JP2001169578A - Method for estimating and method for regulating current offset in ac motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for estimating and regulating the current offset in an AC motor for reducing a torque ripple by reducing an offset error. SOLUTION: The method for regulating the current offset in the AC motor comprises the steps of integrating a current command value of the multiplied value of a torque command in constant speed control, by a value corresponding to an electric angle by an integrator 10 at each sampling period of a plurality of periods at the electric angel under the control of the AC motor; estimating the offset of a current detecting system with the value obtained by dividing by sampling times (n) by a divider 11 as an offset value; and subtracting the estimated offset value from the current detected value by a subtracter 13 or adding it to the current command value by an adder, thereby regulating the current offset.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a current offset value for compensating for an offset generated in a current detection system of an AC motor and a method for adjusting the current offset value.

[0002]

2. Description of the Related Art Conventionally, in a current control of a three-phase AC motor as shown in FIG. 8, a DC current offset exists in a current detection system. This current offset becomes a torque ripple that occurs once for one cycle of the electrical angle, and is a problem in controlling the AC motor. As a conventional method for estimating and adjusting such a current offset, there is, for example, an estimation / compensation method disclosed in Japanese Patent Application Laid-Open No. Hei 8-9691.
In this method, in the control of an AC motor, a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle is integrated for one electrical angle, and the current detection system of each phase is based on the integrated value. The current offset is adjusted by estimating the current offset and subtracting the estimated current offset value from the detected current value. This method utilizes the fact that the integrated value of the current command value during one cycle of the electrical angle is theoretically zero except for the offset component. The specific operation will be described with reference to FIG. 8. Under the condition that the speed command is given at a constant speed, the current command calculation unit 101 calculates a current command that is a product of the torque command and the electrical angle. Integrator 1
Reference numeral 07 samples a current command as shown in FIG. At this time, an offset value is created as a result of counting the number of samples n and dividing the integrated value by n. Offset setting unit 10 if there is an offset update request
The offset value created before is set to 9 and the offset setting unit 109 performs offset compensation with the new offset value. In this way, the current offset value could be obtained by integrating the current commands for one electrical angle cycle in the constant speed command state.

[0003]

However, in the above-mentioned conventional example, it is determined that the integrated value of the current command value during one cycle of the electrical angle is theoretically 0 except for the offset component. In this case, the sampling interval of the current command is a fixed value on the computer side because it is a speed control cycle at which the torque command is updated as shown in FIG. 9, and one cycle of the electrical angle is a speed command given at a constant speed. Therefore, the variable value varies depending on the value of each speed command. Therefore, in the case of FIG. 9, when the current command is sampled in the speed control cycle, the electrical angle = 0 in the speed control cycle 0.
At this point, the sampling is started from the speed control cycle 1 and the sampling is performed again until the speed control cycle 12 immediately before the speed control cycle 13 exceeding the electrical angle = 0, but the electrical angle is accurately calculated. The timing when = 0 is between the speed control periods 12 and 13. Since the sampling cannot be performed during this period, an error Er as shown in FIG. 9 occurs in the integrated value of the current command in the speed control periods 1 to 12. In the finally obtained offset value, this error Er is determined by the number of sampling times 1
The value divided by 2 is the offset value error. With an offset value including such an error, the offset adjustment is not performed correctly and torque ripple remains. For this reason, if the multiple of the speed control cycle exactly matches one electrical angle cycle, there is no problem with the conventional method, but it is actually difficult to match them. In this case, since the current command for one cycle of the electrical angle cannot be integrated, an error occurs in the integrated offset value, and there is a problem that correct offset adjustment cannot be performed. Further, the integration process of the current command for one cycle of the electrical angle is performed for each speed control cycle, but the speed control cycle tends to be shortened with the recent improvement in the performance of servo control. Although it is desired that the processing in the speed control cycle is minimized, the load of the speed control processing is increased in the conventional method, and there is a problem that such a demand cannot be satisfied. Further, in the conventional method, since the number of integrations in one cycle of the current command is increased by shortening the speed control cycle, the integrated value of the current command is increased, so that the integrated value does not overflow when designing with the conventional method. Had to be considered. Therefore, an object of the present invention is to provide a current offset estimating method and an adjusting method of an AC motor capable of reducing an error included in a calculated offset value, increasing the accuracy of offset adjustment, and reducing torque ripple. And Further, the present invention can simplify the calculation process of the offset value, reduce the influence of the offset value calculation process on the load of the speed control process, increase the accuracy of the calculated offset value, and improve the torque ripple. It is an object of the present invention to provide a method for estimating and adjusting a current offset of an AC motor.

