• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.421-428
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• 2015

An advanced direct torque control (DTC) with pulse width modulation (PWM) method is presented in this paper. The duty ratio calculation of the selected voltage vector is based on the voltage functions of the selected voltage vector according to the sector angle. The proposed DTC uses a conventional DTC scheme with six sector divisions and switching rules. However, the winding voltages are supplied by the PWM approach. Furthermore, the duty ratio of the switching voltage vector is determined by the flux, torque error, and motor speed. The base voltage that shall determine the duty ratio can be calculated by approximate voltage functions according to the voltage angle. For the calculation of base voltages, second-order quadratic functions are used to express the output voltage of the selected voltage vector according to voltage angle. The coefficients for the second-order quadratic functions are selected by the voltage vector, which is determined by the switching rules of the DTC. In addition, the voltage functions are calculated by the coefficients and voltage angle between the voltage vector and rotor position. The switching voltages from the calculated duty ratio can supply the proper torque and flux to reduce the ripple and error. The proposed control scheme is verified through practical experimental comparisons.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.268-277
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• 2009

This paper presents an DTC-PWM (Direct Torque Control-Pulse Width Modulation) of PMSM (Permanent Magnet Synchronous Motor). The proposed DTC-PWM method combines a conventional DTC and PWM approach for switching signal generation. The actual torque is estimated by the torque estimator in conventional method, but the switching signal is generated by PWM method according to the switching rules and torque error. A effective voltage vector and zero vector are used to generate the switching signals and asymmetric switching method is applied. A simple calculation of PWM without any complex determination of space vector can assure the constant switching frequency with an constant torque and flux. The proposed torque control scheme for PMSM is verified by experimental results.