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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Flux Estimators for Speed-Sensorless Induction Motor Drives

Marko Hinkkanen

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 S4 at Helsinki University of Technology (Espoo, Finland) on the 17th of September, 2004, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-7189-3)   [441 KB]
Dissertation is also available in print (ISBN 951-22-7188-5)

Abstract

This thesis deals with flux estimators for speed-sensorless induction motor drives. To enhance the stability and the performance of state-of-the-art sensorless drives, new flux estimator designs based on the standard motor model are proposed. Theoretical and experimental research methods are both used. The dynamics and stability of flux estimators are analyzed using linearized models, and the effects of parameter errors are investigated using steady-state relations. Performance is evaluated using computer simulations and laboratory experiments. It was found that most sensorless flux estimation methods proposed in the literature have an unstable operating region at low speeds (typically in the regenerating mode) and that the damping at high speeds may be insufficient. A new stable design of the speed-adaptive full-order flux observer is proposed: the observer gain is designed especially for nominal and high-speed operation, while the low-speed operation is stabilized by modifying the speed-adaptation law. Compared to estimators proposed in the literature, the effects of parameter errors on the proposed observer design are shown to be small. To further improve the robustness, the speed-adaptive observer is enhanced with a low-frequency signal-injection method, allowing long-term zero-frequency operation under rated load torque. Furthermore, a computationally efficient version of a voltage-model-based flux estimator and two computationally efficient digital implementations for full-order flux observers are proposed.

This thesis consists of an overview and of the following 7 publications:

  1. Hinkkanen M. and Luomi J., 2003. Modified integrator for voltage model flux estimation of induction motors. IEEE Transactions on Industrial Electronics 50, number 4, pages 818-820.
  2. Hinkkanen M. and Luomi J., 2002. Zero-speed operation of sensorless induction motors using full-order flux observer. In: Proceedings of the 2002 Nordic Workshop on Power and Industrial Electronics (NORPIE 2002). Stockholm, Sweden, 12-14 August 2002, on CD-ROM.
  3. Hinkkanen M. and Luomi J., 2002. Digital implementation of full-order flux observers for induction motors. In: Proceedings of the 10th International Power Electronics and Motion Control Conference (EPE-PEMC 2002). Cavtat & Dubrovnik, Croatia, 9-11 September 2002, on CD-ROM.
  4. Hinkkanen M. and Luomi J., 2003. Parameter sensitivity of full-order flux observers for induction motors. IEEE Transactions on Industry Applications 39, number 4, pages 1127-1135.
  5. Hinkkanen M., 2004. Analysis and design of full-order flux observers for sensorless induction motors. IEEE Transactions on Industrial Electronics 51, number 5, in press.
  6. Hinkkanen M. and Luomi J., 2004. Stabilization of regenerating-mode operation in sensorless induction motor drives by full-order flux observer design. IEEE Transactions on Industrial Electronics 51, number 6, in press.
  7. Hinkkanen M., Leppänen V.-M. and Luomi J., 2005. Flux observer enhanced with low-frequency signal injection allowing sensorless zero-frequency operation of induction motors. IEEE Transactions on Industry Applications 41, number 1, in press.

Keywords: flux estimation, induction motor, sensorless control, flux observer

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© 2004 Helsinki University of Technology

Last update 2011-05-26