JP3159330B2 - Induction motor vector control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control device for automatically measuring a primary resistance of an induction motor to which an inverter is connected and automatically setting a compensation value.

[0002]

2. Description of the Related Art As a variable speed control of an induction motor, a slip frequency control system excellent in both responsiveness and accuracy is known. In particular, the primary current of the motor is controlled by dividing it into an excitation current and a torque current. A vector control system which can obtain a response equivalent to that of a DC motor by controlling the secondary magnetic flux and the torque current so as to be always orthogonal to each other is disclosed in, for example,
No. 9-165982 is known. In such slip frequency control and vector control, it is necessary to calculate a slip frequency and the like by calculation from motor constants (for example, primary and secondary resistances, primary and secondary inductances, excitation inductances) of an induction motor to be controlled. Among the motor constants, the primary resistance has a high compensation error sensitivity at low frequencies, and in particular, vector control (hereinafter referred to as P
In G-less vector control), the detection accuracy of the primary resistance is directly related to the starting characteristics at the time of starting the motor, so that it is necessary to perform the measurement with high accuracy. Conventionally, the primary resistance of the motor has been determined from the design value or measured value of the motor.

[0003]

However, in the prior art, not only the calculation and the measurement from the design value of the motor are troublesome, but also the primary resistance value may change with the temperature, so that accurate measurement is difficult. There was a problem. Therefore, an object of the present invention is to automatically and accurately measure a primary resistance of a motor and set a compensation value thereof.

[0004]

In order to solve the above problems, an induction motor using an inverter as a driving power source, an AC current having a predetermined frequency and phase as an inverter output, and a DC having a predetermined polarity and magnitude with respect to each winding. A converter capable of generating a current and a magnetic flux calculator for calculating a voltage model magnetic flux and a current model magnetic flux in which an integral element for calculating a magnetic flux of the induction motor is replaced by a first-order lag element, and an output current of the converter A control device for controlling the frequency and phase of the measurement of the primary resistance of the induction motor and its measurement so that the amplitude value of the voltage model magnetic flux vector when the DC current is output from the converter becomes zero. The compensation value is automatically set. Further, the measurement of the primary resistance of the induction motor and the setting of its compensation value are automatically performed so that the amplitude values of the current model magnetic flux vector and the motor model magnetic flux vector become equal.

[0005]

By the above means, a DC current is applied to each winding of the induction motor as an inverter output to generate a magnetic flux without rotating the motor so that the amplitude value of the voltage model magnetic flux vector at that time becomes zero. The primary resistance of the motor is measured and set by performing the primary resistance compensation of the motor. Similarly, the primary resistance of the motor is measured and set by performing the primary resistance compensation of the motor of the control device so that the amplitude values of the current model magnetic flux vector and the motor model magnetic flux vector become equal.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description, a vector A is generally represented by simply abbreviating the vector A as an expression of a vector symbol. The absolute value of the vector A is represented as ABS (A).
Hereinafter, specific examples of the present invention will be described. FIG. 1 is a circuit diagram of an induction motor vector control device according to an embodiment of the present invention. 1 is a converter (converter) unit including a diode and a capacitor for converting an AC power supply to a DC, and U,
An inverter (inverter) that modulates the voltage command of the current controller output of each phase of V and W into a PWM signal using a switching element such as a thyristor or IGBT to generate an AC voltage.
, A voltage-type PWM inverter, 2 is an induction motor,
3 is an encoder as a speed detector provided to detect the speed of the induction motor, 4 is a coefficient unit, 5 is an integrator,
6 takes phase θ ₁ ^* as input, and exp (jθ ₁ ^* ), ie, co
A function generator for generating sθ ₁ ^* + jsin θ ₁ ^* , 7 is a vector having components in the direction of the magnetic flux vector (hereinafter referred to as d-axis) and the direction perpendicular thereto (hereinafter referred to as q-axis), U, V,
Two-phase / three-phase converters 8 and 9 for converting the W-phase into components having a phase difference of 120 degrees, and γ = α + jβ, that is, amplitude ABS (γ), for the d-axis component α and the q-axis component β = (Α
² + β ² ) ^1/2 , phase arg (γ) = tan ^-1 (β /
α) to calculate the vector γ and e
xp (jθ) as an input, and set the phase to θ + tan ⁻¹ (β /
α), a vector rotator, 11 is a current detector for detecting a current flowing in each phase of U, V, W, 12 is a voltage detector for detecting a voltage between each phase of U, V, W, and 13 is A magnetic flux calculating unit for detecting magnetic flux based on a primary voltage vector v ₁ , a primary current vector i ₁ , and an exciting current command vector i _F ^*; a speed calculating unit 14 for detecting a speed by differentiating an encoder output signal; A magnetic flux command calculation unit for performing field weakening according to the magnitude of the rotor electrical angular speed (hereinafter, referred to as speed), 16 is a divider, and 17 is a unit that sets a deviation between the speed command ω _r ^* and the detected speed ω _r to zero. Speed controller for performing proportional-integral control (hereinafter abbreviated as PI control) provided for
Reference numeral 18 denotes a deviation (Δ ⁾ of the detected magnetic flux ψ _{2 from} the magnetic flux command ψ ₂ ^*.
A flux controller 19 for performing PI control provided to make ψ ₂ ) zero, 19 is provided to make the deviation between the command value of the primary current and the detected value zero for each of the U, V, and W phases. For example, a current controller that performs P control. The torque current command I _t ^* by dividing the torque command T ^* which is the output of the speed controller 17 in the magnetic flux command [psi ₂ ^* is the magnetic flux command computation unit 15 outputs the excitation current command I _F ^* is the magnetic flux controller 18 Required as output.

