JPH03215181A - Magnetic flux computing system of induction motor - Google Patents

Abstract

PURPOSE:To enable secondary interlinkage magnetic-flux vector computing to be exactly performed over a full frequency area by adding a current line magnetic flux computing system to a voltage line magnetic-flux computing system, and by amplifying the error of each output, to feed it back to the input of the integrator of the voltage line magnetic-flux computing system. CONSTITUTION:A computing system formed with the voltage line magnetic-flux computing means 21 of conventional technology is provided with means 4, 5 for detecting or computing the rotational speed of the rotor of an induction motor 3, and a current line magnetic-flux computing means 20 for computing a secondary interlinkage magnetic-flux vector from a primary current vector and the rotational speed from the detecting or computing means 4, 5. Then, a difference between the output of the voltage line magnetic-flux computing means 21 and the output of the current line magnetic-flux computing means 20, multiplied by a constant is contrived to be included as a correction term, in the voltage line magnetic-flux computing means 21. As a result, the problems of offset, drift, and the like due to an integrator 9 in the conventional technology are solved, and even if the secondary resistance value of the induction motor 3 fluctuates, magnetic flux computing can exactly be performed except in a low frequency area.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of magnetic flux calculation suitable for magnetic flux control of an induction motor and torque control using the same.

(Prior art) Conventionally, when controlling the secondary flux linkage vector of an induction motor or calculating and controlling torque using it, the secondary flux linkage vector of the induction motor is calculated by integral calculation. Was.

In other words, the characteristic equation of the induction motor is...■ It is expressed as here, ■I: 11: φ2 R: Primary voltage hector -Next current vector : Secondary flux linkage vector – next resistance value Tor Rt: Secondary resistance value Ll: Primary self-inductance L2: Secondary self-inductance M: Mutual inductance ω． Two rotor rotational angular speed p: differential operator It is.

■From the first line of the equation, φt = f (Lx/M) (ν+-R+i+-(L
+-M”/Lx)I)it) dt...■ is derived, and the secondary flux linkage vector is easily calculated by the integral operation of the formula (■). However, since it does not include secondary resistance values that are difficult to measure, it has the advantage that calculation errors due to constant fluctuations can be reduced.

FIG. 2 is an example of a calculation diagram when the calculation method of the prior art is applied to an induction motor drive system using an inverter. PWM inharter (hereinafter referred to as I) from DC power source I
Electric power is supplied to an induction motor (hereinafter abbreviated as group) 3 via an induction motor (hereinafter abbreviated as group) 2. Voltage detection section 4 is IM
3 human power voltages Vulν9, ν1 are detected, and v.3 is detected. =h million (ν1-νv/2-ν,/2) +j,
<E/2> (V, -V,)...■ The primary voltage vector Vl is calculated and output.

The current detection unit 5 receives the input current 1u+ 1v+ of ll'l3.
Detect lw, v, = fi million (tu-iv/2-tw/2) +jJ
'20,000<En)<r. -1. ＞・1・■ Calculate and output the primary current vector iI.

The voltage drop calculation unit 6 calculates the voltage drop due to the primary resistance and leakage inductance, and calculates the second and third terms in the integral calculation on the right side of equation (2). The adder/subtractor 7 subtracts the output of the voltage drop calculation section 6 from the primary voltage vector V, and the output is multiplied by Lx/M by the quadratic conversion multiplier 8.
is integrated to become the secondary flux linkage vector φ2.

(Problem to be Solved by the Invention) In the prior art as described above, if the integral calculation of formula There is a problem that a calculated value cannot be obtained.

(Means for solving the problem) In the conventional technology, the calculation formula for the secondary flux linkage vector was derived using the characteristic equation of the primary side of the induction motor (the first line of the formula ■). In the characteristic equation...■ is derived. In formula (2), in order to distinguish it from the secondary flux linkage vector φ2 of the voltage system determined by formula (2), the secondary flux linkage vector of the t-current system determined by formula (2) is defined as φ2. It is shown closed.

