JPH05336786A - Vector control equipment for induction motor - Google Patents

Abstract

PURPOSE:To enable suppression of a current pulsation component by a method wherein a variable gain value obtained on the basis of the polarity of a fluctuation of a delta-axis component of a primary current of a second coordinate transformation part from a target value, an output frequency and a rotational direction are added to an addition value of the target value of the delta-axis component of a primary voltage and a fluctuation thereof. CONSTITUTION:A first coordinate transformation part 5 computes a primary current I1, an i1gamma-axis in gamma-delta coordinates as a reference axis and a phase difference phi between a delta-axis and a gamma-axis on the basis of target values i1d and i1q. These computed values and i1d* being used, voltage target values v1gamma' and v1delta' are determined. These target values and deviations of I1gamma and I1delta obtained by a second coordinate transformation part 6 from i1d and i1q are inputted to PI amplifiers 7 and 8 and fluctuations DELTAv1gamma and DELTAv1delta are obtained in outputs of the PI amplifiers 7 and 8. These fluctuations and the preceding target values are added up. Moreover, a fluctuation of a PI amplifier 12 is added to the addition value of DELTAv1delta and v1delta' and a value thus obtained is inputted to a polar- coordinate transformation part 9. In this way, a current pulsation component can be suppressed.

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 an induction motor.

[0002]

2. Description of the Related Art Vector control of an induction motor that controls a secondary magnetic flux and a secondary current orthogonal thereto has been widely applied. In the vector control described in this publication, in the case of a three-phase induction motor, the current and the magnetic flux rotate at the same speed as the rotating magnetic field generated by the power supply. It is a method of handling as a vector of the coordinate system and converting the calculation result into a current command value of each phase of the three-phase power source for control. Next, the specific method will be described. The voltage equation in the dq coordinate system is as follows (1)
It is represented by a formula.

[0003]

[Equation 1]

However, ω _s = ω-ω _r Lσ = (L ₁ L ₂ −
M ² ) / L ₂ .

Here, v _1d and v _1q are _d and v of the primary voltage, respectively.
q-axis components, i _1d and i _1q are d- and q-axis components of the primary current,
λ _2d and λ _2q are d and q axis components of the secondary magnetic flux, R ₁ and R ₂ are primary and secondary resistances, respectively, L ₁ , L ₂ and M are primary and secondary, respectively.
Excitation inductance, ω, ω _r , and ω _s are primary power source angular frequency, rotor angular frequency, slip angular frequency, and P is d / dt.
It represents.

If the d axis is on the secondary magnetic flux in the dq coordinate system, then λ _2q = 0. At this time, λ _2d = Φ ₂ = constant, i
_{Since 2d} = 0 and i _2q = i ₂ , the same orthogonal control of torque and magnetic flux as in a DC machine becomes possible.

On the other hand, the secondary magnetic flux has the following relationship.

[0008]

[Equation 2] From the vector control condition, i _2d = 0, and from equation (2), λ
_2d = Mi _1d .

From λ _2q = 0, i _1q = -L ₂ × i _2q
/ M, and i _1q is proportional to the torque current.

Next, from the fourth line of the equation (1), the equation (3) is obtained. When the condition of the slip angular frequency is obtained from the equation (3), ω _s is expressed by the equation (4).

[0011]

[Equation 3]

[0012]

[Equation 4]

The above are the vector control conditions when the secondary magnetic flux is controlled to match on the d-axis. Therefore, in order to perform vector control, it is necessary to set i _1d to Φ ₂ / M and control ω _s so that equation (4) holds.

Since the resistance value of the secondary resistance R ₁ used for calculating the slip angular frequency ω _s changes due to the ambient temperature and temperature changes such as self-heating of the rotor, the resistance value of the secondary resistance R ₁ changes based on the output voltage of the motor. It is necessary to estimate the variation and correct the target value of the slip angular frequency ω _s by this variation to compensate for the generated torque variation due to the secondary resistance variation. If the change in the secondary resistance is ignored, the torque control accuracy and torque response deteriorate. If the output voltage of the inverter is used as it is to estimate the change in the secondary resistance,
Since the amount of change in the secondary resistance is captured, it is desirable that the signal used for estimation be a signal that is not affected by the primary resistance.

