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Low-Speed Performance Improvement of Direct Torque Control for Induction Motor Drives Fed by Three-Level NPC Inverter

Department of Electrical and Computer Engineering, Ajou University, 206, World cup-ro, Yeongtong-gu, Suwon 16499, Korea
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Electronics 2020, 9(1), 77; https://doi.org/10.3390/electronics9010077
Received: 10 December 2019 / Revised: 19 December 2019 / Accepted: 24 December 2019 / Published: 1 January 2020
(This article belongs to the Special Issue High Power Electric Traction Systems)
Classical direct torque control (DTC) is considered one of the simplest and fastest control algorithms in motor drives. However, it produces high torque and flux ripples due to the implementation of the three-level hysteresis torque regulator (HTR). Although, increasing the level of HTR and utilizing multilevel inverters has a great contribution in torque and flux ripples reduction, stator flux magnitude of induction motor (IM) droops at every switching sector transition, particularly at low-speed operation. This problem occurs due to the utilization of a zero voltage vector, where the domination of stator resistance is very high. A simple flux regulation strategy (SFRS) is applied for low-speed operation for DTC of IM. The proposed DTC-SFRS modifies the output status of the five-level HTR depending on the flux error, torque error, and stator flux position. This method regulates the stator flux for both forward and reverse rotational directions of IM with retaining the basic structure of classical DTC. By using the proposed algorithm, the stator flux is regulated, hence pure sinusoidal current waveform is achieved, which results in lower total harmonics distortion (THD). The effectiveness of the proposed DTC-SFRS is verified through simulation and experimental results. View Full-Text
Keywords: direct torque control; flux-regulation; induction motor; low-speed; three-level neutral-point-clamped inverter direct torque control; flux-regulation; induction motor; low-speed; three-level neutral-point-clamped inverter
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Hakami, S.S.; Mohd Alsofyani, I.; Lee, K.-B. Low-Speed Performance Improvement of Direct Torque Control for Induction Motor Drives Fed by Three-Level NPC Inverter. Electronics 2020, 9, 77.

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