JPS62173995A - Flux operation circuit of induction motor - Google Patents

Abstract

PURPOSE:To make it possible to perform the flux operation accurate in all rotary regions and strong against the constant fluctuations by forming a flux operation circuit with a high-speed system operation means and a low-speed system operation means. CONSTITUTION:When an induction motor 2 is rotating on high speed, outputs Ppsi1qTc and Ppsi1dTc of operational amplifiers 9a and 9b become greater than the outputs psi1q and psi1d of operational amplifiers 21a and 21b, while the operation of flux elements which is based on the integration is performed because the primary lag active filters 10a and 10b actuate as integrators. Conversely, when the induction motor 2 is rotating on low speed, the output psi1q and psi1d of operational amplifiers 21a and 21b become greater than the outputs of operational amplifiers 9a and 9b, while the filters 10a and 10b actuate as transfer function 1; so that the operation of the flux elements which is based on the rotary coordination conversion is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic flux calculation circuit suitable for magnetic flux control or magnetic flux measurement of an induction motor.

[Background technology of the invention and its problems]

Conventionally, the magnetic flux of induction motors has been controlled or calculated.
In the case of ll, an arithmetic circuit is used that calculates the primary flux linkage vector by integration. That is, if we take a three-phase induction motor as an example, the instantaneous values of the phase voltage and current of each phase a, b, and c are υla, υlb, υIC, tea, tub,
Assuming t1c, the primary voltage vector υ1d1 and the primary current vector Ctd% in the stationary orthogonal coordinate system (d-1 coordinate system, where the d axis is the real axis and the 1st axis is the imaginary axis) are: ...(1) It is obtained as follows. Now, the primary winding resistance of the induction motor is R
1, the primary flux linkage vector l1ltd'j is obtained from equations (1) and (2) as follows. That is, the primary flux linkage can be calculated by subtracting the voltage drop due to the primary winding resistance and current from the primary voltage and integrating the result. According to this method, since the calculation itself is very simple, it is easy to construct an actual calculation circuit, and furthermore, there is an advantage that accurate calculation can be performed during relatively high-speed operation.

That is, since the primary winding resistance R1 is a constant on the stator side,
This is because it does not change much due to temperature changes in the induction motor, and there is almost no difference between the set value of the primary winding resistance R1 in the arithmetic circuit and the actual value. On the other hand, in the case of the secondary resistance R2 of the induction motor, since it is measured by the rotor, unlike the primary winding resistance R1, it is relatively susceptible to temperature changes.

Therefore, by using only the primary winding resistance R1 without using the secondary resistance R2, formula (3) is strong against constant fluctuations due to temperature changes in the induction motor, and accurate calculation can be achieved. . However, when an induction motor rotates at a low speed such as zero speed or a speed close to zero speed, the integration circuit made up of an operational amplifier does not operate perfectly due to offsets, drifts, etc. There is a problem that calculations cannot be performed.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic flux calculation circuit for an induction motor that is capable of calculating magnetic flux accurately over the entire rotation range of the induction motor and resistant to constant fluctuations.

[Summary of the invention]

The present invention calculates the primary magnetic flux linkage by integration in the relatively high speed rotation region of the induction motor to take advantage of the advantage of equation (3), and calculates the primary magnetic flux linkage by another calculation method at and near zero speed. It solves the conventional problems by performing calculations, and is characterized in that the switching between these calculation methods is performed automatically, continuously, and smoothly.

