JPH08172798A - Variable speed drive control circuit for induction motor - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To enable correct voltage feedback control even if there is an offset or drift in the voltage detector. [Configuration] q-axis voltage data V output by the coordinate conversion circuit 8
_The offset compensation circuit 21 _{includes fq} and the rotation angle data θ.
To the offset data of U phase and W phase from these values. When the U-phase has an offset, the pulsation components of the q-axis voltage data V _fq are maximum and minimum when the rotation angle data θ is 60 ° and 240 °, respectively. U-phase offset data is obtained from the difference between the maximum value and the minimum value. Similarly, when there is a W-phase offset, the W-phase offset data is obtained from the maximum and minimum values of the pulsating component of the q-axis voltage and the rotation angle data. These offset data are given to the adders 4 and 5,
Compensate for the offset of the U and W phase voltage detectors. Thus, the pulsation of the q-axis voltage data is compensated by the osset arithmetic circuit provided with the appropriate algorithm, and the feedback control of the instantaneous voltage vector can be correctly performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for driving an induction motor at a variable speed with a power converter such as an inverter.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional example of a control circuit for controlling a power converter for variable speed drive of an induction motor. In this prior art circuit, a voltage detector (not shown) detects the first phase voltage e _u of the induction motor, A / D conversion circuit 2 converts the detected voltage e _u into digital data, the adder 4 The first phase offset data OF _u is subtracted, and the subtraction result is input to the PU data operation circuit 6. Similarly, the third-phase voltage detection value _ew also applies to the A / D conversion circuit 3
After being converted into digital data by, the adder 5 subtracts the third phase offset data OF _w , and the subtraction result is PU
It is input to the data operation circuit 6.

The PU data operation circuit 6 standardizes these input values by the motor rated voltage, and the first phase standardized data P
U _u and the third-phase standardized data PU _w are converted by the three-phase / two-phase conversion circuit 7 into α-axis voltage data V _a and β-axis voltage data V _b of the orthogonal stator coordinate system. Further, the coordinate conversion circuit 8 inputs these α-axis voltage data V _a , β-axis voltage data V _b , and rotation angle data θ into d-axis voltage data V _fd and q-axis voltage data V _{fq of} the rotor coordinate system. To be converted.

The first voltage adjusting circuit 9 obtains the d-axis voltage control signal V _pd by performing a calculation by multiplying the deviation between the d-axis voltage data V _fd and the q-axis voltage command value V _1q, which is set separately, by a gain. The q-axis voltage control signal V _pq is calculated by multiplying the deviation between the q-axis voltage data V _fq and the separately set q-axis voltage command value V _1q by a gain. The d-axis voltage control signal V _pd and the q-axis voltage control signal V _pq are input to the voltage vector command calculation circuit 10 to set the voltage control vector absolute value | V | and the voltage control vector phase angle δ ^* to the three-phase voltage command value. It outputs to the arithmetic circuit 11, and the three-phase voltage command value arithmetic circuit 11 inputs these and inputs the first phase voltage command signal V _u ^* , the second phase voltage command signal V _v ^*, and the third phase voltage command signal V _w ^*. Feedback control of the instantaneous voltage vector is performed by outputting and. The induction motor is driven at a desired speed by applying these phase voltage command signals V _u ^* , V _v ^* , V _w ^* to a power converter (not shown) such as an inverter.

[0005]

When the voltage detector described above has an offset or drift, the q-axis voltage data V _fq output from the coordinate conversion circuit 8 pulsates. FIG. 4 shows the q-axis voltage data V when the first phase has a positive offset.
₆ is a graph showing a pulsating state of _fq , and FIG. 5 is a graph showing a pulsating state of the q-axis voltage data V _fq when the third phase has a positive offset. As is clear from the above, the q-axis voltage data V _fq pulsates at a frequency component that is one time the output frequency of the power converter, so that there is a problem that the voltage feedback control cannot be performed correctly.

Therefore, an object of the present invention is to enable voltage feedback control to be performed correctly even if the voltage detector has an offset or drift.