For this reason, the control circuit shown in FIG. 2 has already been proposed. In the figure, 1 is an excitation current command section,
A secondary magnetic flux command value Φ ₂ until it exceeds a certain value angular frequency ω _r to the target value i _1d of i _1d *, exceeds a certain value ω _r i _1d
Reduce *. In the following, the target value or the ideal value is indicated by a symbol *, and the deviation of the speed commands ω _r * and ω _r is set to i _1q * via the speed amplifier 2, and dq is _calculated based on i _1d *, i _1q *. The ideal values v _1d *, v _1q * of the primary voltage on the axis are calculated, and the voltage fluctuations due to changes in the primary resistance and the secondary resistance are corrected to i _1d * = i _1d , i _1q * = i _1q. Control of i _1d * = i _1d , the PI amplifier 3 ₁ has Δv _1d
Is obtained, and Δv _1q is obtained in the PI amplifier 3 ₂ that controls i _1q * = i _1q . Since Δv _1d and Δv _1q include both the voltage fluctuation due to the change of the primary resistance and the secondary resistance, if the component not including the voltage fluctuation due to the change of the primary resistance is obtained to compensate for the change of the secondary resistance, It is possible to perform compensation without being affected by the change in primary resistance. Therefore, the rotational coordinate γ-δ axis is set with the reference axis γ on the vector of the primary current I ₁ ,
The slip correction calculation unit 3 ₃ obtains the primary voltage variation Δv ₁ δ on the δ-axis. This Δv ₁ δ is expressed by an equation that does not include the primary resistance R ₁ , and therefore is not affected by the primary resistance R ₁ .

FIG. 3 is a vector diagram showing the relationship between the dq axes and the γ-δ axes and the voltage and current, and FIG. 4 is a vector diagram showing the primary voltage fluctuations. In the figure, V ₁ and E are respectively primary. Voltage, secondary voltage, Δv ₁ is the primary voltage fluctuation, Δv ₁ γ, Δv ₁ δ are the γ-axis component and δ-axis component of the fluctuation, respectively, φ is the phase difference between the γ-axis and the d-axis, and I ₀ is Excitation current, I ₂ is torque current. Δv ₁ δ is expressed by the following equation (5).

[0017]

[Formula 5] Δv ₁ δ = −Δv _1d · sin φ + Δv _1q cos φ (5) where cos φ = I ₀ / I ₁ = i _1d / i _1q , sin φ = I
₂ / I ₁ = i _1q / i ₁ γ Then, the slip correction calculation unit 3 ₃ calculates the correction amount Δω _s of the slip angular frequency corresponding to the secondary resistance change based on Δv ₁ δ, and calculates the slip angular frequency. The added value of ω _s * and Δω _s obtained in part 3 ₄ is set as the target value of the slip angular frequency, and the rotor angular frequency ω _r is added to this value to add the angular frequency ω of the primary voltage.
= Θ / t is the target value. 2 3 ₅ polar conversion unit figure, 3 ₆ coordinate conversion unit, the 4 ₁ PWM circuit, 4 ₂ inverters, IM induction motor, PP pulse pickup unit, 4 ₃ is a speed detecting unit.

[0018]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Japanese Patent No. 35388 discloses an invention in which the prior art is improved. However, in the invention, it has been found that the output phase current pulsates near zero current. 5 (a), (b)
Is the waveform of the current ripple component in the u phase.
The circles A and B shown in (b) are the above-mentioned pulsations.
Although this pulsation shows only one phase in the figure, it is common to all three phases. Since this pulsation occurs 6 times in one cycle (twice for each phase), it causes torque pulsation, and therefore it is desired to suppress it.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a vector control device for an induction motor capable of reliably suppressing a current pulsation component.

[0020]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides rotational coordinates that rotate in synchronism with the power source angular frequency of an induction motor, where the secondary magnetic flux is the reference axis. Assuming −q coordinates, the target values i _1d * and i _1q * of the d-axis component and the q-axis component of the primary current of the induction motor are calculated, and the slip angle is calculated based on these target values and the set value of the secondary time constant. In a vector controller for an induction motor having a slip angle frequency calculator for calculating a frequency, a phase ψ is tan ⁻¹ (i _1d * / i _1q *) different with respect to the dq axes and a primary current I
_If the coordinates with ₁ as the reference axis are γ-δ coordinates, i _1d *,
Target value i ₁ γ * of the γ-axis component of the primary current based on i _1q *
(= I ₁ ) and the first coordinate conversion unit for calculating the phase ψ, and the target values v ₁ γ *, v ₁ δ * of the γ and δ axis components of the primary voltage based on i ₁ γ *, ψ. The means for calculating each and the location where the primary current of the induction motor is detected are each axis component i of the γ-δ coordinates.
_A second coordinate conversion unit for converting into ₁ γ, i ₁ δ, a target value i ₁ δ * (= 0) of i ₁ γ * and a δ-axis component of the primary current, and i from the second coordinate conversion unit. _{Based on 1} γ, i ₁ δ, a variation Δv ₁ γ from v ₁ γ * in the γ-axis component of the current primary voltage and v ₁ γ * in the δ-axis component of the current primary voltage
Means for calculating a variation Delta] v ₁ [delta] from, i _1d *, i
_1q *, i _{1 γ} * and Δv is provided a secondary resistance variation calculator for calculating a variation with respect to the set value of the rotor resistance based on ₁ [delta], the target value of [delta] axis component of the primary current i ₁ [delta] * And a deviation ΔI ₁ δ from the deviation between i ₁ δ from the second coordinate conversion unit and
A means for calculating a variable gain value for the output according to the polarity of this variation is provided, and the added value of v ₁ γ * and Δv ₁ γ is set as the target value v ₁ γ of the γ-axis component of the primary voltage, and v ₁ δ * and adds the variable gain value to the sum of the delta ₁ [delta] and the target value v ₁ [delta] of [delta] axis component of the primary voltage and the added value, these target values v ₁
The power supply voltage is controlled on the basis of γ, v ₁ δ, and the slip angular frequency calculation unit is based on the set value of the secondary time constant and the calculation result obtained by the secondary resistance change calculation unit. Is obtained, and the calculation is performed using this secondary time constant.

