JPH09327200A - Controller for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a synchronous motor capable of reducing the size and the cost of a synchronous motor by preventing deterioration in torque control accuracy in an operating state with a high magnetic saturation level and also a decrease in the power factor of a motor. SOLUTION: In a vector control system in which the armature current of a synchronous motor is controlled by separating into a d-axis component and q-axis component, a magnetic flux computing element 8 is provided for calculating d-axis component and q-axis component of the magnetic flux of the armature current as well as d-axis component and q-axis component of the magnetic flux of a motor from the field current; and this magnetic flux computing element 8 is equipped with at least one of the computing elements such as a computing element for correcting a computed value of a q-axis component of a magnetic flux of motor based on the d-axis component of armature current, a computing element for correcting d-axis component of the magnetic flux of motor based on q-axis component of armature current, and a computing element for correcting q-axis component of magnetic flux of a motor based on field current. Even though the magnetic saturation level becomes high, there is no lowering in computing accuracy of the magnetic flux of a motor, so that the accuracy of vector control can be improved and the density of magnetic flux of a synchronous motor can be made higher in design, so that compactness and cost reduction can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for calculating a magnetic flux of an electric motor based on an armature current and a field current and controlling a synchronous electric motor through a power converter, and more particularly to a vector control method based on a current model. The present invention relates to a control device for a synchronous motor using.

[0002]

2. Description of the Related Art A DC electric motor has been mainly used for driving equipment that requires high-accuracy torque control, such as driving a roll of a rolling mill, but in recent years, it has been applied to a power converter such as an inverter. With the expansion of the range, the drive by the synchronous motor of the vector control system has come to be used.

Therefore, first, the vector control of the synchronous motor will be described. Vector control of an electric motor means that the armature current is a torque component that is a two-axis component orthogonal to the rotation axis.
(T-axis component) and excitation component (M-axis component) are coordinate-converted and each is controlled independently. Here, in the vector control device of the synchronous motor, based on the motor magnetic flux estimated value by the magnetic flux calculator. Coordinate conversion.

Then, the calculation method by the magnetic flux calculator at this time is to obtain the magnetic flux from the armature current and the field current (called a current model), and to calculate the magnetic flux from the armature current and the armature voltage. There are two known types of methods (called voltage models) that are used.

For example, in the magnetic flux calculator based on the current model method, the magnetic flux is calculated based on the basic equation of the synchronous motor based on the well-known dq-axis quantities.
The main part of the basic equation at this time can be expressed by the following equation 1 and equation 2.

[0006]

[Equation 1]

[0007]

[Equation 2]

As described above, in the conventional vector control device, the d-axis component of the motor current (here, the d-axis component I _d of the armature current, the d-axis component I _kd of the damper current, and the field current I _f ). The d-axis component of the motor magnetic flux (here, the d-axis component φ _d of the armature interlinkage magnetic flux) is calculated, and the q-axis component of the motor current (here, the q-axis component I _q of the armature current and the damper) is calculated. The q-axis component of the electric motor magnetic flux (here, the q-axis component φ _q of the armature flux linkage) is calculated based only on the q-axis component I _{kq of the} current.

As conventional examples of such a vector control device, those described in JP-A-55-136890, JP-A-4-101691, and JP-A-6-237592 can be cited. it can.

[0010]

It cannot be said that the prior art described above takes into consideration both the miniaturization of the synchronous motor and the high precision of the torque control, and it is an object of the present invention to provide a compact and high precision device. There was a problem that it was difficult.

The reason for this is that in order to reduce the size, it is necessary to increase the magnetic flux density in the magnetic circuit of the synchronous motor to raise the magnetic saturation level. However, in the prior art, the magnetic saturation level of the synchronous motor is raised. Then, the accuracy of the torque control is reduced and the power factor is reduced, so that the magnetic saturation level cannot be increased, and therefore, a small-sized and highly accurate device cannot be provided.

An object of the present invention is to prevent deterioration of torque control accuracy and reduction of electric power factor of an electric motor in an operating state where the magnetic saturation level is high, so that the synchronous electric motor can be miniaturized and its cost can be reduced. Another object is to provide a control device for a synchronous motor.

[0013]

SUMMARY OF THE INVENTION The above object is achieved by taking into consideration the magnetic interaction between an armature d-axis circuit and an armature q-axis circuit, and a field circuit and an armature q-axis circuit of a synchronous motor. This is achieved by configuring the device.

More specifically, the object is to set a coordinate system with a d-axis that coincides with the magnetic pole direction of the synchronous motor and a q-axis that coincides with the direction orthogonal to the d-axis, and set the d-axis of the armature current. Calculate the d-axis magnetic flux component based on the axial component and the field current,
A synchronous motor having a magnetic flux calculating means for calculating a q-axis magnetic flux component based on the q-axis component of the armature current and controlling the power converter for driving the synchronous motor based on the calculation result by the magnetic flux calculating means. In the control device, the calculating means for correcting the calculation result of the d-axis magnetic flux component by the magnetic flux calculating means based on the q-axis component of the armature current and outputting the corrected d-axis magnetic flux component, and the d-axis component of the armature current Based on the magnetic flux calculation means, at least one of the calculation means for correcting the calculation result of the q-axis magnetic flux component and outputting the corrected q-axis magnetic flux component is provided, and at least one of the corrected d-axis magnetic flux component and the corrected q-axis magnetic flux component is used. This is achieved by controlling the power converter.

First, according to the Technical Report of the Institute of Electrical Engineers of Japan (Part I) No. 135, "Saturation of Reactance of Synchronous Machine" (SHO 58), when magnetic saturation occurs in the iron core of such a synchronous motor, d Between axis circuit and q-axis circuit, and between field circuit and q
It is conceptually described that magnetic interactions may each occur between the axial circuits.

Also, Takase and Ueda: “Nonlinear Model Representing Magnetic Saturation of Synchronous Machine” The Institute of Electrical Engineers, Rotating Machinery Study Group Material RM93
At -95 (1993), the q-axis magnetic flux is d
It is shown by theory and experiment that it is affected by the axial current.

And, according to the examination result of the present inventor,
When the magnetic saturation level of the synchronous motor increases, the d-axis and q
It was found that the axis and the magnetic interaction between the field and the q axis cannot be ignored.

As a result, if a magnetic flux calculator that does not consider the magnetic interaction between the d-axis and the q-axis and the magnetic interaction between the field and the q-axis is used, the calculated value of the magnetic flux of the motor is There will be an error. If an error is generated in the magnetic flux calculation in this way, the torque control accuracy is deteriorated and the electric power factor of the electric motor is decreased.

From the above, the reason why the control accuracy of the conventional control device is deteriorated is that the magnetic interaction between the d axis and the q axis and the magnetic interaction between the field and the q axis are not taken into consideration. I understand.

That is, when the magnetic saturation level of the synchronous motor is low, the calculation result of the magnetic flux calculator based on the current model method is in good agreement with the actual magnetic flux state of the motor. You get control,
However, when the magnetic saturation level becomes high, the calculation result and the actual magnetic flux are out of agreement with each other, and as a result, in the conventional technology, when the magnetic saturation level is increased, the accuracy of the vector control is lowered, It is not possible to achieve both miniaturization and high precision.

However, in the present invention, as described above,
For the armature d-axis circuit and the armature q-axis circuit, and for the field circuit and the armature q-axis circuit, the control device is configured in consideration of the magnetic interaction, and therefore, the operating state in which the magnetic saturation level is high. Since the deterioration of the torque control accuracy and the reduction of the electric power factor of the electric motor are prevented, the synchronous motor can be downsized and the cost can be reduced.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION A control device for a synchronous motor according to the present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 shows an embodiment of the present invention.
1 is a speed command generator, 2 is a speed controller, 3 is a magnetic flux command calculator, 4 is a field current command calculator, 5, 6 and 7 are current controllers, 8 is a magnetic flux calculator, and 9 is a magnetic flux phase calculator. Bowls, 10, 1
1, 12 and 13 are coordinate converters, 14 and 15 are power converters, 16 is a field current detector, 17 is an armature current detector,
Reference numeral 18 is a synchronous motor, 19 is a speed position detector, and 33 is a parameter calculator.

Therefore, the main difference of this embodiment from the prior art is that in the illustrated magnetic flux calculator 8 and field current command calculator 4, the armature d-axis circuit, armature q-axis circuit and field magnet are shown. The magnetic interaction between the circuit and the armature q-axis circuit is taken into consideration, and accordingly, the magnetic flux calculator 8 and the field current command calculator are set by the parameter calculator 33. 4 is that the number of calculation coefficients to be given to 4 is large.

In the embodiment of FIG. 1, the current control loop is provided inside the speed control loop. Further, in the vector control of the synchronous motor 18 in the embodiment example of FIG. 1, the MT coordinate axis rotated by the armature reaction angle δ from the dq coordinate which is the magnetic pole axis is used.
Here, the T-axis is selected so that the T-axis magnetic flux φ _T becomes zero.
That is, the composite vector direction of the armature d-axis magnetic flux φ _d and the armature q-axis magnetic flux φ _q is the M axis, and the direction electrically orthogonal to the M axis is the T axis.

At this time, since the armature interlinkage magnetic flux Φ exists only in the M axis (Φ = φ _M ), the magnetic flux is controlled by controlling the armature q axis magnetic flux φ _M , and the magnetic flux Is constant, the torque is proportional to the T-axis component I _T of the armature current. Therefore, the torque is controlled by controlling the T-axis component I _T.

Then, if the M-axis component I _M of the armature current is set to zero, the orthogonal state (Φ⊥I _T ) of the magnetic flux and the current can be obtained. Therefore, the power factor is always controlled to 1 as necessary. be able to. The relationship of the coordinate axes at this time is shown in FIG.

Next, the operation of the embodiment shown in FIG. 1 will be described. First, the required speed command ω * is output from the speed command generator 1. On the other hand, the rotor speed ω and the rotor position θ of the synchronous motor 18 are detected by the speed position detector 19. Then, the rotor speed command ω * and the rotor speed ω are added to the adder 40A with the polarities shown, and the rotor speed deviation, which is the difference between them, is output.

The rotor speed deviation output from the adder 40A is input to the speed controller 2 to output a torque current command value I _T * corresponding to the deviation between the rotor speed ω and the rotor speed command ω *. , By this, the rotor speed ω becomes
Make sure that you get control that matches *.

Then, this torque current command value I _T *
Torque current I output from dq / MT coordinate axis converter
_T is added to the adder 40B with the polarity shown, and the torque current deviation that is the output of the adder 40B is input to the torque current controller 7.

The torque current controller 7, the torque current I _T is so controlled is obtained which matches the torque current command value I _T *, a torque voltage command value V _T corresponding to the torque current deviation
Output *.

On the other hand, the magnetic flux component current command value I _M * and dq /
The magnetic flux component current I _M output from the MT coordinate axis converter 11 is
This polarity is added to the adder 40C with the polarity shown in FIG.
The magnetic flux component current deviation, which is the output of C, is input to the excitation component current controller 6.

The magnetic flux component current command value I _M * is 0 here because the condition for controlling the power factor to 1 is
This is because the M-axis component I _M of the armature current is set to zero as described above. Therefore, when controlling the power factor to a state other than 1, the magnetic flux component current command value I _M * Is 0
You can set it to a value other than.

[0033] Then, this exciting component current controller 6, so that control of the magnetic flux component current I _M becomes equal to the magnetic flux current command value I _M * is obtained, the magnetic flux component voltage command corresponding to the magnetic flux component current deviation The value V _M * is output.

Thus, the magnetic flux component voltage command value V _M * output from the excitation current controller 6 and the torque voltage command value V _T * output from the torque current controller 7 are the MT / dq coordinate axis converter 10 , Where d from the MT coordinate axis
Conversion to the q coordinate axis is performed, and the armature d axis voltage command value V _d
* And the armature q-axis voltage command value V _q * are output and supplied to the dq / three-phase coordinate axis converter 12.

The dq / three-phase coordinate axis converter 12 converts the input armature d-axis voltage command value V _d * and armature q-axis voltage command value V _q * from the dq coordinate axes to the three-phase AC coordinate axes. The three-phase AC voltage command values V _u *, V _v *, V _w * are output and supplied to the power converter 15.

The power converter 15 generates three-phase armature voltages V _u , V _v , V _w proportional to these three-phase AC voltage command values V _u *, V _v *, V _w *, and the synchronous motor 18 is generated. Supply to.
As a result, the phase currents I _u , I _v ,
I _w flows, which is detected by the armature current detector 17.

The three-phase / dq coordinate converter 13 uses the rotor position θ detected by the speed position detector 19 and the three-phase armature phase currents I _u , I _v detected by the armature current detector 17. , I _w are converted to dq coordinates, and the armature d-axis current I _d
And the armature q-axis current I _q is output. On the other hand, the dq / three-phase coordinate converter 12 uses the rotor position θ similarly detected by the speed position detector 19 to perform a conversion operation opposite to that of the three-phase / dq coordinate converter 13.

The magnetic flux calculator 8 is a three-phase / dq coordinate converter 1
3, the armature d-axis current I _d and the armature q-axis current I _q , the field current I _f of the synchronous motor 18 detected by the field current detector 16, and the parameters given from the parameter calculator 33. The calculation coefficient is input, and the armature d-axis magnetic flux φ _d and the armature q-axis magnetic flux φ _q are calculated based on these. Then, the calculated armature d-axis magnetic flux φd and armature q-axis magnetic flux φ
Input q to the magnetic flux phase calculator 9.