First, a primary flux linkage calculation method other than equation (3) will be described. The primary voltage vector υlαB in the rotating coordinate system (α-β coordinate system) that rotates in synchronization with the rotor of the induction motor,
Primary current vector L1αB, secondary current vector Lm
Using , the characteristic equation of the induction motor is: ・・・・・・・・・(4) However, L1□ is the secondary side self-inductance and 22:
Secondary self-inductance M: Mutual inductance θIll: Obtained as rotation angle. When the secondary current vector L- is determined from the second line of this equation (4), it becomes R2+PL22 (5). On the other hand, on the α-β coordinate, the primary flux linkage vector 1! ItαB is W1αB = LttLtαB + MLχ−...
...... (6) Therefore, by substituting equation (5) into equation (6), 1 +p (R22/R2) ...... (7) However, <- (LttL22 M')/L11 is obtained. Therefore, on the α-β coordinate, it is possible to obtain the primary flux linkage vector by simply inputting the primary current vector into an element consisting of an incomplete differential and a first-order lag. However, the formula (
7) is an equation that holds true in rotating coordinates, and the primary flux linkage vector ψlαB and the primary current vector LlαB cannot be directly observed. Therefore, the primary flux linkage vector ψ1
It is necessary to transform αB and primary current vector CIαB into a formula in stationary coordinates (d-1 coordinates) by performing rotational coordinate exchange on primary flux linkage vector 1d) and primary current vector Ltai. Therefore, the primary flux linkage vector ψld'i and Li1αB, the primary current vector Ltat
The rotational coordinate transformation that relates LxαB to LxαB is expressed as follows.

tilld'i -QhCXθ ・ejθ1Llcxβ
-Lld)・e-6ell... (8) From the above, by using equations (7) and (8), it is possible to find the primary flux linkage vector IAltd% in the stationary coordinate system. It is possible. If we formulate this,...
...(9) becomes. That is, according to equation (9), the primary flux linkage vector Qtdl can be calculated from the observable primary current vector j1d% and the rotation angle θm using rotational coordinate transformation. Since this method does not include an integral calculation, a great advantage is that accurate calculations are possible even at and near zero speed of the induction motor. On the other hand, it is necessary to set the secondary resistance R2 in the arithmetic circuit, and as mentioned above, this is caused by the temperature change of the induction motor.
A problem arises in that error fluctuations are likely to occur between the set value and the actual value. As a result, it can be said that equation (9) is relatively weak against constant fluctuations due to temperature changes in the induction motor. FIG. 2 is a block diagram showing a calculation method based on equation (3), and FIG. 3 is a block diagram showing a calculation method based on equation (9).

In addition, in Fig. 1 and Fig. 2, 1 is the power supply (power conversion 2
), 2 is a three-phase induction motor, 3 is R1 constant element,
4 is an integral element, 5 is a rotation angle detector, and 6 is (d-'l/α
-B) Rotary coordinate transformation element, 7 is an incomplete differential/first-order lag element, and 8 is a (α-β/d-1) rotational coordinate transformation element.

In order to compare both of the above formulas, these characteristics are summarized as shown in the table below.

From the comparison of both formulas in the table, we can see that formula (3) is used during high-speed operation.
), and it can be seen that it is desirable to perform calculations based on equation (9) during low speed operation. However, switching between the two magnetic flux calculation methods must be performed automatically, continuously, and smoothly. An overview of the method is given below.

FIG. 4 shows a block diagram of the present invention. Here, 9 is a Tc constant element and 10 is a first-order lag element. The variable to be detected is the primary voltage vector υ1d)
, primary current vector Ltd%.

The rotation angle θn is visible from the stator side.
1I11. First, the signal flow is roughly divided into two parts, one is Pψ1dc which is a constant times the differential of equation (3).
The other route is based on equation (9) to find kTe.
This is the route to find 11dl. The results of these operations are added together and input to a simple first-order delay element 10. This first-order lag element 10 has a time constant Tc,
Input is 1lItd'i + pHltd'l TC
Therefore, the term l+PTc is eliminated, and as a result, l
ha'l is output. For example, when the induction motor 2 is operating at low speed, the term PTe is sufficiently small and can be ignored, so the transfer function of the first-order lag element 10 can be approximated to 1, and the human power is calculated based on equation (9).
It can be considered only. Therefore, the final calculation result during low-speed operation is < 1lI based on equation (9).
tc+'l is output. On the other hand, when the induction motor 2 is operating at high speed, the term PTc is sufficiently large compared to 1, so
The transfer function of the first-order lag element 1o can be approximated as 1/P T c, and the human power is Pt111a'j Tc
It can be considered only. Therefore, the final calculation result during high-speed operation is < tul based on equation (3).
d'i is output.

[Embodiments of the invention]

An embodiment of the magnetic flux calculation circuit for an induction motor according to the present invention will be described below with reference to FIG. 1.
Parts having the same or similar functions as those in FIGS. 3 and 4 are designated by the same reference numerals.

