JP2002335700A - Vector control method and vector control device for induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an operation in the rotative direction different from the commanded rotative direction which is caused by malfunctioning. SOLUTION: The rotative direction detection signal obtained from a pulse encoder 16 and the rotative direction command signal set separately are inputted to a limiting operation discriminator 41. A disagreement signal, which is outputted by the limiting operation discriminator 41 when both the input signals do not agree with each other, makes a speed detection value ωr , given to a rotor frequency calculator 20 by a culated speed value limiter 42, zero. An electrical angle limiter 43 comprising a previous value holding device 44 and a changeover device 45 changes an electrical angle Γ2 calculation value, given to a second coordinate converter 10 and a first coordinate converter 11 from an integrator 15, to the previous value held by the previous value holding device 44 corresponding to the disagreement signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control method and a vector control apparatus for an induction motor, which can cope with an abnormality in a detected rotational direction of the induction motor during operation by vector control.

[0002]

2. Description of the Related Art FIG. 3 is a block circuit diagram showing a conventional example in which the torque and the rotation speed of an induction motor are controlled by vector control. In the conventional circuit shown in FIG.
The inverter 13 converts the AC power into AC power having a predetermined voltage and frequency, drives the induction motor 17 with a desired torque, and drives the load 18. This induction motor 1
The rotation speed and the rotation direction of 7 are obtained by performing arithmetic processing on a signal output from the pulse encoder 16 coupled thereto in a speed calculator 19.

The speed setting unit 1 sets a speed setting value ω _r ^# to be operated by the induction motor 17. Speed command calculation circuit 2
Outputs a speed command value ω _r ^* that finally matches the speed set value ω _r ^# input thereto while changing according to a predetermined acceleration. The speed controller 3 inputs a deviation between the speed command value ω _r ^* and the detected speed value ω _r output from the speed calculator 19, and outputs a torque command value τ ^* that makes the input deviation zero by an adjusting operation. I do. On the other hand, the magnetic flux command value calculating circuit 4 secondary flux command value from the speed detection value omega _r of the aforementioned φ
Calculate ₂ ^* .

The M-axis current command value calculator 7 receives a secondary magnetic flux command value φ ₂ ^*, and calculates a current component command value parallel to the secondary magnetic flux of the motor primary current by an operation shown in the following equation 1. An M-axis current command value I _M ^* is obtained. Where L _m is the induction motor 1
7 is the excitation inductance.

[0005]

[Expression 1] I _M ^* = (1 / L _m ) · φ ₂ ^* Also, the divider 5 outputs the torque command value τ ^* and the secondary magnetic flux command value φ.
_{From 2} ^* , a T-axis current command value _IT ^* , which is a command value of a current component perpendicular to the secondary magnetic flux, is calculated according to Equation 2 below.

[0006]

[Number 2] _{^{I T * = τ * / φ}} 2 * first coordinate converter 11 phase current detected by the current detector 14 I _U, I _V, the I _W, parallel to the secondary flux of the primary current and M-axis current detection value I _M is a current component, there is to be converted to T-axis current detection value I _T is a perpendicular current component in the secondary flux, and the U-phase winding and the motor secondary magnetic flux Make the electrical angle
_If it is set to ₂ , the conversion is performed by the following Expressions 3 and 4.

[0007]

Equation 3] _{I T = I U · cosΓ 2} + I V · cos (Γ 2 -2
π / 3) + I _W · cos (Γ ₂ + 2π / 3)

[0008]

Equation 4] _{I M = I U · sinΓ 2} + I V · sin (Γ 2 -2
_{π / 3) + I W ·} sin (Γ 2 + 2π / 3) T -axis current regulator 8 inputs the deviation between T-axis current command value I _T ^* and T-axis current detection value I _T, the input by adjustment operation A T-axis voltage command value V _T ^* that makes the deviation zero is output. Also M
The shaft current adjuster 9 inputs a deviation between the M-axis current command value I _M ^* and the M-axis current detection value I _M, and outputs an M-axis voltage command value V _M ^* that makes the input deviation zero by an adjusting operation. .

The second coordinate converter 10 has a T-axis voltage command value V _T
^* And M-axis voltage command value V _M ^*
_U ^*, V _V ^*, and outputs a V _W ^*, when formed electrical angle between the U-phase winding and the motor secondary magnetic flux is gamma _2, converted by Equation 5, Equation 6, Equation 7 below I do.