The magnetic flux phase calculator 9 calculates the trigonometric function values sin δ and cos δ of the armature reaction angle δ by the following equations 3 and 4.

[0040]

(Equation 3)

[0041]

(Equation 4)

The dq / MT coordinate axis converter 11 calculates the trigonometric function values sin δ, co calculated by the magnetic flux phase calculator 9.
Using sδ, the armature d-axis current I _d and the armature q-axis current I _q , which are the outputs of the three-phase / dq coordinate converter 13, are converted to MT coordinates by the following formula 5, and the torque current IT and the magnetic flux are converted. Current I
Output M.

[0043]

(Equation 5)

The MT / dq coordinate axis converter 10 calculates the trigonometric function values sin δ, co calculated by the magnetic flux phase calculator 9.
The inverse conversion operation of the dq / MT coordinate axis converter 11 is performed using sδ.

The magnetic flux command calculator 3 determines the rotor speed command ω *.
The magnetic flux command value Φ * corresponding to is output to the field current command calculator 4. Therefore, the field current command calculator 4
The magnetic flux command value Φ *, the trigonometric function values sin δ, cos δ calculated by the magnetic flux phase calculator 9, and the speed controller 2
The field current command value I _f * is calculated by inputting the torque current command value I _T *, which is the output of, and each calculation coefficient given from the parameter calculator 33.

On the other hand, the field current detector 16 is the synchronous motor 1
The field current I _f of 8 is detected. The field current I _f detected by the field current detector 16 and the field current command value I _f * calculated by the field current command calculator 4 have the polarities shown in the adder 40D. In addition, the field current deviation is output and input to the field current controller 5.

[0047] Therefore, the field as current I _f is the control that matches the field current command value I _f * obtained from the field current controller 5, the field voltage command value corresponding to the field current deviation V _f
* Is output and input to the power converter 14. As a result, the power converter 14 generates a field voltage V _f proportional to the field voltage command value V _f * and supplies it to the field of the synchronous motor 18 so that excitation can be obtained.

Next, the configurations of the magnetic flux calculator 8 and the field current command calculator 4 will be described in detail. The calculation coefficients set in these blocks are not constant values, but the magnetic saturation of the synchronous motor 18 is determined. It changes according to the condition. And
Each calculation coefficient at this time can be regarded as a function of the armature d-axis current I _d , the armature q-axis current I _q , and the field current I _f .

Therefore, in the embodiment shown in FIG. 1, a parameter calculator 33 is provided, and the armature d-axis current I _d and the armature q-axis current I _q , which are the outputs of the three-phase / dq coordinate converter 13, and the fields thereof. Synchronous motor 1 detected by magnetic current detector 16
8 as an input the field current I _f of, to determine the respective operation coefficients of the flux calculator 8 and the field current command calculator 4 receives them to the magnetic flux computing unit 8 and the field current command calculator 4, set It is done.

Next, FIG. 2 shows an example of the magnetic flux calculator 8, which is a magnetic interaction between the armature d axis and the armature q axis, and a magnetic interaction between the field and the armature q axis. In the embodiment in consideration of the above, in the figure, the arithmetic system numerical values M _d and M _q in each block of 20 and 21 represent the mutual inductance of the synchronous motor 18.

Next, the arithmetic system value l _a of the block 22 is the armature leakage inductance of the synchronous motor 18, and the arithmetic system values T _dk , T _qk , T _dkσ and T _qkσ of the blocks 23 and 24 are the _same.
Represents the damper circuit constant of the synchronous motor 18 in the block 25,
The calculation system value L _dq of 26 represents the d-axis q-axis mutual inductance of the synchronous motor 18, and the calculation system value L _fq of the block 27 represents the field q-axis mutual inductance of the synchronous motor 18.

Here, L _dq of the blocks 25 and 26 and L _{fq of} the block 27 are the armature d-axis circuit and the armature q-axis circuit,
And the calculation coefficient in consideration of the magnetic interaction between the field circuit and the armature q-axis circuit. 40E, 40F, 40G,
40H represents an adder, respectively.

Next, the process of deriving the transfer function by the magnetic flux calculator 8 shown in FIG. 2 will be described. In the synchronous motor, the magnetic flux in the iron core changes variously depending on the load and other conditions. At this time, if the magnetic flux density in the iron core is high, local magnetic saturation occurs depending on the load condition. In this case, the magnetic saturation site in the iron core is asymmetrical with respect to the d-axis, so that a magnetic interaction occurs between the d-axis circuit and the q-axis circuit, and the field circuit and the q-axis circuit.

