JPH0993997A - Ac motor drive inverter control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the abnormality of a motor current due to the discontinuous change of a deviation angle δ between a d-axis value and a q-axis value when an AC motor operated by a VVVF inverter for analysing it into the d-axis value and the q-axis value to perform vector control is reversed. SOLUTION: An electrical angle holding circuit 31 holds an electrical angle θobtained at the time of the inversion of an electric motor as it is to give it to a vector rotation device 23 as a d-q axis computing electrical angle θ1 and however, if a comparator 32 detects θ1 =θ, the holding state is released. Therefore, it can be avoided that a d-axis voltage detection value Vd and a q-axis voltage detection value Vq computed by the vector rotation device 23 become an abnormal value. Further, a pattern generating circuit 33 avoids that a d-axis adjustment computing value Vd1 and a q-axis adjustment computing value Vq1 outputted from an adjustment device 13 become an abnormal value by weakening the adjustment device gains K1 , K2 of the adjustment device 13, and the current jump or the generation of an abnormal sound of an induction motor 4 driven by a VVVF inverter 3 is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling an inverter when switching the rotation direction of an AC electric motor operated by an inverter that outputs AC power of variable voltage and variable frequency by vector control.

[0002]

2. Description of the Related Art FIG. 6 is a circuit diagram showing a conventional example of an inverter for driving an AC motor by outputting AC power of variable voltage and variable frequency by vector control. In this conventional circuit, the AC power from the AC power supply 2 is supplied to a VVVF inverter 3 which converts the AC power into a variable voltage / variable frequency AC power and outputs it. The VVVF inverter 3 controls the voltage and frequency so that the ratio of the output AC voltage and frequency is constant, and the output AC power drives the induction motor 4 at a desired rotation speed. Here, the VVVF inverter 3 is controlled by the procedure described below.

The three-phase voltage detector 21 detects the U-phase voltage detection value V of the three-phase AC voltage output from the VVVF inverter 3.
Three-phase / two-phase converter 2 by detecting the _U and W phase voltage detection value V _W
Give to 2. The three-phase / two-phase converter 22 is operated by the following mathematical formula 1 to detect the two-phase AC amounts on the a-axis and the b-axis which are orthogonal to each other on the fixed axis, that is, the a-axis voltage detection value V _a and the b-axis voltage detection. Convert to the value V _b .

[0004]

[Equation 1]

The a-axis voltage detection value V _a and the b-axis voltage detection value V _b are the frequency command value f set by the frequency setter 11.
By using the electrical angle θ obtained by integrating ^* , the DC amount on the rotation coordinate axis is calculated by the following mathematical formula 2.
It is converted into the axial voltage detection value V _d and the q-axis voltage detection value V _q .

[0006]

[Equation 2]

On the other hand, the voltage command value generator 12 generates the d-axis voltage command value V _d ^* and the q-axis voltage command value V _q ^* from the frequency command value f ^* set by the frequency setting device 11. Controller 1 composed of a proportional calculator or a proportional integral calculator
3, the deviation between the d-axis voltage command value V _d ^* and the d-axis voltage detection value V _d , and the q-axis voltage command value V _q ^* and the q-axis voltage detection value V
By inputting the deviation from _q and separately performing the adjusting operation to make these deviations zero, the adjuster 13 outputs the d-axis adjustment calculation value V _d1 and the q-axis adjustment calculation value V _q1. . Note that K ₁ and K ₂ input to the adjuster 13 are the d-axis and q-axis adjuster gains, respectively.

The command value calculation circuit 14 inputs the d-axis adjustment calculation value V _d1 and the q-axis adjustment calculation value V _q1 output from the controller 13, and calculates the deviation from the voltage command value V ₁ by the calculation of the following formula 3. Output the angle δ.

[0009]

(Equation 3)

As described above, the electrical angle θ is obtained by integrating the frequency command value f ^* set by the frequency setting device 11 by the integrator 16. By adding the electrical angle θ and the deviation angle δ output from the command value calculation circuit 14, the a-d axis phase angle ε is obtained. The three-phase voltage command value calculator 15 uses this a-
Input the d-axis phase angle ε and the voltage command value V ₁ described above,
The U-phase voltage command value V _U ^* , the V-phase voltage command value V _V ^*, and the W-phase voltage command value V _W ^* are obtained by performing the calculation of the following formula 4. These phase voltage command values V _U ^* ,
By applying V _V ^* and V _W ^* to the VVVF inverter 3, the phase voltages V _U , V _V and V _W output by the VVVF inverter 3 can be made to match the command values.

