JP3302159B2 - 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 a motor control device for driving an induction motor using vector control, and more particularly to a motor control device for driving a plurality of induction motors connected in parallel by one inverter. Regarding improvement.

[0002]

2. Description of the Related Art A large number of induction motors connected in parallel are driven by the output of one inverter to drive a transport table roller and the like. FIG. 7 shows a configuration of a conventional motor control device of this kind.

In FIG. 7, 1 is a DC power supply, 2 is an inverter circuit for converting the power of the DC power supply 1 into AC power, 3
.. 3n are induction motors driven by the output of the inverter circuit 2, and these main circuits are generally configured as shown in FIG.

The total current of the currents flowing through these induction motors is detected as i _1f by a current detector 12, and the actual torque current i _1qf and the actual excitation current i _1df are detected by a coordinate conversion circuit 13.
Is separated into

The speed control circuit 5 subtracts the speed feedback ω _rf from the speed reference ω _r ^* of the speed reference setting circuit 4 so that the speed deviation ω _re becomes zero so that the speed reference ω _re becomes zero. i _1q ^* (hereinafter referred to as “torque current reference”).

The field control circuit 7 receives the field reference Φ ^* from the field reference setting circuit 6 and receives a current reference i _1d contributing to the generation of magnetic flux.
^* (Hereinafter referred to as "excitation current reference"). The current control circuit 8 _{calculates the} torque current reference i _1q ^* and the excitation current reference i _1d ^* , the actual torque current i _1qf and the actual excitation current i
_1df, and outputs a torque voltage reference V _1q ^* and a field voltage reference V _1d ^* such that the torque current deviation i _1qe and the excitation current deviation i _1de are zero.
The voltage coordinate conversion circuit 9 calculates the voltage references V _1q ^* and V _1d ^*
And outputs a voltage reference V ^* to be applied to the induction motor.

The speed estimating circuit 11 _generates a torque voltage reference V _1q ^*
Determine the speed ω _o of the rotating magnetic field to be applied to the induction motor from the ^* door magnetic field voltage reference V _1d. The slip calculation circuit 14 calculates the slip speed ω from the actual torque current i _1qf and the actual excitation current i _1df.
Ask for _s . Then, the value obtained by subtracting whether slip velocity omega _s of velocity omega _o of the rotating magnetic field speed Fi - Dobakku omega
_rf . The PWM control circuit 10 calculates the voltage reference V ^*
The inverter from the velocity omega _o of the rotating magnetic field - so that the output voltage of the capacitor circuit 2 becomes the voltage reference V ^*, and outputs a driving signal G.
The inverter circuit 2 converts the DC power of the DC power supply 1 into a desired AC power based on the driving signal G, and converts the DC power into the induction motor 3a.
... supplied to 3n.

Such control is generally called vector control, and it is known that the same control performance as that of a separately excited DC motor is given to an induction motor. In particular, the control of FIG. 7 without using a speed sensor is called speed sensorless vector control. In vector control, stable field control can be performed by controlling the excitation current, and excellent speed response and speed control accuracy can be obtained by controlling the torque current.

[0009]

However, in the conventional apparatus described above, a plurality of induction motors are driven in parallel by one inverter circuit, and when the load of each induction motor becomes unbalanced, a high load is applied. However, there is a problem that the required electric power cannot be satisfactorily supplied to the induction motor, and the high-load induction motor stalls and stops.

For example, among the N induction motors 3a to 3n,
When only 3a receives a high load and 3b... 3n becomes a low load, the primary current of the induction motor detected by the current detector 12 is the detected value i of the sum of the primary currents of the induction motors 3a.
_1f , and the increased primary current of the induction motor 3a performs the same operation as when a uniform load is applied to each induction motor. Therefore, there is a problem that the excitation current or the torque current of the induction motor 3a with a high load is not compensated according to the high load, the torque becomes insufficient, and the motor stalls and stops.

The present invention has been made in view of the above problems, and all the induction motors are stalled even if an imbalance occurs in the loads of a plurality of induction motors driven in parallel by one inverter. An object is to provide a motor control device that can be driven stably without stopping.