Therefore, as described above, in the prior art, since the magnetic flux calculator does not consider these interactions, an error occurs in the magnetic flux calculation at the time of magnetic saturation. In the magnetic flux calculator 8 according to the embodiment, these magnetic interactions are taken into consideration.

By the way, in these magnetic interactions,
For example, between the armature d-axis circuit and the armature q-axis circuit, between the armature field circuit and the armature q-axis circuit, between the damper d-axis circuit and the damper q-axis circuit, between the armature d-axis circuit and the damper q-axis circuit, Armature q
Between axis circuit and damper d axis circuit, or between field circuit and damper q
There are various magnetic interactions such as between shaft circuits.

Therefore, considering all of these interactions, the armature d-axis magnetic flux φ _d is expressed by the equation 6, and the armature q-axis magnetic flux φ _q is expressed by the equation 7.

[0057]

(Equation 6)

[0058]

(Equation 7)

Regarding the damper d-axis magnetic flux φkd and the damper q-axis magnetic flux φkq, the following equations 8 to 11 are established.

[0060]

(Equation 8)

[0061]

[Equation 9]

[0062]

(Equation 10)

[0063]

[Equation 11]

However, as is clear from these equations, if the magnetic flux calculator 8 is constructed in consideration of all the magnetic interactions described above, the magnetic flux calculator 8 has an extremely complicated structure and is not realized. It will be difficult. Therefore, in this embodiment, the magnetic flux calculator 8 can be simplified within a range where there is practically no problem.

First, considering the damper current of the synchronous motor, since the damper current of the synchronous motor is small during steady operation, the influence of the damper circuit on the magnetic flux of the motor can be ignored, while the damper current is large during transient operation. Since the current flows, the influence of the damper circuit on the magnetic flux of the motor appears significantly.

Therefore, in this embodiment, as a precondition, emphasis is placed on increasing the control accuracy of torque, speed, power factor, etc., particularly during steady operation of the synchronous motor.
As a result, regarding the damper circuit, the magnetic interaction between the d-axis circuit and the q-axis circuit, and the magnetic field circuit and the q-axis circuit is ignored, which simplifies the magnetic flux calculator sufficiently. You can get it.

That is, when the magnetic flux calculator 8 is constructed, d
Among the magnetic interactions of the axis circuit and the q-axis circuit, and the field circuit and the q-axis circuit, the damper d-axis circuit and the damper q-axis circuit, the armature d-axis circuit and the damper q-axis circuit, and the armature q-axis circuit Ignoring the magnetic interaction between the damper d-axis circuit and the field circuit and the damper q-axis circuit, the magnetic field of the armature d-axis circuit and the armature q-axis circuit, the armature field circuit and the armature q-axis circuit It was decided to consider the dynamic interaction, and as a result,
Significant simplification has been obtained.

In this simplified magnetic flux calculator, the armature d-axis magnetic flux φ _d and the armature q-axis magnetic flux φ _q are replaced by the equations 6 and 7, and the simplified equation 12 is used. And is expressed by the equation (13).

[0069]

(Equation 12)

[0070]

(Equation 13)

Further, the damper d-axis magnetic flux φ _kd and the damper q-axis magnetic flux φ _k q are expressed by the following Equation 14 obtained by simplifying Equations 8 and 9:
It is expressed by the equation and the equation (15).

[0072]

[Equation 14]

[0073]

(Equation 15)

Further, according to the equations (14) and (15) and the equations (10) and (11), the damper d-axis current I _kd and
The transfer function of the damper q-axis current I _kq is the following Expression 16 and Expression 17
It will be represented by a formula.

[0075]

(Equation 16)

[0076]

[Equation 17]

Therefore, by substituting the equations 16 and 17 into the equations 12 and 13, the armature d-axis current I _d and the armature q
The armature d-axis magnetic flux φ _{d is determined} by the axis current I _q and the field current I _f .
And the transfer function expressing the armature q-axis magnetic flux φ _q is
Equation 8 and equation 19 are given.

[0078]

(Equation 18)

[0079]

[Equation 19]

When the transfer functions of the equations (18) and (19) are expressed as a block diagram, the configuration of the magnetic flux calculator 8 shown in FIG. 2 is obtained. That is, the magnetic flux calculator 8 calculates the armature d-axis current I _d and the armature q-axis current I _q , which are the outputs of the three-phase / dq coordinate converter 13, based on the equations (18) and (19). is the output field current I _f of the current detector 16, it as an input the values of the calculation coefficients are output parameters calculator 33, estimates the armature d-axis magnetic flux phi _d armature q-axis magnetic flux phi _q Work.

