JP2000342000A - Equipment and method for controlling induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control driving of an induction motor by accurately tuning the constants of an induction motor while taking drop in the on-state voltage of an inverter main circuit power element taken into consideration, with the induction motor in an out-of-operation state. SOLUTION: A controller of an induction motor 2 is provided with a PWM generation circuit 11, which generates a PWM signal from the output voltage command of each phase and supplies it to a power converter 1. In this case, the controller is also provided with a motor constant tuning means 12, which tunes the resistance of the induction motor 2, the drop of on-state voltage of a main circuit power element, the leakage inductance and the mutual inductance based on the output voltage command and a primary current detected value, with the induction motor 2 kept in an out-of-operation state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for an induction motor for controlling the induction motor with high precision by tuning the resistance, leakage inductance and mutual inductance of the induction motor with the induction motor stopped. And its control method.

[0002]

2. Description of the Related Art As a prior art, as a method of tuning the constant of an induction motor while the induction motor is stopped, a single-phase alternating current is supplied to the induction motor, and a d-axis current detection value or a q-axis current detection value is used. Was expanded to a Fourier series to determine the constant of the induction motor.

[0003]

In order to control the induction motor with high accuracy, it is necessary to know the constant of the induction motor accurately, but for that purpose, it was necessary to rotate the induction motor. However, in order to respond to a request for tuning the constant of the induction motor while the induction motor is stopped, a single-phase alternating current is applied and a Fourier series expansion is used as in the related art. However, this method has a problem that the software is complicated, the processing time of the software is long, and the software requires a large storage capacity. Furthermore, the amount of ON voltage drop of the inverter main circuit element has not been able to be easily compensated so far because of the variation of the main circuit element itself. For example, the ON voltage drop amount of the inverter main circuit element has a value of 0.5 to 2 volts when the IGBT is used, but the ON voltage drop amount of this element has not been considered in the past and the measurement accuracy was poor. In particular, in the sensorless vector control, the influence of the on-voltage drop becomes large in the low-speed region, and the measurement accuracy of the induction motor constant is reduced. Therefore, the speed control performance in the low-speed region is poor. Therefore, the present invention tunes the constant of the induction motor with high accuracy in consideration of the on-voltage drop of the inverter main circuit power element while the induction motor is stopped, and drives the induction motor with high accuracy using the result. And a control method thereof.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a power converter that converts a direct current into an alternating current of an arbitrary frequency and voltage and supplies the alternating current to an induction motor. A current detection circuit for detecting a secondary current, a coordinate conversion circuit for converting a primary current supplied to the induction motor into an excitation current detection value and a torque current detection value and outputting the same, and a given excitation current command value and a given excitation current command value. A voltage command calculation circuit that calculates an excitation current direction voltage command and a torque current direction voltage command from the received torque current command value, and an excitation current direction voltage such that the excitation current command value matches the excitation current detection value. An exciting current control circuit for controlling, a torque current control circuit for controlling a torque current direction voltage so that the torque current command value matches the torque current detection value, A voltage command coordinate conversion circuit that inputs a value compensated by the output of the exciting current control circuit and a value obtained by compensating the torque current direction voltage command with the output of the torque current control circuit, and outputs a voltage command and a voltage phase command, An output voltage phase angle command calculation circuit for calculating an output voltage phase angle command to which a phase angle command obtained by integrating the voltage phase angle command and a given output frequency command is added, and the output voltage phase angle command; A two-phase / three-phase conversion circuit that receives the voltage command and converts it into an output voltage command for each phase; a PWM generation circuit that generates a PWM signal from the output voltage command for each phase and supplies the signal to the power converter; In the induction motor control device provided with, while the induction motor is stopped,
Motor constant tuning means for tuning the resistance of the induction motor, the on-voltage drop of the main circuit power element, the leakage inductance, and the mutual inductance from the output voltage command and the primary current detection value. . Further, the induction motor is controlled by a constant of the induction motor tuned by the motor constant tuning means. Further, the motor constant tuning means gives at least two types of DC current commands to the induction motor, obtains the output voltage command value such that the current detection value matches the DC current command value, and obtains the DC current value. , And a constant value that is not proportional to the on-voltage drop amount of the main circuit power element. Further, the motor constant tuning means applies a high-frequency voltage having a frequency sufficient to maintain the stopped state to the induction motor in the rotation stopped state, maintains the induction motor in the stopped state, and sets the voltage command value and It is characterized by comprising means for tuning a secondary resistance and a leakage inductance based on the detected current value. Further, the amount of on-voltage drop of the power element of the power converter main circuit is approximated to a component proportional to the current and a constant value V ₀ with respect to the current Ifb flowing through the power element, and a component proportional to the current is: on the voltage drop amount V ₀ which the power device included in the primary resistance r ₁ of the induction motor is a constant value proportional to the current, set the torque current command value Iqref and frequency command fref zero, two exciting current command Value I