[0007]

In order to achieve the above-mentioned object, the variable speed drive control circuit for an induction motor according to the present invention has three components.
A, which separately converts the first-phase voltage detection value and the third-phase voltage detection value of the voltage-type inverter that outputs phase alternating current into a digital value
A / D conversion circuit, an adder for separately subtracting offset data from the digital amount, and a three-phase / two-phase conversion circuit for converting the subtraction result into a stator coordinate system having orthogonal α and β axes. , A coordinate conversion circuit for converting the stator coordinate system into a rotor coordinate system composed of orthogonal d and q axes, and a deviation between a voltage amount obtained from the coordinate conversion circuit and a voltage command value set separately. To zero, a voltage vector command calculation circuit that calculates the magnitude and phase angle of the voltage vector from the control signal output by this voltage control circuit, and a three-phase output signal from this voltage vector command calculation circuit. A variable speed drive control circuit for an induction motor, comprising: a three-phase voltage command value calculation circuit that calculates a voltage command value, and a configuration that controls the voltage source inverter that drives an induction motor by the three-phase voltage command value. Q obtained from the coordinate conversion circuit
Input the axial voltage amount and the separately obtained rotation angle data θ, and subtract the q-axis voltage amount at θ = 60 ° from the q-axis voltage amount at θ = 240 °. Outputs the first phase offset data of -1 and q when θ = 240 °
If the value obtained by subtracting the q-axis voltage amount at θ = 60 ° from the axial voltage amount is negative, the 1st phase offset data that is +1 is output, and from the q-axis voltage amount at θ = 330 °, θ = 150. If the value obtained by subtracting the q-axis voltage amount at ° is positive, the third phase offset data of -1 is output, and q at θ = 330 ° is output.
If the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the axial voltage amount is negative, the offset compensation circuit that outputs the third phase offset data that becomes +1 is provided. The output of this offset compensation circuit is used as the offset data. It shall be given to the adder.

Alternatively, a voltage vector absolute value calculation circuit for calculating the magnitude of the voltage vector from the output of the three-phase / two-phase conversion circuit, and a voltage vector angle for calculating the phase angle of the voltage vector from the output of the coordinate conversion circuit. An arithmetic circuit, a voltage instruction arithmetic circuit for inputting the voltage instruction value to calculate the magnitude and phase angle of the voltage instruction vector, and the magnitude of the voltage instruction vector output by the voltage instruction arithmetic circuit and the voltage vector absolute value operation. Adjust the deviation from the output of the circuit to zero,
And a second adjustment for adjusting the deviation between the phase angle output by the voltage command arithmetic circuit and the output of the voltage vector angle arithmetic circuit to zero.
And the voltage signal obtained from the voltage vector absolute value calculation circuit, and the output signal of the second voltage adjustment circuit is supplied to the three-phase voltage command value calculation circuit. Input the rotation angle data θ, and if the value obtained by subtracting the q-axis voltage amount at θ = 60 ° from the q-axis voltage amount at θ = 240 ° is positive, it is -1st phase offset data. Is output, and if the value obtained by subtracting the q-axis voltage amount at θ = 60 ° from the q-axis voltage amount at θ = 240 ° is negative, the 1st phase offset data of +1 is output and θ = 330 If the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the q-axis voltage amount at ° is positive, the third phase offset data of -1 is output, and the q-axis at θ = 330 °. The third phase is off when the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the voltage amount is negative is +1. Includes an offset arithmetic circuit for outputting a Ttodeta, it shall be given the output of the offset compensation circuit to the adder as the offset data.

[0009]

FIG. 6 is a vector diagram showing each phase voltage vector. If the first phase voltage detection value e _u detected by the voltage detector has an offset e _uo and the third phase voltage detection value e _w has an offset e _wo , the second phase voltage is the first phase voltage detection value e. Since it is calculated from _u and the third-phase voltage detection value e _w , the offset vectors e _uo ^* and e _wo ^* are as shown in the vector diagram of FIG.

As shown in the graph described above in FIG. 3, the first
If the phase has a positive offset, the rotation angle data θ is 6
The pulsation component of the q-axis voltage data V _fq becomes maximum when it is 0 °, and becomes minimum when the rotation angle data θ is 240 °. When the third phase has a positive offset, the rotation angle data θ is as shown in the graph described above with reference to FIG.
The pulsation component of the q-axis voltage data V _fq becomes maximum when the angle is 150 °, and the pulsation component becomes minimum when the rotation angle data θ is 330 °. Therefore, the q-axis voltage data V _fq when the theta = 60 ° and e (0), the V _fq when the theta = 0.99 ° and e (1), the V _fq when the θ = 240 ° e ( 2) and θ = 3
Let V _fq at 30 ° be e (3).

FIG. 7 is a graph _showing the pulsating state of the q-axis voltage data V _fq when there is a positive offset in the first phase by e (0) and e (2), and FIG. 8 shows the third phase. The pulsating state of the q-axis voltage data V _fq when there is a positive offset at e (1) and e
(3) is a graph represented by. Here, if (a) e (2) −e (0)> 0, the first phase offset data OF _u = −1 (b) e (2) −e (0) <0, then If the one-phase offset data _OFu = + 1 (c) e (3) -e (1)> 0, the third-phase offset data _OFw = -1 (d) e (3) -e (1) <0. In this case, the offset of each phase voltage detector can be compensated by performing the calculation with the third phase offset data OF _w = + 1. The above algorithm is the same for the magnitude of the voltage vector.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention. An A / D conversion circuit 2 described in this first embodiment circuit is shown.
And 3, adder 4 and 5, PU data operation circuit 6, 3 phase / 2
Phase conversion circuit 7, coordinate conversion circuit 8, first voltage adjustment circuit 9,
Since the names, applications, and functions of the voltage vector command calculation circuit 10 and the three-phase voltage command value calculation circuit 11 are the same as those of the conventional circuit described above with reference to FIG. 3, their description will be omitted.

