JP2596232B2 - AC motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a drive power supply when an AC motor is driven at a variable speed by so-called vector control.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional AC motor of this kind disclosed in the paper "High-performance Variable Speed Control of Synchronous Motors" published in, for example, IEICE Transactions D, Vol. 107, No. 2, pp. 175-182. FIG. 4 is a control circuit diagram showing the control device of FIG. In the figure, reference numeral 1 denotes a speed controller which operates based on a speed deviation es between a speed reference of a motor and an actual speed (neither is shown), and 2 denotes a torque (q-axis) current by suppressing an abrupt change in the output of the speed controller 1. lamp circuit for outputting a reference iq ^*, 3 are calculator for calculating a torque component deviation eq of torque current reference iq ^* and the actual torque current iq, 4 is torque current controller operated by the torque component deviation eq, A torque control voltage Vq is output.

Reference numeral 5 denotes an arithmetic unit for adding a magnetic flux component (d-axis) current reference id ^** and a field deviation ef described later, and 6 denotes a magnetic flux component current reference id ^* output from the arithmetic unit 5 and an actual magnetic flux component current. id
The arithmetic unit 7 calculates a magnetic flux deviation ed. The magnetic flux current controller 7 operates based on the magnetic flux deviation ed, and outputs a magnetic flux control voltage Vd. Reference numeral 8 denotes a magnetic flux controller that operates based on a magnetic flux deviation eφ between a magnetic flux reference of a field circuit of a motor and an actual magnetic flux (neither is shown), and 9 denotes a field current reference if which suppresses a rapid change in the output of the magnetic flux controller 8. ^* , A ramp circuit for outputting ^* , 10 a calculator for calculating a field deviation ef between the field current reference if ^* and the actual field current if, 11 a field current controller operated by the field deviation ef, and a field control voltage Vf is output.

Next, the operation will be described. In the vector control, as shown in FIG. 3, the d-axis is set on the field current if, and the q-axis is set orthogonal to the d-axis, and the armature current Ia is separated into the respective axis components id and iq to set the field current. If is controlled together with If, and its basic operation is widely known, its description is omitted. Hereinafter, the reason for supplementing the insufficient magnetic flux on the field side with the magnetic flux component current on the armature side and its operation will be described in detail. I do.

As shown in FIG. 2, a predetermined field magnetic flux is output by the voltage Vf from the field current controller 11, but when a field voltage limit state occurs at the time of so-called forcing or the like, the field magnetic field is limited. The current if does not sufficiently follow the reference value if ^* , and there is a possibility that the deviation ef becomes excessive and control becomes impossible. In general, the field reactance of a synchronous motor is large, so that a high forcing voltage is required. If it is attempted to secure this by only the field current, the power supply device becomes large, which is uneconomical.

Therefore, the field deviation ef input to the field current controller 11 is also input to the magnetic flux component current controller 7 via the calculators 5 and 6. Therefore, the magnetic flux component current controller 7 operates according to the deviation ed between the current reference (id ^** + ef) = id ^* and the actual current id. In other words, the portion of the required field magnetic flux that is insufficient by the field current if is supplemented by the magnetic flux component current id of the armature current.

[0007]

By the way, in the so-called non-circulating current type cycloconverter which is generally employed, the switching between the positive group converter and the negative group converter is performed according to the polarity of the load current. Therefore, in the case of the vector control, the AC current references iu ^* , i obtained by converting the torque component current reference iq ^* and the magnetic flux component current reference id ^* into two-phase three-phase conversion.
This is performed by switching the current polarity of v ^* and iw ^* .
In this case, if the torque component current reference iq ^* is zero with no load and the magnetic flux component current reference id ^* becomes zero, the AC current reference is not output and switching between the positive and negative group converters becomes impossible. This mechanism prevents the occurrence of the inconvenience as about 5% of the magnetic flux component current reference id ^{* *} To avoid getting flux component current reference id ^* is zero when the torque current reference iq ^* is zero.

However, in the conventional AC motor control device described above, the field deviation between the field current reference if ^* obtained by the computing unit 10 and the actual field current if is added to the magnetic flux component current reference id ^{** .} Since ef is added, its field deviation ef
Depending on the polarity and the absolute value of the current, the torque component current reference iq ^* and the magnetic flux component current reference id ^* both become zero, and the switching between the positive and negative group converters becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an AC motor capable of preventing a torque component current and a magnetic flux component from both becoming zero to obtain a stable converter operating characteristic. Is realized.