[0021]

[Action] target value of [delta] axis component of the primary current i ₁ [delta] * and the deviation amount is variation .DELTA.i ₁ [delta] of the i ₁ [delta] than the second coordinate conversion unit
To get After that, a variable gain value is obtained from the polarity of this variation Δi ₁ δ and the rotation direction of the output frequency. This variable gain value is added to the added value of v ₁ δ * and Δv ₁ δ for obtaining the target value v ₁ δ of the δ-axis component of the primary voltage. As a result, the current pulsation component can be suppressed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawings. Figure 1
In the above, 5 is a first coordinate conversion unit, and the first coordinate conversion unit 5 calculates i ₁ γ * in the γ-δ coordinates with the primary current I ₁ as the reference axis based on i _1d *, i _1q *. It has a function of calculating the phase difference φ between the d-axis and the γ-axis, and specifically, tan ^-1
_{(I 1q * / I 1d *} ) = φ√ (i 1d * 2 + i 1q * 2) = I 1
Perform the operation of. Then, using sin φ, I ₁ , cos φ output from the first coordinate conversion unit 5 and i _1d * from the excitation current command unit 1, the following formulas (6) and (7) are calculated. , V ₁ γ *, v ₁ δ * are obtained.

[0023]

[Equation 6]

Reference numeral 6 denotes a second coordinate conversion unit, which converts the detected values i _u and i _w of the primary current into respective axis components i ₁ γ and i ₁ δ of the γ-δ coordinate. To do. These i ₁ γ and i ₁ δ are compared with target values i ₁ γ * and i ₁ δ * (= 0), respectively,
The deviations are input to the PI amplifiers 7 and 8 which are voltage control amplifiers, respectively. The PI amplifiers 7 and 8 output primary voltage fluctuations Δv ₁ γ and Δ ₁ δ from the input deviations, respectively.
To get The obtained Δv ₁ γ and Δ ₁ δ are target values v ₁ γ * and v ₁
δ * is added to each.

The output of the PI amplifier 12 shown below is added to the added value of Δv ₁ δ and Δ ₁ δ *. PI amplifier 12 is for to suppress the torque pulsation, this PI amplifier 12, i ₁ [delta] and i ₁ [delta] * and deviations .DELTA.i ₁ [delta] in is inputted. Since this deviation is generated in the direction opposite to the rotation direction of the current space vector, the PI amplifier 12 has the polarity of Δi ₁ δ, the output frequency in the clockwise direction (CW) and the counterclockwise direction (CC
The variable gain is set according to W). This is shown in the table below.

[0026]

[Table 1]

The PI amplifier 12 obtains Δv ₁ δ at the output by using Δi ₁ δ as a variable gain, and this Δv ₁ δ is used for the above-mentioned Δv ₁
Add to the added value of δ and v ₁ δ *. This addition output v ₁ δ
And the above-mentioned addition output v ₁ γ of Δv ₁ γ and v ₁ γ * are input to the polar coordinate conversion unit 9. This polar coordinate conversion unit 9
_{From 1} γ and v ₁ δ, the magnitude | V ₁ | of the vector V ₁ of the primary voltage and the phase angle φ with the γ axis are output. The phase angle φ is summed with θ will be described later (= ω _ot), transformation and these sum values and │V ₁ │ is inputted to the PWM circuit 4 ₁ U, V, the primary voltage command value corresponding to the W-phase The voltage of the inverter 4 ₂ is controlled by this.

Numeral 10 is a secondary resistance change amount calculation unit, and this calculation unit 10 takes in i _1d *, i _1q *, i ₁ γ * and Δv ₁ γ and executes the calculation of the following equation (8). The secondary resistance change K is calculated.

[0029]

[Equation 7]

Numeral 11 is a slip angular frequency calculator, which has a function of taking in K, i _1d * and i _1q * and executing the following equation (9) to obtain ω _s. There is.

