JPS6091897A - Controller of ac motor - Google Patents

Abstract

PURPOSE:To improve the operating efficiency and to prevent the noise from generating by limiting the deviation between the actual current value and the current command value to the prescribed limit value or lower. CONSTITUTION:A PI controller 10 inputs a current command value i* outputted from a current command value generator 1 and the actual current value (i) supplied from a current detector 8, controls so that the value (i) coincides with the current command value i* in a proportional integration and supplies it as the final current command value i** to the PWM circuit 3. A hysteresis comparator 14 has the upper limit in the prescribed hysteresis width H0 at the up side with the current command value i* as the lower limit, and a hysteresis comparator 15 has the lower limit in the prescribed hysteresis width H0 at the lower side from the upper limit. These outputs A, B, C are supplied to the driver circuit 4 through an AND circuit 16, and an OR circuit 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an AC motor control device that can efficiently perform speed change control of an AC motor.

(Background of the Invention) The applicant previously disclosed in Japanese Patent Application No. 58-82110M,
We are proposing an AC motor control device suitable for electric vehicles.

FIG. 1 shows an example of such an AC motor control device. In the figure, a current command value generator 1 generates a corresponding torque or rotational speed based on an external torque command or speed command. In order to realize this, a command value (hereinafter referred to as current command value) i* of the current to be given to the AC motor 7 is generated.

The current command value i8 and the current actual value i obtained by detecting the current applied to the AC motor 7 (hereinafter referred to as the actual current value) with the current detector 8 are inputted into the current regulator.
Adjust the current command value so that the actual current value i matches the current command value i*, and output it as the final current command value (hereinafter referred to as the final current command value) i** It is b.

The output i'' from the current regulator 2 is the PWM circuit 3.
After being pulse width modulated, this pulse signal P
+ is supplied to the driver circuit 4.

The power converter 5 is driven by the driver circuit 4, and converts the power supply voltage given from the power supply 6 into the final current command value i1*.
It converts into three-phase alternating current corresponding to the current and supplies it to the motor 7. This power converter 5) is composed of an inverter circuit if the power supply 6 is a DC power supply, and is composed of a 1-noise inverter circuit or the like if the power supply 6 is an AC power supply.

Although the number 1 in the cylinder is omitted in the same figure, the actual current value i is two-phase, and the R final voltage method command value 2''', , P
Output P1 of WM circuit 3. The output of the driver circuit 4 is for three phases.

FIG. 2 is a diagram showing an example of the configuration of the current regulator 2 and PWM circuit 3. As shown in FIG.

As shown in the figure, the current regulator 2 is
The control circuit 10 is configured to output a final current command value i*8 by following the deviation between the current command value i* and the actual current value i.

The PWM circuit 3 is composed of a triangular wave Tr from a triangular wave generator 12 and a comparator 11 that discriminates the final current command value i''*which level. A modulated pulse signal @P1 is output.

FIG. 3 is a diagram showing another example of the configuration of the current regulator 2. This is a diagram showing another example of the configuration of the current regulator 2, and this is a diagram showing the current command value i8 and the current actual value. i8
It is constituted by a hysteresis comparator 13 that adjusts. The output of this hysteresis comparator 13 becomes the ON/OFF pulse signal Pa, which is l)
The signal is supplied to the driver circuit 4 without passing through the WM circuit 3.

Figure 4 shows the current command 1a 2' and the actual current l when a 1-control circuit is configured with the current regulator shown in Figure 2 above.
FIG. 1 shows the waveform of ai. As shown in the figure, the actual current value i changes so as to coincide with the current command value 18, with slight ripple fluctuations, following the change in the current command value i1'.

However, the actual current 1tJi controlled by the l)1 control circuit 10 has a problem of followability to the current command value i7.
)] dU - Current commands 1, 1 . An outlier signal that deviates significantly from i* may occur.

This may interfere with the smooth operation of the motor, or
This causes JSij sound.

Figure 5 shows 1. 3 is a waveform diagram showing a current command 1llfi* and an actual current value i when a control circuit is configured with the current regulator 2 shown in FIG. 3. FIG.

In this case, between the two thresholds 1u and 14 set above and below the current command planting grass 7 with a hysteresis width (hysteresis width) -1 of the hysteresis inverter 13, the current actually flows while the planting grass reciprocates. It makes a noise to follow the command value i'.

However, in this case, the actual current value i is due to the current change as it moves back and forth between the hysteresis width t1.
This may adversely affect motor efficiency or cause motor noise.

(Object of the Invention) The object of the invention is to reduce the fluctuation of the actual current value with respect to the current command value and improve the operating efficiency of the motor.
An object of the present invention is to provide a control device for an AC motor that can prevent and cover the generation of noise.

(Structure of the Invention) In order to achieve the above object, the present invention feeds back the actual current value and compares it with the current command value to adjust the current command value so that the actual current value matches the current command value. By using a current regulator configured to limit the deviation between the actual current value and the current command (1) so that the deviation is below a predetermined limit value, extremely high-performance current control can be achieved. It is characterized by the fact that it has been strained.

(Description of Embodiment) Hereinafter, one embodiment of the present invention will be described in detail using the drawings from FIG. 6 onwards.

