Field Weakening Control Method for Maximum Torque Output of Asynchronous Motor

Abstract

The invention discloses a field weakening control method for realizing output of the maximum torque of an asynchronous motor. The field weakening control method includes operating the asynchronous motor in a weak field; at the time the asynchronous motor runs in a first weak field, controlling the d-axis component of stator flux linkage of the asynchronous motor to be equal to the first optimum value the d-axis component of stator flux linkage and controlling the q-axis component of stator current of the asynchronous motor to be lower than the first limit value of the q-axis component of the stator current so as to output the maximum torque; at the time the asynchronous control runs in a second weak field, driving the asynchronous motor to run at the maximum slip ratio sm, controlling the d-axis component of the stator flux linkage of the asynchronous motor to be the second optimum value of the d-axis component of the stator flux linkage as well as the q-axis component of stator current of the asynchronous motor to be lower than the second limit value of the q-axis component of stator current, thereby outputting the maximum torque. The field weakening control method is implemented on the basis of stator field directional control technology without dependency on speed sensors, and has effect of realizing stable operation of the asynchronous motor within the whole weak field by the maximum torque based on consideration on related voltage limit, current limit, and torque limit.

Description

technical field [0001] The invention relates to a field-weakening control method for the maximum torque output of an asynchronous motor that does not rely on a speed sensor and is realized based on a stator magnetic field oriented control technology, and belongs to the technical field of variable frequency speed regulation of asynchronous motors. Background technique [0002] The driving motors used in electric vehicles are becoming more and more diversified. The asynchronous motors are currently used in electric vehicle drive systems, especially in high-power applications, because of their low price, high reliability, easy maintenance and manufacturing, and mature control technology. important position. In actual use, the constant torque area of ​​the asynchronous motor used in electric vehicles is designed to be small, and the required speed range is relatively wide, so it often runs above the rated speed. Under the limited DC bus voltage, only through weak Magnetic can o...

AI Technical Summary

Problems solved by technology

Although this technology can fully utilize the limit values ​​of voltage and current, and the entire field-weakening operating range can produce the maximum steady-state torque and has fast dynamic response capability, but this control technology needs to increase the control loop and control variables, requiring four PI regulator, which complicates the control algorithm

[0005] At present, most of the research on the field-oriented control technology without speed sensor is only for below the rated speed, but there are relatively few studies on the problems that the speed estimation method may encounter when the motor is working in the field-weakening area.

And in the case of very high speed, the pulse of the encoder will lose symmetry, and if the pulse frequency output by the encoder is too high, the output pulse frequency of the speed sensor may exceed the processing speed of the control chip. Speed ​​sensorless vector control technology is of great significance in industrial applications

The main difficulty encountered by the vector control asynchronous motor based on the rotor field orientation in the field weakening region is the large-scale change of the excitation inductance, while the stator field orientation control without speed sensor has a relatively good robustness to the change of the excitation inductance. Rod

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