[0012]

[Means for Solving the Problems]

(1) As an invention corresponding to claim 1, in an electric motor control device provided with an inverter that controls an excitation component current and a torque component current independently and drives a plurality of induction motors in parallel, the current of the induction motors is controlled. And a maximum current of the individual currents detected by the current detection means is compared with an average current per one induction motor driven in parallel. A current correcting means is provided for correcting one of the excitation component current and the torque component current, or one of the excitation component current and the torque component current. (2) As an invention corresponding to claim 2, the current correction means further compares the maximum current of the individual currents detected by the current detection means with the average current per induction motor driven in parallel. When the deviation value exceeds a predetermined value, one of the excitation component current and the torque component current or one of the excitation component current and the torque component current is corrected. (3) As an invention corresponding to claim 3, the current correction means further includes a number setting means for setting the number of induction motors driven in parallel, and the total current of the induction motors driven in parallel is calculated by the number. Divide it into the average current. (4) According to a fourth aspect of the present invention, the number setting means sets the number by detecting the on state of a switch provided between the inverter and the inverter for each of the induction motors driven in parallel. . (5) According to a fifth aspect of the present invention, in the motor control device provided with an inverter that controls an excitation component current and a torque component current independently and drives a plurality of induction motors in parallel, the current of the induction motors is controlled. Current detection means for individually detecting the current, and when the maximum current of the individual currents detected by the current detection means exceeds a predetermined value, the excitation component current and the torque component current or the excitation Current correction means for correcting one of the component current and the torque component current is provided.

[0013]

[Action]

(1) According to the first aspect of the invention, when an imbalance occurs in the loads of the induction motors driven in parallel, the current of the induction motor having the maximum load is detected as the maximum current, and a deviation occurs from the average current. Both the excitation component current and the torque component current, or any one thereof, are corrected by the current correction unit,
It acts to generate the torque required by the induction motor with the maximum load. (2) In the invention corresponding to claim 2, the current correction means performs the correction when the value of the deviation exceeds a predetermined value, and does not perform the correction in a load imbalance range generated in a steady operation. Works. (3) In the invention corresponding to claim 3, in the current correction means, the total current of the induction motors driven in parallel is divided by the value set by the number setting means to obtain an average current per induction motor. Can be (4) The invention according to claim 4 is that, in the number setting means, the number of induction motors driven in parallel by detecting the number of turned-on states of the switch such as an electromagnetic contactor is automatically set. You. (5) According to a fifth aspect of the present invention, when an imbalance occurs in the loads of the induction motors driven in parallel, the current of the induction motor with the maximum load is detected as the maximum current, and when the value exceeds a predetermined value, The current correction means corrects both or one of the excitation component current and the torque component current, and acts so as to generate the torque required by the induction motor with the maximum load.

[0014]

FIG. 1 shows a first embodiment of a motor control device according to the present invention.
Shown in In FIG. 1, 1 is a DC power supply, 2 is an inverter circuit, 3
a ... 3n is an induction motor, 4 is a speed reference setting circuit, 5 is a speed control circuit, 6 is a field reference setting circuit, 7 is a field control circuit, 8 is a current control circuit, 9 is a voltage coordinate conversion circuit, and 10 is PWM. Control circuit, 11 is speed estimation circuit, 12 is current detector,
Reference numeral 13 denotes a current coordinate conversion circuit, and reference numeral 14 denotes a slip operation circuit, all of which have the same functions as conventional ones.

15a to 15n are current detectors for individually detecting the current of the induction motor. _{Reference numeral} 16 denotes a maximum current detection circuit, which is the largest current detection value i _1max among a plurality of current detection values.
Is selected and output. Reference numeral 17 denotes a number setting device, which sets the number N of induction motors driven in parallel by the inverter circuit 2.
_{Reference numeral} 18 denotes an average calculation circuit that divides the total current value i _1f detected by the current detector 12 by the set number N to output an average current i _1av per unit. Coefficient units 19 to 21 output signals multiplied by _{predetermined} coefficients K _md , K _mq1 and K _mq2 , respectively.

In the above configuration, each of the induction motors 3a to 3a
When the load n is balanced, the primary currents are balanced, so that the output i _1max of the maximum current detection circuit 16 and the average calculation circuit 18
Output i _1av becomes equal, and the current correction value i
_1h becomes zero, and the outputs of the coefficient units 19 to 21 also become zero, thereby performing the same operation as the conventional speed sensorless vector control.

Here, it is assumed that an imbalance has occurred in the loads of the plurality of induction motors 3a to 3n, and only the induction motor 3a has a high load. At this time, the primary current 3a increases, and the total current i _1f detected by the current detector 12 increases accordingly, and the coordinate conversion circuit 13 causes the torque current feedback i _1qf and the excitation current feedback i _1df. And operates similarly to the conventional control.

On the other hand, the total current i _1f is input to the average calculation circuit 18 and is divided by the set value N of the number setting unit 17 to be converted into the average value i _1av of the primary current flowing per induction motor. The individual currents flowing through the induction motors 3a... 3n are detected by individually provided current detectors 15a... 15n, and the maximum individual current is output by the maximum current detection circuit 16 as i _1max . In this case, since only the induction motor 3a has a high load, the individual current of the induction motor 3a is output as _i1max . Accordingly, i _1max becomes larger than i _1av , and a current correction value i _1h of the deviation value is output.

