Flux estimation algorithms for electric drives: a comparative study

Author: Mohamad Koteich

Conference: REDEC – International Conference on Renewable Energies for Developing countries, July 2016, Lebanon.

DOI: 10.1109/REDEC.2016.7577558

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Abstract: This paper reviews the stator flux estimation algorithms applied to the alternating current motor drives. The socalled voltage model estimation, which consists of integrating the back-electromotive force signal, is addressed. However, in practice, the pure integration is prone to drift problems due to noises, measurement error, stator resistance uncertainty and unknown initial conditions. This limitation becomes more restrictive at low speed operation. Several solutions, reported in the literature, are reviewed and compared. Emphasis is placed on the low-pass filter based algorithms that show good performance in steady-state as well as in transient operating conditions.

Energy Equalization Module for Modular Multilevel Converters in Variable Speed Motor Drives

Authors: Mohammad Sleiman, Mohamad Koteich, Handy Fortin Blanchette, Hadi Kanaan, Kamal Al-Haddad

Conference: REDEC – International Conference on Renewable Energies for Developing countries, July 2016, Lebanon.

DOI: 10.1109/REDEC.2016.7577559

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Abstract: Modular Multilevel Converters (MMC) processing phase quantities at low frequency are vulnerable to high cell voltage ripples. MMC upper and lower arms processes pulsating power at fundamental and second harmonic phase components. As a consequence, arms are expected to buffer the energy difference exchanged between DC-link and each AC-phase. This buffered energy is translated into increased cell voltage ripple when operating at low phase frequency. Several remedies have been presented in literature, which can be classified under software and hardware methods. To address this short-come we introduced a plug-in hardware alternative that permit energy exchange between cells from upper and lower arms thus remarkably reducing capacitor voltage ripples caused by out of phase energy variations. The proposed method can improve MMC performance over the full operation region and is mainly attractive to low frequency operation such as in variable-speed motor drives where higher-than-nominal torques might be required for a wide speed range. Performed simulations over a synchronous machine using maximum torque per current control technique, conforms well with the analytical findings and shows the effectiveness of the proposed method.

A unified model for low-cost high-performance AC drives: the Equivalent Flux concept

Authors: Mohamad Koteich, Gilles Duc, Abdelmalek Maloum, Guillaume Sandou

Conference: The Third International Conference on Electrical, Electronics, Computer Engineering and their Applications (EECEA2016), Apr 2016, Beirut, Lebanon.

DOI: 10.1109/EECEA.2016.7470768

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Abstract: This paper presents a unified modeling approach of alternating current (AC) machines for low-cost high-performance drives. The Equivalent Flux concept is introduced. Using this concept , all AC machines can be seen as a non-salient synchronous machine with modified (equivalent) rotor flux. Therefore, complex salient-rotor machines models are simplified, and unified shaft-sensorless AC drives can be sought. For this purpose, a unified observer-based structure for rotor-flux position and speed estimation is proposed. The equivalent flux concept generalizes the existing concepts, such as the extended back-electromotive force, the fictitious flux and the active flux.

Discussion on “AC Drive Observability Analysis”

Authors: Mohamad Koteich, Abdelmalek Maloum, Gilles Duc, Guillaume Sandou

Journal: IEEE Transactions on Industrial Electronics, 62(11):7224–7225.

DOI: 10.1109/TIE.2015.2438777

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Abstract: In the paper by Vaclavek et al. ( IEEE Trans. Ind. Electron., vol. 60, no. 8, pp. 3047-3059, Aug. 2013), the local observability of both induction machine and permanent-magnet synchronous machine (PMSM) under motion-sensorless operation is studied. In this letter, the “slowly varying” speed assumption is discussed, and the PMSM observability condition at standstill is revisited.

Discussion on “A Differential Algebraic Estimator for Sensorless Permanent-Magnet Synchronous Machine Drive”

Authors: Mohamad Koteich, Abdelmalek Maloum, Gilles Duc, Guillaume Sandou

Journal: IEEE Transactions on Energy Conversion, 30 (3), 1137-1137.

DOI: 10.1109/TEC.2015.2459791

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Abstract: Diao et al. are to be commended for proposing a new approach for permanent magnet synchronous machine (PMSM) position estimation, using the differential algebraic theory. In the following comments, we would like to highlight some points concerning the machine observability under the applied approach.