[0011]

V _U = V ₁ · cos ε V _V = V ₁ · cos (ε-120 ^O ) V _W = V ₁ · cos (ε-240 ^O ) The conventional circuit shown in FIG. The concept of
In this example, the voltage control system is constructed by incorporating it into an open loop inverter that does not have a speed control system. Here, it is considered that the d-axis corresponds to the exciting current and the q-axis corresponds to the torque current.

[0012]

When switching the rotation direction of the induction motor 4 in the conventional circuit shown in FIG. 6, the drive mode of the forward rotation is changed to the braking mode of the forward rotation, and then the drive mode of the reverse rotation. Will be moved to. Therefore, the polarity of the q-axis voltage detection value V _q is reversed when switching from the normal rotation to the reverse rotation (as described above, the q-axis corresponds to the torque current). At this time, since the d-axis voltage detection value V _d is zero, the deviation angle δ changes from +90 ^O to −90 ^O , so a−
The d-axis phase angle ε also correspondingly changes discontinuously.
As a result, the current phase of the induction motor 4 jumps, causing inconveniences such as jerky rotation of the electric motor and generation of abnormal noise.

Therefore, when the induction motor 4 reversely rotates, the electrical angle θ is discontinuously changed in response to the deviation angle δ changing from +90 ^O to −90 ^O , whereby the phase between the a and d axes is changed. The angle ε does not become discontinuous. In the conventional circuit of FIG. 7, the broken line from the reverse rotation commander 24 to the integrator 16 is a command for changing the electrical angle θ discontinuously during reverse rotation.

However, when the electrical angle θ is changed discontinuously, the d-axis voltage detection value V _d and the q-axis voltage detection value V _q (see Formula 2) calculated by the vector rotator 23 become abnormal values. Therefore, the d-axis adjustment calculation value V _d1 which is the output of the adjuster 13 that inputs these V _d and V _q to perform the adjustment operation.
And the q-axis adjustment calculation value V _q1 become an abnormal value, and eventually a problem such as a current jump of the induction motor 4 occurs.

FIG. 7 is an operation waveform diagram showing the operation of each part when the electric motor is rotated in the reverse direction in the conventional circuit shown in FIG. 6, FIG. 7 shows changes in the electrical angle θ, and FIG. FIG. 7 shows changes in the inter-axis phase angle ε, FIG. 7 shows changes in the deviation angle δ, and FIG. 7 shows changes in the output of the adjuster 13. This FIG.
At time t ₀ , the induction motor 4 reverses, and the electrical angle θ which is the output of the integrator 16 is discontinuously changed corresponding to the discontinuous change of the deviation angle δ at this time. However, because of this, it can be seen that the output of the controller 13 (see FIG. 7) has an abnormal value.

Therefore, an object of the present invention is to deviate the d-axis value and the q-axis value from each other, and to reverse the alternating-current motor operated by a VVVF inverter which performs vector control by dividing the value into a d-axis value and a q-axis value. It is to suppress the abnormality of the electric motor current due to the discontinuous change of the.

[0017]

In order to achieve the above-mentioned object, a method of controlling an inverter for driving an AC motor according to the present invention comprises a fixed shaft for detecting a three-phase AC detected from an output side of an inverter for driving an AC motor. After converting into the two-phase alternating current amount on the a-axis and the b-axis which are orthogonal to each other, the two-phase alternating current amount is vector-rotated by the electrical angle obtained by the integral calculation of the frequency command value separately determined, and the two-phase alternating current amount is on the rotating coordinate axis. An adjustment calculation for converting the d-axis detected value and the q-axis detected value, which are direct current amounts, to match the d-axis detected value and the q-axis detected value separately with the d-axis command value and the q-axis command value. Go to d axis adjustment calculation value and q
The axis adjustment calculation value is obtained, the voltage command value and the deviation angle are obtained from the d axis adjustment calculation value and the q axis adjustment calculation value, and the phase angle between the a axis and the d axis is calculated from the deviation angle and the electrical angle. Obtained, calculate a three-phase voltage command value from this phase angle and the voltage command value,
In the method for controlling an AC motor driving inverter configured to control the inverter with the three-phase voltage command value, the electrical angle calculation by the integral calculation of the frequency command value is continued even when the rotation direction of the AC motor is switched. Separately, the electrical angle held at the value at the time of switching the rotation direction is maintained, and the held electrical angle is used for the calculation of the d-axis detected value and the q-axis detected value. Further, the holding state is released when the electric angle which is being calculated by the integral calculation becomes the same value as the held electric angle, and the d-axis detected value and the q-axis detected value are calculated by the integration. It is assumed that the electrical angle whose calculation is being continued is used again.