The output voltage command values when dref ₁ and Idref ₂ are given are Vref ₁ and Vref ₂ , respectively, and the primary resistance r ₁ of the induction motor and the on-voltage drop V _{0 of the} power element are r ₁ = (Vref ₁ −Vref ₂ ) / {2 (Idref ₁ −Idref ₂ )} V ₀ = (Vref ₁ Idref ₂ −Vref ₂ Idref ₁ ) / (Idref ₂ −Idr
ef ₁ ) This is a control method characterized by being obtained as Also,
The amount of on-voltage drop of the power element of the power converter main circuit is approximated to a component proportional to the current and a constant value V ₀ with respect to the current Ifb flowing through the power element, and a component proportional to the current is an induction motor. on the voltage drop amount V ₀ which the power device included in the primary resistance r ₁ of the constant value which is not proportional to the current, set the torque current command value Iqref and frequency command fref to zero,
A plurality of excitation current command values Idref ₁ , Idref ₂ ,. . . , Idref _N
(N is an integer of 3 or more), and output voltage command values Vref ₁ , Vref ₂ ,. . . , Vref _N, and a primary resistance r ₁ of the induction motor and an on-voltage drop V ₀ of the power element based on the plurality of excitation current command values and the output voltage command values. Is a control method. Further, the torque current command value Iqref and the frequency command fref are set to zero, and the exciting current command value is set to Idref = Idref ₃
And apply it to the induction motor, and after a while,
In a state where the output voltage command is limited by the voltage command value Vref ₃ , the frequency command fref is changed to a frequency fref3 sufficient to maintain the stop state of the induction motor, and the limit of the output voltage command is removed after a predetermined time has elapsed. Current control is resumed, and at this time the post-compensation excitation current direction voltage command value Vdcr
ef ₃ and the compensated torque current direction voltage command Vqcref ₃ are obtained, and the secondary resistance r ₂ and the leakage inductance L of the induction motor are calculated as r ₂ = Vdcref ₃ / Idref ₃ -r ₁ L = Vqcref ₃ / (Idref ₃ × 2πfref). Also,
The motor constant tuning means applies a voltage for DC excitation to the induction motor, maintains the induction motor in a stopped state, and superimposes a signal for slightly changing the DC-excited secondary magnetic flux on a voltage command or a current command. 3. The control device for an induction motor according to claim 1, wherein a mutual inductance is calculated based on a current detection value and the voltage command or the voltage detection value, and the mutual inductance is tuned.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a control device for an induction motor according to the present invention. The control device of the induction motor according to the present embodiment includes:
Power converter 1, induction motor 2, current detector 3, current coordinate conversion circuit 4, voltage command calculation circuit 5, excitation current control circuit 6, torque current control circuit 7, voltage command coordinate conversion circuit 8,
An output voltage phase angle command calculation circuit 9, a two-phase three-phase coordinate conversion circuit 10, a PWM generation circuit 11, a motor constant tuning means 12 for tuning the resistance of the induction motor, the on-voltage drop of the power element, the leakage inductance and the mutual inductance. Have. The power converter 1 converts a given DC voltage or a DC voltage obtained by converting three-phase AC by a power element into an AC having an arbitrary frequency and voltage by a PWM control method, and supplies the AC to the induction motor 2. The current detector 3 detects a current supplied to the induction motor 2. The current coordinate conversion circuit 4 converts the current detected by the current detector 3 into an excitation current detection value Idfb and a torque current detection value Iqfb and outputs the same. The voltage command calculation circuit 5 calculates an excitation current direction voltage command Vdref and a torque current direction voltage command Vqref from the given excitation current command value Idref and the given torque current command value Iqref. The exciting current control circuit 6 calculates the exciting current direction voltage compensation value Vdc such that the exciting current command value Idref and the exciting current detection value Idfb match. The torque current control circuit 7 calculates the torque current direction voltage compensation value Vqc such that the torque current command value Iqref and the excitation current detection value Iqfb match. The voltage command coordinate conversion circuit 8 includes a compensated exciting current direction voltage command value Vdcref obtained by compensating the exciting current direction voltage command Vdref with the exciting current direction voltage compensation value Vdc, and the Vqcref torque current direction voltage command Vqre.
A compensated torque current direction voltage command value obtained by compensating f with the torque current direction voltage compensation value Vqc is input, and a voltage command Vref and a voltage phase command θv are output. The output voltage phase angle command calculation circuit 9 integrates the voltage phase angle command θv and a given output frequency command to obtain a phase angle command θfref.
And outputs the output voltage phase angle command θref. 2 phase 3
The phase coordinate conversion circuit 10 receives an output voltage command V1ref obtained by compensating the voltage command Vref with a voltage compensation amount which is an output of a phase angle dependent voltage compensation circuit described later and the output voltage phase angle command θref, and outputs the output of each phase. Convert to voltage command. The PWM generation circuit 11 generates a PWM signal from the output voltage command of each phase output from the two-phase / three-phase coordinate conversion circuit, and drives the power converter 1. The motor constant tuning means 12, which tunes the resistance of the induction motor and the amount of on-voltage drop and the leakage inductance of the power element, controls the resistance of the induction motor based on the output voltage command and the primary current detection value when the induction motor is stopped. In addition, the on-voltage drop amount, the leakage inductance and the mutual inductance of the power element are tuned. This tuning is performed before operation or immediately after an operation command is input, and the induction motor is driven using the tuned constant of the induction motor.

