JPH09294400A - Induction motor drive equipment by vector control - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge control limit and stabilize control by calculating exciting inductance from parallel sum of first and second exciting inductance by a function element and then calculating secondary magnetic flux based on the multiplication of an exciting current coordinatet-ransformed by this inductance and a coordinate converter. SOLUTION: An exciting inductance is calculated from the parallel sum of the first exciting inductance based on the function corresponding to the magnetic saturation phenomenon of the secondary magnetic flux of an induyxction motor 2 by means of function element 5a and the second exciting inductance based on a ratio to the square root of a torque current coordinate- converted by a coordinate converter 4 and the function having a weight in a weal magnetic flux region of its secondary magnetic flux. Then, the secondary magnetic flux is calculated from the multiplication of an exciting current coordinate-converted by the exciting inductance and the coordinate converter 4. By doing this, the secondary magnetic flux presumed by the function element 5a van be coincided with the secondary magnetic flux of actual induction motor 2, by which the control limit can be extended and control stability can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor drive device by vector control.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional vector-controlled induction motor driving device. In the figure, 1 is an electric power based on an input torque command value T _e and a secondary magnetic flux command φ _d ^*. And a control device 1 for supplying the
It is an induction motor driven by. 3u and 3w are current detectors for detecting u-phase and w-phase currents i _u and i _w supplied from the control device 1 to the induction motor 2, and 4 is a horizontal axis current of the phase currents i _u and i _w. It is a coordinate converter that performs coordinate conversion into a torque current i _q and an exciting current i _d that is a direct current. Reference numeral 5 is a function unit for calculating the secondary magnetic flux φ _d from the exciting inductance M obtained from the exciting inductance characteristic and the exciting current i _d .

Reference numeral 6 is a divider for dividing the input torque command T _e by the secondary magnetic flux φ _d to calculate a torque current command value i _q ^* , and 7 is a torque current i from the torque current command value i _q ^*.
_A first subtractor 8 for subtracting _q is a horizontal axis current regulator for calculating a horizontal axis current control signal from the subtracted torque current command value. Further, 9 is the input secondary magnetic flux command value φ _d ^*
The second subtractor 10 for subtracting the secondary magnetic flux φ _d from is a magnetic flux adjuster for calculating the exciting current command value i _d ^* from the subtracted secondary magnetic flux command value. 11 is the exciting current command value i
_A third subtracter that subtracts the exciting current i _d from _d ^* , and 12 is a direct-axis current regulator that calculates a direct-axis current control signal from the subtracted exciting current command value. Reference numeral 13 denotes a power supply device such as an inverter that supplies power to the induction motor 2 based on the horizontal axis current control signal and the direct axis current control signal.

FIG. 5 is a characteristic diagram showing an exciting inductance characteristic used in the function unit 5, in which the horizontal axis represents the secondary magnetic flux φ _d and the vertical axis represents the exciting inductance M. FIG. 6 is a circuit diagram showing an equivalent circuit of the induction motor 2 to be controlled by these conventional induction motor drive devices. In the figure, R ₁ is a primary resistance, L ₁ is a primary leakage reactance, and M is an exciting inductance. , R ₂ / s is the quotient of secondary resistance and slip. The exciting inductance characteristic in FIG. 5 represents the exciting inductance M in the equivalent circuit of FIG. 6 as a variation of the secondary magnetic flux φ _{d due to} the magnetic saturation phenomenon.

Next, the operation will be described. In the control device 1 of the induction motor by vector control, first, the currents i _u and i _w detected by the current detectors 3 _u and 3 _w are coordinate-converted into the torque current i _q and the exciting current i _d by the coordinate converter 4, and the function The exciting inductance M and the exciting current i obtained from the exciting inductance characteristic shown in FIG.
_The secondary magnetic flux φ _d is calculated from _d . Further, the torque command T _e is divided by the secondary magnetic flux φ _d by the divider 6 to calculate the torque current command value i _q ^* , and the first subtractor 7 calculates the torque current command value i _q ^* from the torque current i _q ^*. And subtract
The horizontal axis current regulator 8 calculates the horizontal axis current control signal from the subtracted torque current command value.

The second subtractor 9 subtracts the secondary magnetic flux φ _d from the secondary magnetic flux command value φ _d ^* , and the magnetic flux adjuster 10 calculates the exciting current command value i from the subtracted secondary magnetic flux command value. Calculate _d ^* . Further, the third subtracter 11 subtracts the exciting current i _d from the exciting current command value i _d ^* , and the direct axis current adjuster 12 calculates a direct axis current control signal from the subtracted exciting current command value. . Further, the power supply 13
At, the electric power is supplied to the induction motor 2 based on the horizontal axis current control signal and the direct axis current control signal.

Generally, in the induction motor 2, the secondary magnetic flux φ _d
Since the torque T is generated by the product of and the torque current i _q ,
The secondary magnetic flux φ _d and the torque current i _q must be controlled accurately. Based on the principle of the control device 1, the torque command command value i _q ^* is calculated by dividing the torque command T _e by the secondary magnetic flux φ _d in the divider 6, so that the accuracy of the secondary magnetic flux φ _d is high. It can be seen that this is important for accurate torque control.

Generally, the secondary magnetic flux φ _d is generated by supplying the exciting current i _d to the induction motor 2, but it can be estimated from the product of the exciting current i _d and the exciting inductance M by calculation. . Also in the control device 1, the magnetic flux inside the induction motor 2 is not directly detected, but the secondary magnetic flux φ _d is estimated from the exciting inductance M and the exciting current i _d obtained from the exciting inductance characteristic in the function unit 5. . Therefore, its estimated secondary magnetic flux φ
Matching _d with the actual secondary magnetic flux φ _d of the induction motor 2 is important for accurate torque control.

By the way, the value of the exciting inductance M of the induction motor 2 decreases as the secondary magnetic flux φ _d increases due to the magnetic saturation phenomenon as shown in the characteristic diagram of FIG. Therefore, the characteristic shown in FIG. 5 is used as the excitation characteristic used in the magnetic flux calculation so that the change in the excitation inductance M due to the magnetic saturation phenomenon is taken into consideration. As a result, the secondary magnetic flux φ _d estimated by the magnetic flux calculation matches the actual secondary magnetic flux of the induction motor 2, and accurate torque control is realized. Since the magnetic saturation phenomenon is a phenomenon that occurs when the magnetic flux density of the iron core increases, the exciting inductance M does not change with changes in the torque current i _q under normal operating conditions, and the secondary magnetic flux φ _d changes. It was thought that in a small region, the magnetic saturation phenomenon did not cause a decrease in the exciting inductance M.

On the other hand, the induction motor 2 having a simple structure and having high maintainability and reliability is expanding its application, and the secondary magnetic flux φ
There is a case in which _d is weakened and a remarkably large torque current i _q is used. In such operation range, excitation inductance M that has been considered invariant to changes in the conventional torque current i _q is may vary depending on the magnitude of the torque current i _q. In such a case, the exciting inductance characteristic as shown in FIG. 5 cannot express the characteristic of the exciting inductance M. As a result, the secondary magnetic flux φ _d estimated by the magnetic flux calculation of the control device 1 does not match the actual secondary magnetic flux of the induction motor 2 to be controlled, which deteriorates the accuracy of torque control and the control stability. Will worsen. Such a situation has been one of the factors that determine the control limit in the conventional vector control.

[0011]

Since the conventional induction motor drive apparatus by vector control is constructed as described above, the application of the induction motor 2 is such that the exciting inductance M does not change with respect to the change of the torque current i _q. However, when there is an operating region in which the exciting inductance M changes with the torque current i _q , there is a problem that the control stability decreases. For example, in an induction motor, the weak magnetic flux range is about 1: 3,
That is, in the characteristic diagram of FIG. 5, the secondary magnetic flux φ _d is 100 /
Even when 3 = 33% is the control limit of the conventional vector control, there is a demand that the weakening magnetic flux range can be extended to about 1: 6 (17%) to enable the construction of a wide range of devices. In this case, there was a problem such as a decrease in control stability.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain an induction motor drive device by vector control which can expand the control limit and further improve the control stability. .

[0013]

According to another aspect of the present invention, there is provided a vector control induction motor drive apparatus, wherein a function unit performs a first excitation based on a function corresponding to a magnetic saturation phenomenon of a secondary magnetic flux of the induction motor. The exciting inductance is determined based on the inductance and the parallel sum of the second exciting inductance based on the ratio of the function of giving a weight to the weakening magnetic flux region of the secondary magnetic flux and the square root of the torque current coordinate-transformed by the coordinate transformer. The secondary magnetic flux is calculated based on the multiplication of the calculated excitation inductance and the excitation current coordinate-converted by the coordinate converter.