An induction motor 2 is connected to a power source (including a power converter) 1, and Y-connected resistors 11a, ll
b, llc are also connected. Y-wired resistor 1
1a, llb, llc neutral point and each resistor 11a,
The power supply sides of 11b and 11c are connected to inverting input terminals (-) and non-inverting input terminals (+) of isolated amplifiers 12a, 12b, and 12c, respectively. The output terminals of these isolation amplifiers 12a, 12b, and 12c are connected to the input terminal of a three-phase/two-phase conversion circuit 13a. On the other hand, there is a Hall CT 14a between the power supply 1 and the induction motor 2.
, 14b, and 14c are installed, and their output terminals are also connected to the input terminal of the three-phase/two-phase conversion circuit 13b. The detection calculation means A is configured as described above. 15a is an operational amplifier whose non-inverting input terminal (
+) is connected to one component output terminal of the three-phase/two-phase conversion circuit 13a, and the inverting input terminal (-) is connected to the l-axis component output terminal of the three-phase/two-phase conversion circuit 13b via the operational amplifier 3a. connected. Similarly, 15b is an operational amplifier,
Its non-inverting input terminal (+) is connected to the d-component output terminal of the three-phase/two-phase conversion circuit 13a, and its inverting input terminal (-) is connected to the d-component output terminal of the three-phase/two-phase conversion circuit 13b. An output terminal is connected via an operational amplifier 3b. Furthermore,
The output terminals of operational amplifiers 15a and 15b are operational amplifier 9a.
, 9b, and constitute a high-speed calculation means C.

On the other hand, the rotation angle detector 5 is composed of, for example, an incremental encoder and is directly connected to the rotor of the induction motor 2, and its output terminal is connected to the input terminal of the counter 16. Further, the output terminal of the counter 16 is connected to the input terminals of the ROM tables 17a and 17b, and the detection means B is configured as described above. 18a to 18b are D/A converters, and the D/A converter 18a
The output terminals of one component of the three-phase/two-phase conversion circuit 13b are connected to each input terminal of the ROM table 17a. In addition, each input terminal of the D/A converter 18b has a three-phase/
The d component output terminal of the two-phase conversion circuit 13b is connected. Furthermore, R is connected to each input terminal of the D/A converter 18c.
The component output terminal of the three-phase/two-phase conversion circuit 13b is connected together with the output terminal of the OM table 17b.

Same) Each input terminal of the D/A converter 18d has RO
The d component output terminal of the three-phase/two-phase conversion circuit is connected together with the output terminal of the M table 17b. And D/
The output terminals of A converters 18a and 18d are operational amplifier 1.
The output terminals of the D/A converters 18b and 18C are connected to the inverting input terminal (-) and the non-inverting input terminal (+) of the operational amplifier 19b. The output terminal of the operational amplifier 19a is connected to the input terminal of the incomplete differential/first-order lag active filter 7a,
Apart from this, the output terminal of the operational amplifier 19b is connected to the input terminal of another incomplete differential/first-order lag active filter 7b. The output terminals of these filters 7a and 7b are connected to the D/A converters 20a and 20b as described above.
, 20c, and 20d. That is, each input terminal of the D/A converter 20a is connected to the output terminal of the ROM table 17a as well as the output terminal of the incomplete differential/first-order lag active filter 7a. Further, the input terminal of the D/A converter 20b3 is connected to the output terminal of the ROM table 17a as well as the output terminal of the incomplete differential/first-order lag active filter 7b. Further, each input terminal of the D/A converter 20c is connected to the output terminal of the ROM table 17b as well as the output terminal of the incomplete differential/first-order lag active filter 7a.

Similarly, RO is applied to each input terminal of the D/A converter 20d.
The output terminal of the incomplete differential/first-order lag active filter 7b is connected together with the output terminal of the M table 17b. The output terminals of the D/A converters 20a and 20d are connected to each non-inverting input terminal (+) of the operational amplifier 21a, and the output terminals of the D/A converters 20b and 20C are respectively connected to the inverting input terminal (-) of the operational amplifier 21b. ), connected to the non-inverting input terminal (+). As described above, the low-speed system calculation means is configured.

