JP3752896B2 - Vector control device for electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vector control device for an electric motor that can avoid inconvenience caused by a mismatch between a torque command value and a load torque when the electric motor is vector-controlled.
[0002]
[Prior art]
FIG. 5 is a block circuit diagram showing a first conventional example of a vector control apparatus for an electric motor. In FIG. 5, the inverter 2 converts the AC power from the AC power source 1 into variable voltage / variable frequency AC power by vector control, and supplies the motor to, for example, the induction motor 3, thereby driving the load 4. Can be operated at a desired rotational speed. Here, the vector control means that the primary current of the induction motor 3 is divided into an excitation current component parallel to the secondary magnetic flux and a torque current component orthogonal thereto, so that both current components coincide with the command values described below. Separately.
[0003]
In other words, it calculates a magnetic flux command value [Phi ₂ ^* speed detection value N the speed detector 5 which is attached to the induction motor 3 is detected by inputting the flux command calculator 7, the magnetic flux command value [Phi ₂ ^* exciting current Input to the arithmetic circuit 8 to obtain the excitation current command value I _m ^* . Further, the torque current command value I _t ^* is obtained by causing the divider 10 to perform an operation of dividing the torque command value τ ^* set by the torque command setting device 9 by the magnetic flux command value Φ ₂ ^* . The vector control circuit 6 performs control for matching the excitation current component described above with the excitation current command value I _m ^* and control for matching the torque current component with the torque current command value I _t ^* . Here, the operation of the vector control circuit 6 is well known and is irrelevant to the present invention, so that the description of the operation of the vector control circuit 6 is omitted. Since the inverter 2 outputs AC power having a desired voltage and frequency according to the control signal output from the vector control circuit 6, the induction motor 3 is driven at a desired rotational speed to drive the load 4.
[0004]
FIG. 6 is a block circuit diagram showing a second conventional example of a vector control device for an electric motor. The AC power source 1, inverter 2, induction motor 3, load 4, speed detection described in the second conventional example of FIG. The names, applications, and functions of the detector 5, the vector control circuit 6, the magnetic flux command calculator 7, and the exciting current calculator 8 are the same as those of the first conventional circuit described above with reference to FIG. Is omitted.
[0005]
In the second prior art example circuit of FIG. 6, a torque current command setting device 11 which is installed in place of the torque command setting unit 9 and the divider 10 is set to the torque current command value I _t ^*. By inputting the torque current command value I _t ^* and the excitation current command value I _m ^* described above to the vector control circuit 6, the induction motor 3 can have a desired value as in the case of the first conventional circuit shown in FIG. 5. The load 4 is driven at the rotational speed.
[0006]
[Problems to be solved by the invention]
For the load 4 driven by the induction motor 3, the load torque may change depending on the operating condition, and the load torque may change abruptly for some reason. For example, if the torque current command value I _t ^* set by the torque current command setter 11 (see FIG. 6) remains the same as before, even though the load torque has decreased, the rotational speed of the induction motor 3 is increased. Thus, the torque current component is increased until it matches the torque current command value I _t ^* . That is, there is a disadvantage that the rotation speed of the induction motor 3 becomes larger than the scheduled value, but in some cases, the rotation speed may exceed a dangerous value.
[0007]
That is, if the torque current command value I _t ^* or the torque command value τ ^* is set to an inappropriate value with respect to the load torque, there is a risk that the rotational speed will increase excessively and become dangerous. is there.
[0008]
Therefore, an object of the present invention is to prevent an excessive increase in the motor speed even if the torque command value of an electric motor operated by vector control is not compatible with the torque of a load driven by the electric motor.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a vector control apparatus for an electric motor according to the present invention includes:
The primary current flowing through the motor is divided into an excitation current component parallel to the secondary magnetic flux of the motor and a torque current component orthogonal thereto, and vector control is performed so that these both current components are individually matched to the command values. A first torque command correction value calculation circuit for calculating a proportional control of a deviation between the speed detection value of the motor and the forward or reverse speed limit value of the motor, and a torque command correction value output from the first torque command correction value Correct the value.
