial Electronics (NORPIE 2002). Stockholm, Sweden, 12-14 August 2002, on CD-ROM.
  4. Leppänen V.-M. and Luomi J., 2002. Rotor flux angle tracking controller for sensorless induction motor drives. Conference Record of the 2002 IEEE Industry Applications Conference (IAS 2002). Pittsburgh, PA, USA, 13-18 October 2002, Vol. 2, pages 856-863.
  5. Leppänen V.-M. and Luomi J., 2002. Speed sensorless induction machine control for zero speed and frequency. Conference Record of the 28th Annual Conference of the IEEE Industrial Electronics Society (IECON'02). Sevilla, Spain, 5-8 November 2002, pages 400-405.
  6. Leppänen V.-M. and Luomi J., 2003. Observer using low-frequency injection for sensorless induction motor control – parameter sensitivity analysis. Conference Record of the IEEE International Electric Machines and Drives Conference (IEMDC 2003). Madison, WI, USA, 1-4 June 2003, pages 609-616.
  7. Leppänen V.-M., 2003. Low-frequency injection-based speed sensorless control of induction motors – applicability and implementation aspects. Proceedings of the 10th European Conference on Power Electronics and Applications (EPE 2003). Toulouse, France, 2-4 September 2003, on CD-ROM.
  8. Hinkkanen M., Leppänen V.-M. and Luomi J., 2003. Flux observer enhanced with low-frequency signal injection allowing sensorless zero-frequency operation of induction motors. Conference Record of the 2003 IEEE Industry Applications Conference (IAS 2003). Salt Lake City, UT, USA, 12-16 October 2003, pages 1150-1156.
  9. Kereszty T., Leppänen V.-M. and Luomi J., 2003. Sensorless control of surface magnet synchronous motors at low speeds using low-frequency signal injection. Conference Record of the 29th Annual Conference of the IEEE Industrial Electronics Society (IECON'03). Roanoke, VA, USA, 2-6 November 2003, pages 1239-1243.

Keywords: induction motor, sensorless control, rotor flux angle estimation, full-order flux observer

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© 2003 Helsinki University of Technology

Last update 2011-05-26