The current correction value i _1h is converted into an excitation current correction value i _1dh via a coefficient unit 19 and added to the excitation current reference i _1d ^* . As a result, the voltage V output from the inverter circuit 2 is obtained.
Is increased, and the necessary 1
It acts to supply the next current.

The current correction value i _1h is converted into torque current correction values i _1qh1 and i _1qh2 via coefficient units 20 and 21.
_1qh1 is added to the actual torque current _i 1qf, i 1qh2 is added to the actual exciting current i _df. Then, these values are input to the slip operation circuit 14, and the values of the slip ω _s are i _1qh1 , i
_Acts to be increased by the addition of _1qh2 . That is, while the average slip calculation of the induction motors 3a to 3n is conventionally performed, the present invention approximates the slip of the induction motor having the maximum load. Since the slip ω _s thus obtained is subtracted from the estimated field speed ω _{o, the} speed feedback ω _rf is reduced by the correction.

Accordingly, the torque current reference i _1q ^* output from the speed control circuit 5 is increased compared to the conventional control configuration, and as a result, the voltage V output from the inverter circuit 2 is increased.
, The required torque current flows through the induction motor 3a which has become heavily loaded, and all the induction motors 3a
.. Can be operated without stopping or stopping 3n.

In the above description of the operation, the number of induction motors with a high load is limited to one. If the number of induction motors with a high load increases, the total current i _1f increases, and the average value i of the primary current flowing per induction motor
_1av increases, and the difference i _{1h from} the maximum individual current i _1max decreases. In other words, the unbalance component of the load viewed from the average value i _{1av of the} primary current is reduced, and the increased total current i _1f tends to supply the desired power by the conventional control. The amount of correction to the current reference may be small.

The maximum current detecting circuit 16 can be realized with a circuit configuration as shown in FIG. That is, each detection current i _11f from the individual current detector 15a.
_Diode rectification bridge to DC voltage proportional to _i1nf
Conversion is performed at 25a to 25n, and the maximum voltage among them is output as _i1max .

According to the present invention, six induction motors M1 to M6 are provided.
FIG. 2 shows an example of a load response when drive control is performed. The actual speed of each of the six induction motors is measured by attaching a speed detector to each of the motors. A 250% step load is applied to only one motor M1 and the other motors M2-
M6 is left unloaded. In this case, in the conventional control configuration, the maximum torque output was only about 60%, and the stall of the high-load electric motor M1 was not prevented. However, by adopting the control configuration according to the present invention, as shown in FIG. , Electric motor M1
Is stably controlled at a torque output of 250%.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, a function unit 24 that outputs a predetermined function value according to a deviation value between an average value i _1av flowing per induction motor and a maximum individual current i _1max is provided. In this example, the function value is a current correction value i _1h .

As a characteristic of the function unit 24, i _1max -i
_When the value of _1av exceeds a predetermined value, the characteristic is such that a current correction value i _1h proportional to the amount of the excess is output.
The normal operation can be stably performed without responding to the load imbalance occurring in the normal operation.

FIG. 4 shows a third embodiment of the present invention. In the third embodiment, when the maximum individual current i _1max exceeds a predetermined value i _1p without _obtaining an average value per induction motor, the corresponding value is used as a current correction value. output as i _1h , i
_In the case of _1max <i _1p , this is an example in which a function circuit for making the output i _1h zero is provided. That is, _when the value of the maximum individual current i _1max becomes larger than the set value i _1p of the current setter 22, the limit circuit 23 outputs a current correction value i _1h according to the difference.

In the third embodiment, when the primary current of an arbitrary induction motor driven in parallel exceeds a predetermined value, the exciting current or the torque current is forcibly corrected according to the amount,
This is to prepare for a case where the load of each induction motor becomes largely unbalanced. The set value i _1p may be set according to the characteristics or driving condition of the induction motor.

When i _1max <i _1p , the current correction value i _1h is zero and operates in the same manner as the conventional speed sensorless vector control. In the above description, both the excitation current reference and the torque current reference are corrected at the same time.
The same effect can be obtained even if only one of them is corrected.

1 and 3, each of the induction motors 3a... 3n is connected to the inverter 2 via a switch such as an electromagnetic contactor, and the number setting device 17 is used to determine the number of the switches. By detecting and setting, it is also possible to adopt a configuration capable of coping with a change in the number of induction motors driven in parallel.