Alternatively, even when the rotation direction of the AC motor is switched, the calculation of the electrical angle by the integral calculation of the frequency command value is continued, but the electrical angle held separately at the value at the time of switching the rotation direction is maintained, The held electrical angle is used for the calculation of the d-axis detected value and the q-axis detected value. Furthermore, when the electric angle that continues to be calculated by the integral calculation becomes the same value as the held electric angle, this hold state is released,
For the calculation of the d-axis detected value and the q-axis detected value, the electrical angle that continues to be calculated by the integral calculation is used again, and the d-axis command for separately setting the d-axis detected value and the q-axis detected value It is assumed that the adjustment gain when performing the adjustment calculation to match the value and the q-axis command value is weakened during the period from the holding start time of the electrical angle to the holding release time.

As described above, when the AC motor operated by the VVVF inverter which is decomposed into the d-axis value and the q-axis value and is vector-controlled is reversed, the deviation angle δ between the d-axis value and the q-axis value is not correct. Since it changes continuously, the electrical angle θ is changed discontinuously in order to cope with this, but when calculated using this electrical angle θ, the d-axis voltage detection value V _d and the q-axis voltage detection value V _q are abnormal. It becomes a value. Therefore, the electric angle θ at the time when the electric motor reverses is held and its value is set to θ _1, and this θ ₁ is used to calculate the d-axis voltage detection value V _d and the q-axis voltage detection value V _q .
This hold state is released when θ ₁ = θ. Furthermore, the adjustment gain when performing the adjustment calculation for matching the d-axis detected value and the q-axis detected value with the d-axis command value and the q-axis command value that are separately set is also a period during which the electrical angle θ is held. By weakening only in the middle, the abnormality of the AC voltage output by the VVVF inverter is eliminated, and inconvenience such as current jump of the electric motor is avoided.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This first embodiment circuit includes an electrical angle holding circuit 31 in addition to the conventional example circuit described in FIG. Comparator 32
It is configured by adding and. Therefore, the description of the same parts as those of the conventional circuit of FIG. 6 will be omitted. In this first embodiment circuit, the electrical angle θ output by the integrator 16 is the electrical angle holding circuit 3
1 to the vector rotator 23. Since the electrical angle holding circuit 31 does not perform the holding operation during normal operation,
The electrical angle θ ₁ for dq axis calculation output by the electrical angle holding circuit 31 has the same value as the electrical angle θ output by the integrator 16. When the reverse rotation command of the induction motor 4 is issued here, the reverse rotation command device 24 gives a holding command to the electrical angle holding circuit 31, so that the electrical angle θ at this point is the electrical angle θ ₁ for dq axis calculation. To the vector rotator 23. Therefore, the d-axis voltage detection value V _d and the q-axis voltage detection value V _q output by the vector rotator 23 are obtained from the calculation of the following Equation 5.

[0021]

(Equation 5)

The electrical angle θ output from the integrator 16 and the electrical angle θ ₁ for dq axis calculation held and output by the electrical angle holding circuit 31 are input to the comparator 32. When they match, the comparator 32 causes the electrical angle holding circuit 31 to
Since the command to cancel the holding operation is issued to, the electrical angle θ is again input to the vector rotator 23 as it is.

FIG. 2 is a flow chart showing the operation of the portion of the present invention in the first embodiment circuit shown in FIG.
That is, the electrical angle holding circuit 31 holds the output value at that time (processing 42) by issuing the reverse rotation command (processing 41). Next, the electrical angle θ ₁ for dq axis calculation held by the comparator 32 and the electrical angle θ output by the integrator 16 are compared (Processing 4
3) Then, when both values match (decision 45), the electric angle holding circuit 31 is instructed to cancel the holding operation (process 44).