The present invention is based on the secondary flux linkage vector φ of the current system obtained using the formula
The problems of the prior art are solved by using 2.2, and the calculation block is shown in FIG.

The current system magnetic flux calculation unit 20 in FIG. 1 is a bronch that calculates the secondary flux linkage vector φ, , using equation (2), and the corresponding block that calculates the secondary flux linkage vector φ2 of the prior art. is the voltage system magnetic flux calculation section 21. The explanation of the blocks common to those in FIG. 2 explained earlier will be omitted, and the following will be explained below.
Only the different blocks will be described.

The speed detector 10 detects the rotational angular velocity ω of the rotor of the IM 3, and the multiplier 12 calculates the product of its output and a secondary flux linkage vector φ2, which is the output of an integrator 16, which will be described later. The phase of the output of the multiplier 12 is advanced by 90' by a phase advancer 13. The primary current vector i, from the current detection unit 5 is multiplied by (M/Lz)Rz by the constant multiplier 11, and the secondary flux linkage vector φ2, is multiplied by Rz/L by the secondary constant multiplier 14.
Multiplied by x. The adder/subtractor 15 adds or subtracts the outputs of the constant multiplier 11 , the phase advancer 13 , and the quadratic constant multiplier 14 , and inputs the results to the integrator 16 . The output of the integrator 16 becomes the calculated value of the secondary flux linkage vector φ2 using the equation (2). This secondary flux linkage vector φ2. is compared with the secondary flux linkage vector φ2 of the output of the integrator 9 in the prior art in the adder/subtractor 17, and the output is multiplied by K in the error amplifier 18, and then the integrator 9
The secondary flux linkage vector φ2 is corrected by being subtracted by the subtractor 19 from the human power.

(Function) As shown in FIG. 1, the secondary flux linkage vector φ28, which is the output of the current system magnetic flux calculation unit 20, is generated by the integrator, similar to the secondary flux linkage vector φ2 in the prior art shown in FIG. is the output of the secondary flux linkage vector φ2. This secondary flux linkage vector φ2, is input to the integrator 16 of R! /L!
Since it is multiplied and fed back negatively, problems of integrator offset and drift as in the prior art do not occur even in the low frequency range. Therefore, the secondary flux linkage vector φ2 of the current system becomes an accurate calculated value of the secondary flux linkage vector in any frequency range. However, this calculation requires the secondary resistance R. , the actual secondary resistance changes due to temperature fluctuations, making accurate calculations impossible. Therefore, the secondary interlinkage magnetic flux vector φ2, which is the output of the t-flow system magnetic flux calculation section 20, is not used as the output of this magnetic flux calculation method, but is shown in FIG. It is used only for offset and drift compensation of the integrator of the voltage system magnetic flux calculating section 21 of the prior art.

In other words, the secondary flux linkage vector φ which is the output of the integrator 9
2 includes errors due to offset and drift, the secondary flux linkage vectors φ2 and φ8 of the voltage system and current system
An error occurs in (2), which is multiplied by K and fed back to the input of the integrator 9, which works to reduce errors caused by the offset and drift of the integrator 9. The effect of compensating for offset and drift of the integrator becomes smaller as the frequency becomes higher if the error amplification factor K is constant, but since the amount of drift decreases at higher frequencies, this does not pose a problem.

In addition, the decrease in the drift compensation effect in the high frequency range is due to the secondary flux linkage vector φ, which is the output of the voltage system flux calculation unit 21.
2, the secondary flux linkage vector φ! which is the output of the current system magnetic flux calculation unit 2o! 8 will be less affected,
The secondary flux linkage vector φ2 due to the variation of the secondary resistance value R2 described above. This means that the influence of the calculation error on the secondary flux linkage vector φ2 is reduced.

As described above, according to the magnetic flux calculation method of the present invention, problems such as offset and drift due to the integrator in the conventional technology are solved, and even if the secondary resistance value of the induction motor changes, it is accurate except in the low frequency range. Magnetic flux calculations can be performed.