Next, a method of tuning the resistance of the induction motor, the amount of on-voltage drop of the power element, the leakage inductance, and the mutual inductance in the stopped state, which is one of the present invention, will be described. First, a method of measuring the primary resistance of the induction motor and the amount of on-voltage drop of the power element will be described. Here, the amount of ON voltage drop of the power element of the power converter can be approximated to a constant value and a component proportional to the current Ifb flowing through the power element in a normally used region. Thus, components proportional to the current, including the primary resistance r ₁ of the induction motor, on-state voltage drop V ₀ which the power element of the power converter is a constant value proportional to the current. This relationship is expressed by equation (1).

V = r ₁ Ifb + V ₀ (1)

Then, a torque current command value Iqref = 0 and a frequency command fref = 0 are set, two or more types of excitation current command values Idref are set, a DC current is supplied to the induction motor, and an output voltage command Find the relationship of Vref. Here, as an example, a case where two types of excitation current command values Idref ₁ and Idref ₂ are given will be described. At this time, assuming that the output voltage command values become Vref ₁ and Vref ₂ respectively, the primary resistance r ₁ of the induction motor and the on-voltage drop V _{0 of the} power element are (2) and (3), respectively. Obtained from the formula.

R ₁ = (Vref ₁ −Vref ₂ ) / {2 (Idref ₁ −Idref ₂ )} (2) V ₀ = (Vref ₁ Idref ₂ −Vref ₂ Idref ₁ ) / (Idref ₂ −Idref ₁ ) ( 3)

Is required. Here, two types of excitation current command values have been described, but three or more types can be similarly obtained. That is, the torque current command value Iqref and the frequency command fref are set to zero, and a plurality of excitation current command values Idre
f ₁ , Idref ₂ ,. . . , Idref _N (N is an integer of 3 or more), and an output voltage command value Vref corresponding to the exciting current command value
_1, Vref _2,. . . , Vref _N , and calculates the primary resistance r ₁ of the induction motor and the on-voltage drop V ₀ of the power element by a least square method or the like based on the plurality of excitation current command values and the output voltage command values, You can ask. Further, the present method provides a DC current command to measure the resistance r ₁ of the induction motor and the ON voltage drop amount of the power element, so that the excitation current command value and the torque current command value are arbitrarily set, It may be a DC current command value. Next, the induction motor
A method of tuning the secondary resistance and the leakage inductance will be described. Torque current command value Iqref = 0, frequency command f
ref = 0, sets the excitation current command value Idref = Idref _3, applied to the induction motor. After some time has elapsed, while limiting the output voltage command in the voltage command value Vref ₃ at this time, to change the frequency command fref to fref3 a high frequency. With this operation, the induction motor is out of step, and the induction motor can be stopped even though three-phase alternating current is being applied. Then, the limit of the output voltage command is removed, and the current control is restarted. At this time, the compensated excitation current direction voltage command value Vdcref ₃ and the compensated torque current direction voltage command Vqcref ₃ are obtained. Here, the compensation excitation current direction voltage command value and the compensated torque current direction voltage command value correspond to a voltage drop due to the resistance of the induction motor and a voltage drop due to the leakage inductance, respectively. Then, the secondary resistance r ₂ and the leakage inductance L of the induction motor are

R ₂ = Vdcref ₃ / Idref ₃ -r ₁ (4) L = Vqcref ₃ / (Idref ₃ × 2πfref) (5)

Is required. In this method, the leakage inductance on the secondary side is converted to primary and included in the leakage inductance on the primary side.

