JP2881957B2 - Induction motor control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for an induction motor (also simply referred to as a motor) controlled via an inverter.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional example of such a control device.

In the figure, reference numeral 9 denotes a control circuit including a current control circuit (ACR: automatic current regulator current regulator) for controlling the current by the amount of alternating current, and a current command value i _u ^* , i _v ^* , i for each phase of the induction motor. _w ^* and the current detection values i _u , i _v , i _w obtained by the current detector 1 are input, and current command values v _u ^* , v _v ^* for supplying a current according to the command value to the motor 2 ^. , v _w
^{* Is} output. 10 is a power converter, including ^{_{inverters, v u *, v v *}} , the voltage generates in response to v _w ^*.

In the vector control, based on the torque command value τ ^* and the secondary magnetic flux command value Φ ₂ ^* , a current command value i _M ^{* of} a component parallel to the secondary magnetic flux of the primary current is calculated based on the following equations (1) and (2). , And a current command value i _T ^{* of} a component perpendicular thereto.

Here, M indicates mutual inductance.

The arithmetic circuit 7 calculates the above equation (1), and the divider 6 calculates the above equation (2).

The coordinate converter 8 converts various quantities (i _M , i _T ) of the secondary magnetic flux coordinate system into various quantities (i _u , i _v , i _w ) of the stator coordinate system, and estimates the estimated position of the secondary magnetic flux. Is φ ₂ , conversion based on the following equation is performed.

Further, the slip frequency ω _SL is obtained by the following equation.

(R ₂ represents a secondary resistance of the motor) operation circuit 5 calculates the equation (4). The slip frequency ω _SL thus obtained is added to the rotational speed ω _{2 of the} motor detected by using, for example, the pulse encoder 3, and the result is integrated by the integrator 4 to determine the position φ _{2 of the} secondary magnetic flux. presume.

[Problems to be solved by the invention]

By the way, since the current command value of the AC ACR is an AC amount, there is a problem that as the command frequency becomes higher than the response frequency of the AC ACR, a phase shift occurs between the command value and the detected value.

FIG. 5 shows the relationship between the excitation current command value i _M ^* and the torque current command value i _T ^* and the actual values i _M ^* and i _T ^* when a phase shift occurs.

Here, considering the motor generated torque τ, Therefore, if a phase shift occurs between the command value and the actual value as shown in FIG. 5, there is a possibility that torque cannot be generated in accordance with the command value.

Therefore, an object of the present invention is to make it possible to obtain a torque amount according to a command value even during high-speed rotation.

[Means for solving the problem]

Based on the motor speed, a secondary resistance calculation circuit is provided that outputs a value that gradually increases as the motor speed increases in a high motor speed region as a secondary resistance value R2.

[Action]

By correcting the slip frequency command value according to the speed, a phase shift between the current command value and the actual value in the high-speed rotation range is eliminated.

〔Example〕

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

As is apparent from FIG. 7, this embodiment is characterized in that an arithmetic circuit 11 is added to the conventional example shown in FIG. The speed of the motor speed is input as an inverter output frequency signal to the arithmetic circuit 11, calculates and outputs the secondary resistance R ₂ as gradually increases in accordance with its size.

Incidentally, the secondary resistance R _2, since those that gradually increases in a high-speed rotation area of the motor, as the inverter output frequency signal used for the operation of the secondary resistance R _2,
Motor speed can be used. The inverter output frequency versus resistance R ₂ Characteristics of the arithmetic circuit 11 shown in Figure 2.

That is, in order to correct the torque fluctuation when the inverter output frequency is increased (when the 3-phase current command value frequency becomes higher), when the inverter output frequency is high, as in FIG. 2 the values of R ₂ By changing the slip frequency ω _SL so as to be slightly larger, the current command value is set to the position shown in FIG. 3, and the torque is generated according to the command value. That is,
In FIG. 5, the area S1 surrounded by the solid line is not equal to the area S2 surrounded by the dotted line, but in FIG. 3, the areas of both are equal, and the command value and the actual value can be matched. Become.

The other points are the same as in the case of FIG.

According [Effect of the Invention] This invention, the slip frequency command value in the motor speed higher region, and such that operation using the secondary resistance R ₂ as to gradually increase as the motor speed increases Therefore, even in the high-speed rotation region, a torque amount according to the command value can be obtained, and control performance can be improved.

[Brief description of the drawings]

Figure 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an inverter output frequency versus resistance R ₂ Characteristics of the arithmetic circuit 12 in FIG. 1, FIG. 3 is a current vector diagram according to the present invention FIG. 4 is a block diagram showing a conventional example of the vector control system, and FIG. 5 is a current vector diagram in FIG. 1 ... current detector, 2 ... motor, 3 ... pulse encoder, 4 ... integrator, 5, 7, 11 ... arithmetic circuit, 6 ... divider, 8 ... coordinate converter, 9 ... Control circuit, 10 ... Power converter.

Claims (1)

(57) [Claims] 1. A control device for performing torque control of an induction motor by decomposing a primary current of an induction motor into a component (magnetizing current) parallel to a secondary magnetic flux and a component (torque current) perpendicular to a secondary magnetic flux, comprising: value (tau ^*) and the flux command value (phi _{2 ^*)} because the torque current command value (i _T ^*) torque current command value calculating means for calculating a (6), the magnetic flux from the magnetic flux command value (phi _{2 ^*)} current command value (i _M ^*) magnetization current command value calculating means for calculating a and (7), the torque current command value (i _T ^*) and the magnetization current command value (i _M ^*) and the secondary following the induction motor A slip frequency calculating circuit (5) for calculating a slip frequency (ω _s1 ) from the resistance value (R ₂ ), a detecting means (3) for outputting a rotation speed (ω ₂ ) of the induction motor, and the detecting means (3) secondary magnetic calculates the sum of the output (omega ₂₎ and the slip frequency arithmetic circuit output (omega _s1) of) Estimate the secondary flux estimation circuit for outputting a (φ _{2) (4),} the torque current command value (i _T ^*),
AC current command value calculation means (AC ^* ) for calculating an AC current command value (i _u ^* , i _V ^* , i _W ^* ) from the magnetizing current command value (i _M ^* ) and the secondary magnetic flux estimation value (φ ₂ ). 8) and the inverter output currents (i _u , i _V , i _W ^* ) to the AC current command values (i _u ^* , i _V ^* , i _W ^* ).
i _W) to match the includes alternating amount of current regulator for regulating the components (ACR), the voltage command based on the output of the current regulator _{^{(V u *, V v *}} , V w *) an inverter control circuit for outputting (9), the voltage command of the inverter control circuit _{^{(V u *, V v *}} , V w *) control of the induction motor having an inverter (10) for generating an AC voltage based on In the device, in a region where the output frequency of the inverter is high, a secondary resistance calculation circuit (11) that calculates a value that gradually increases as the inverter output frequency signal increases and outputs the value as the secondary resistance value (R ₂ ). A control circuit for an induction motor, comprising: