JP2817123B2 - Method and apparatus for adjusting magnetic flux of induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor, and more particularly to a method and an apparatus for adjusting magnetic flux of an induction motor.

[0002]

2. Description of the Related Art In general, when the speed of an induction motor is calculated from a detected primary voltage and primary current, it can be explained as follows by characteristic equations (1) and (2) in a steady state of the induction motor. In these equations, the primary voltage V ₁ and the primary current I
₁ and the secondary current I ₂ are all vectors.

V ₁ = (R ₁ + jωL ₁ ) I ₁ + jωMI ₂ (1)

0 = jω _s MI ₁ + (R ₂ + jω _s L ₂ ) I ₂ (2) where R ₁ : primary resistance R ₂ : secondary resistance L ₁ : primary inductance L ₂ : secondary Inductance M: Mutual inductance.

If the primary voltage V ₁ , the primary current I ₁ , and the primary angular frequency ω are obtained, the secondary current I ₂ is determined from the equation (1),
The slip angular frequency ω _s is obtained from equation (2). Therefore, the rotation angular frequency ω _m of the induction motor can be obtained by the following equation (3).

[Number 3] _{ω m = ω-ω s ......} (3)

[0004]

When the rotation speed of the induction motor is detected by detecting the primary voltage and the primary current supplied to the induction motor, the primary angular frequency ω becomes ω = 0.
In this case, the secondary current I ₂ cannot be obtained from the equation (1), and the slip angular frequency ω _s cannot be obtained from the equation (2).
Further, there is a disadvantage that the rotational angular frequency ω _m cannot be obtained from the equation (3).

[0005]

Means for achieving the object are as follows: 1) In claim 1, the rotational angular frequency (ω) of the induction motor
m) and torque (T), and the relationship among the rotational angular frequency (ωm), torque (T), magnetic flux command (φ2 *), and secondary resistance (R2) of the induction motor is not T = ωm = 0. , Ωm +
A magnetic flux adjustment method for an induction motor, characterized by outputting a magnetic flux command (φ2 *) satisfying TR2 / φ2 * 2 ≠ 0. 2) The multiplier according to claim 2, wherein the multiplier outputs a product of the torque (T) and the constant (K1), and the multiplier (22) outputs a product of the torque (T) and the constant (K2). , An adder (23) for outputting a difference between the rotation angular frequency (ωm) and the output of the multiplier (21), and a rotation angular frequency (ωm) and a multiplier (2).
An adder (24) that outputs a difference from the output of 2), a comparator (25) that outputs 1 if the output of the adder (23) is 0 or more, and 0 if the output is less than 0, and an output of the adder (24) Is 0
A comparator that outputs 1 if it is greater than 0 and 0 if it is less than 0 (2
6), a negation circuit (27) that outputs 0 if the output of the comparator (25) is 1 and 1 if the output is 0, and a comparator (2
6) If the output of 1 is 1, 0 if it is 0, 1 if it is 0, and AND circuit (2) that outputs the logical product of the output of the comparator (25) and the output of the NOT circuit (27).
9), the output of the comparator (26) and the NOT circuit (2)
AND circuit (210) for outputting a logical product with the output of 8)
And the output of the AND circuit (29) and the AND circuit (210)
An OR circuit (211) that outputs the logical sum of the output of
A secondary magnetic flux selection switch for selecting and outputting one value from binary secondary magnetic flux command candidate values based on the output of the R circuit (211).

[0006]

[Function] The relationship between the slip angular frequency ω _s and the torque T is as follows, where the magnitude of the magnetic flux on the secondary system side is φ ₂ , and the secondary resistance is R _2.

Ω _s = ｛R ₂ / (φ ₂ ) ² ｝ T (4). By changing φ ₂ , it is possible to change the slip angular frequency ω _s without changing the torque T. it can. The present invention utilizes this principle, to adjust the magnetic flux φ by the magnetic flux adjusting means, by varying the slip angular frequency omega _s, not to zero the primary angular frequency omega of the formula (3) This solves the above problem. However, since a steady state is assumed here,
Rotation angular frequency ω _m is assumed to immediately does not change. If when the rotational angular frequency omega _m varies with external factors are no longer able to primary angular frequency omega remains near zero,
This is no longer the case.