FIG. 3 is an operation waveform diagram showing the operation of each part when the electric motor is rotated in the reverse direction in the circuit of the first embodiment shown in FIG. 1. FIG. 3 shows changes in the electrical angle θ, and FIG. 3 shows d. -Changes in the electrical angle θ ₁ for q-axis calculation, FIG. 3 shows changes in the phase angle ε between the a-d axes, FIG. 3 shows changes in the deviation angle δ, and FIG. 3 shows changes in the output of the controller 13. ing. In FIG. 3, at time t ₀ when the induction motor 4 reversely rotates, the electrical angle θ which is the output of the integrator 16 is discontinuously changed in response to the discontinuous change of the deviation angle δ. The electrical angle θ ₁ for d-q axis calculation output by the holding circuit 31 holds the value of the electrical angle at the time of reverse rotation as it is, and this holding state is released at time t ₁ when θ ₁ = θ. As a result, it can be seen that the change in the output of the adjuster 13 (see FIG. 3) is suppressed to be small.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention. In this second embodiment circuit, a pattern generation circuit 33 is added to the first embodiment circuit described in FIG. I am configuring. Therefore, the description of the same parts as those of the first embodiment circuit of FIG. 1 will be omitted. In the circuit of the first embodiment described above, the electrical angle θ output from the integrator 16 is given to the vector rotator 23 via the electrical angle holding circuit 31, and the electrical angle θ at that time is d by the reverse rotation command.
The q-axis calculation electrical angle θ ₁ is given to the vector rotator 23, and the comparator 32 instructs the electrical angle holding circuit 31 to cancel the holding operation at the time of θ ₁ = θ.
The second embodiment circuit of FIG. 4 is further provided with a pattern generation circuit 33. The pattern generation circuit 33 weakens the controller gains K ₁ and K ₂ input to the controller 13 at the same time when the reverse rotation command is issued, but the comparator 32 outputs θ ₁ =.
When θ is detected, the weakening of the controller gains K ₁ and K ₂ is restored.

FIG. 5 is an operation waveform diagram showing the operation of each part when the electric motor is rotated in the reverse direction in the circuit of the second embodiment shown in FIG. 4. FIG. 5 shows changes in the electrical angle θ, and FIG. -Change of q-axis calculation electrical angle θ ₁ , Fig. 5 is change of a-d axis phase angle ε, Fig. 5 is change of deviation angle δ, Fig. 5 is d-q-axis calculation electrical angle θ ₁ D-axis voltage detection value V _d and q
FIG. 5 shows changes in the axial voltage detection value V _q , FIG. 5 shows changes in the gain of the controller 13, and FIG. 5 shows changes in the output of the controller 13. In FIG. 5, at time t ₀ when the induction motor 4 reversely rotates, the electrical angle θ which is the output of the integrator 16 is discontinuously changed in response to the discontinuous change in the deviation angle δ. The electrical angle θ ₁ for dq axis calculation output from the holding circuit 31 holds the value of the electrical angle during reverse rotation as it is,
This holding state is released at time t ₁ when ₁ = θ.
At the same time, the gain of the adjuster 13 is weakened. As a result, d
It can be seen that the change in the axial voltage detection value V _d and the q-axis voltage detection value V _q is suppressed, and the output change of the controller 13 is also suppressed to a small level.

[0027]

When the AC motor operated by the VVVF inverter which is decomposed into the d-axis value and the q-axis value and is vector-controlled, is reversed, the deviation angle δ between the d-axis value and the q-axis value changes discontinuously. . On the other hand, in the present invention, the electrical angle θ used for calculating the d-axis voltage detection value V _d and the q-axis voltage detection value V _q is held at the value at the time of reverse rotation, and this value is used as the d-q axis calculation electrical value. Used as the angle θ ₁ . Further, a controller that performs adjustment calculation to match the d-axis voltage command value V _d ^* and the q-axis voltage command value V _q ^* that separately set the d-axis voltage detection value V _d and the q-axis voltage detection value V _q By temporarily weakening the gain during reverse rotation, even if the deviation angle δ changes discontinuously, the calculated values of the d-axis voltage detection value V _d and the q-axis voltage detection value V _q become abnormal values, or the controller Since it is possible to suppress the output value from becoming abnormal, it is possible to obtain the effect of suppressing the occurrence of current jump and abnormal noise of the electric motor.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the portion of the present invention in the first embodiment circuit shown in FIG.

