Weak magnetic control method and device for running speed of AC motor

Abstract

The invention relates to the technical field of automatic control, and discloses a weak magnetic control method and device for a running speed of an AC motor. The method comprises the steps of acquiring a direct-axis output voltage output from a torque inner ring; determining weak magnetic rotational speed compensation according to the direct-axis output voltage; and adjusting an actual given rotational speed according to the weak magnetic rotational speed compensation, and controlling the rotational speed of the AC motor according to the adjusted actual given rotational speed. According to the method disclosed by the embodiment of the invention, the weak magnetic rotational speed compensation is determined by acquiring the direct-axis voltage, the actual given rotational speed after the weak magnetic rotational speed compensation is adjusted according to the weak magnetic rotational speed compensation so as to further control the rotational speed of the AC motor; and therefore, during deep weak magnetic running of the motor, the rotational speed of the AC motor is controlled according to the actual given rotational speed after the weak magnetic rotational speed compensation, and meanwhile, the working stability of the motor is improved.

Description

technical field [0001] The invention relates to the technical field of automatic control, in particular to a field weakening control method and device for the running speed of an AC motor. Background technique [0002] In the conventional AC motor vector control method, as the motor speed increases, the output voltage of the power converter needs to show a linear increase trend. However, the output voltage of the power converter is limited. When the motor control demand voltage exceeds the maximum output voltage of the power converter (that is, the maximum output voltage of the power converter cannot meet the actual working voltage requirements of the motor), it is necessary to perform field-weakening control on the motor. [0003] However, in field weakening control (such as voltage closed-loop methods), as the motor speed gradually increases and the load applied to the motor increases, the field weakening depth will be deepened. Take the motor running in electric mode as...

AI Technical Summary

Problems solved by technology

Take the motor running in electric mode as an example: e.g. figure 1 As shown, after the motor enters the field-weakening control, as the field-weakening depth deepens, the direct-axis output voltage (that is, U in the figure d curve) gradually decreases to -1p.u (by The meaning of the formula is that the DC bus voltage and The corresponding physical meaning is the limit value that can be reached in the peak linear operation area of ​​the inverter output phase voltage, and the unit of the limit value of this phase voltage is -1p.u), while the output voltage of the quadrature axis (that is, in the figure u q Curve) gradually drops to 0p.u, at this time, the motor is prone to saturation and out of control

That is to say, when the absolute value of the direct-axis output voltage of the power converter increases gradually and reaches the limit value of the output voltage of the power converter, the motor will appear saturated and out of control or even the motor will be damaged.

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