(Embodiment) FIG. 3 is an embodiment of the present invention, which is a Bronnock diagram in which calculation is performed by a microcomputer at every fixed sampling period. Each input/output in the figure is shown as a subscript (
n-1). (n) is the (n-th
1) the (n)th sampling point (hereinafter referred to as (n)
−1) and (n) time). Also, Figure 1. In Figure 2, the variables are shown as vectors, but in reality, each component of the variable vector is used for calculations, so in Figure 3, the calculations are performed using each component, and the real part of the variable vector is marked with a subscript d. The imaginary part is associated with the subscript q. Also, regarding the codes of each calculation pronoc, a subscript a is added for the real part and a subscript b is added for the imaginary part to match the codes in FIG.

The voltage detection unit 4 detects the input voltage Vu of the IM3 at time (n).
(R) + Vv (nl + Vw (A) is detected, and the formula (2) is calculated and output. The current detection unit 5 similarly calculates the input current 1a (+s) + lv of the IM3 at the same time.
Detects (+, l + lw (n), calculates and outputs from equation (2).

6a and 6b are voltage drop calculation units for each component, and delay units 63a and 63b output the value at the previous sampling point.
and adder/subtractor 62a. 62b performs a differential operation using a backward difference, and the leakage inductance LL (LL = L+-M"/L
x) is the sampling period T. The result divided by is multiplied by constant multipliers 64a and 64b. Also, the primary resistance R
, are also calculated by multiplying the primary current jldT*l+IIQ(R) by R1 using constant multipliers 61a and 6lb, respectively.

The outputs of the voltage drop calculation units 6a and 6b are added to the adder/subtractor 7a,
7b? The primary voltage v1■II)l is subtracted from Vl41(a), and the output is converted to Lg/ by the secondary conversion multipliers 8a and 8b.
The outputs of the error amplifiers 18a, 18b are multiplied by M, and the outputs of the error amplifiers 18a, 18b are sent to the subtracters 19a. After subtraction and correction in 19b, integrator 9a,
9b. In the integrators 9a, 9b, the sampling period T. After multiplying, 1
Both output magnetic flux components φt4 (R-
11 + φZQ (l1 - 1 1 is calculated by adders 92a and 92b, and both components φt4 (nl + φt,.

, is output. The above is the operation of the voltage system magnetic flux calculation section 21. In the current system magnetic flux calculation unit 20, both components 114 (R) + IIQ + II) of the primary current at time (n) are multiplied by a constant multiplier 1.
MR in 1a, llb! /L! Multiply. Further, the rotation angular velocity ω1R of the rotor of the IM 3 at the time (n) is detected by the speed detector 10, and the current system magnetic flux calculation unit 2 at the time (n-1)
0 output φRid (R-11 + φZiq
(The product with r+-11 is calculated by multipliers 12a and 12b. Also, this φlid (n-11'+ φ!iq(
+s-11 is Rz/ by the quadratic constant multipliers 14a and 14b.
Multiplied by Lz. These constant multipliers 11a, llb, multipliers 12a, 12b, and quadratic? Number multiplier 14a, 1
The output of 4b is added/subtracted for each component by adder/subtractor 15a, 15b. However, by adding or subtracting the outputs of the multipliers 12a and 12b to different components, the phase advancer 13 shown in FIG. 1 can be omitted.

Adder/subtractor 15a. The output of 15b is a constant multiplier 161
a, 16lb, adders 162a, 162b, and delay units 163a, 163b.
16b. That is, the integrator 16a, 1
6b, inputs from adders/subtracters 15a, 15b are processed by constant multipliers 161a, 16lb at a sampling period of T. After the multiplication, the delay unit 163a . 163
Both output magnetic flux components of b φt1d (m- 1) + φ
Adders 162a, 162
b is calculated and input to delay sections 163a and 163b. These are both components φ of the current system secondary flux linkage at time (n)
2■. ,,φ2,,1.

