JP3535735B2 - Induction motor control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of an inverter for driving an AC electric motor, and particularly to smooth start.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. The start-up related signal generator 55 is 1 when the start is ON and 0 when the start is OFF, and the power converter start signal S0 and the start ON
Speed estimation signal S1 which becomes 1 only for the subsequent t2 period and start ON
After that, the controller start signal S2 which becomes 1 after the lapse of t2 is output.

The power converter 1 uses the power converter start signal S.
The command Vc is given to the induction motor 2 when 0 is 1.
0 voltages are applied. When the speed estimation signal S1 is 0, the switch 54 selects the voltage command Vc1 of the output of the control device 40 of the induction motor and sets it as Vc0, and the power converter 1
Output to. On the other hand, when the speed estimation signal S1 is 1, the voltage command Vc2 output from the second speed estimation means 51 is selected and output to the power converter 1 as Vc0.

The second speed estimating means 51 is a current detector 1
4 outputs a voltage command Vc2 such that the input current vector i of the induction motor 2 having the output of 4 becomes a direct current of zero magnitude or a magnitude close to zero.

The second speed estimating means 51 receives the voltage vector v of the output of the voltage detecting means 15 and time-integrates the voltage vector v to obtain a voltage integrated value Fx. When the speed estimation signal S1 is 1, the F at any three time points
x is Fx1, Fx2, Fx3, and Fx1, Fx2, F
The center Fx0 of the circle passing through x3 is obtained, and Fx1-Fx0 and Fx0
The rotational angular frequency w corresponding to the rotational speed of the induction motor is obtained by dividing the phase difference with x3-Fx0 by the time from the Fx1 detection time point to the Fx3 detection time point, and the last time point when the speed estimation signal S1 is 1. Let Fx4 be Fx4,
Fx4-Fx0 is output as the secondary interlinkage magnetic flux vector f2 at the last time when the speed estimation signal S1 is 1.

The induction motor control device 40 uses the second speed estimation means 5 when the controller start signal S2 becomes 1.
The rotation angular frequency w of one output and the secondary interlinkage magnetic flux vector f2 are respectively used as the initial value of the speed calculation and the initial value of the magnetic flux calculation inside the control device 40 of the induction motor.

[0007]

The speed estimation by the second speed estimation means 51 shown in the prior art is applied to the induction motor when the induction motor 2 is rotating because the residual magnetic flux remains in the induction motor 2. The fact that back electromotive force is generated is used. In other words, in order to control the current to a value close to 0, the power converter needs to apply the same voltage as the back electromotive force to the induction motor, so by observing the input voltage of the induction motor, Since the back electromotive force can be detected, the rotational angular frequency of the induction motor and the secondary flux linkage, which is the residual flux, can be obtained.

However, when there is no residual magnetic flux, such as when the induction motor is not operated for a long time, the counter electromotive force does not occur and it becomes impossible to obtain the rotational angular frequency of the induction motor. Since the initial value of speed calculation in the control device of the induction motor cannot be set, correct speed calculation cannot be performed and the induction motor cannot be controlled to a desired speed.
The present invention has been made in view of the above-mentioned points, and an object thereof is to provide an initial value in a control device for an induction motor and control the induction motor so that the control device can be started without problems. To get the equipment.

[0009]

[Means for Solving the Problems] That is, the means for achieving the object is, immediately after executing the second speed estimating means, when the rotational angular frequency cannot be estimated by the second speed estimating means. A pre-excitation current control means for controlling the power converter so that the input current of the induction motor becomes a predetermined DC current during the micro period, and the input of the induction motor during the micro period. Voltage detecting means for detecting or estimating the voltage vector of the voltage detecting means, and secondary voltage calculating means for calculating the voltage vector of the output of the voltage detecting means minus the voltage drop due to the primary resistance of the induction motor and the voltage drop due to the leakage inductance. , And speed estimation means for estimating the rotational angular frequency of the induction motor from the output of the secondary voltage calculation means.