Further, the detection of the total current of the induction motors driven in parallel may be performed by calculating the sum of the current values detected by the individual current detectors 15a... 15n of each induction motor, and omitting the current detector 12. it can.

In the embodiment, the speed sensorless vector control is used. However, a speed detector is installed in part or all of the induction motor to be driven, and the speed is represented by the speed of one induction motor. The present invention can also be applied to a case in which speed control is performed by using speed control or a case in which speed control is performed using the average speed of all induction motors.

[0033]

According to the motor control device of the present invention, the following effects can be obtained when a plurality of induction motors are driven in parallel by using one inverter. (1) According to the invention corresponding to claim 1, when a large load is applied to a part of the plurality of induction motors driven in parallel, the current of the part and one induction motor The torque can be compensated by the deviation from the average current per hit, and the operation can be continued without stalling or stopping. (2) According to the second aspect of the present invention, torque correction is not performed in a load imbalance range caused by steady operation of a plurality of induction motors driven in parallel, so that stable steady operation can be performed. It becomes possible. (3) According to the third aspect of the present invention, it is possible to obtain the average current per induction motor from the total current of the induction motors driven in parallel. (4) According to the invention corresponding to claim 4, furthermore, even when the number of induction motors driven in parallel changes, the average current per induction motor is obtained from the total current of the induction motors driven in parallel. It becomes possible. (5) According to the invention corresponding to claim 5, when a large load is applied to a part of the plurality of induction motors driven in parallel and the current of the part exceeds a predetermined value, The torque can be compensated, and the operation can be continued without stalling or stopping.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment by a motor control device of the present invention.

FIG. 2 is a time chart showing an example of a load response of an actual machine driven by the motor control device of the present invention.

FIG. 3 is a configuration diagram of a second embodiment by the motor control device of the present invention.

FIG. 4 is a configuration diagram of a third embodiment by the motor control device of the present invention.

FIG. 5 is a detailed configuration diagram of a maximum current detector circuit 16 used in the present invention.

FIG. 6 is a configuration diagram of a main circuit.

FIG. 7 is a configuration diagram of a conventional motor control device.

[Explanation of symbols]

1: DC power supply 2: Inverter circuits 3a to 3n: Induction motor 4: Speed reference setting circuit 5: Speed control circuit 6: Field reference setting circuit 7: Field control circuit 8: Current control circuit 9: Voltage coordinate conversion circuit 10: PWM control circuit 11: Speed estimation circuit 12: Current detector 13: Current coordinate conversion circuit 14: Slip operation circuit 15a to 15n: Individual current detector 16: Maximum current detection circuit 17: Number setting unit 18: Average Operation circuit 19: (Field correction gain) coefficient unit 20, 21: (Torque correction gain) coefficient unit 22: Current setting unit 23: Limit circuit 24: Function unit 25a to 25n: Diode rectification bridge

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-343293 (JP, A) JP-A-51-31820 (JP, A) JP-A-57-148587 (JP, A) 22801 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 5/46 H02P 21/00

Claims (5)

(57) [Claims] 1. A motor control device comprising an inverter for controlling an excitation component current and a torque component current independently and driving a plurality of induction motors in parallel, wherein currents for individually detecting the currents of the induction motors are provided. Detecting means, comparing the maximum current of the individual currents detected by the current detecting means with the average current per induction motor driven in parallel, and according to the deviation, the excitation component current and the torque component current. Or a current control means for correcting any one of the excitation component current and the torque component current. 2. The motor control device according to claim 1, wherein the current correction means calculates an average current per induction motor driven in parallel with a maximum current of the individual currents detected by the current detection means. A motor control device for correcting one of the excitation component current and the torque component current or one of the excitation component current and the torque component current when the deviation value exceeds a predetermined value. 3. The motor control device according to claim 1, wherein said current correcting means includes a number setting means for setting the number of induction motors driven in parallel, and said total current of said induction motors driven in parallel. A motor control device, wherein the average current is divided by the number of units. 4. The motor control device according to claim 3, wherein the number setting means detects the on state of a switch provided between the inverter and the inverter for each of the induction motors driven in parallel to determine the number of the motors. A motor control device characterized by setting. 5. A motor control device comprising an inverter for controlling an excitation component current and a torque component current independently and driving a plurality of induction motors in parallel, wherein currents for individually detecting the currents of the induction motors are provided. Detecting means, when the maximum current of the individual currents detected by the current detecting means exceeds a predetermined value, the excitation component current and the torque component current, or the excitation component current and the torque component current, according to the maximum current. An electric motor control device comprising a current correction means for correcting any one of the above.