Next, the operation of the above device will be described. The relationship between the voltage and current of the induction motor is expressed by the following equation in a stationary coordinate system.

[0008]

(Equation 1)

Here, circuit constants are constants in the asymmetric T-type equivalent circuit shown in FIG. 2, R: resistance of each phase, L ₁ , M: self and mutual inductance l: total leakage inductance (= L ₁ −M) ) Ω _r : speed, p = d / dt: differential operator Subscripts ₁ , ₂ : primary and secondary quantities Also, secondary flux linkage vector ψ ₂ , exciting current vector i
_F is represented by equations (2) and (3). ψ ₂ = M (i ₁ + i ₂ ) (2) i _F = i ₁ + i ₂ (3) Equation (1) is expanded into equations (4) and (5) using equations (2) and (3). You. v becomes ₁ = a _{(R 1 + lp) i 1} + pψ 2 (4) O = R 2 i 2 + (p-jω r) ψ 2 (5). Next, considering the rotation coordinates of the magnetic flux and letting a unit vector of the magnetic flux be u _F , the primary current vector i ₁ and the secondary current vector i ₂ are expressed by the equations (6) and (7), and i ₁ = _{(I F + jI t) u} F (6) i 2 = (- 1 / R 2) {pψ 2 + j (ω F -ω r) ψ 2} u F (7) where, u _F = exp (jθ _F ), Θ _F : the angle of the magnetic flux vector. (6) command operation corresponding to the I _F + jI _t of expression 8 vector calculator of, u _F is calculated by the function generator 6. Also, from these two elements, the primary current vector i corresponding to the equation (6)
₁ is found. Also, I _t ^* is expressed by the following equation. ^{_{I t * = (1 / R}} 2) (ω F * -ω r) ψ 2 = (1 / R 2) ω S * ψ 2 (8) Here, omega _F: Thus the flux vector angular velocity slip angular velocity since command omega _S ^* is expressed by the following ^{_{equation, ω S * = R 2 *}} I t * / ψ 2 * (9) ω S * is, ψ ₂ ^*, divider 16 and to an input of the I _t ^* The calculation is performed using the coefficient unit 4. Also, the angle θ _{F of the} magnetic flux vector
Is determined by the following equation.

[0010]

(Equation 2)

The sum of the output ω _r of the speed calculation unit 14 and the slip angular velocity command ω _S ^* is integrated by the integrator 5 and becomes an input to the function generator 6. The output value _IF ^* of the magnetic flux controller 18 is calculated as follows using the vector calculator 9 and the vector rotator 10 and becomes an input to the magnetic flux calculator 13. i _F ^* = _IF ^* u _F (11) The output value i ₁ ^* of the vector rotator 10 is converted into U, V, and W phases by the two-phase / three-phase converter 7 and detected by the current detector 11. For example, P control is performed by the current controller 19 which receives the respective deviations from the current detection value of each phase as input, and the voltage source PW
It is passed to the M inverter 1. This output value is modulated into a PWM signal and becomes an AC voltage, which becomes a voltage command to the induction motor 2. The voltage between the U, V, and W phases is detected by the voltage detector 12 and becomes an input value of the magnetic flux calculator 13 together with the detected current value. Next described method of measuring the primary resistance R ₁ of the operation and the induction motor magnetic flux calculation unit 13. FIG. 3 shows a detailed block diagram of the magnetic flux calculator 12. (2),
(5) current model flux equation for the primary current vector i ₁ (12) equation is led by formula is modified as follows.

