JPH07231700A - Variable-speed driver of induction motor - Google Patents

Abstract

PURPOSE:To shorten the operation time required for performing the correction of exciting inductance by a digital operation by operating the correction with two multipliers, one of which corrects the component corresponding to the exciting inductance by multiplying it by the reciprocal of the correction factor of a correction factor generator and the other which corrects magnetic flux command output by multiplying it by the reciprocal of correction factor. CONSTITUTION:As the operations equivalent to a multiplier 15A and a multiplier 15B, this driver multiplies a magnetic flux command phi2/M and a magnetic flux estimate (phi2/M)' of one sample before by correction factor 1/KM each. Next, as the operation equivalent to a magnetic flux feedback controller 12, this performs the corrective operation according to the deviation between the magnetic flux command phi2/M determined before and the magnetic flux estimate (phi2/M)'. Lastly, as the operation equivalent to a magnetic flux operation mode 11A, the present magnetic flux estimate (phi2/M)' is found, using a present excitation current command i0, constants DELTAT, M, and R2, a magnetic flux estimate (phi2/M)Z<-1>, and a correction factor 1/KM. Hereby, the correction can be made with two times of multiplication, so the operation time can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed driving device for an induction motor, and more particularly to a variable speed driving device for obtaining an exciting current command for vector control in a constant output range of the induction motor by digital calculation.

[0002]

2. Description of the Related Art At present, a vector control system is widely used for a variable speed drive device of an induction motor. In the vector control, the torque current and the output torque can be linearly controlled by controlling the secondary interlinkage magnetic flux component to be constant in the constant torque range of FIG.

Unlike the general-purpose V / f constant control, in the constant output range where the rotation speed is high, a control calculation of the excitation axis current command value for controlling the magnetic flux is performed.

FIG. 4 is a block diagram of a vector control system when the constant output range is taken into consideration. The exciting current command i ₀ and the torque current command i _T , which are orthogonal components, are calculated by the current control amplifiers 1 and 2 using the respective detected values of the axis current as feedback signals, and the calculation result is calculated by the rotary coordinate conversion unit 3. The two-phase / three-phase conversion is performed, and the PWM power converter 4 obtains the pulse width-modulated output to obtain the induction motor 5
To drive.

The exciting current and the torque current of the induction motor 5 are detected by the three-phase / two-phase conversion by the reverse rotation coordinate conversion unit 6 from the input current detection signal of the induction motor 5.

For the rotational phase angle θ required for the calculation of the rotational coordinate conversion unit 3 and the inverse rotational coordinate conversion unit 6, the slip frequency ω _slip is calculated by the slip frequency calculation unit 7, and the rotor rotation of the induction motor 5 is set to this slip frequency. The output angular frequency ω ₁ is calculated by adding the speed ω _r , and the output angular frequency ω ₁ is calculated by the integral calculation unit 8.

In this configuration, in the operation in the constant output range, the exciting current command i ₀ is the rotational speed ω _r of the output shaft of the electric motor 5.
The exciting current command i ₀ is adjusted as a magnetic flux command by the magnetic flux commanding section 9 so as to maintain an inversely proportional relationship with.

In adjusting the exciting current command i ₀ , it is convenient to use a secondary magnetic flux φ ₂ of the induction motor 5 divided by the exciting inductance M. Therefore, the magnetic flux command section 9
The magnetic flux calculator 9A generates the pattern data of φ ₂ / M or the calculation result corresponding to the rotation speed ω _r as an exciting current command.

Further, since the magnetic flux follows the exciting current with a first-order lag, in order to improve the responsiveness of the magnetic flux, the differential component of the magnetic flux command is obtained by the differential operation section 9B and superposed on the magnetic flux command as feedforward.

The torque current command i _T is obtained by a speed control system or torque control system (not shown), but division is performed by the divider 10 in order to match the ratio with the excitation current command.

[0011]

The magnetic flux command section 9 shown in FIG.
As shown in the waveform diagram, since the magnetic flux command is differentiated by the differential calculation unit 9B, the value of the differential component of the magnetic flux command increases when the rotation speed ω _r changes rapidly.

However, since there is a current output limit, when the exciting current limit is applied by the current limiting limiter provided in the magnetic flux command section 9 or the current control amplifier 1, etc., the exciting current command i corresponding to the change in the rotation speed is applied. You cannot get ₀ outputs. At this time, the slip frequency calculation unit 7 causes a deviation between the secondary magnetic flux φ ₂ used for slip calculation and the actual secondary magnetic flux, which deviates from the vector control condition and causes a torque error or unstable control.

As a countermeasure against this, as shown in FIG. 6, a magnetic flux calculation model 11 for estimating and calculating a magnetic flux from an exciting current command instead of the differential feedforward, and a magnetic flux estimation value (φ ₂ / A magnetic flux control unit 12 may be provided to feed back so that M) ′ coincides with the command φ ₂ / M. Reference numeral 13 is an exciting current limiting limiter.