The first embodiment circuit of FIG. 1 is a coordinate conversion circuit 8
The q-axis voltage data V _fq output by the above is input to the offset compensation circuit 21 together with the rotation angle data θ, and the algorithms (a), (b), (c), and (d) described above are used from these V _fq and θ. According to the first phase offset data OF _u and the third phase offset data OF _w , the adder 4 and the adder 5 are calculated.
To compensate the offset of each phase voltage detector, as described above.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The A / D conversion circuit 2 and 3, adder 4 and 5, PU data operation circuit described in the second embodiment circuit are shown. 6,3 phase /
The two-phase conversion circuit 7, the coordinate conversion circuit 8, and the three-phase voltage command value calculation circuit 11 have the same names, uses, and functions as those of the conventional example circuit described above with reference to FIG. .

In the circuit of the second embodiment shown in FIG. 2, the voltage command calculation circuit 33 sets the difference between the voltage command vector absolute value | V ₁ | and the voltage data vector absolute value | V _f | The voltage control vector absolute value | V | is output, and the voltage control vector phase angle δ ^* is output by performing an adjustment operation to make the difference between the voltage command vector phase angle δ ₁ and the voltage data vector phase angle δ _f zero. . Therefore, the voltage vector absolute value calculation circuit 31 calculates the voltage data vector absolute value | V _f | from the α-axis voltage data V _a and the β-axis voltage data V _b output by the three-phase / two-phase conversion circuit 7, and the voltage vector The angle calculation circuit 32 calculates the voltage data vector phase angle δ _f from the d-axis voltage data V _fd and the q-axis voltage data V _fq output by the coordinate conversion circuit 8. Further, the voltage command calculation circuit 3
3 receives the d-axis voltage command value V _1d and the q-axis voltage command value V _1q and calculates the voltage command vector absolute value | V ₁ | and the voltage command vector phase angle δ ₁ . Second voltage adjustment circuit 34
Is the voltage control vector absolute value | V | and the voltage control vector phase angle δ ^* output by the adjustment calculation operation. The three-phase voltage command value calculation circuit 11 calculates each phase voltage command signal V _u ^* , V _v ^* , and V _w. Converted to ^* .

Further, the offset calculation circuit 35 inputs the voltage data vector absolute value | V _f | output from the voltage vector absolute value calculation circuit 31 together with the rotation angle data θ,
According to the above-mentioned algorithm, the first phase offset data O
The F _u and the third phase offset data OF _w are output to the adder 4 and the adder 5.

[0017]

Since the q-axis voltage data pulsates due to the offset of the voltage detector, the feedback control of the instantaneous voltage vector may not be performed correctly. However, according to the present invention, the appropriate algorithm is provided. Since the pulsation of the q-axis voltage data can be suppressed by providing the offset calculation circuit, the effect that the feedback control of the instantaneous voltage vector can be correctly performed can be obtained.

[Brief description of drawings]

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

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

FIG. 3 is a circuit diagram showing a conventional example of a control circuit for controlling a power converter for variable speed drive of an induction motor.

FIG. 4 is a graph showing a pulsating state of the q-axis voltage data V _fq when the first phase has a positive offset.

FIG. 5 is a graph showing a pulsating state of the q-axis voltage data V _fq when the third phase has a positive offset.

FIG. 6 is a vector diagram showing each phase voltage vector.

FIG. 7 is a _{graph in which} the pulsating state of the q-axis voltage data V _fq when the first phase has a positive offset is represented by e (0) and e (2).

FIG. 8 is a graph _showing the pulsating state of the q-axis voltage data V _fq when there is a positive offset in the third phase, as e (1) and e (3).