According to a second aspect of the present invention, there is provided a vector-controlled induction motor driving apparatus, wherein a function unit uses a slip angular frequency of the induction motor instead of the square root of the torque current.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1. 1 is a block diagram showing an induction motor drive device by vector control according to Embodiment 1 of the present invention. In the figure, 1 is based on an input torque command T _e and secondary magnetic flux command value φ _d ^*. A control device 2 for supplying electric power is an induction motor driven by the control device 1. 3u and 3w are current detectors that detect u-phase and w-phase currents i _u and i _w supplied from the control device 1 to the induction motor 2, and 4 is a torque that is the horizontal axis current of these currents i _u and i _w. It is a coordinate converter that performs coordinate conversion into a current i _q and an exciting current i _d that is a direct-axis current. Reference numeral 5a denotes a first exciting inductance M based on a function corresponding to the magnetic saturation phenomenon of the secondary magnetic flux φ _d of the induction motor 1, a function in which a weakening magnetic flux region of the secondary magnetic flux φ _d is weighted, and a torque current i. calculating a magnetizing inductance M _t based on the parallel sum of the second excitation inductance M _e based on the ratio of the square root of _q, the secondary magnetic flux phi _d based on the multiplication of its excitation inductance M _t between the excitation current i _d Is a function unit for calculating.

Reference numeral 6 is a divider for dividing the input torque command T _e by the secondary magnetic flux φ _d to calculate a torque current command value i _q ^* , and 7 is a torque current i from the torque current command value i _q ^*.
_A first subtractor 8 for subtracting _q is a horizontal axis current regulator for calculating a horizontal axis current control signal from the subtracted torque current command value. Further, 9 is the input secondary magnetic flux command value φ _d ^*
The second subtractor 10 for subtracting the secondary magnetic flux φ _d from is a magnetic flux adjuster for calculating the exciting current command value i _d ^* from the subtracted secondary magnetic flux command value. 11 is the exciting current command value i
_A third subtracter that subtracts the exciting current i _d from _d ^* , and 12 is a direct-axis current regulator that calculates a direct-axis current control signal from the subtracted exciting current command value. Reference numeral 13 denotes a power supply device such as an inverter that supplies power to the induction motor 2 based on the horizontal axis current control signal and the direct axis current control signal.

FIG. 2 is a characteristic diagram showing an exciting inductance characteristic used in the function unit 5a, in which the horizontal axis represents the secondary magnetic flux φ _d and the vertical axis represents the exciting inductance M _t . FIG. 3 is a circuit diagram showing an equivalent circuit of the induction motor 2 to be controlled by the induction motor driving device according to the first embodiment of the present invention, in which R ₁ is a primary resistance,
L ₁ is the primary leakage reactance, M is the first exciting inductance, _Me is the second exciting inductance, and R ₂ / s is the quotient of the secondary resistance and the slip. The exciting inductance characteristic in FIG. 2 represents the parallel sum of the first exciting inductance M and the second exciting inductance M _e in the equivalent circuit of FIG. 3 as the exciting inductance M _t , and the first exciting inductance M _t Fluctuates due to the magnetic saturation phenomenon of the secondary magnetic flux φ _d , and the second exciting inductance M
_e fluctuates based on the ratio of the function of weighting the weakening magnetic flux region of the secondary magnetic flux φ _d to the square root of the torque current i _q .

Next, the operation will be described. In the control device 1 of the induction motor by vector control, first, the currents i _u and i _w detected by the current detectors 3 _u and 3 _w are coordinate-converted into the torque current i _q and the exciting current i _d by the coordinate converter 4, and the function In the device 5a, the secondary magnetic flux φ _d is calculated from the exciting inductance M _t and the exciting current i _d obtained from the exciting inductance characteristic shown in FIG. Further, the torque command T _e is divided by the secondary magnetic flux φ _d by the divider 6 to calculate the torque current command value i _q ^* , and the first subtractor 7 calculates the torque current command value i _q ^* from the torque current i _q ^*. And the horizontal axis current regulator 8 calculates a horizontal axis current control signal from the subtracted torque current command value.

The second subtractor 9 subtracts the secondary magnetic flux φ _d from the secondary magnetic flux command value φ _d ^* , and the magnetic flux adjuster 10 uses the subtracted secondary magnetic flux command value to generate the exciting current command value i. Calculate _d ^* . Further, the third subtracter 11 subtracts the exciting current i _d from the exciting current command value i _d ^* , and the direct axis current adjuster 12 calculates a direct axis current control signal from the subtracted exciting current command value. . Further, the power supply 13 supplies power to the induction motor 2 based on the horizontal axis current control signal and the direct axis current control signal.

Generally, in the induction motor 2, the secondary magnetic flux φ _d
Since the torque T is generated by the product of and the torque current i _q ,
The secondary magnetic flux φ _d and the torque current i _q must be controlled accurately. Based on the principle of the control device 1, the torque command command value i _q ^* is calculated by dividing the torque command T _e by the secondary magnetic flux φ _d in the divider 6, so that the accuracy of the secondary magnetic flux φ _d is high. It can be seen that this is important for accurate torque control.

