Flexible VF control method for asynchronous motor

Abstract

The invention discloses a flexible VF control method for an asynchronous motor, and the method comprises the following steps: setting a limit speed, and enabling the speed to serve as a speed instruction of a control unit; in the VF control mode, under the fundamental frequency, acquiring the output voltage Us according to the speed instruction and Us/f1 = const, wherein above the fundamental frequency, the output voltage cannot be increased unlimitedly, and Us = UsN needs to be kept; and calculating the voltage according to the final speed value f and Us/f1 = const, and performing the torqueboosting to obtain a final output voltage value. According to the invention, the defect of poor low-frequency torque characteristic of the traditional VF control method is overcome; according to the invention, the defects that the load response is not timely, current oscillation is easy to occur during no-load or light-load operation and the like are overcome, the operation characteristics of themotor under VF control are improved, and the output speed of the driving unit is adjusted according to the torque control requirement of the application working condition, so that the flexible controlof a controlled object is realized.

Description

technical field [0001] The invention relates to the technical field of asynchronous motor drive control, in particular to a flexible VF control method for an asynchronous motor. Background technique [0002] The VF control method is an open-loop speed control for the motor, without introducing any speed, position, or voltage and current feedback signals from the motor end, and the control circuit is simple. This control method is characterized by easy implementation, low price, and stronger versatility than the constant control method. However, this VF open-loop control system cannot obtain the working state of the motor in real time, and cannot obtain the best electromagnetic torque through precise control. Therefore, The response of the speed dynamic characteristic is poor, the torque utilization efficiency of the motor is low, and the control parameters must be adjusted according to the load change, especially when the speed command changes or the load is suddenly added, ...

AI Technical Summary

Problems solved by technology

The characteristics of this control method are that it is easy to implement, low in price, and more versatile than the constant control method. However, this VF open-loop control system cannot obtain the working state of the motor in real time, and cannot obtain the best electromagnetic torque through precise control. Therefore, The response of the speed dynamic characteristic is poor, the torque utilization efficiency of the motor is low, and the control parameters must be adjusted according to the load change. Especially when the speed command changes or the load is suddenly added, the system is prone to instability and the motor will lose its step. or shut down

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