[0010]

[Expression 5] V _U ^* = V _M ^* · cos ^* ₂ + V _T ^* · sinΓ ₂

[0011]

V _V ^* = V _M ^* · cos (Γ ₂ −2π / 3) + V
^{_{T * · sin (Γ 2 -2π}} / 3)

[0012]

V _W ^* = V _M ^* · cos ( ^* ₂ + 2π / 3) + V
_T ^* · sin (Γ ₂ + 2π / 3) The three-phase voltage command values _VU ^* , _VV ^* , and _VW ^*
The electric power is converted into an AC point force having a predetermined voltage and frequency by the power supply 3 and supplied to the induction motor 17.

The slip frequency calculator 6 calculates the slip frequency ω _sl by performing the calculation of the following equation (8). However R ₂ is the time constant motor secondary.

[0014]

Ω _sl = R ₂ · I _T ^* / φ ₂ ^{* The} rotor frequency calculator 20 performs the calculation shown in Expression 9, and
Converting the speed detection value omega _r of the induction motor 17 to the motor rotor frequency omega _2. Here, P is the number of motor poles.

[0015]

Ω ₂ = ω _r · P / 120 The motor rotor frequency ω ₂ calculated by Expression 9 and Expression 8
Adding the slip frequency omega _sl obtained by, by integrating by integrator 15, it is possible to determine the electrical angle gamma ₂ formed by the U-phase winding and the motor secondary magnetic flux.

[0016] Incidentally, the magnetic flux command value calculating circuit 4 is 100% less than the base speed of the speed detection value omega _r is the induction motor 17
The secondary magnetic flux command value φ ₂ ^* is output, and when it is equal to or higher than the base rotational speed, the secondary magnetic flux command value φ ₂ ^* is reduced in inverse proportion to the rotational speed.

[0017]

By the way, the pulse encoder 16 determines the rotation direction of the induction motor 17 based on which of the A pulse and the B pulse that it generates outputs first. Here, for example, if noise is superimposed during operation of the induction motor 17 at an extremely low rotation speed, a signal is output as if the rotation direction of the induction motor 17 was reversed. As a result, the rotation direction command value and the rotation direction detection value become inconsistent even though the induction motor 17 is not reversed, and an attempt is made to reverse the rotation direction of the induction motor 17 in order to correct the inconsistency. When the load 18 connected to the induction motor 17 is, for example, a printing machine, there is a possibility that a large accident such as damage to the printing machine due to reversal may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent operation in a rotation direction different from the rotation direction command value due to a malfunction.

[0019]

In order to achieve the above-mentioned object, a vector control method and a vector control device for an induction motor according to the present invention provide a method for controlling a primary current of the induction motor to a current component parallel to a secondary magnetic flux. In the vector control method of the induction motor for controlling the torque and the rotation speed of the induction motor by separating each current component to each current command value, the rotation speed detection of the induction motor is performed. When the rotation direction detection signal obtained from the value does not coincide with the separate rotation direction command signal, the rotation speed detection value used when calculating the angle between the winding and the motor secondary magnetic flux is limited to zero. It is assumed that the angle calculation value immediately before performing the limiting process is used.

Alternatively, a rotation direction detection signal obtained from a rotation speed calculator and a separate rotation direction command signal are inputted,
A limiting operation determiner that outputs a mismatch signal when these two inputs do not match, and a speed calculation that limits the speed calculation value output by the rotational speed calculator to zero when the limit operation determiner outputs a mismatch signal. It is provided with a value limiter and an electrical angle limiter that holds the electrical angle calculated by the integrator based on the mismatch signal at a previous value.

[0021]

FIG. 1 shows a first embodiment of the present invention.
FIG. In the flowchart of FIG.
The rotation direction detection value of the induction motor is set separately.
It is determined whether or not there is a mismatch with the turning direction command value (decision 22)
And if they match, the speed detection value ω _rIs selected (Process 3
1) and the speed detection value ω_rThe
Tarota frequency ω_TwoAfter converting to (process 33),
Slip frequency ω_slAre added (process 34) and then integrated (process 3).
5) Do it. Here, the rotation direction detection value of the induction motor is separately calculated.
If the specified rotation direction command value matches,
Step 23) The current integration value is selected (process 36), and the logical sum 2
6, the angle resulting from the integration is converted into a coordinate conversion operation (process 3).
8) is used.

It is determined that the rotation direction detection value of the induction motor does not match the separately determined rotation direction command value (decision 2).
2) zero in place of the speed detection value omega _r If it is is selected (step 32), further from the previous integral value is selected (step 37) by decision 23, the abnormal rotation direction detection value appears due to noise or the like However, the rotation direction of the induction motor does not reverse,
You can continue driving.