By the way, even when the magnetic interaction is neglected and simplified as described above, the magnetic flux calculation error occurs only when the synchronous motor 18 is magnetically saturated and is in a transient operation state. .

Moreover, even in this case, if the magnetic interaction between the d-axis circuit and the q-axis circuit on the armature side and the field circuit and the q-axis circuit on the armature side is taken into consideration, the control of the conventional synchronous motor is controlled. It is possible to calculate the magnetic flux with higher accuracy than the device.

Therefore, according to this embodiment, more accurate magnetic flux calculation can be obtained than in the prior art in both operating states of steady operation and transient operation, so that the magnetic flux density of the synchronous motor is increased. As a result, a larger output can be obtained with a synchronous motor of the same size.

Further, if the magnetic flux calculation accuracy of the magnetic flux calculator 8 is improved in this way, the calculation accuracy of the trigonometric function values sin δ and cos δ output from the magnetic flux phase calculator 9 is also improved, and further the MT / dq coordinates are calculated. The calculation accuracy of the converter 10, the dq / MT coordinate converter 11, and the field current command calculator 4 is also improved.

From the above results, the following can be understood. That is, first, in the conventional magnetic flux calculator, if the q-axis component of the electric motor current does not change, the q-axis component of the electric motor magnetic flux does not change even if the d-axis component of the electric motor current changes. Similarly,
If the d-axis component of the electric motor current does not change, the d-axis component of the electric motor magnetic flux does not change even if the q-axis component of the electric motor current changes.

On the other hand, in the magnetic flux calculator 8 of the present invention, even if the q-axis component of the electric motor current does not change, only the d-axis component of the electric motor current changes and the q-axis component of the electric motor magnetic flux changes. Also, similarly, even if the q-axis component of the electric motor current does not change, the q-axis component of the electric motor magnetic flux changes only by changing the d-axis component of the electric motor current.

If a high degree of control accuracy is required even in the transient operation as in the steady operation, as described above, the damper d-axis circuit and the damper q-axis circuit, and the field circuit and the damper q-axis circuit. A control system may be configured for each of the armature d-axis circuit and the damper q-axis circuit, and the armature q-axis circuit and the damper d-axis circuit in consideration of magnetic interaction. In this case, the magnetic flux calculator 8 is configured by obtaining the transfer function using the equations 6 to 9 instead of the equations 12 to 15.

Next, the structure and operation of the field current command calculator 4 will be described in detail. FIG. 3 is a block diagram of a transfer function of the field current command calculator 4 in consideration of the magnetic interaction between the d-axis circuit and the q-axis circuit, and the field circuit and the q-axis circuit, as an embodiment of the present invention. Then, in FIG. 3, 30 is
A block having a difference L _q −L _d between the q-axis self-inductance L _q and the d-axis self-inductance L _d of the synchronous motor 18 as a calculation coefficient value, 31 represents a multiplier, and 32 represents a divider.

Regarding the other elements in FIG. 3, the same elements as those in FIG. 2 are denoted by the same reference numerals. Here, the calculation coefficient value L _q −L _d of the block 30 is M _q −M _d
be equivalent to.

Next, the process of deriving the transfer function of the field current command calculator 4 shown in FIG. 2 will be described. First, as in the case where the transfer function of the magnetic flux calculator 8 is obtained, the armature d
The transfer function of the field current command calculator 4 is derived in consideration of the magnetic interaction between the shaft circuit and the armature q-axis circuit, and between the armature field circuit and the armature q-axis circuit. Note that the influence of the damper will be ignored in this derivation.

At this time, the armature d-axis magnetic flux φ _d is expressed by the following formula 20, and the armature q-axis magnetic flux φ _q is expressed by the formula 21.

[0092]

(Equation 20)

[0093]

(Equation 21)

Therefore, using these equations (20) and (21) and equations (3) to (5), the field current command value _If * is expressed by the following equation (22).

[0095]

(Equation 22)

When the equation (22) is expressed as a block diagram, the field current command calculator 4 shown in FIG. 3 is obtained. In the embodiment of FIG. 3, the magnetic flux command value Φ * calculated by the magnetic flux command calculator 3 and the torque current I _T calculated by the speed controller 2 are used.
*, Trigonometric function values Sinδ, C calculated by the magnetic flux phase calculator 9
The field current command value _If * is calculated using the relationship of the equation (22) by inputting osδ and the value of each calculation coefficient which is the output of the parameter calculator 33.