Next, a method of tuning the mutual inductance of the induction motor will be described. Normally, it is necessary to perform no-load operation to tune the mutual inductance. However, the present invention has a feature that tuning is performed by stopping the induction motor. The rotor of the induction motor is stopped by DC excitation of the induction motor. When a DC current is flowing, no current flows in the secondary circuit, and thus it is necessary to change the secondary magnetic flux in order to flow the current in the secondary circuit. As this method, a signal for slightly changing the DC-excited secondary magnetic flux is superimposed on a voltage command or a current command. This signal is desirably a sine wave, a triangular wave, a sawtooth wave, or the like having a low frequency. At this time, since the induction motor can be represented by the equivalent circuit of FIG. 2, the equations (6) and (7) are established. If the voltage command and the current detection value are known, the mutual inductance M can be obtained by solving equations (6) and (7).

[0014]

(Equation 1)

In this embodiment, the description will be made based on the current command value. However, the above equation can be similarly solved using the voltage command as a reference. First, as a current command, as a signal for changing the exciting current command I ₁ and the secondary magnetic flux, providing an alternating current command I _^'1 e ^j ω ^t of low frequencies. The voltage command is controlled by the current control so that the current command matches the current detection value. At this time, the voltage and current of the equivalent circuit of FIG.

[0016]

(Equation 2)

By substituting into equations (6) and (7),

[0018]

(Equation 3)

## EQU1 ## Solving this equation by dividing it into DC and AC components gives

[0020]

(Equation 4)

Is obtained. In considering the AC component,

[0022]

(Equation 5)

Considering only the real component of the equation (9),

[0024]

(Equation 6)

Is obtained. The mutual inductance can be tuned by substituting the voltage command value and the current detection value into the equation (13). In the present embodiment, the solution is performed by focusing on the real component. However, the solution may be performed by focusing on the imaginary component, or the solution may be performed by using the absolute value or the phase component.

[0026]

As described above, according to the present invention, the resistance, leakage inductance and mutual inductance of the induction motor are measured while the induction motor is stopped and the amount of on-voltage drop of the inverter main circuit power element itself is measured and taken into consideration. Can be tuned with high accuracy. Further, by driving the induction motor using the tuning result, there is an effect that the induction motor can be controlled with high accuracy. Since the present invention can measure and set the motor constant based on the voltage command value and the current detection value, the present invention is ideal for sensorless vector control in which the induction motor does not have a position / speed detector and a voltage detector for detecting an inverter output voltage. It is. Since the amount of on-voltage drop of the inverter main circuit element is also taken into consideration, speed control performance can be improved even in a low-speed region in sensorless vector control.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of an induction motor control device according to the present invention.

FIG. 2 Equivalent circuit of an induction motor (for one phase of a motor)

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power converter 2 Induction motor 3 Current detector 4 Current coordinate conversion circuit 5 Voltage command calculation circuit 6 Excitation current control circuit 7 Torque current control circuit 8 Voltage command coordinate conversion circuit 9 Output voltage phase angle command calculation circuit 10 Two phase three phase Coordinate conversion circuit 11 PWM generation circuit 12 Motor constant tuning means

Claims (8)