[0031]

[Equation 8]

By the way, when the computer executes the calculation of each part of the circuit of FIG. 1, ω _s is calculated as follows. That is, a series of calculations including K calculation and slip angular frequency calculation are instantaneously performed by the clock signal, and the secondary resistance value obtained by the (n-1) th calculation in the slip angular frequency calculation unit 11 is calculated as the nth calculation. Set value in. n
Representing K and R ₂ obtained in the second calculation as K _n and R _2n , _respectively , and assigning a preset value R ₂ * to the initial value R ₂₀ of R _2n , the first to nth calculations are as follows. Like

First R ₂₁ = (1 + K ₁ ) · R ₂₀ = (1 + K ₁ ) · R ₂ * Second R ₂₂ = (1 + K ₂ ) · R ₂₁ = (1 + K ₂ ) · (1 + K ₁ ) · R ₂ * : _Nth R _2n = (1 + K _n ) ・ R _{2 (n-1)} = (1 + K _n ) (1 + K _n-1 ) ... (1 + K ₁ ) ・ R ₂ * Therefore, ω _s obtained by the nth calculation is ω _sn When expressed as
ω _sn becomes the following equation (10), and ω _sn = (1 + K _{n )} ω _{s (n-1)} (10) (n -1) ω _{s (n-1)} Is stored and ω _sn is obtained by using K _n obtained by the equation (10).

In this case, the initial value ω _s1 is ω _s1 = (1 + K ₁ ) · R ₂ * · 1 / L ₂ * · i ₁ δ * / i ₁
γ *.

The thus obtained ω _s and the rotor angular frequency detection value ω _{r of the} electric motor IM are added, and the added value ω ₀ is set as the target value of the power source angular frequency.

[0036]

As described above, according to the present invention,
The current pulsation component can be reliably suppressed, which has the advantage of reducing torque ripple and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention,

FIG. 2 is a block diagram showing a conventional vector control device,

FIG. 3 is a vector diagram of current and voltage,

FIG. 4 is a vector diagram of current and voltage,

5A is a current command waveform diagram, and FIG. 5B is a current pulsation component waveform diagram.

[Explanation of symbols]

 5 ... 1st coordinate conversion part, 6 ... 2nd coordinate conversion part, 7, 8 and 12 ... PI amplifier 9 ... Polar coordinate conversion part

Claims (1)

[Claims] 1. A d-q component of a primary current of an induction motor and a d-q coordinate, which is a rotation coordinate that rotates in synchronization with a power source angular frequency of the induction motor and has coordinates of a secondary magnetic flux as a reference axis. Vector of an induction motor equipped with a slip angular frequency calculator that calculates the target values i _1d *, i _1q * of the q-axis component and calculates the slip angular frequency based on these target values and the set value of the secondary time constant. In the controller, if the phase φ is different from tan ⁻¹ (i _1d * / i _1q *) with respect to the d-q axes and the coordinates with the primary current I ₁ as the reference axis are γ-δ coordinates, i _1d *, i _A first coordinate conversion unit for calculating the target value i ₁ γ * (= I ₁ ) of the γ-axis component of the primary current and the phase ψ based on _1q *, and the primary voltage of the primary voltage based on i ₁ γ *, φ A means for calculating the target values v ₁ γ *, v ₁ δ * of the γ and δ axis components, and a detection value of the primary current of the induction motor A second coordinate conversion unit for converting each axis component i ₁ γ, i ₁ δ of the γ-δ coordinates, and i ₁ γ * and a target value i ₁ δ * (= of the δ axis component of the primary current).
0) and i ₁ γ, i ₁ δ from the second coordinate conversion unit, the variation Δv ₁ γ from v ₁ γ * in the γ-axis component of the current primary voltage and the current primary voltage. Means for calculating the variation Δv ₁ δ from v ₁ γ * in the δ-axis component of the above, and a change in the secondary resistance with respect to the set value based on i _1d *, i _1q *, i ₁ γ * and Δ ₁ δ. a secondary resistance variation calculating unit for calculating the amount provided, the variation [Delta] ₁ [delta] from deviations from the target value i ₁ [delta] * and i ₁ [delta] than the second coordinate conversion unit of [delta] axis component of the primary current And a means for calculating a variable gain value in the output according to the polarity of this variation is provided, and the added value of v ₁ γ * and Δv ₁ γ is set as the target value v ₁ γ of the γ-axis component of the primary voltage, and v ₁ [delta] * and the delta ₁ [delta] and the by adding a variable gain value to the addition value and the target value v ₁ [delta] of [delta] axis component of the primary voltage and the added value of these target values v ₁ γ, v ₁ δ While controlling the power supply voltage based on, the slip angular frequency calculation unit based on the setting value of the secondary time constant and the calculation result obtained by the secondary resistance change amount calculation unit, the secondary time constant at that time. A vector control device for an induction motor, characterized in that the calculation is performed using this quadratic time constant.