[0010]
Or a first torque current command correction value calculation circuit that divides and calculates the calculation result of the proportional control of the deviation between the speed detection value of the motor and the forward or reverse speed limit value of the motor by the magnetic flux command value; The torque current command value is corrected by the torque current command correction value output by this.
[0011]
Or a second torque command correction value calculation circuit that adds the torque command value to the calculation result of proportional integral control of the deviation between the detected speed value of the motor and the forward or reverse speed limit value of the motor, This is the torque command correction value that is output, and the torque command value is corrected corresponding to the rotation direction of the motor.
[0012]
Alternatively, the calculation result of the proportional integral control of the deviation between the speed detection value of the motor and the forward or reverse speed limit value of the motor is divided by the magnetic flux command value, and the torque current command A second torque current command correction value calculation circuit for adding the values is provided, and the torque current command correction value output from the second torque current command correction value calculation circuit is used to correct the torque current command value corresponding to the rotation direction of the motor.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In each of the embodiments of the present invention described below, the rotational speed in the forward direction of the motor is a positive value, the rotational speed in the reverse direction is a negative value, and the torque that applies force to the forward direction is a positive value. Thus, the torque that gives force to the reverse rotation is expressed by a negative value.
[0014]
FIG. 1 is a block circuit diagram showing a first embodiment of the present invention. This first embodiment circuit is different from the first conventional circuit described in FIG. Since the first adder 24 is added, the description of the same parts as those of the first conventional circuit in FIG. 5 is omitted.
[0015]
In the circuit of the first embodiment shown in FIG. 1, the limit circuit 21 constituting the first torque command correction value calculation circuit 20 converts the speed detection value N detected by the speed detector 5 into a predetermined forward rotation speed limit value or reverse rotation. Limited by the speed limit value. Therefore, a deviation between the output value of the limiting circuit 21 and the speed detection value N is calculated by the adder 22 to obtain a speed deviation ΔN. The proportional controller 23 inputs this speed deviation ΔN and outputs a torque command correction value Δτ. The first adder 24 adds the torque command value τ ^* set by the torque command setter 9 and the torque command correction value Δτ with the polarity shown in the figure, so that the torque command value τ set by the torque command setter 9 is set. ^* Is corrected.
[0016]
For example, if the speed detection value N of the induction motor 3 is smaller than the limit value determined by the limit circuit 21, the two input values to the adder 22 are the same value. The speed deviation ΔN is zero. Accordingly, the torque command correction value Δτ is also zero, and the torque command value τ ^* is not corrected. However, if the speed detection value N exceeds a predetermined limit value during the forward rotation of the induction motor 3, the speed detection value N becomes larger than the output value of the limit circuit 21. Accordingly, the speed deviation ΔN, which is the calculation result of the adder 22, is a negative value, and the torque command correction value Δτ is also negative, so that a torque command correction value Δτ that gives a force to reverse rotation is obtained. Therefore, the calculation result of the first adder 24 is smaller than the set value of the torque command setter 9 by the torque command correction value Δτ. If the induction motor 3 is operating in reverse, the torque command correction value Δτ takes a positive value, as opposed to the above, so that a torque command correction value Δτ that gives a force to forward rotation is obtained. That is, since the negative torque command value τ ^* set by the torque command setting device 9 is corrected by the positive torque command correction value Δτ, the calculation result of the first adder 24 is a negative value as described above. The torque command correction value Δτ is reduced.
[0017]
FIG. 2 is a block circuit diagram showing a second embodiment of the present invention. This second embodiment circuit is different from the second conventional circuit already described with reference to FIG. And the second adder 32 are added, the description of the same parts as those of the second conventional circuit in FIG. 6 is omitted.
[0018]
In the circuit of the second embodiment of FIG. 2, the names, uses, and functions of the limiting circuit 21, the adder 22, and the proportional regulator 23 that constitute the first torque current command correction value calculation circuit 30 are already described in FIG. The proportional control device 23 outputs a torque command correction value Δτ. The divider 31 is divided by the flux command value [Phi ₂ ^* and outputs the torque command correction value Δτ flux command calculator 7 to obtain a torque current command correction value [Delta] I _t. The torque current command setter 11 sets the torque current command value I _t ^* and this torque current command correction value ΔI _t with the polarity shown in the figure in the second adder 32, so that the torque current command setter 11 corrects the torque current command correction value [Delta] I _t to be set.