[0007]

FIG. 1 shows an embodiment in which the present invention is applied to vector control of an induction motor driven by a PWM inverter. Reference numeral 11 denotes a PWM inverter control unit, 12 denotes a PWM inverter, 13 denotes an induction motor, and 14 denotes a speed. And a torque calculation unit, 15 is a magnetic flux adjustment unit, and the PWM inverter control unit 11 receives the torque command T ^* , the secondary magnetic flux command φ ₂ ^* , the rotation angle frequency ω _m of the induction motor, and the primary current I ₁ , PWM inverter
Output control signal to 12. The arithmetic unit 14 of the speed and torque inputs of the primary voltages V ₁ and the primary current I _1, and outputs the rotational angular frequency omega _m and the torque T. The magnetic flux adjusting unit 15, the rotational angular frequency omega _m and the torque T and the secondary flux command candidate value phi ₂₁ ^*,
Enter the phi ₂₂ ^*, in accordance with the rotational angular frequency omega _m and the torque T, the secondary flux command candidate value φ ₂₁ ^*, φ ₂₂ ^* of either the selected secondary magnetic flux command phi ₂ ^* Output.

FIG. 2 shows the magnetic flux adjusting section 15 of FIG.
Multipliers 21 and 22 multiply torque T by constants K ₁ and K ₂ , and adders 23 and 24 output ω _m −K ₁ T and ω _m −K ₂ T, respectively. 0 in comparator 25
When ≦ ω _m −K ₁ T, ₁ is output, and when 0> ω _m −K ₁ T, 0 is output.
When 0 ≦ ω _m −K ₂ T, 1 is satisfied, and 0> ω _m −K ₂ T
In the case of, 0 is output. The outputs of the comparators 26 and 25 are inverted by the NOT circuits 27 and 28, respectively, and the AND circuit 29 outputs _{1 when} K ₁ T ≦ ω _m <K ₂ T, and outputs 0 at other times. Similarly, in the AND circuit 210,
When K ₂ T ≦ ω _m <K ₁ T, 1 is output, and at other times, 0 is output.

By the OR circuit 211, K ₁ T ≦ ω _m <K ₂
When T or K ₂ T ≦ ω _m <K ₁ T, 1 is output, and at other times, 0 is output. The secondary flux selection switch 212 selects the secondary flux command candidate value phi ₂₂ ^* when the signal is 1 from the OR circuit 211, when the 0 selects the secondary flux command candidate value phi ₂₁ ^*, secondary Output as magnetic flux command φ ₂ ^* .

The secondary magnetic flux command φ ₂ thus output
^* , In the torque T to rotation angular frequency coordinates of FIG. 3, a secondary magnetic flux command candidate value φ ₂₂ ^* is selected in a hatched portion except a dashed line and (0, 0), and a secondary magnetic flux command candidate is selected in other regions. The value φ ₂₁ ^* will be selected. Where the straight lines n ₁ and n
₂ , 1, and m are represented by the following equations.

N ₁ : ω _m = K ₁ T (5)

N ₂ : ω _m = K ₂ T (6)

L: ω _m = −７R ₂ / (φ ₂₁ ^* ) ² ｛T (7)

M: ω _m = −ΔR ₂ / (φ ₂₂ ^* ) ² ΔT (8)

As described above, K ₁ and K ₂ are constants, and the conditions of the constants K ₁ and K ₂ include a straight line 1 in a region sandwiched between the straight lines n ₁ and n ₂ as shown in FIG. Should not be included. The straight lines l and m represented by the formulas (7) and (8) are the torque T and the rotation angle at which the primary angular frequency ω becomes zero when the magnitude of the magnetic flux is φ ₂₁ ^* and φ ₂₂ ^* , respectively. and shows the relationship between the frequency omega _m, can be obtained by substituting (3) and the slip angular frequency omega _s of (4) to the equation, ω = 0. Incidentally, in this embodiment, K ₁ , K ₂ and φ ₂₂ ^* are determined with respect to φ ₂₁ ^{* as} follows, and the above-mentioned conditions are satisfied.