FIG. 2 is a block circuit diagram showing a second embodiment of the present invention. The circuit of the second embodiment is similar to the conventional circuit shown in FIG. Since the configuration is such that the limiter 42 and the electrical angle limiter 43 are added, only the added portions will be described, and the description of the remaining portions will be omitted. In the circuit of the second embodiment shown in FIG. 2, the limiting operation discriminator 41 constantly compares the rotation direction detection value obtained from the pulse encoder 16 with the rotation direction command value obtained from the speed command calculation circuit 2, The output of the limiting operation discriminator 41 is zero when the directions match, but when the rotation directions do not match due to the above-described abnormal phenomenon, the limiting operation discriminator 41 is connected to the speed calculation value limiter 42 and the electrical angle. A switching operation is commanded to the limiter 43.

[0024] that the speed detection value omega _r from the speed calculator 19 during normal is input directly to the rotor frequency calculator 20, a switching command, the rotor frequency calculator 2
Zero is input to zero. On the other hand, the electric angle limiter 43 is constituted by a previous value holder 44 and a switch 45, and responds to a switching command from the limit operation discriminator 41 in response to the second coordinate converter 10 and the first coordinate converter. the value of the electrical angle gamma ₂ to give the 11 switches the value of the previous value retainer 44 from the calculated value of the integrator 15.

[0025]

According to the conventional vector control device, when the induction motor drives the load at an extremely low rotational speed,
The pulse encoder may output a signal as if the rotation direction of the induction motor was reversed due to noise or the like. If the induction motor is reversed in response to the false rotation direction reversal signal, a large accident that may damage the load machine may occur in some cases. In the present invention, on the other hand, if detecting that the detection value of the rotation direction and the command value becomes mismatched, since the calculated value of the electrical angle gamma ₂ is adapted to hold the previous value, the induction motor This has the effect of avoiding problems such as suddenly reversing the direction of rotation and damaging the load machine.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is a block circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a block circuit diagram showing a conventional example in which the torque and the rotation speed of an induction motor are controlled by vector control.

[Explanation of symbols]

2 Speed command calculation circuit 3 Speed controller 4 Magnetic flux command value calculation circuit 5 Divider 6 Slip frequency calculator 7 M-axis current command value calculator 10 Second coordinate converter 11 First coordinate converter 14 Current detector 15 Integrator 16 Pulse encoder 19 Speed calculator 20 Rotor frequency calculator 41 Limit operation discriminator 42 Speed calculation value limiter 43 Electric angle limiter 44 Previous value holder 45 Switcher ω ₂ Motor rotor frequency ω _r Speed detection value ω _r ^* Speed command Value ω _sl slip frequency Γ ₂ electrical angle φ ₂ ^* secondary magnetic flux command value

Continuation of the front page F term (reference) 5H576 BB06 CC05 DD02 DD04 EE01 EE10 FF07 GG02 GG04 HB02 JJ03 KK02 LL07 LL22 LL37 MM17

Claims (2)

[Claims] An electric angle between a secondary magnetic flux and a winding of the induction motor is calculated from a detected rotation speed of the induction motor, and a primary current of the induction motor is coordinate-converted using the electric angle to be parallel to the secondary magnetic flux. After the current component is separated into a vertical current component and each of these current components are matched with the respective current command values, these are converted into the original AC amount by performing coordinate conversion using the electric angle,
In the vector control method for an induction motor that controls the torque and the rotation speed of the induction motor, the electrical angle is calculated when a rotation direction detection signal obtained from the rotation speed detection value does not match a separate rotation direction command signal. A method for controlling a vector of an induction motor, characterized in that the rotational speed detection value used at this time is limited to zero, and an electrical angle calculation value immediately before performing the limiting process is used. 2. An adder for adding a speed calculation value of an induction motor output from a rotation speed calculator and a slip frequency obtained separately, and integrating the addition result to obtain an electrical angle between a secondary magnetic flux and a winding. And a first coordinate converter that separates the primary current of the induction motor into a current component parallel to the secondary magnetic flux and a current component perpendicular to the secondary magnetic flux using this electrical angle. And a second coordinate converter for converting the voltage command values output by these two current controllers into respective phase voltage command values using the electrical angle. In an induction motor vector control device that controls the torque and rotation speed of an induction motor, a rotation direction detection signal obtained from the rotation speed calculator and a separate rotation direction command signal are input, and when these two inputs do not match. The mismatch signal A limit operation judging device to output,
A speed calculation value limiter that limits the speed calculation value output by the rotation speed calculator to zero when the limiting operation determiner outputs a mismatch signal, and an electric angle calculated by the integrator based on the mismatch signal in the previous time. A vector control apparatus for an induction motor, comprising: an electric angle limiter that holds a value.