In this embodiment, since the magnetic interaction between the armature d axis and the armature q axis, and the magnetic field and the armature q axis is taken into consideration, the arithmetic unit of FIG. The parameters L _dq and L _fq appear _therein .

Next, the configuration and operation of the parameter calculator 33 will be described in detail. When the operating state of the synchronous motor 18 changes and the magnetic saturation state changes, the synchronous motor 18
The inductance of changes. Therefore, the magnetic flux calculator 8
And each calculation coefficient M _d set in the field current command calculator 4,
_{M q, L dq, L fq} , each coefficient value, such as l _a does not become a constant value, at least the armature current I _d, I _q, and the field current I _f
Varies as a function of

However, among these operation coefficients, those with little numerical change may be regarded as constant values. In this case, they are set as constants and it is difficult to consider them as constant values. Only with respect to the above, the parameter calculator 33 determines the coefficient value according to the values of the armature currents I _d , I _q and the field current _If .

FIG. 5 shows an embodiment in which a parameter table is used as an example of the parameter calculator 33.
In this case, the parameter table means the armature current I _d ,
It is a table in which the calculation coefficient values according to the values of I _q and the field current _If are stored in advance as data.

The data of this parameter table is created, for example, by performing a synchronous machine internal magnetic field analysis by the finite element method. By using the magnetic field analysis by the finite element method, the calculation coefficients such as M _d , M _q , L _dq , L _fq , and l _a can be calculated as _follows .
It can be represented by the three variables I _d , I _q , and I _f , but
As it is, the parameter table becomes a three-dimensional table, and the amount of data to be prepared becomes considerably large.

Therefore, it is advisable to examine the change characteristic of each operation coefficient to reduce the amount of data. That is, first, if there is one of the calculation coefficients that has a small value variation and can be always regarded as a constant value, a table for the calculation coefficient is not prepared. In addition, for example, when M _d can be regarded as a function having only I _d, or when M _q can be regarded as a function having only I _q , these M _d and M _q are respectively I _d and I _q.
It is represented as a one-dimensional parameter table having as a variable.

In addition to this, the parameter calculator 33 shown in FIG. 5 reduces the data amount as follows. Normally, in a synchronous motor, the values of L _dq and L _fq become 0 when the magnetic flux is not saturated, and when magnetic saturation appears, the absolute values thereof increase according to the degree of saturation. On the other hand, the absolute values of M _d and M _q become smaller as the magnetic saturation increases.

The value of l _a also changes depending on the degree of magnetic saturation, but compared with the changes appearing in M _d and M _q , la
The change range of is often small. Based on the above consideration,
The parameter calculator 33 of FIG. 5 prepares a parameter table for four calculation coefficients of M _d , M _q , L _dq , and L _fq .

In the parameter calculator 33 of FIG. 5, l
_{Although a} is regarded as _a constant value and a parameter table for l _a is not provided, however, this may increase the magnetic flux calculation error depending on the characteristics of the synchronous motor. Then, in this case, the parameter table of l _a may be added to the parameter calculator 33.

In the synchronous motor, since the armature d-axis winding axis and the field winding axis are always on the same axis, the magnetic flux distribution generated by the armature d-axis current is similar to that generated by the field current. Often becomes.

Therefore, in the embodiment of FIG. 5, the d-axis component I _d of the armature current and the field current I _f are collectively set to approximately 1
By setting the number of variables as I _d + I _f , one variable in the parameter table is reduced. That is, each calculation coefficient as a two-dimensional parameter table using the two variables of the sum I _d + I _f, and the armature current q-axis component I _q and d-axis component I _d and the field current I _f of the armature current Is expressed, and the amount of data in the parameter table is greatly reduced.

When there is a calculation coefficient that causes a large error due to such an approximation, only the calculation coefficient of a three-dimensional variable which is changed by three variables I _d , I _q , and I _{f is} added. A parameter table should be prepared.

The parameter calculator 33 shown in FIG. 5 is provided with respective parameter tables of calculation coefficients M _d , M _q , L _dq , and L _fq , and according to the input values of I _d , I _q , and I _f. The parameter table is searched and each calculation coefficient M _d , M _q , L _dq , L _fq
Is configured to be extracted.

Here, the data of each parameter table is given discretely. Therefore, the input I _d ,
The calculation coefficient values corresponding to the values of I _q and I _f are obtained by interpolating between discretely given data. Then, each calculation coefficient value thus obtained becomes an output of the parameter calculator 33, and is used as a calculation coefficient of the magnetic flux calculator 8 and the field current command calculator 4.