Generally, the secondary magnetic flux φ _d is generated by supplying the exciting current i _d to the induction motor 2, but the exciting current i _d and the exciting inductance M _t are calculated by calculation.
It can be estimated from the product of Also in the control device 1, the magnetic flux inside the induction motor 2 is not directly detected, but the secondary magnetic flux φ _d is estimated from the exciting inductance M _t and the exciting current i _d obtained from the exciting inductance characteristic in the function unit 5 a. To do. Therefore, to match its estimated secondary flux phi actual secondary flux of the induction motor 2 _d phi _d is important for accurate torque control.

Generally, in a squirrel-cage induction motor, an eddy current does not flow because the main magnetic circuit of the rotor through which the secondary magnetic flux φ _d of the slip frequency ωs passes is composed of laminated iron cores.
However, since the secondary conductor is short-circuited to the laminated iron core in the region close to the outer diameter of the rotor, when the secondary magnetic flux φ _d of the slip frequency ωs passes, the action of canceling out a part of the secondary magnetic flux φ _d An eddy current that has is induced. That is, the action of the eddy current that cancels a part of the secondary magnetic flux φ _d appears in the magnetic flux passing through a part of the region close to the outer diameter of the rotor. Also, when the total amount of the secondary magnetic flux φ _d decreases under the operating condition where the magnetic flux of the induction motor is weakened,
The magnetic flux is unevenly distributed in a region close to the outer diameter of the rotor. Secondary magnetic flux φ
_{If d} is unevenly distributed in a region that is easily affected by the action of eddy current, the action of canceling a part of the secondary magnetic flux φ _d due to the eddy current becomes significant. When the slip frequency ωs rises, the action of the eddy current becomes remarkable, and the slip frequency ωs of the induction motor is proportional to the ratio between the torque current i _q and the secondary magnetic flux φ _d . Therefore, the action of the eddy current was measured using a test machine, can slow down the second excitation inductance M _e in proportion to the square root of the torque current i _q is the secondary magnetic flux phi _d is under certain conditions It was confirmed that, under the condition that the torque current i _q is constant, the second exciting inductance _Me is lowered when the secondary magnetic flux φ _d is weakened.

Therefore, in this embodiment, the control device 1
Of the secondary magnetic flux φ canceled by the eddy current by expanding the characteristic of the exciting inductance M _t of the induction motor 2 used in the magnetic flux calculation of
_Allow compensation for _d . Excitation inductance M _t of the induction motor 2, in addition to the characteristic that the secondary magnetic flux phi _d is the value greatly decreases because the magnetic saturation phenomenon as indicated by the characteristic of FIG. 2, the torque current i _q as described above It shows a characteristic that the value decreases even in a region where the secondary magnetic flux φ _d is small when the value increases. Therefore, even in such a case, the function unit 5a of the control device 1 is configured so that the accurate secondary magnetic flux φ _d can be estimated.
The characteristic shown in FIG. 2 is used as the characteristic of the exciting inductance M _t used in. As a result, when the excitation inductance M _t of the induction motor 2 is changed by the magnitude of the torque current i _q is also secondary flux of the function unit actual induction and secondary flux phi _d is estimated by 5a motor 2 phi _d Can be matched, and accurate torque control can be performed.

Therefore, the function shown in FIG.
In order to use it for the magnetic flux calculation of a, first, the exciting inductance M _t of the induction motor 2 is expressed by the parallel inductance of the first exciting inductance M and the second exciting inductance M _e . That is, M _t = 1 / {(1 / M) + (1 / M _e )} (1) Next, the action of the eddy current becomes remarkable under the operating condition where the magnetic flux is weakened as described above. Second under certain conditions
Excitation inductance M decrease in _e is it is considered to be proportional to the square root of the torque current i _q, the second excitation inductance M _e is a function f (φ _d) for giving weight to the flux-weakening region the torque current i Expressed as the ratio of the square root of _q . That is, M _e = f (φ _d ) / (i _q ) ^1/2 (2) It should be noted that the function f (φ
_{Since d} ) is determined by the complicated interaction between magnetic flux and eddy current,
It is difficult to obtain an accurate mathematical expression in advance. However, since it is monotonic function to reduce towards the flux-weakening region second excitation inductance M _e, it is possible to find the optimum function by the adjustment operation.