[0019]
FIG. 3 is a block circuit diagram showing a third embodiment of the present invention. This third embodiment circuit is different from the first conventional circuit shown in FIG. Since the torque command correction circuit 52 is added, the description of the same parts as those of the first conventional circuit in FIG. 5 is omitted.
[0020]
In the circuit of the third embodiment of FIG. 3, the speed limit value switching unit 41 is switched in accordance with the polarity of the speed detection value N. That is, when the induction motor 3 is in the forward rotation operation (that is, N> 0), the forward rotation speed limit value is given to the adder 44. input. On the other hand, the speed detection value N is also input to the adder 44, and the deviation between the two inputs is given to the proportional controller 45 and the integral controller 46. On the output side of the integral controller 46, the calculation result is positive. If it is a value, a limiter 47 for limiting to +0 is installed. By adding the output of the proportional regulator 45 and the output of the integral regulator 46 via the limiter 47 by the adder 48, the torque command auxiliary correction value τ ₁ ^* is obtained.
[0021]
If the induction motor 3 is in the forward rotation operation (N> 0), the polarity switch 50 is in the state shown in the figure, and the torque command auxiliary correction value τ ₁ ^* is supplied to the adder 51 as it is. During reverse operation (N <0), the polarity switcher 50 is switched, and the torque command auxiliary correction value τ ₁ ^* is supplied to the adder 51 via the multiplier 49. Here, since the multiplier 49 multiplies the torque command auxiliary correction value τ ₁ ^* by −1, the torque command auxiliary correction value τ ₁ ^* having a polarity opposite to that during the forward rotation operation is input to the adder 51 during the reverse rotation operation. Will do.
[0022]
The adder 51 calculates a torque command correction value τ _LIM that is the sum of the torque command auxiliary correction value τ ₁ ^* via the polarity switcher 50 and the torque command value τ ^* set by the torque command setting unit 9. Yes. The calculation in the adder 51 is expressed by the following formula 1.
[0023]
[Expression 1]
τ _LIM = τ ^* + τ ₁ ^*
The torque command correction circuit 52 corrects the torque command value τ ^* set by the torque command setter 9 with the above-described torque command correction value τ _LIM , and this correction situation is based on the polarity of the speed detection value N (that is, the induction motor 3 Is normal or reverse). The correction situation is as follows.
[0024]
(A) When N> 0 (during forward operation)
(1) If τ ₁ ^* > 0 and τ _LIM > τ ^* , the torque command value τ ^* remains unchanged and is not corrected.
(2) If τ ₁ ^* <0 and τ _LIM <τ ^* , the torque command value τ ^* is corrected with the torque command correction value τ _LIM .
[0025]
(B) When N <0 (during reverse operation)
(1) If τ ₁ ^* <0, τ _LIM <τ ^* , the torque command value τ ^* is not corrected as it is.
(2) If τ ₁ ^* > 0 and τ _LIM > τ ^* , the torque command value τ ^* is corrected with the torque command correction value τ _LIM .
[0026]
For example, when the induction motor 3 is in a forward rotation operation (N> 0) and the speed detection value N is within a predetermined speed limit value, the calculation result in the adder 44 exhibits a positive value. Τ ₁ ^* input to the device 51 is also a positive value. Therefore, with reference to Equation 1, τ _LIM > τ ^* . This corresponds to the above (A) {circle around (1)}, and the torque command value τ ^* set by the torque command setter 9 is not corrected.
[0027]
In addition, when the forward rotation operation is being performed (N> 0) and the speed detection value N exceeds a predetermined speed limit value, the calculation result of the adder 44 exhibits a negative value. _LIM <τ ^* . This corresponds to (A) {circle around (2)}, and the torque command value τ ^* is corrected by the torque command correction value τ _LIM . This is a limit operation for the forward rotation speed limit value, and when the torque command auxiliary correction value τ ₁ ^*, which is the calculation result of the adder 48 (ie, proportional integral adjustment operation), is negative, that is, when reverse torque is output. Torque command correction is performed.