In this case, the exciting current command is the limiter 1
Although limited by 3, a command equivalent to the actual magnetic flux can be estimated.

Here, since the value of the exciting inductance M fluctuates due to the change of the magnetic flux, as shown in FIG. 7, the correcting coefficient generating section 14 having the exciting inductance correcting coefficient K _M as table data is provided, and the exciting inductance M is set. Correct the part related to.

This correction is performed by division or multiplication as the operation coefficient of the divider 15, the multiplier 16, and the magnetic flux model 11.

From the above, in the method in which the magnetic flux command is feedback-controlled by the estimated magnetic flux value estimated by the magnetic flux calculation model, and the exciting inductance M is corrected, the correction is required at three places. Also mixes multiplication and division.

For this reason, in the case of a digital control device in which a microprocessor or the like is used for highly accurate calculation and control of each part of the control device, the calculation time for division is longer than that for multiplication, and the response of the vector control is increased. In some cases, it may not be possible to secure the sex.

An object of the present invention is to provide a variable speed drive device for an induction motor, which shortens the calculation time for digitally correcting the excitation inductance.

[0020]

In order to solve the above-mentioned problems, the present invention provides a secondary speed control of an induction motor in a variable speed drive device for vector-controlling an induction motor in a constant output range. A magnetic flux calculation unit that generates a magnetic flux pattern of a ratio φ ₂ / M of the magnetic flux φ ₂ and the exciting inductance M as a magnetic flux command, and a correction coefficient K _M that corrects the change of the exciting inductance M due to the change of the secondary magnetic flux φ ₂ is the reciprocal thereof. 1
/ K _M as a correction coefficient generator that is generated according to the rotation speed of the induction motor, and a secondary magnetic flux φ ₂ for the exciting current command i ₀ .
Sampling cycle of exciting current command Δ
Ratio of T to secondary resistance R ₂ and exciting inductance M ΔT /
'And the discrete values based flux calculation model to obtain, the flux estimation value obtained by the magnetic flux calculation model (φ ₂ / M)' flux estimate is approximated by _{(M / R 2) (φ} 2 / M) the correction A first multiplication unit that multiplies the correction coefficient 1 / K _M of the coefficient generation unit to correct the excitation inductance M, and the correction coefficient 1 / K _M of the correction coefficient generation unit to the magnetic flux command output of the magnetic flux calculation unit. A second multiplication unit that multiplies and corrects the excitation inductance M, and adds to the output of the second multiplication unit according to the deviation between the magnetic flux estimation value of the magnetic flux calculation model and the magnetic flux command value of the magnetic flux calculation unit. A magnetic flux feedback control unit for correction, and a limiter unit for limiting the current of the added and corrected value to the excitation current command are provided.

[0021]

When the magnetic flux calculation model 11 of FIG. 7 is represented by a discrete value system (sampling period ΔT), it can be replaced with the block shown by 11A in FIG. Here, the block of Z ⁻¹ is the magnetic flux estimation calculation result (φ ₂ / M) Z ⁻¹ one sample before.

The result of replacing the replacement block 11A with the corresponding portion of FIG. 7 is as shown in FIG. The amount of calculation for the correction by the correction coefficient K _{M at} this time is still large.

Here, in a general induction motor, the relationship of (M / R ₂ ) >> ΔT is established in the coefficient part of the magnetic flux calculation model 11A, so the magnetic flux calculation model 11A is approximated as shown in FIG. 10 (a). Further, it is possible to transform into an arithmetic block configuration in which one divider is reduced as shown in FIG.

In applying this modified magnetic flux calculation model to FIG. 9, if the reciprocal 1 / K _M is used instead of the correction coefficient K _M , it becomes as shown in FIG. 1 in which each division part is changed to multiplication. , 1 / K _M can be corrected by only multiplying at two places.

[0025] Therefore, in the present invention, the correction coefficient generating unit 14A generates the inverse 1 / K _M of the correction coefficient K _M, the magnetic flux calculation model 11A magnetic flux estimation value is approximated by _{ΔT / (M / R 2)} ( φ ₂ / M) ′ is obtained, and the multipliers 15 at two locations are used.
A correction calculation of the exciting inductance M is made possible by multiplication by A and 15B.

[0026]

FIG. 2 is a flow chart showing an embodiment of the present invention, and shows only a portion for obtaining an exciting current command by digital calculation by a microprocessor.

When the processor reaches the time of the sampling period ΔT for calculating the exciting current command (step S
1) As the calculation of the magnetic flux command unit 9A, the data of the magnetic flux command φ ₂ / M corresponding to the detected value of the rotation speed ω _r of the induction motor 5 is read from the table data or the like (step S2), and the correction coefficient generation unit 14A is also used. As the calculation of, the data of the correction coefficient 1 / K _M corresponding to the detected rotation speed ω _r is read (step S3).

