Direct torque control of brushless DC motor with non-sinusoidal back-EMF

Salih Baris Ozturk*, Hamid A. Toliyat

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

84 Citations (Scopus)

Abstract

In this paper, a direct torque control (DTC) technique for brushless dc (BLDC) motors with non-sinusoidal back-EMF operating in the constant torque region is presented. This approach introduces a two-phase conduction mode as opposed to the conventional three-phase DTC drives. In this control scheme, only two phases conduct at any instant of time. Unlike conventional six-step PWM current control, by properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table at a predefined sampling time, the desired quasi-square wave current is obtained. Therefore, a much faster torque response is achieved compared to conventional PWM current control. In this paper, it is also shown that in the constant torque region under the two-phase conduction DTC scheme, the amplitude of the stator flux linkage cannot easily be controlled due to the sharp changes and the curved shape of the flux vector between two consecutive commutation points in the stator flux linkage locus. Furthermore, to eliminate the low-frequency torque oscillations caused by the non-ideal trapezoidal shape of the actual back-EMF waveform of the BLDC motor, a pre-stored back-EMF versus position look-up table is designed. As a result, it is possible to achieve DTC of a BLDC motor drive with faster torque response due to the fact that the voltage space vectors are directly controlled while the stator flux linkage amplitude is deliberately kept almost constant by ignoring the flux control in the constant torque region. Since the flux control along with PWM generation is removed, fewer algorithms are required for the proposed control scheme. A theoretical concept is developed and the validity and effectiveness of the proposed DTC scheme are verified through the simulations and experimental results.

Original languageEnglish
Title of host publicationProceedings of 2007 IEEE International Electric Machines and Drives Conference, IEMDC 2007
Pages165-171
Number of pages7
DOIs
Publication statusPublished - 2007
Externally publishedYes
EventIEEE International Electric Machines and Drives Conference, IEMDC 2007 - Antalya, Turkey
Duration: 3 May 20075 May 2007

Publication series

NameProceedings of IEEE International Electric Machines and Drives Conference, IEMDC 2007
Volume1

Conference

ConferenceIEEE International Electric Machines and Drives Conference, IEMDC 2007
Country/TerritoryTurkey
CityAntalya
Period3/05/075/05/07

Keywords

  • Brushless dc motor drives
  • Direct torque control
  • Fast torque response
  • Low-frequency torque ripples
  • Non-sinusoidal back-emf
  • Two-phase conduction

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