A speed tracking method of an AC motor, a speed regulating device and an AC motor

Abstract

The invention discloses an AC motor revolving speed tracking method which is used to track a revolving speed when an AC motor restarts. The method includes the following steps: 1, a current flux linkage angle is estimated; 2, a stator current vector carries out coordinate conversion so as to obtain a first current value and a second current value which are respectively in line with and perpendicular to the flux linkage angle; 3, the first current value and a preset non-zero current values serve as input, and through calculation of a current regulator, a voltage is obtained (img file = 'dest_path_image002. TIF' wi = '24' he = '16' / ); the second current value and 0 serve as input, and through calculation of the current regulator, a voltage is obtained (img file = 'dest_path_image004. TIF' wi = '16' he = '16' / ); 4, voltages (img file ='891979dest_path_image002. TIF' wi = '24' he = '16' / ) and (img file ='996071dest_path_image004. TIF' wi ' = '16' he = '16' / ) carry out pulse width modulation to generate a driving control signal to drive the AC motor; and 5, steps from 1 to 4 are repeated, until the second current value is lower than a current threshold value and maintains for a period of a preset time, and differential calculation of a current flux angle is carried out to get the revolving speed when the AC motor restarts. The invention also discloses an AC motor speed control device and the AC motor. According to the invention, the advantages of being fast, accurate and low-cost are realized.

Description

Technical field [0001] The invention relates to a speed tracking method of an AC motor, a speed regulating device and an AC motor, and belongs to the technical field of AC motors. Background technique [0002] Due to the complexity of the industrial application site and the diverse process requirements, it is determined that the frequency conversion speed control system must have sufficient processing capacity for abnormal operating conditions in addition to the performance requirements during normal operation. For example: large ventilation equipment may cause the motor to rotate freely due to the residual air volume in the air duct. After a large inertia load encounters a sudden power failure, the motor will rotate freely for a long time, which can be as long as tens of minutes; if the motor is started directly at this time, it will The motor may be in a large slip state and fail to start (overcurrent protection). In order to prevent this phenomenon, after the power supply ret...

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Problems solved by technology

[0005] The technical solutions recorded in the above documents have the following problems: 1) It is not easy to determine the first control signal. If the setting is not appropriate, it is likely to cause overcurrent or overvoltage faults.

2) If there is a large gap between the current searched stator magnetic field frequency and the actual speed of the induction motor, especially when the stator magnetic field frequency is in the opposite direction to the actual speed of the induction motor, then the search time of the speed search device will be longer

Therefore, this scheme has certain limitations in practical application.

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