FIG. 6 is a block diagram showing the structure of an embodiment of an AC motor control device according to the present invention. In addition, in the same figure,
As shown in FIG. 1 above, 1. : Components that are the same as those in the conventional example are designated by the same reference numerals, and their explanations are omitted, and the driver circuit 4 shown in FIG. Power converter5. Power supply 6. motor 7
Since they have the same configuration, illustration and description thereof will be omitted.

As shown in the figure, the current regulator 20 of this embodiment device includes a PI control circuit 10 as shown in the conventional example of FIG. 2, two hysteresis comparators 14 and 15, and an AND
Circuit 16. It is also configured with an OR circuit 17.

The PI control circuit 10 inputs the current command value i8 outputted from the current command value generator 1 and the current actual value i supplied from the current detector 8, so that the current actual value i becomes the current command value i.
8, the proportional-integral ()) I) is controlled to match the final current command value i** to the PWM circuit 3.

One of the two hysteresis comparators 14 and 15, the hysteresis comparator 14, has a current command value i11 as its lower limit, and sets the upper limit with a constant hysteresis width tlo above the current command value i11.
2, when i>Iz, the output is at the 1-1io1+ level, and when i<i'', the output is at the low level.

The hysteresis comparator 15 used has the current command value i* as the upper limit and a predetermined hysteresis width below this (lower limit 11rJ I2 at -1o, and when i>i'', the output l↓ The I-l-1i level is a roar, and when i<12, the output is a low level.

The AND circuit 16 also outputs the output B of the hysteresis comparator 14 and the output A of the PWM circuit 3.
ND! The OR circuit 17 outputs the output C of the hysteresis comparator 15, the AND
The OR logic of the output of the circuit 16 is taken. The output of this OR circuit 17) is supplied to the driver circuit 4.

FIG. 7 is a waveform diagram showing changes in the current command value i8 and the actual current value i in the device of this embodiment. As shown in the figure, the actual current value i is 1. J-Note PIlliIJ111 circuit 10
Due to the function of J:, it follows minute ripple fluctuations as the actual current value i* changes.

In addition, the above two hysteresis ': I comparator 14
．． The current is limited by the upper limit 11 and lower limit 12 set by 15 so that the actual current lai does not exceed the upper or lower limit.

FIG. 8 is a main output waveform diagram showing the current limiting operation of the current regulator 20 (1). As shown in the figure 4, P I
1lillillllfl 10(7) output i”
'L;l PWM The signal J3 is in the circuit 3 and is pulse width modulated as shown by △ in the same figure.

When the actual current value i exceeds the upper limit ■1 as shown at 81 in FIG. 7, the output B of the comparator 14 becomes l
The level changes from -1-1i+ level to LOW level, and therefore, the AND circuit 16 is closed and the pulse from the PWM circuit 3 is cut off, so that it does not appear at the output P of the OR circuit 17.

As a result, the actual current value i decreases, and the upper limit value 11
The value is as follows.

In addition, as shown in @7 Figure 82, when the actual current value i becomes less than or equal to the lower limit value 12, the output of the hysteresis comparator 15 changes to ! -11g1 Lebel roar, above PW
Regardless of the output A of the M circuit 3, =f' The OR circuit 17 outputs a positive pulse.

As a result, the current actual value i increases and the current lower limit value 12
The value is as follows.

As described above, in the device of this embodiment, the actual value 2 of the current supplied to the AC motor 7 follows the current command value i8 with slight ripple fluctuations, and the deviation between the two is kept small. Moreover, even if a sudden large fluctuation occurs in the F''1 control output, the deviation between the actual current value i and the current command value i* will be suppressed to a predetermined hysteresis width or less.

(Effects of the Invention) As explained in detail above, in the AC overnight control device of the present invention, it is possible to make the current applied to the AC motor follow the command value while minimizing deviation from the command value. The AC motor can be operated as efficiently as possible.
Noise generated from the motor can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of an AC motor control device, and Fig. 2 is a conventional control l! Figure 1 shows the configuration of the current regulator and I) W fv1 circuit 3, and Figure 3 shows the same block. Figure 4 is a waveform diagram showing the current actual value and current command value according to the configuration shown in Figure 2, and Figure 5 is a waveform diagram showing the current actual value and current command value according to the configuration shown in Figure 3. 6th
Figure 7 shows an embodiment of an AC motor opening device according to the present invention. Figure 8 shows the main output at current regulator J3 in this embodiment and shows the timing timing. 1...Current command value generator 20... Current regulation Device 3...PWM circuit 4...Driver circuit 5...
・・・・・・・・・・・・Electric) J converter 6・・・・・・
・・・・・・・・・・Power supply 7・・・・・・・・・・・・
...AC motor 8...Current detector 10...P I 1li
lJ I11 circuit 14', 15...Hysteresis comparator 1G......AND circuit 17
・・・・・・・・・・・・OR circuit patent applicant Nissan Motor Co., Ltd. (J1

Claims (1)

[Claims] (1) A current command value generator that outputs a command value of the current to be applied to the AC motor in response to an external command; an actual current value detector that detects the current actually applied to the AC motor; and the actual current value. is fed back and the current command value is adjusted so that the actual current value matches the current command value by comparison with the current command value. a current regulator that limits the deviation so that the deviation is as follows; a power converter that supplies current to the AC motor; 1. A control device for an AC motor, comprising: a drive circuit for driving a motor.