[0012]

(Equation 3)

Is derived and transformed as follows.

[0014]

(Equation 4)

Θ _r = ω _r t Further, the motor flux type (14) based on the voltage and current of the induction motor 2 is derived from the equation (4).

[0016]

(Equation 5)

Equation (14) is a problem relating to an arithmetic method such as a drift for integration operation and a primary resistance value error being enlarged at a low speed, and an initial position of a magnetic flux vector cannot be determined.
Further, since there is a problem that the compensation error of the motor primary parameter is included in the magnetic flux calculation value, the motor flux type integrator of the equation (14) is replaced with the primary delay circuit 22, and the voltage model flux vector ψ ₂ ^v which is the output thereof is output. When seeking motor model flux vector which is the sum of those subjected to a primary delay circuit 23 to the current model flux vector [psi ₂ ⁱ as the magnetic flux detection vector [psi ₂ ^c. This is represented by equation (15).

[0018]

(Equation 6)

In the amplitude calculating section 24, ψ ₂ = ABS (ψ
Computation of ₂ ^c) is carried out. When a tuning command signal is generated from a command generator (not shown), the magnetic flux calculation unit 13
Detected magnetic flux vector (motor model magnetic flux vector) ψ
The output of the amplitude calculator 24 with ₂ ^c as input is set to “0”, the magnetic flux controller 18 outputs the product of the input value and the reciprocal value of the coefficient unit 21, and the speed controller 17 outputs The value is “0”. Therefore, the torque current command value I _t ^* and the slip angular velocity command omega _s ^* is "0", because not rotate the induction motor 2 is in this state (omega _r = 0), the angle theta _F of the flux vector becomes a constant value, DC current will flow through the induction motor 2. As described above, a DC current flows in the state where the DC excitation is performed before the motor operation is started. Therefore, if p = jω = 0 in Expression (15), ψ ₂ ^c = ψ ₂ ⁱ + (1 / K _F ) ・ ΔR ₁ i ₁ (16) Here, ΔR ₁ = R ₁ −R ₁ ^* R _{1 is} the actual value of the primary resistance of the motor. Here, if the primary resistance R ₁ is correctly compensated, the motor model magnetic flux vector ψ ₂ ^C becomes equal to the current model magnetic flux vector ψ ₂ ⁱ from ΔR ₁ = 0. Therefore, conversely, if the primary resistance compensation value R ₁ ^* is made variable and the magnetic flux calculation unit is simply a magnetic flux simulator so that the amplitude values of the two magnetic flux vectors become equal, ΔR ₁ becomes zero. Also,
Since the motor model magnetic flux vector ψ ₂ ^c is the sum of the voltage model magnetic flux vector ψ ₂ ^v and the current model magnetic flux vector ψ ₂ ^{i in which} the integrator is replaced by a first-order lag circuit, ψ ₂ ^c =
ψ ₂ ⁱ holds, and ψ ₂ ^v = 0. Therefore, the output value ABS of the amplitude calculation unit 25 of the voltage model magnetic flux vector ψ ₂ ^v
The proportional term R ₁ ^* of the compensation circuit 20 is adjusted so that the voltage model magnetic flux vector ψ ₂ ^v becomes zero at the output of the comparator 27 between (ψ ₂ ^v ) and zero, and the voltage model magnetic flux vector ψ ₂ ^v becomes “0”. Then, the tuning operation is completed, and the command generator is notified of the completion, and the command generator stops the tuning command signal. Thus, the speed flux calculating unit 13 returns the output value to the magnetic flux detection value [psi _2, the magnetic flux controller 18 PI control of the magnetic flux deviation [Delta] [phi] _2, the speed controller 17, it is detected that the speed command omega _r ^* and with the operation of the PI control of the difference between ω _r, it performs a normal operation thereafter. With the above operation, the automatic measurement and setting of the primary resistance of the induction motor can be performed.