In the first embodiment described above, the exciting inductance M _t is estimated using the torque current i _q as a parameter, but the slip angular frequency ω of the induction motor 2 is shown.
Since s is proportional to the ratio of the torque current i _q and the secondary magnetic flux φ _d , the exciting inductance M _t may be estimated using the slip angular frequency _{ω s} as a parameter.

As described above, in the first embodiment, the exciting inductance M _t used in the function unit 5a of the controller 1 is as follows.
The properties, in addition to the characteristic that the secondary magnetic flux phi _d is the value greatly decreases because the magnetic saturation phenomenon as indicated by the characteristic of FIG. 2, when the torque current i _q increases secondary magnetic flux phi _d
Since the characteristic is such that the value decreases even in a small area,
The exciting inductance M _t of the induction motor 2 is the torque current i.
to vary according to the size of _q also can match the secondary flux phi _d function unit actual induction and secondary flux phi _d is estimated by 5a motor 2 allows the precise torque control effective.

[0027]

As described above, according to the first aspect of the present invention, the function unit causes the first exciting inductance based on the function corresponding to the magnetic saturation phenomenon of the secondary magnetic flux of the induction motor,
And the exciting inductance is calculated based on the parallel sum of the second exciting inductance, which is based on the ratio of the function giving a weight to the weakening magnetic flux region of the secondary magnetic flux and the square root of the torque current coordinate-transformed by the coordinate transformer. Since the secondary magnetic flux is calculated based on the multiplication of the exciting inductance and the exciting current coordinate-converted by the coordinate converter, even when the exciting inductance of the induction motor changes depending on the magnitude of the torque current. The secondary magnetic flux estimated by the function unit and the actual secondary magnetic flux of the induction motor can be matched, the control limit can be expanded, and the control stability can be further improved.

According to the second aspect of the present invention, in the function device, the slip angular frequency of the induction motor is used instead of the square root of the torque current. Therefore, the slip angular frequency of the induction motor is used to There is an effect that the control limit can be expanded and the control stability can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an induction motor drive device by vector control according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an exciting inductance characteristic used in a function unit.

FIG. 3 is a circuit diagram showing an equivalent circuit of an induction motor to be controlled by the induction motor driving device according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional vector-controlled induction motor drive device.

FIG. 5 is a characteristic diagram showing an exciting inductance characteristic used in a conventional function unit.

FIG. 6 is a circuit diagram showing an equivalent circuit of an induction motor to be controlled by a conventional induction motor driving device.

[Explanation of symbols]

2 induction motor, 4 coordinate converter, 5a function unit, 6
Divider, 8 horizontal axis current regulator, 10 magnetic flux regulator, 12
Direct current regulator, 13 power supply.

Front page continuation (72) Kensuke Miyano 2-3-3 Marunouchi 2-3, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. (72) Inventor Kenji Mori 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd. In-house (72) Inventor Ken Kou Yamaguchi, Hikari City, Yamaguchi 3434 Shimada, Nippon Steel Co., Ltd.Hikari Steel Co., Ltd. (72) Inventor, Yoshiyuki Yamaguchi, Hikari City, Yamaguchi Prefecture, 3434 Shimada, Nippon Steel Corporation (72) Inventor Asahi Shino 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division

Claims (2)

[Claims] 1. A coordinate converter for converting at least two phase currents supplied to an induction motor into a torque current and an exciting current, and a first function based on a function corresponding to a magnetic saturation phenomenon of a secondary magnetic flux of the induction motor. Of the second exciting flux, and the exciting inductance is calculated based on the parallel sum of the second exciting inductance based on the ratio of the function of giving a weight to the weakening magnetic flux region of the secondary magnetic flux and the square root of the torque current. A function unit that calculates the secondary magnetic flux based on the multiplication of the inductance and the exciting current, a divider that calculates the torque current command value by dividing the torque command value by the secondary magnetic flux calculated by the function unit, and that A horizontal axis current regulator that calculates a horizontal axis current control signal based on a value obtained by subtracting the torque current coordinate-converted by the coordinate converter from the torque current command value, A magnetic flux regulator that calculates the exciting current command value based on the value obtained by subtracting the secondary magnetic flux calculated by the function unit from the secondary magnetic flux command value, and the coordinate conversion was performed by the coordinate converter from the exciting current command value. A direct-axis current regulator that calculates a direct-axis current control signal based on a value obtained by subtracting an exciting current, and a power supply that supplies power to the induction motor based on the horizontal-axis current control signal and the direct-axis current control signal. And a vector control induction motor drive device. 2. The induction motor drive apparatus according to claim 1, wherein the function unit uses a square root of a slip angular frequency of the induction motor instead of the square root of the torque current.