[0010]

SUMMARY OF THE INVENTION A control device for an AC motor according to the present invention determines whether a reference for a torque component current or a current for an actual torque is zero. The input to the controller is canceled.

[0011]

[Function] If the torque component current reference or the actual torque component current is detected, and this is not zero, the field deviation is input to the magnetic flux component current controller, and the deficiency in the field current with respect to the required field magnetic flux is determined by the armature current. Is replenished by the current of the magnetic flux. If the torque component current is determined to be zero, the field deviation is not input to the magnetic flux component current controller, the armature current control system operates independently, and the magnetic flux component current is kept constant by the usual method. It has the above value and does not become zero.

[0012]

FIG. 1 is a circuit diagram showing a control device for an AC motor according to an embodiment of the present invention. Hereinafter, a description will be given focusing on a portion different from the conventional case of FIG. However, the magnetic flux deviation eφ
Is set as the field current reference if ^* via the magnetic flux controller 8 and the ramp circuit 9, and the field deviation ef is further calculated by the calculator 10.
Is input to the field current controller 11 as in the prior art.

On the other hand, the output side of the arithmetic unit 10 and the arithmetic unit 5
A switch circuit 12 is newly inserted between the input side and the input side. Further, the switch circuit 12 is provided with a comparator 13 for sending an on / off control signal and an absolute value circuit 14 for calculating the absolute value of the actual torque current iq.

Next, the operation will be described. The actual torque component current iq is input to the absolute value circuit 14, where it is converted into an absolute value and becomes the actual torque component current absolute value | iq | eiq is a torque current zero determination value set to determine whether or not | iq | is substantially zero. Assuming that | iq | ≧ eiq, the comparator 13 sends an ON signal to the switch circuit 12. That is, it is determined that the actual torque component current iq is not zero, and the field deviation ef is sent to the arithmetic unit 5 via the switch circuit 12, and the field magnetic flux is supplemented by the magnetic flux component current of the armature current. Naturally, in this case, since there is no possibility that both the torque component current and the magnetic flux component current become zero, the switching between the positive and negative group converters is performed normally.

When | iq | <eiq is satisfied, the comparator 13 sends an off signal to the switch circuit 12. That is, it is determined that the actual torque component current iq is zero, and the calculation unit 5 does not add the field deviation ef. This is because the torque component current and the magnetic flux component current both become zero depending on the level of the field deviation ef, which may hinder the switching of the converter. In this case, the magnetic flux component current reference id
^** is the magnetic flux component current reference id ^{* as} it is, and a necessary AC current reference is reliably generated as in the conventional case, and a stable converter switching operation is achieved.

Note that the comparator 1 in the above embodiment is
Although 3 has been described as having only a normal comparison function, an on / off signal to the switch circuit 12 may be provided with a hysteresis characteristic. In this case, there is an advantage that a chattering phenomenon of the switch circuit 12 due to a ripple or the like of the torque component current iq is prevented.

In the above embodiment, the current iq
Is determined to be zero or not. However, the same effect can be obtained by determining whether or not the torque current reference iq ^* is zero.

[0018]

As described above, according to the present invention, when the torque component current is zero, the addition of the field deviation to the magnetic flux component current reference is not performed. Stable and stable in all operating ranges.

[Brief description of the drawings]

FIG. 1 is a control circuit diagram showing a control device for an AC motor according to an embodiment of the present invention.

FIG. 2 is a control circuit diagram showing a conventional control device for an AC motor.

FIG. 3 is a vector diagram showing each current component.

[Explanation of symbols]

2, 9 Ramp circuit 3, 5, 6, 10 Operation unit 4 Torque current controller 7 Magnetic flux current controller 11 Field current controller 12 Switch circuit 13 Comparator 14 Absolute value circuit iq ^* Torque current reference iq Actual torque current eq Torque component deviation id ^* Magnetic flux component current reference id Actual magnetic flux component current ed Magnetic flux component deviation if ^* , if ^{** *} Field current reference if Real field current ef Field deviation

Claims (1)

(57) [Claims] A torque component current controller that operates based on a torque component deviation between a torque component current reference and an actual torque component current, and a magnetic flux component current controller that operates based on a magnetic flux component deviation between a magnetic flux component current reference and an actual magnetic flux component current. An armature current control system, and a field current control system including a field current controller that operates based on a field deviation between a field current reference and a real field current. By inputting also to the current controller, in order to compensate for the insufficient magnetic flux on the field side by the magnetic flux component current on the armature side, it is determined whether or not the torque component current reference or the actual torque component current is zero, A control device for an AC motor, wherein the input of the field deviation to the magnetic flux component current controller is canceled when the value is zero.