Field Weakening Control Method for Asynchronous Motor Based on Bandgap Variable Step Size Method

Abstract

The invention discloses a field weakening control method of an asynchronous motor based on a bandgap variable step size method. The method comprises the steps of obtaining particular value coefficients P1 and P2 according to a specific application condition and a test condition to determine particular values Umax and Umin of a three-phase voltage resultant vector us of the asynchronous motor, then determining bandgap width as shown in the specification, determining initial step size as shown in the specification, determining restraint coefficients a1, a2, b1 and b2 according to a practical application condition and the test condition, determining a variable step size coefficient beta and a direction coefficient alpha according to direct current busbar voltage and control voltage vectors, determining a set value of exciting current of the asynchronous motor, and finally resetting an exciting current component according to an equation as shown in the specification. The method avoids an influence of parameters of the motor on control, and is simple in algorithm and quick in field weakening response; the algorithm achieves smooth transition within a full-speed range of the asynchronous motor; and a field weakening control requirement of the asynchronous motor is met.

Description

technical field [0001] The invention relates to the control technology of an asynchronous motor, in particular to a field-weakening control method of an asynchronous motor based on a band gap variable step size method. Background technique [0002] Asynchronous motors are widely used in automobile drives and industrial transmission systems because of their simple structure, low cost, and high reliability. In order to realize the high-performance control requirements in the full speed range of the asynchronous motor, a vector control algorithm is generally used for it. When the asynchronous motor is running, its line voltage will be limited by the power supply voltage. Therefore, in the vector control algorithm of the asynchronous motor, the field-weakening control method is used at high speeds to obtain high-performance control effects. [0003] In the asynchronous motor vector control algorithm, the rotor magnetic field is excited by the stator current, and the field weake...

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Problems solved by technology

[0004] One is to directly reduce the stator excitation current, that is, the field weakening control method that artificially reduces the magnetic flux with the increase of the speed. In this method, because the excitation current is artificially given or obtained through the inverse proportional function of the speed, resulting in Poor control performance under different working conditions;

[0005] The second is the field-weakening control based on the steady-state voltage equation of the asynchronous motor. This method is strictly dependent on the parameters of the motor. In actual situations, the parameters of the motor, especially the parameters of the rotor, vary greatly, so this method cannot achieve optimal control performance;

[0006] The third is to carry out the field weakening control of the motor based on the voltage closed-loop control method. This method avoids the influence of the motor parameters, but this method requires closed-loop adjustment of the voltage, and only cuts into operation when field weakening is required, and the algorithm implementation is relatively complicated.

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