FIG. 3 is an operation waveform diagram showing the operation of each part when the electric motor is reversed in the first embodiment circuit shown in FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

5 is an operation waveform diagram showing the operation of each part when the electric motor is reversed in the circuit of the second embodiment shown in FIG.

FIG. 6 is a circuit diagram showing a conventional example of an inverter that drives an AC electric motor by outputting AC electric power of a variable voltage / variable frequency by vector control.

FIG. 7 is an operation waveform diagram showing the operation of each part when the electric motor is reversed in the conventional circuit shown in FIG.

[Explanation of symbols]

 2 AC power supply 3 VVVF inverter 4 Induction motor 11 Frequency setter 12 Voltage command value generator 13 Controller 14 Command value calculation circuit 15 Three-phase voltage command value calculator 16 Integrator 21 Three-phase voltage detector 22 Three-phase / two-phase Converter 23 Vector rotator 24 Reverse rotation command device 31 Electrical angle holding circuit 32 Comparator 33 Pattern generation circuit 41-44 Processing 45 Judgment

Claims (2)

[Claims] 1. A three-phase AC detection amount detected from the output side of an inverter for driving an AC motor is converted into a two-phase AC amount on an a-axis and a b-axis orthogonal to each other on a fixed axis, and then separately determined. The two-phase alternating current amount is vector-rotated by the electrical angle obtained by the integral calculation of the frequency command value to be converted into a d-axis detected value and a q-axis detected value which are direct-current amounts on the rotation coordinate axis, and these d
The d-axis adjustment calculation value and the q-axis adjustment calculation value are obtained by performing an adjustment calculation to match the d-axis command value and the q-axis command value, which separately set the axis detection value and the q-axis detection value, and obtain these d-axis adjustment values. The voltage command value and the deviation angle are calculated from the calculated value and the q-axis adjustment calculation value, the phase angle between the a-axis and the d-axis is calculated from the deviation angle and the electrical angle, and from the phase angle and the voltage command value. In a method of controlling an inverter for driving an AC motor, which is configured to calculate a three-phase voltage command value and control the inverter with this three-phase voltage command value, when switching the rotation direction of the AC motor, the d-axis detection value and Only the electric angle used for the calculation of the q-axis detection value is held at the value at the time of switching the rotation direction, and the holding state is released when the electric angle obtained by the integral calculation matches the held value. A method for controlling an inverter for driving an AC motor. 2. A three-phase AC detection amount detected from the output side of an inverter for driving an AC motor is converted into a two-phase AC amount on an a-axis and a b-axis, which are orthogonal to each other on a fixed axis, and then separately determined. The two-phase alternating current amount is vector-rotated by the electrical angle obtained by the integral calculation of the frequency command value to be converted into a d-axis detected value and a q-axis detected value which are direct-current amounts on the rotation coordinate axis, and these d
The d-axis adjustment calculation value and the q-axis adjustment calculation value are obtained by performing an adjustment calculation to match the d-axis command value and the q-axis command value, which separately set the axis detection value and the q-axis detection value, and obtain these d-axis adjustment values. The voltage command value and the deviation angle are calculated from the calculated value and the q-axis adjustment calculation value, the phase angle between the a-axis and the d-axis is calculated from the deviation angle and the electrical angle, and from the phase angle and the voltage command value. In a method of controlling an inverter for driving an AC motor, which is configured to calculate a three-phase voltage command value and control the inverter with this three-phase voltage command value, when switching the rotation direction of the AC motor, the d-axis detection value and Only the electric angle used for the calculation of the q-axis detection value is held at the value at the time of switching the rotation direction, and the holding state is released when the electric angle obtained by the integral calculation matches the held value. From the start of holding the corner to the end of the holding state. During the period, the gain of the adjustment calculation for matching the d-axis detected value and the q-axis detected value with the d-axis command value and the q-axis command value is weakened.