Thus, the output terminals of the operational amplifiers 21a and 21b are connected to the non-inverting input terminal (+) of each one of the operational amplifiers 22a and 22b, respectively.
), and the other non-inverting input terminal (+) of the operational amplifiers 22a, 22b is connected to the aforementioned operational amplifier 9a,
The output terminals 9b are connected to each other. Finally, an operational amplifier 22a.

The output terminals of 22b are separately connected to the input terminals of first-order lag active filters 10a and 10b.

Next, the operation of this embodiment configured as described above will be explained.

First, power is supplied from a power source (including a power converter) 1 to an induction motor 2 via a three-phase line, and in order to detect the phase voltage, Y-connected resistors 11a, llb, l
lc is used. That is, since the phase voltages of the a, b, and c phases are obtained in the form of voltage drops across the resistors 11a, 11b, and lie, both ends of the resistors 11a, llb, and 12c are connected to isolated amplifiers 12a, 12b, and 12c. Phase voltage can be detected by connecting to c. For example, the a-phase voltage υ1a is obtained by the resistor 11a and the isolation amplifier 12a.

Each phase voltage L/1a, υlb obtained in this way
.

υ1c is converted into a two-phase component (d-axis component, one component) by a three-phase/two-side B conversion circuit 13a. When formula (1) is expressed in matrix form, it becomes... (10), and this calculation is performed.

On the other hand, the line current of each of the three phases is Hall CT14a.

14b and 14c. The phase line currents Lea, L1b, and Llc thus obtained are also converted into two-phase components by the three-phase/two-phase conversion circuit 13b in the same way as before. From equation (2), the conversion at this time is also...
(11) It can be expressed as: Output Lt of the three-phase/two-phase conversion circuit 13b
d+ L1'i are operational amplifiers 3a, 3bl: rfufuR
It is multiplied by 1. Therefore, the following operations are performed in the operational amplifiers 15a and 15b. The differential Pvl(1, Pvl%) of each component of the primary flux linkage obtained in this way is further multiplied by Tc in the operational amplifiers 9a and 9b to obtain PWl(I
Tc and PV1'lTc are obtained.

On the other hand, the pulse signal output from the rotation angle detector 5 is counted by a counter 16, and the rotation angle of the rotor can be obtained as a parallel binary digital signal. By the way, the formula (8
) can be expressed in matrix form using orthogonal two-axis components as follows (13). Therefore, the three-to-11/two-to-two conversion circuit 13b
The output of Lld, Lt% is U1α, Li3
Equation (14) must be executed in order to perform rotational coordinate transformation to . Therefore, the output θm of the counter 16 mentioned above
The sine function table and the COS function table are referred to to obtain the trigonometric functions necessary for rotational coordinate transformation. That is,
The ROM table 17a stores sin θm and the ROM table 17b stores cos θm in advance as data, and by using the output θm of the counter 16 as an address signal, sin θm, according to the rotation angle, can be calculated.
Obtain cos θm.

In order to perform multiplication of these trigonometric functions by Lld and Lt'i, a multiplication type D/A converter is used in this embodiment. For example, the D/A converter 18a calculates the product of the digital signal sinθm and the analog signal 11, and outputs the analog signal 5'1sLnθm. Similarly, from the D/A converter 18b, L1dsinθat
, from the D/A converter 18C, Lt%cosθm,
Each D/A converter 18d outputs Lldcosθm. Upon receiving these outputs, operational amplifier 19a adds the outputs of D/A converters 18a and 18d, and operational amplifier 19b subtracts the output of D/A converter 18b from the output of D/A converter 18c.

Therefore, the output of the operational amplifier 19H is 1α in equation (14), and the output of the operational amplifier 19b is also Lld. Are the outputs Ltα and LLβ an incomplete differential/first-order lag active filter? are input into a and 7b respectively,
These two active filters 7a and 7b are exactly the same and have the following transfer function.

・・・・・・・・・(15) Therefore, incomplete differential/first-order lag active filter 7a
, 7b, formula (16), i.e.,...
The calculation (16) will be performed. MA lα and IV1β in the rotating coordinate system thus obtained must be converted to ψ1d and hyt% in the stationary coordinate system.

For this reason, rotational coordinate transformation expressed by the above-mentioned equation (13) is performed. This operation is also a multiplication type D/A similar to the one mentioned earlier.
Converters 20a, 20b.