The delay units 163a and 163b output the secondary magnetic flux linkage φZr4 at time (n-1) as the output of the current system magnetic flux calculation unit 20.
(A1,, φ2iq(R-11 is output, but this is the voltage system magnetic flux calculation unit 2l? output φ2■n-11+ φtg at the time (n-1) in the adder/subtractor 17a, 17b
This is to compare with 4 (+a- 1>.Adder/subtractor 1
7a and 17b are voltage system magnetic flux calculation unit 2 at time (n-1)
1 output φ2■ゎ−1)+φ! q(+a-11 and the output φ■d(n-11+φ!) of the current system magnetic flux calculation section 20.
The difference between i*(a-+1 is calculated and the error amplifier 18a,
After multiplying the error amplification factor K by 18b, subtracters 19a, 19
integrator 9a.b via integrator 9a.b. 9b.

(Effects of the Invention) The present invention adds a current-based magnetic flux calculation method to the conventional voltage-based magnetic flux calculation method in calculating the secondary flux linkage vector of an induction motor, and amplifies the error of each output to By feeding back to the input of the integrator of the magnetic flux calculation method, the calculation errors of the integrator caused by offset and drift, which are problems with the conventional method, can be effectively reduced, especially in the low frequency range where they are noticeable. I can do it.

According to the magnetic flux calculation method for an induction motor according to the present invention, as explained in detail above, it is possible to accurately calculate the secondary flux linkage vector over the entire frequency range, and it is possible to perform calculations that are resistant to constant fluctuations except in the low frequency range. .

[Brief explanation of drawings]

Fig. 1 is a block diagram for calculating the secondary flux linkage vector of an induction motor according to the present invention, Fig. 2 is a block diagram for calculating the conventional secondary flux linkage vector, and Fig. 3 is a block diagram for calculating the secondary flux linkage vector of the induction motor according to the present invention. It is a calculation block diagram of the secondary flux linkage vector by a computer. 1... DC power supply 2, PWM inharter (INV) 3... Induction motor (IM) 4... Voltage detection section 5... Current detection section 6, 6a, 6b... Voltage drop calculation section 7, 7a,
7b...addition/subtraction device 8. 8a. 8b... Quadratic conversion multiplier 9. 9a.
9b... Integrator 10... Speed detector 11.
lla, llb...constant multiplier 12. 12a, 1
2b... Multiplier 13... Phase advancer 14, 14
a, 14b...quadratic constant multiplier 15, 15a.
15b--addition/subtraction unit 16. 16a, 16b---・
Integrator 17. 17a, 11b...addition/subtraction device 1B
, 18a. IBb...Error amplifier 19, 19a
．． 19b... Subtractor 20... Current system magnetic flux calculation section 21... Voltage system magnetic flux calculation section 61a, 6lb...
Constant multiplier 62a, 62b = addition/subtraction device 63a.
63b=delay section 64a. 64b...Constant multiplier
91a, 9lb...constant multiplier 92a. 92b-
Adder 93a. 93b...Delay unit 161a.
16lb...Constant multiplier 162a, 162b-adder 163a. 163b...Delayed Part Figure 1 Procedural Amendment Statement March 9, 1990

Claims (1)

[Claims] 1. Detection calculation means for detecting the primary voltage and primary current of the induction motor and calculating the primary voltage vector and primary current vector, and a detection calculation means for calculating the primary voltage vector and primary current vector from the detection calculation means, and In a magnetic flux calculation method for an induction motor comprising a voltage-based magnetic flux calculation means for calculating a secondary flux linkage vector, a means for detecting or calculating the rotational speed of a rotor of the induction motor, and a primary current vector and rotation from the detection calculation means. A current system magnetic flux calculation means is provided for calculating a secondary flux linkage vector from the speed, and a constant times the difference between the output of the voltage system magnetic flux calculation means and the output of the current system magnetic flux calculation means,
A magnetic flux calculation method for an induction motor, characterized in that it is included in a voltage system magnetic flux calculation means as a correction term.