A Direct Torque Control Method of Asynchronous Motor Based on Synthetic Voltage Vector Technology

Abstract

The invention discloses an asynchronous motor direct torque control method based on synthesized voltage vectors. The method includes three-phase current voltage is converted under alpha and beta coordinates through 3 / 2 conversion by detecting the current and voltage of the stator end of a motor, feedback torque and stator flux linkage vectors are calculated through an estimation module, the feedback value is compared with a given value, a torque hysteresis comparator is a zero hysteresis band, and a flux linkage PI controller replaces a flux linkage hysteresis controller to reduce flux linkage trajectory distortion; voltage spatial vectors are selected from a voltage vector selecting table to obtain voltage vector output; the control voltage vectors and zero voltage vectors in a sampling cycle are synthesized into a new voltage vector in a synthesized voltage vector pulse width modulation output signal controller. The method has the advantages that the given signals can be fast tracked by the flux linkage and torque controllers without offset, torque fluctuation and flux linkage trajectory distortion are reduced evidently, torque fluctuation is reduced greatly, and torque performance of system output is increased greatly.

Description

technical field [0001] The invention relates to a motor torque control method, in particular to a direct torque control method of an asynchronous motor. Background technique [0002] Direct torque control is a new AC variable frequency speed regulation technology developed after the vector control technology in the 1980s. Up to now, direct torque control and vector control have become the two most commonly used methods in the field of high-performance AC frequency conversion speed regulation. Different from vector control, direct torque control adopts space vector analysis method, and calculates the detected stator voltage and current signals directly in the stator coordinate system, eliminating the need for complicated coordinate transformation and current regulation. It uses two hysteresis comparators to change the stator flux and torque to their respective setpoints according to the instantaneous error, so it can produce a very fast dynamic torque response. In addition,...

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Problems solved by technology

However, in the direct torque control system, the actual control effect of the torque is emphasized. Only by improving the outer loop PI speed controller can not solve the problems of excessive torque fluctuation and flux linkage track distortion, which is not effective for improving the torque performance. good

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