[0028]
FIG. 4 is a block circuit diagram showing a fourth embodiment of the present invention. This fourth embodiment circuit is the same as the second conventional circuit already described in FIG. And the torque current command correction circuit 62 are added, and the description of the same parts as those of the second conventional circuit in FIG. 6 is omitted. Further, the second torque current command correction value calculation circuit 60 has a configuration in which a divider 61 is added to the second torque command correction value calculation circuit 40 described in the circuit of the third embodiment already described with reference to FIG. The divider 61 is not less different're converting the torque command auxiliary correction value tau ₁ ^* in the magnetic flux command value [Phi ₂ ^* torque current command auxiliary correction value by dividing by I _t1 ^*, Otherwise the same It is.
[0029]
In the circuit of the fourth embodiment shown in FIG. 4, the adder 51 adds the torque current command auxiliary correction value I _t1 ^* calculated by the divider 61 and the torque current command value I _t ^* set by the torque current command setter 11. Thus, the torque current command correction value _ItLIM is obtained, and this calculation is expressed by the following formula 2.
[0030]
[Expression 2]
I _tLIM = I _t ^* + I _t1 ^*
The torque current command correction circuit 62 corrects the torque current command value I _t ^* set by the torque current command setter 11 with the torque current command correction value I _tLIM described above. It depends on the polarity of the value N. The correction situation is as follows.
[0031]
(C) When N> 0 (during forward operation)
(1) If I _t1 ^* > 0 and It _tLIM > I _t ^* , the torque current command value I _t ^* is not corrected as it is.
(2) If I _t1 ^* <0, It _tLIM <I _t ^* , the torque current command value I _t ^* is corrected with the torque current command correction value It _tLIM .
[0032]
(D) When N <0 (during reverse operation)
^{_{▲ 1 ▼ I t1 * <0}} , I tLIM <I t * If the torque current command value I _t ^* is not corrected as is.
^{_{▲ 2 ▼ I t1 *> 0}} , I tLIM> I t * If the torque current command value I _t ^* is corrected by the torque current command correction value I _tLIM.
[0033]
For example, when the induction motor 3 is in a forward rotation operation (N> 0) and the speed detection value N is within a predetermined speed limit value, the calculation result in the adder 44 exhibits a positive value. I _t1 ^* input to the device 51 is also a positive value. Therefore, with reference to Equation 2, I _tLIM > I _t ^* . This corresponds to the above (C) ▲ 1 ▼, ^* torque current command value I _t to be set by the torque current command setting unit 11 does not receive a correction.
[0034]
Further, when the forward rotation operation is being performed (N> 0) and the speed detection value N exceeds a predetermined speed limit value, the calculation result of the adder 44 exhibits a negative value. _tLIM <I _t ^* . This corresponds to (C) ▲ 2 ▼, ^* torque current command value I _t will be corrected by the torque current command correction value I _tLIM. This is a limiting operation for the forward rotation speed limit value, and when the torque current command auxiliary correction value _It1 ^*, which is the calculation result of the adder 48 (i.e., proportional integral adjustment operation), is negative, that is, reverse torque is output. In this case, torque current command correction is performed.