20c, 20d and operational amplifiers 21a, 21b. However, since the operation of this part is the same as described above, it will be omitted.

With the above circuit configuration, the operational amplifiers 9a and 9b output PWl 'l Te and PIFl(1, respectively, and the operational amplifiers 21a and 21b output 'I't
'N, vxd will be output. Therefore, the addition of these outputs in the operational amplifiers 22a and 22b is as follows.

・・・・・・・・・(17) It is done as follows. The calculation result of equation (17) is manually input to first-order delay active filters 0a and 10b, and these filters 10a and 10b are completely the same and have the transfer function of the following equation.

Therefore, the calculation of equation (19) is performed in the first-order lag active filters 0a and 10b, and finally Wld, '
Ft'i is obtained.

(19) According to this embodiment, the primary flux linkage vector ψ
It is possible to calculate td'l as an orthogonal two-axis component "!'ld, ca 1). At this time, if the induction motor 2 is rotating at a relatively high speed, the operational amplifier 21a
, 21b outputs v1'l,'Ftd from the operational amplifier 9a.
, 9b output P'J11 'f, Tc, P
At the same time that WldTe becomes dominant, the first-order lag active filters 10a and 10b operate as approximate integrators, so that calculation of the magnetic flux component based on integration is performed. Conversely, when the induction motor 2 is rotating at a low speed, the outputs of the operational amplifiers 9a and 9b p11r1%Tc, Pvt
Compared to dTc, the outputs of operational amplifiers 21a and 21b Wt'
1. 'Ftd is not only dominant, but also the filter 10a,
Since 10b operates as a transfer function 1, calculation of magnetic flux components based on rotational coordinate transformation is executed. In this way, the method of calculating the magnetic flux component changes depending on the rotation speed of the induction motor 2, but the first-order lag active filter ioa, 1
The effect of -ob allows automatic, continuous, and smooth switching.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but may be implemented with appropriate modifications within the scope of the invention.

〔Effect of the invention〕

According to the present invention, in the relatively high speed rotation region of the induction motor, the primary flux linkage vector is calculated based on the integral [Equation (3)], and conversely, in the zero speed and its vicinity region, the rotational coordinate transformation [Equation (9)] Since the calculation of the primary magnetic flux linkage vector is performed based on the above equation, it is possible to calculate the magnetic flux accurately and resistant to constant fluctuations over the entire rotation range, and in addition, these calculation methods can be switched automatically and This has an excellent effect in that it can be performed continuously and smoothly.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an electrical configuration showing one embodiment of the present invention, and FIGS. 2 to 4 are block diagrams for explaining the present invention in detail. In the drawing, 1 is a power supply, 2 is an induction motor, 3a, 3b are operational amplifiers, 5 is rotation angle detection 2;, 7a, 7b are incomplete differential/first-order lag active filters, 9a, 9b are operational amplifiers, 10a, 10b is a first-order lag active filter (first-order lag element), lla. 11b, 11C are resistors, 12a, 12b, 12C are isolation amplifiers, 13a, 13b are three-phase/two-phase conversion circuits, 14
a, 14b, 14c are Hall CTs. 15a, 15b are operational amplifiers, 16 is a counter, i7a
, 17b is a ROM table, 18a, 18b, 18c,
18d is a D/A converter, 19a. 19b is an operational amplifier, 20a, 20b, 2
0 c. 20d is a D/A: + inverter, 21a and 21b are operational amplifiers, 22a and 22b are operational amplifiers, A is a detection calculation means, B is a detection means, C is a high speed system calculation means, and D is a low speed system calculation means. show.

Claims (1)

[Claims] 1. detection and calculation means for detecting the primary voltage and primary current of the induction motor and calculating the primary voltage vector and primary current vector; detection means for detecting the rotation angle of the rotor of the induction motor; High-speed calculation means for calculating the differential of the primary flux linkage vector from the primary voltage vector and the primary current vector, and calculating the primary flux linkage vector from the primary current vector from the detection calculation means and the rotation angle from the detection means. 1. A magnetic flux calculation circuit for an induction motor, comprising: a low-speed calculation means; and a first-order lag element which inputs the sum of the output results of the high-speed calculation means and the low-speed calculation means.