[Explanation of symbols]

 2,3 A / D conversion circuit 4,5 Adder 6 PU data operation circuit 7 3-phase / 2-phase conversion circuit 8 Coordinate conversion circuit 9 First voltage adjustment circuit 10 Voltage vector command operation circuit 11 3-phase voltage command value operation circuit 21 Offset Compensation Circuit 31 Voltage Vector Absolute Value Calculation Circuit 32 Voltage Vector Angle Calculation Circuit 33 Voltage Command Calculation Circuit 34 Second Voltage Adjustment Circuit 35 Offset Calculation Circuit

Claims (2)

[Claims] 1. An A / D conversion circuit for separately converting a first-phase voltage detection value and a third-phase voltage detection value of a voltage source inverter that outputs a three-phase alternating current into a digital quantity, and an offset from this digital quantity separately. An adder for subtracting data, a three-phase / two-phase conversion circuit for converting the subtraction result into a stator coordinate system having orthogonal α-axis and β-axis, and a d-axis and a q-axis orthogonal to the stator coordinate system. A coordinate conversion circuit that performs coordinate conversion into a rotor coordinate system that is composed of an axis, a voltage adjustment circuit that adjusts the deviation between the voltage amount obtained from this coordinate conversion circuit and a separately set voltage command value to zero, and this voltage adjustment circuit. A voltage vector command calculation circuit that calculates the magnitude and phase angle of a voltage vector from a control signal output from the circuit, and a three-phase voltage command value calculation circuit that calculates a three-phase voltage command value from the output signal of this voltage vector command calculation circuit. With and invite In a variable speed drive control circuit for an induction motor configured to control the voltage source inverter that drives a conductive motor with the three-phase voltage command value, a q-axis voltage amount obtained from the coordinate conversion circuit and a rotation angle obtained separately. Input the data θ and the q-axis voltage amount at θ = 240 ° to q at θ = 60 °.
If the value obtained by subtracting the axial voltage amount is positive, the first phase offset data of -1 is output, and the q-axis voltage amount when θ = 240 ° is changed to q when θ = 60 °.
If the value obtained by subtracting the axial voltage amount is negative, the 1st phase offset data of +1 is output, and the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the q-axis voltage amount at θ = 330 °. If is positive, it outputs the third phase offset data of -1, and if the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the q-axis voltage amount at θ = 330 ° is +1, A variable speed drive control circuit for an induction motor, comprising: an offset compensating circuit for outputting the third phase offset data, wherein the output of the offset compensating circuit is given to the adder as offset data. 2. An A / D conversion circuit for separately converting a first phase voltage detection value and a third phase voltage detection value of a voltage source inverter which outputs a three-phase alternating current into a digital quantity, and an offset from this digital quantity separately. An adder for subtracting data, a three-phase / two-phase conversion circuit for converting the subtraction result into a stator coordinate system having orthogonal α-axis and β-axis, and a d-axis and a q-axis orthogonal to the stator coordinate system. A coordinate conversion circuit that performs coordinate conversion into a rotor coordinate system that is composed of an axis, a voltage adjustment circuit that adjusts the deviation between the voltage amount obtained from this coordinate conversion circuit and a separately set voltage command value to zero, and this voltage adjustment circuit. A voltage vector command calculation circuit that calculates the magnitude and phase angle of a voltage vector from a control signal output from the circuit, and a three-phase voltage command value calculation circuit that calculates a three-phase voltage command value from the output signal of this voltage vector command calculation circuit. With and invite In a variable-speed drive control circuit for an induction motor configured to control the voltage source inverter that drives a conductive motor with the three-phase voltage command value, the magnitude of a voltage vector is calculated from the output of the three-phase / two-phase conversion circuit. A voltage vector absolute value calculation circuit, a voltage vector angle calculation circuit for calculating the phase angle of the voltage vector from the output of the coordinate conversion circuit, and a voltage command value input to calculate the magnitude and phase angle of the voltage command vector. The deviation between the voltage command calculation circuit, the magnitude of the voltage command vector output by the voltage command calculation circuit and the output of the voltage vector absolute value calculation circuit is adjusted to zero, and the phase angle output by the voltage command calculation circuit and A second voltage adjusting circuit for adjusting the deviation from the output of the voltage vector angle calculating circuit to zero, and outputting the output signal of the second voltage adjusting circuit to the three-phase voltage. The magnitude of the voltage vector obtained from the voltage vector absolute value calculation circuit and the separately obtained rotation angle data θ are input to the command value calculation circuit, and the q-axis voltage amount at θ = 240 ° is calculated. q when θ = 60 °
If the value obtained by subtracting the axial voltage amount is positive, the first phase offset data of -1 is output, and the q-axis voltage amount when θ = 240 ° is changed to q when θ = 60 °.
If the value obtained by subtracting the axial voltage amount is negative, the 1st phase offset data of +1 is output, and the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the q-axis voltage amount at θ = 330 °. If is positive, it outputs the third phase offset data of -1, and if the value obtained by subtracting the q-axis voltage amount at θ = 150 ° from the q-axis voltage amount at θ = 330 ° is +1, A variable speed drive control circuit for an induction motor, comprising: an offset calculation circuit for outputting the third-phase offset data, and providing the output of the offset compensation circuit as offset data to the adder.