Next, as an operation corresponding to the multiplier 15A and the multiplier 15B, the magnetic flux command φ ₂ / M and the magnetic flux estimated value (φ ₂ / M) 'one sample before are respectively corrected by the correction coefficient 1 / K _M.
Is multiplied by (step S4).

Next, as a calculation corresponding to the magnetic flux feedback control unit 12, the magnetic flux command φ ₂ obtained in step S2.
/ M and the estimated magnetic flux value (φ ₂ /
M) 'and the correction calculation according to the deviation (step S
5).

Next, as an operation corresponding to the current limiter 13, the value obtained in step S4 is added to the value obtained in step S4, and the added value is subjected to limiter processing and output as an exciting current command i ₀ . (Step S6).

Finally, it corresponds to the magnetic flux calculation model 11A.
As the calculation, the current exciting current command i ₀And constants ΔT, M,
R₂Magnetic flux estimation value (φ₂/ M) Z^-1,correction
Coefficient 1 / K_MCurrent flux estimate (φ₂/ M) ’
Obtained (step S7).

Therefore, in order to obtain the exciting current command in which the exciting inductance is corrected, the calculation of the dividing of the exciting inductance M is not required, and it can be corrected by multiplying twice.
The calculation time can be shortened.

[0033]

As described above, according to the present invention, the excitation current command for vector-controlling the induction motor in the constant output range can be obtained by the calculation using the magnetic flux calculation model and the excitation inductance corrected. The correction coefficient K _M for correcting the fluctuation of the inductance M is set to its reciprocal 1 / K _M, and in the magnetic flux calculation model, the first-order lag gain of the secondary magnetic flux φ _{2 with} respect to the exciting current command i ₀ and the sampling cycle ΔT of the exciting current command are used. Ratio of secondary resistance R ₂ and exciting inductance M ΔT / (M
/ R ₂ ) is used to obtain the estimated magnetic flux value (φ ₂ / M) ', so that only two multiplications are required to correct the exciting inductance, and the calculation time of digital calculation processing by a processor or the like can be shortened. is there.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a flowchart showing an embodiment of the present invention.

FIG. 3 shows constant torque operation and constant output operation characteristics of the induction motor.

FIG. 4 is a block diagram of a conventional vector control system having a constant output operation range.

FIG. 5 is an explanatory diagram of a conventional magnetic flux command section.

FIG. 6 shows an example of a configuration based on a magnetic flux calculation model.

FIG. 7 shows an example of correcting the excitation inductance M.

FIG. 8: Replacement of magnetic flux calculation model.

FIG. 9 is a diagram in which a magnetic flux calculation model is replaced.

FIG. 10 is a modification of the magnetic flux calculation model.

[Explanation of symbols]

 9A ... Flux calculation unit 11A ... Flux calculation model 12 ... Flux feedback control system 13 ... Current limiter 14A ... Correction coefficient generation unit 15A, 15B ... Multiplier

Claims (1)

[Claims] 1. A variable-speed drive device for vector-controlling an induction motor in a constant output range, comprising: a secondary magnetic flux φ of the induction motor depending on a rotation speed of the induction motor.
₂ and a magnetic flux calculation unit that generates a magnetic flux pattern with a ratio φ ₂ / M of the exciting inductance M as a magnetic flux command, and a correction coefficient K _M that corrects the change of the exciting inductance M due to the change of the secondary magnetic flux φ ₂ is its reciprocal 1 / A correction coefficient generating section that is generated according to the rotation speed of the induction motor as K _M , a primary delay gain of the secondary magnetic flux φ _{2 with} respect to the exciting current command i _0, a sampling cycle ΔT of the exciting current command, and a secondary resistance R ₂
And a magnetic flux calculation model of a discrete value system which is approximated by a ratio ΔT / (M / R ₂ ) of the excitation inductance M to obtain a magnetic flux estimation value (φ ₂ / M) ′, and a magnetic flux estimation value (φ ₂ / M) '
To a correction coefficient 1 / K _M of the correction coefficient generation section to correct the exciting inductance M, and a magnetic flux command output of the magnetic flux calculation section to the correction coefficient 1 / K of the correction coefficient generation section. A second multiplication unit that multiplies K _M to correct the exciting inductance M, and a second multiplication unit of the second multiplication unit according to a deviation between a magnetic flux estimation value of the magnetic flux calculation model and a magnetic flux command value of the magnetic flux calculation unit. A variable speed drive device for an induction motor, comprising: a magnetic flux feedback control unit that performs addition correction on an output; and a limiter unit that current limits the value obtained by the addition correction to obtain the excitation current command.