FIG. 4A shows the adjustment of R ₁ ^* in FIG. 3 by comparing the output value ABS (ψ ₂ ^C ) of the amplitude calculation unit 24 and the output value ABS (ψ ₂ ⁱ ) of the amplitude calculation unit 25. Comparator 2
In which the output of the 7 has to perform the R ₁ ^* adjusted to be equal, thereby making it possible to set the automatic measurement of the primary resistance of the induction motor. In addition, as shown in FIG.
Although the first-order delay circuit 22 is used instead of the integrator in 4), the input of the amplitude calculator 26 is connected to the first-order delay circuit 23.
4 to the output of the coefficient unit 21 or the output of FIG.
The same applies to the configuration shown in FIG. Further, the configuration for comparing the amplitude of the motor magnetic flux vector with the amplitude of the current model magnetic flux vector has been described. However, if vector control is performed using the control current source type, the current model magnetic flux vector ψ
_{Since 2} ⁱ is equal to the magnetic flux command vector ψ ₂ ^* , the same can be applied by comparing the amplitude of the motor magnetic flux vector with the amplitude of the magnetic flux command vector. The embodiment shows a case where the present invention is applied to a slip frequency type PWM inverter controller. However, since the adjustment is performed in a state where DC excitation is performed, the present invention can also be applied to a magnetic flux phase reference type PWM inverter controller.

[0021]

As described above, according to the present invention, by using the voltage model magnetic flux calculator as a mere flux simulator, the magnetic flux calculator has a high gain 1 / K _F , so that the primary voltage of the induction motor can be accurately determined. Automatic resistance measurement and setting can be performed. Therefore, especially in the PG-less vector control, the starting characteristics can be improved. Also, measurement and setting can be performed including the wiring resistance connecting the inverter and the motor. If the primary resistance R ₁ and the secondary resistance R ₂ are compensated in advance at the same predetermined temperature, R ₁ ^* in the present invention can be obtained ^. the result can reverse calculation temperature at the set value temperature compensation can be performed in the secondary resistance R ₂ using.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention.

FIG. 2 is an asymmetric T-type equivalent circuit of an induction motor.

FIG. 3 is a detailed block diagram of a magnetic flux calculation unit.

FIG. 4 is a detailed block diagram of a magnetic flux calculator according to claim 2;

[Explanation of Signs] 1 voltage type PWM inverter 2 induction motor 3 encoder 4 coefficient unit 5 integrator 6 function generator 7 two-phase / three-phase converter 8, 9 vector calculator 10 vector rotator 11 current detector 12 voltage detection Unit 13 Magnetic flux calculation unit 14 Speed calculation unit 15 Flux command calculation unit 16 Divider 17 Speed controller 18 Magnetic flux controller 19 Current controller 20 Compensation circuit 21, 29 Coefficient unit 22, 23 Primary delay circuit 24, 25, 26 Amplitude calculation Section 27 Comparator 28 Integrating circuit

Continuation of the front page (56) References JP-A-3-215181 (JP, A) JP-A-58-218891 (JP, A) JP-A-1-136596 (JP, A) JP-A-3-45190 (JP, A) JP-A-61-231891 (JP, A) JP-A-62-114487 (JP, A) JP-A-61-231891 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00 G01R 31/34

Claims (2)

(57) [Claims] 1. An induction motor using an inverter as a driving power source, a converter capable of generating an AC current having a predetermined frequency and phase as an inverter output and a DC current having a predetermined polarity and magnitude with respect to each winding, and an inverter for the induction motor. A control device for controlling a frequency and a phase of an output current of the converter, the control device including a magnetic flux calculation unit for calculating a voltage model magnetic flux and a current model magnetic flux in which an integral element for calculating a magnetic flux is replaced by a first-order lag element. Automatically measuring the primary resistance of the induction motor and setting the compensation value so that the amplitude value of the voltage model magnetic flux vector when the DC current is output from the converter becomes zero. A vector control device for an induction motor, comprising: 2. The method according to claim 1, wherein the measurement of the primary resistance of the induction motor and the setting of its compensation value are automatically performed so that the amplitude values of the current model magnetic flux vector and the motor model magnetic flux vector become equal. Item 4. The vector control device for an induction motor according to Item 1.