[0035]
【The invention's effect】
When controlling the electric motor by vector control, if the load fluctuates and the torque command value or torque current command value becomes inappropriate, the motor speed may increase abnormally. When the motor speed exceeds a predetermined speed limit value, an increase in the motor speed is suppressed by correcting the set torque command value or torque current command value. This is the same even when the set value is set inappropriately for the load. As a result, it is possible to obtain an effect capable of easily and easily preventing danger such as damage to the apparatus due to overspeed.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing a first embodiment of the present invention. FIG. 2 is a block circuit diagram showing a second embodiment of the invention. FIG. 3 is a block circuit showing a third embodiment of the invention. FIG. 4 is a block circuit diagram showing a fourth embodiment of the present invention. FIG. 5 is a block circuit diagram showing a first conventional example of an electric motor vector controller. FIG. 6 is a second electric motor vector controller. Block circuit diagram showing a conventional example [Description of symbols]
2 Inverter 3 Induction motor 4 Load 5 Speed detector 6 Vector control circuit 7 Magnetic flux command computing unit 8 Excitation current computing circuit 9 Torque command setting unit 10, 31, 61 Divider 11 Torque current command setting unit 20 First torque command correction value Arithmetic circuit 21 Limit circuit 22, 44, 48, 51 Adder 23, 45 Proportional regulator 24 First adder 30 First torque current command correction value calculation circuit 32 Second adder 40 Second torque command correction value calculation circuit 41 Speed limit value changers 42, 43 Absolute value calculator 46 Integration adjuster 47 Limiter 49 Multiplier 50 Polarity switch 52 Torque command correction circuit 60 Second torque current command correction value calculation circuit 62 Torque current command correction circuit I _m ^* exciting current command value I _t ^* torque current command value I _t1 ^* torque current command auxiliary correction value I _tLIM torque current command correction value [Delta] I _t torque current command correction value N speed Detection value ΔN speed deviation [Phi ₂ ^* flux command value tau ^* torque command value tau ₁ ^* torque command auxiliary correction value tau _LIM torque command correction value Δτ torque command correction value

Claims (4)

The primary current flowing through the motor is divided into an excitation current component parallel to the secondary magnetic flux of the motor and a torque current component orthogonal thereto, and the excitation current component is calculated from a magnetic flux command value obtained from the speed detection value of the motor. The torque current component is matched with the torque current command value obtained by dividing the torque command value set by the torque command setter by the magnetic flux command value. In the electric motor vector control device for controlling
A first torque command correction value calculation circuit for calculating a proportional control of a deviation between the speed detection value of the motor and a forward speed limit value or a reverse speed limit value of the motor and outputting a torque command correction value; An electric motor vector control device comprising: a first adder that calculates a new torque command value by adding a torque command correction value and the torque command value. The primary current flowing through the motor is divided into an excitation current component parallel to the secondary magnetic flux of the motor and a torque current component orthogonal to the excitation current component, and the excitation current component is calculated from the magnetic flux command value obtained from the speed detection value of the motor. In the motor vector control device for controlling the torque of the motor by matching the excitation current command value, the torque current component being matched with the torque current command value set by the torque current command setter,
A torque current command correction value is output by dividing the calculation result of the proportional control of the deviation between the detected speed value of the motor and the forward speed limit value or the reverse speed limit value of the motor by the magnetic flux command value. 1. An electric motor comprising: 1 torque current command correction value calculation circuit; and a second adder for calculating a new torque current command value by adding the torque current command correction value and the torque current command value. Vector controller. The primary current flowing through the motor is divided into an excitation current component parallel to the secondary magnetic flux of the motor and a torque current component orthogonal to the excitation current component, and the excitation current component is calculated from the magnetic flux command value obtained from the speed detection value of the motor. The torque current component is matched with the torque current command value obtained by dividing the torque command value set by the torque command setter by the magnetic flux command value. In the electric motor vector control device for controlling
The torque command correction value is output by adding the torque command value to the calculation result of the proportional integral control of the deviation between the speed detection value of the motor and the forward speed limit value or the reverse speed limit value of the motor. A torque command correction value calculation circuit; and a torque command correction circuit that corrects the torque command value with the torque command correction value and outputs a new torque command value corresponding to the rotation direction of the motor. An electric motor vector control device. The primary current flowing through the motor is divided into an excitation current component parallel to the secondary magnetic flux of the motor and a torque current component orthogonal to the excitation current component, and the excitation current component is calculated from the magnetic flux command value obtained from the speed detection value of the motor. In the motor vector control device for controlling the torque of the motor by matching the excitation current command value, the torque current component being matched with the torque current command value set by the torque current command setter,
The calculation result of proportional integral control of the deviation between the detected speed value of the motor and the forward speed limit value or the reverse speed limit value of the motor is divided by the magnetic flux command value, and the torque current A second torque current command correction value calculation circuit for adding a command value and outputting a torque current command correction value; and correcting the torque current command value with the torque current command correction value corresponding to the rotation direction of the motor. And a torque current command correction circuit for outputting a new torque current command value.

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