K ₁ = −R ₂ / (φ ₂₁ ^* −α) ² K ₂ = −R ₂ / (φ ₂₁ ^* + α) ² α = (φ ₂₁ ^* −φ ₂₂ ^* ) / 2 φ ₂₂ ^* = φ ₂₁ ^* / 2

In this embodiment, the magnitude of the secondary magnetic flux is basically φ
₂₁ but ^* than is controlled by induction when the motor is operated in the vicinity linear l (hatched portion shown in FIG. 3), that is, when the primary angular frequency ω is close to zero, the magnitude of the secondary flux phi ₂₁ ^* From φ
_By weakening to ₂₂ ^* , the primary angular frequency can be changed without changing the torque and the rotational angular frequency,
Allows the calculation of the rotation angular frequency omega _m. Supposing (driving in a straight line in FIG. 3 l) the rotational angular frequency omega _m and operated in a torque T satisfying the equation (7) to control φ ₂ ^* = φ ₂₁ ^* when the formula
From (4), (7) and (3), the primary angular frequency ω is zero. Similarly, operated at a rotational angular frequency omega _m and the torque T satisfying the formula (8) (operating at line m in FIG. 3) for controlling φ ₂ ^* = φ ₂₂ ^* when the formula (4), (8) (3), the primary angular frequency ω becomes zero. In other words, by controlling when the rotational angular frequency omega _m and the torque T as in the present embodiment satisfies the formula ^{_{(7), φ 2 * =}} φ 21 * instead φ ₂ ^* = φ ₂₂ ^* in the formula (7 ) And equation (8)
Can be operated so that the primary angular frequency ω does not become zero in a region other than the point (ω _m = T = 0) that simultaneously satisfies the following conditions.

In the present embodiment, the secondary magnetic flux command is selected from binary values. However, this is merely an example of a means for adjusting the magnetic flux so that the primary angular frequency does not approach zero and does not affect the torque and the rotational angular frequency. .

[0014]

As described above, when the rotation angle frequency of the induction motor is calculated from the primary voltage and the primary current of the induction motor, the speed cannot be calculated by the conventional technique in some cases. The invention can improve it.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit for a PWM inverter and an induction motor according to an embodiment of the present invention.

FIG. 2 is a block diagram of a magnetic flux adjusting unit included in FIG. 1 according to one embodiment of the present invention.

By the magnetic flux adjusting portion of an embodiment of the present invention; FIG is a diagram representing the area of the secondary flux selection in rotational angular frequency omega _m coordinates of the torque T~ induction motor.

[Explanation of symbols]

 11 PWM inverter control unit 12 PWM inverter 13 Induction motor 14 Speed and torque calculation unit 15 Magnetic flux adjustment unit 21, 22 Multiplier 23, 24 Adjuster 25, 26 Comparator 27, 28 Negation circuit 29, 210 AND circuit 211 OR circuit 212 Secondary magnetic flux selection switch

Claims (2)

(57) [Claims] 1. A rotation angle frequency (ωm), a torque (T) and a plurality of magnetic flux command candidate values (φ21 *, φ22) of an induction motor.
*, ...), and the relationship among the rotational angular frequency (ωm), the torque (T), the magnetic flux command (φ2 *), and the secondary resistance (R2) of the induction motor is ωm + TR except T = ωm = 0.
A magnetic flux adjusting unit (15) that outputs a magnetic flux command (φ2 *) satisfying 2 / φ2 * 2φ0 by selecting one of a plurality of magnetic flux command candidate values (φ21 *, φ22 *,...). A magnetic flux adjusting method for an induction motor, which is achieved by providing the magnetic flux. 2. A multiplier (21) for outputting a product of a torque (T) and a constant (K1); a multiplier (22) for outputting a product of the torque (T) and a constant (K2); Angular frequency (ω
m) and an output of the multiplier (21), and an adder (23) for outputting a difference between the rotational angular frequency (ωm) and an output of the multiplier (22). Adjuster (2
A comparator (25) that outputs 1 if the output of 3) is 0 or more and 0 if it is less than 0, and a comparator (26) that outputs 1 if the output of the adder / subtractor (24) is 0 or more and less than 0
And 0 if the output of the comparator (25) is 1 and 1 if the output is 0
And a comparator (26)
The negation circuit (2) outputs 0 if the output of
8), the output of the comparator (25) and the NOT circuit (2
AND circuit (29) for outputting a logical product with the output of 7)
An AND circuit (210) that outputs a logical product of the output of the comparator (26) and the output of the NOT circuit (28);
An OR circuit (211) that outputs the logical sum of the output of the ND circuit (29) and the output of the AND circuit (210), and one value from the binary secondary magnetic flux command candidate value based on the output of the OR circuit (211). A magnetic flux adjusting device for an induction motor, comprising a secondary magnetic flux selection switch for selecting and outputting.