Further, the minute period is t1, the direct current supplied by the pre-excitation current control means is idx, the rotational angular frequency obtained by the speed estimation means is w, and the secondary time constant of the induction motor is T2. The mutual inductance is M, the exponential function is represented by exp (), the imaginary unit is represented by j, and the secondary interlinkage magnetic flux vector f2 of the induction motor immediately after the minute period is f2 = {1-exp (-t1 / T2 + j · w · t1)}
M / (1−j · w · T2) · idx, which is provided with an initial magnetic flux calculating means, and the secondary flux linkage vector f2 of the output of the initial magnetic flux calculating means and the rotational angular frequency of the output of the speed estimating means Is the initial value of the numerical value in the induction motor control device. An embodiment of the present invention will be described in detail below with reference to the drawings.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG.
0 is 1 when the start is ON and 0 when the start is OFF, the power converter start signal S0 is 1, the speed estimation signal S1 is 1 only for the t2 period after the start is ON, and is 2 only for the minute period thereafter, and t2 + the minute period is elapsed after the start is turned ON. The controller start signal S2 which becomes 1 later is output.

The power converter 1 uses the power converter start signal S.
The command Vc is given to the induction motor 2 when 0 is 1.
0 voltages are applied. When the speed estimation signal S1 is 0, the switch 54 selects the voltage command Vc1 of the output of the control device 40 of the induction motor and sets it as Vc0, and the power converter 1
Output to. On the other hand, when the speed estimation signal S1 is 1, the voltage command Vc2 output from the second speed estimation means 51 is selected and output to the power converter 1 as Vc0. When the speed estimation signal S1 is 2, the voltage command Vc3 of the output of the pre-excitation current control means 71 is selected to be Vc0 and the power converter 1 is selected.
Output to.

The operation when the speed estimation signal S1 is 1 is the same as described in the prior art. When the induction motor 2 has a residual magnetic flux, the second speed estimation means 51 determines the rotational angular frequency w The next flux linkage vector f2 is output. In this case, the speed estimation signal S1 does not become 2 but becomes 0 as indicated by the broken line of the start-related signal generator 70. Further, the controller start signal S2 also becomes 1 without passing through a minute period. When there is no residual magnetic flux in the induction motor, the second angular velocity estimation means 51 outputs the rotational angular frequency w and the secondary flux linkage vector f2.
Is an induction motor controller 40 and a start-related signal generator 70.
Cannot be output to, and the speed estimation signal S1 shifts to 2.

The pre-excitation current control means 71 outputs a voltage command Vc3 such that the input current vector i of the induction motor 2 at the output of the current detector 14 becomes a predetermined DC current idx.

The secondary voltage calculation means 72 is a voltage detection means 1
The voltage vector v of the output of 5 and the current vector i of the output of the current detector are input, and the secondary voltage obtained by subtracting the voltage drop due to the primary resistance and the leakage inductance as v2 = v−R1 · i−L · di / dt. Output the vector v2. Where R1
Is the primary resistance of the induction motor 2, L is the leakage inductance of the induction motor 2, and di / dt is the time derivative of the current vector i.

The speed estimating means 73 is a secondary voltage calculating means 7
A vector F obtained by time-integrating the two-output secondary voltage vector is obtained. Let F1, F2, F3 be F at any three points when the speed estimation signal S1 is 2, F1, F
Find the center F0 of the circle passing through 2 and F3, and calculate F1-F0 and F3
-A rotational angular frequency w corresponding to the rotational speed of the induction motor is obtained by dividing the phase difference from -F0 by the time from the F1 detection time to the F3 detection time and is output.

The initial magnetic flux calculating means 74 is a speed estimating means 7
By inputting the rotational angular frequency w of 3 outputs, the minute period is t
1, the secondary time constant of the induction motor is T2, the mutual inductance is M, the exponential function is represented by exp (), the imaginary unit is represented by j, and the secondary chain linkage of the induction motor immediately after the minute period. Let the magnetic flux vector f2 be f2 = {1-exp (-t1 / T2 + j · w · t1)}.
・ {M / (1-j ・ w ・ T2)} ・ idx is obtained and output.

When the controller start signal S2 becomes 1, the induction motor control device 40 determines the rotational angular frequency w of the speed estimation means 73 output and the secondary interlinkage magnetic flux vector f2 of the initial magnetic flux calculation means 74 output. , The initial value of the speed calculation and the initial value of the magnetic flux calculation inside the control device 40 of the induction motor.