[Claims] 1. A power converter that converts a direct current into an alternating current of a given frequency and voltage and supplies it to an induction motor, a current detection circuit that detects a primary current supplied to the induction motor, A coordinate conversion circuit that converts the supplied primary current into an excitation current detection value and a torque current detection value and outputs the result;
A voltage command calculation circuit for calculating an excitation current direction voltage command and a torque current direction voltage command from a given excitation current command value and a given torque current command value, and wherein the excitation current command value and the excitation current detection value are An exciting current control circuit that controls an exciting current direction voltage so as to match; a torque current control circuit that controls a torque current direction voltage so that the torque current command value and the torque current detection value match; A voltage command coordinate for inputting a value obtained by compensating a direction voltage command with the output of the exciting current control circuit and a value obtained by compensating the torque current direction voltage command with the output of the torque current control circuit, and outputting a voltage command and a voltage phase command A conversion circuit, and an output for calculating an output voltage phase angle command to which a phase angle command obtained by integrating the voltage phase angle command and a given output frequency command is added. A pressure phase angle command calculation circuit, a two-phase three-phase conversion circuit that receives the output voltage phase angle command and the voltage command, and converts the output voltage command into each phase output voltage command, and a PWM signal based on the output voltage command for each phase. And a PWM generation circuit for generating and supplying the power to the power converter, in a state where the induction motor is stopped, the output voltage command and the primary current detection value, A control device for an induction motor, comprising motor constant tuning means for tuning the resistance of the induction motor, the amount of on-voltage drop of the main circuit power element, and the leakage inductance and mutual inductance. 2. The induction motor control device according to claim 1, wherein the induction motor is controlled by a constant of the induction motor tuned by the motor constant tuning means. 3. The motor constant tuning means gives at least two types of DC current commands to the induction motor, and obtains the output voltage command value whose current detection value matches the DC current command value, 3. The control of an induction motor according to claim 1, further comprising means for setting a component proportional to the DC current as a primary resistance of the induction motor and setting a non-proportional value as an on-voltage drop amount of a main circuit power element. apparatus. 4. The motor constant tuning means applies a high-frequency voltage having a frequency sufficient to maintain a stopped state to the induction motor in a rotation stopped state, and maintains the induction motor in a stopped state. 2. The apparatus according to claim 1, further comprising means for tuning a secondary resistance and a leakage inductance based on a command value and the detected current value.
Or the control device for an induction motor according to 2. 5. An on-voltage drop amount of a power element of a power converter main circuit with respect to a current Ifb flowing through the power element.
The component proportional to the current and a constant value V ₀ are approximated, and the component proportional to the current is included in the primary resistance r ₁ of the induction motor, and the ON voltage drop V ₀ of the power element is a constant value not proportional to the current. The torque motor command value Iqref and the frequency command fref are set to zero, and the output voltage command values when two types of excitation current command values Idref ₁ and Idref ₂ are given are Vref ₁ and Vref ₂ , respectively. oN voltage of the primary resistance r ₁ and a power element drop amount V ₀
R ₁ = (Vref ₁ −Vref ₂ ) / {2 (Idref ₁ −Idref ₂ )} V ₀ = (Vref ₁ Idref ₂ −Vref ₂ Idref ₁ ) / (Idref ₂ −Idr
ef ₁ ) A method for controlling an induction motor, wherein the method is obtained as: 6. An on-voltage drop amount of a power element of a power converter main circuit with respect to a current Ifb flowing through the power element.
The component proportional to the current and a constant value V ₀ are approximated, and the component proportional to the current is included in the primary resistance r ₁ of the induction motor, and the ON voltage drop V ₀ of the power element is a constant value not proportional to the current. The torque current command value Iqref and the frequency command fref are set to zero, and a plurality of excitation current command values Idref ₁ , Idref ₂ ,. . . , Idref _N
(N is an integer of 3 or more), and output voltage command values Vref ₁ , Vref ₂ ,. . . , Vref _N, and a primary resistance r ₁ of the induction motor and an on-voltage drop V ₀ of the power element based on the plurality of excitation current command values and the output voltage command values. Control method. 7. A torque current command value Iqref and a frequency command fre
zero f, excitation current command value is set to Idref = Idref ₃ is applied to the induction motor, while after a lapse, the induction motor the frequency command fref while limiting the output voltage command in the voltage command value Vref ₃ Frequency fref3 is sufficient to maintain
After a certain period of time, the output voltage command limit is removed and the current control is restarted.At this time, the post-compensation excitation current direction voltage command value Vdcref ₃ and the post-compensation torque current direction voltage command Vqcref ₃ are obtained. And a secondary resistance r ₂ and a leakage inductance L of the induction motor are obtained as r ₂ = Vdcref ₃ / Idref ₃ -r ₁ L = Vqcref ₃ / (Idref ₃ × 2πfref). 8. The motor constant tuning means applies a voltage for DC excitation to the induction motor, maintains the induction motor in a stopped state, and outputs a signal for slightly changing the DC-excited secondary magnetic flux to a voltage command. 3. The control device for an induction motor according to claim 1, wherein the control unit superimposes on a current command, calculates a mutual inductance based on the detected current value and the voltage command or the detected voltage value, and tunes the mutual inductance. 4.