Although the parameter calculator 33 using the parameter table is used in the above-described embodiment, a function showing the relation between the current and the calculation coefficient, or a neural network for inputting the current and outputting the parameters. May be used, and a parameter calculator configured to perform parameter calculation may be used.

Therefore, according to the above-described embodiment, d
Since the control system takes into consideration the magnetic interaction between the axis circuit and the q-axis circuit, and the field circuit and the q-axis circuit, the control can be performed with high accuracy even in the magnetic saturation region. As a result, the synchronous motor Miniaturization and cost reduction can be sufficiently obtained.

This will be described in more detail. When the synchronous motor is operated under load, generally, the stronger the magnetic saturation, the greater the magnetic interaction between the d-axis circuit and the q-axis circuit and the field circuit and the q-axis circuit. In the control device according to the present invention, since these magnetic interactions are taken into consideration, the magnetic flux density in the magnetic circuit of the synchronous motor becomes high,
Even if the magnetic saturation becomes strong, it is possible to eliminate the possibility that the accuracy of vector control is lowered.

Therefore, the allowable magnetic flux density in the iron core of the synchronous motor can be made large, and as a result, the volume of the iron core for passing a desired magnetic flux can be reduced, the synchronous motor can be downsized, and the cost can be reduced. It can be transformed.

In the above embodiment, the d-axis circuit and q
The control circuit that represents the magnetic interaction between the axis circuit and the field circuit and the q-axis circuit is provided only in the magnetic flux calculator and the field current command calculator, but should be provided in other control parts in the controller. You can

Further, in the above embodiment, the magnetic flux calculator is constructed based on the basic equation of the synchronous motor, but a function expressing the relationship between the current and the magnetic flux, or a neural network for inputting the current and outputting the magnetic flux. May be used to equivalently consider the magnetic interaction between the d-axis circuit and the q-axis circuit, and the field circuit and the q-axis circuit.

[0117]

According to the present invention, the armature d-axis and the armature q
Since the control device is configured in consideration of the magnetic interaction between the axis and the field and the armature q-axis, the d-axis component and the q-axis component of the armature interlinkage magnetic flux when the magnetic flux density is high and magnetic saturation occurs. And the field current command calculation accuracy are improved, and the vector control accuracy of the synchronous motor is improved.

As a result, it is possible to sufficiently reduce the size and cost of the synchronous motor to be controlled.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing an example of a magnetic flux calculator according to the embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a field current command calculator according to the embodiment of the present invention.

[Fig. 4] Rotor coordinates (dq axes) and magnetic flux coordinates of the synchronous motor
It is explanatory drawing which shows the relationship of (MT axis).

FIG. 5 is a block diagram showing an example of a parameter calculator according to the embodiment of the present invention.

[Explanation of symbols]

 1 Speed command generator 4 Field current command calculator 8 Magnetic flux calculator by current model 9 Magnetic flux phase calculator 16 Field current detector 17 Armature current detector 18 Synchronous motor (SM) 19 Speed position detector 33 Parameter calculation vessel

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Akita 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Electric Power & Electrics Development Division (72) Inventor Toshiaki Okuyama Omi-ka, Hitachi-shi, Ibaraki 7-2-1 Machi Incorporated Hitachi, Ltd. Electric Power & Electric Development Headquarters (72) Inventor Yoshitaka Yoshinari 3-1-1 1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Factory

Claims (2)

[Claims] 1. A coordinate system comprising a d-axis that coincides with the magnetic pole direction of a synchronous motor and a q-axis that coincides with a direction orthogonal to the d-axis is set, and based on the d-axis component of the armature current and the field current. A d-axis magnetic flux component is calculated, and a q-axis magnetic flux component is calculated based on the q-axis component of the armature current, and a magnetic flux calculation means is provided. Based on the calculation result by the magnetic flux calculation means, power conversion for driving the synchronous motor is provided. In a control device for a synchronous motor of a system for controlling a device, a calculation means for correcting a calculation result of a d-axis magnetic flux component by the magnetic flux calculation means on the basis of a q-axis component of an armature current, and outputting a corrected d-axis magnetic flux component. , At least one of calculating means for correcting the calculation result of the q-axis magnetic flux component by the magnetic flux calculating means based on the d-axis component of the armature current and outputting the corrected q-axis magnetic flux component, Corrected q-axis magnetic flux composition A control device for a synchronous motor, wherein the power conversion device is controlled by at least one of the two. 2. The invention according to claim 1, wherein the field magnetic flux command value of the synchronous motor is calculated based on at least one of the corrected d-axis magnetic flux component and the corrected q-axis magnetic flux component. A control device for a synchronous motor, characterized in that