In the following, the rotational angular frequency w and the secondary interlinkage magnetic flux vector f are calculated by the speed estimating means 73 and the initial magnetic flux calculating means 74.
The reason why 2 is obtained will be described. The secondary flux linkage vector f2 when the direct current idx is passed from the state where there is no secondary flux linkage is f2 = {1-exp (-t / T2 + j * wt)}.
It is represented by {M / (1-j · w · T2)} · idx. Here, t is an elapsed time from the time when the direct current idx is started to flow. From this equation, it can be seen that f2 draws a circular locus passing through the origin when t is much shorter than T2. The rotational angular frequency is the same as the rotational angular frequency of the induction motor and is w. Since the time integration of the secondary voltage vector v2 of the output of the secondary voltage calculation means 72 is the secondary interlinkage magnetic flux vector, the time integration of the secondary voltage vector v2 is also f2.
Similarly to, the induction motor rotates at the angular frequency of rotation. Therefore, the speed can be estimated by the method of the speed estimating means 73. Further, since the initial magnetic flux calculating means 74 calculates the secondary interlinkage magnetic flux vector by the same equation as the above equation, the initial magnetic flux calculating means 74 can calculate the secondary interlinkage magnetic flux vector.

[0020]

As described above, according to the present invention, the rotational angular frequency of the induction motor can be estimated even when there is no residual magnetic flux, and the initial value of the numerical value in the control device of the induction motor can be set to an appropriate value. Since it can be set to, it is possible to suppress various transient phenomena such as sudden deceleration immediately after the control device is started, overcurrent and deterioration of control accuracy, and it is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of a conventional technique.

[Explanation of symbols]

1 power converter 2 induction motor 14 Current detector 15 Voltage detection means 40 Induction motor controller 51 Second speed estimating means 54 switch 55,70 Start-related signal generator 71 Pre-excitation current control means 72 Secondary voltage calculation means 73 Speed estimation means 74 Initial magnetic flux calculation means

─────────────────────────────────────────────────── ─── Continued Front Page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02P 21/00 H02P 7/63

Claims (2)

(57) [Claims] 1. An induction motor control device for controlling a power converter for supplying electric power to an induction motor, wherein the residual magnetic flux of the induction motor is utilized immediately after starting to supply electric power to the induction motor. Second speed estimating means for estimating the rotational angular frequency of the induction motor, and a predetermined minute period immediately after execution of the second speed estimating means only when the rotational angular frequency cannot be estimated by the second speed estimating means. A control device for an induction motor, comprising: a pre-excitation current control unit that causes an input current of the induction motor to become a predetermined DC current, wherein a voltage for detecting or estimating a voltage vector of an input of the induction motor in the minute period. Detecting means and calculating a value obtained by subtracting the voltage drop due to the primary resistance of the induction motor and the voltage drop due to the leakage inductance from the voltage vector of the output of the voltage detecting means And the output of the secondary voltage computing means are time-integrated into F, and F at any three time points within the minute period are designated as F1, F2, F3, and F1,
The center F0 of the circle passing through F2 and F3 is found, and F1-F0 and F1
A control device for an induction motor, comprising: speed estimation means for obtaining a rotational angular frequency of the induction motor by dividing a phase difference from 3-F0 by a time from the F1 detection time to the F3 detection time. 2. The secondary period of the induction motor is defined as t1, the minute period is defined as t1, the direct current flowing through the pre-excitation current control means is defined as idx, the rotation angular frequency obtained by the speed estimation means is defined as w. T2, the mutual inductance is M, the exponential function is represented by exp (), the imaginary unit is represented by j, and the secondary flux linkage vector f2 of the induction motor immediately after the micro period is f2 = {1-exp (- t1 / T2 + j · w · t1)}
.. {M / (1-j.w.T2)}. Idx is provided with an initial magnetic flux calculating means, and the secondary flux linkage vector f2 of the output of the initial magnetic flux calculating means and the rotation of the output of the speed estimating means are rotated. The control device for an induction motor according to claim 1, wherein the angular frequency is an initial value of a numerical value in the induction motor control device.