[0004]

According to a first aspect of the present invention, in the control of an AC motor, a multiplication value of a torque command in a constant speed control state and a value corresponding to an electric angle is provided. It is characterized in that an offset of a current detection system is estimated by using a value obtained by integrating a given current command value for each electrical cycle for a plurality of cycles for each sampling cycle and dividing by a number of times of sampling as an offset value. Claim 2
In the control of an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is integrated in the electrical angle every sampling cycle for a plurality of cycles. The current offset is adjusted by estimating the offset of the current detection system using the value divided by the sample period as the offset value, and subtracting the estimated offset value from the current detection value. According to a third aspect of the present invention, in the control of the AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is changed for a plurality of cycles of the electrical angle. The present invention is characterized in that a current detection system offset is estimated by using a value obtained by integrating each sampling period and dividing by the number of times of sampling as an offset value, and the estimated offset value is added to a current command value to adjust the current offset. According to a fourth aspect of the present invention, in the control of the AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is controlled by an electrical command during one electrical angle cycle. It is characterized in that the offset of the current detection system is estimated using the averaged values sampled at 90 ° and 270 ° angles as the offset value. According to a fifth aspect of the present invention, in the control of the AC motor, a current command value which is a multiplication value of a torque command in a constant speed control state and a value corresponding to the electrical angle is changed to an electrical angle for one electrical angle cycle. At 90
The method is characterized in that a sample is taken at the positions of degrees and 270 degrees, the sample is taken over a plurality of cycles of the electrical angle and an average value is used as an offset value to estimate the offset of the current detection system. According to a sixth aspect of the present invention, in the control of the AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is changed to an electrical angle during one cycle of the electrical angle. It is characterized in that the offset of the current detection system is estimated by using the averaged values sampled at the positions of 90 degrees and 270 degrees as the offset value, and the current offset is adjusted by subtracting the estimated offset value from the current detection value. According to a seventh aspect of the present invention, in the control of the AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to the electrical angle, is changed to an electrical angle during one cycle of the electrical angle. The current offset is adjusted by estimating the offset of the current detection system using the sampled and averaged values at the positions of 90 degrees and 270 degrees as the offset value, and adding the estimated offset value to the current command value. . According to an eighth aspect of the present invention, in the control of the AC motor, the torque command and the electrical angle in the constant speed control state are sampled at positions of 90 degrees and 270 degrees, and the sample is obtained over a plurality of cycles of the electrical angle. The current offset is adjusted by estimating the offset of the current detection system using the averaged value as an offset value, and subtracting the estimated offset value from the detected current value. According to a ninth aspect of the present invention, in the control of the AC motor, the torque command and the electrical angle in the constant speed control state are sampled at positions of 90 degrees and 270 degrees, and the sample is obtained over a plurality of cycles of the electrical angle. The current offset is adjusted by estimating the offset of the current detection system using the averaged value as an offset value, and adding the estimated offset value to the current command value. According to the method of estimating and adjusting the current offset of the AC motor, the U
The phase and V-phase current commands IrefU and IrefV are sampled and integrated at a sampling cycle such as a speed control cycle,
The offset components ΔU and ΔV of the U phase and the V phase are estimated by dividing by the number of samples. However, since the sample period and the electrical angle period do not completely match, an error ΔE is included in ΔU and ΔV.
r = Er / n. Here, Er is the error value shown in FIG. 9, n is the number of times the current command is sampled, and in order to reduce the error ΔEr included in the offset component,
What is necessary is just to increase the number of samples n (it can be reduced to 1 / n). For example, as shown in FIG. 3, if the number of samples n is expanded to three periods, which is three times one electric angle period in the case of FIG.
r can be reduced to 1/3. The offset value thus obtained is subtracted from the current detection value as shown in FIG. 1 or added to the current command value as shown in FIG.
High-precision offset adjustment becomes possible. Alternatively, the sampling detection system is simplified, and the number of times of sampling is changed from the speed control cycle of FIG.
The offset components ΔU and ΔV are obtained by narrowing down to two-point samples of 0 degree and the electrical angle of 270 degrees which is the MIN value, and averaging the sample values at 90 degrees and 270 degrees,
In order to reduce the offset error value Er, the current command 9
The sample processing at 0 ° and 270 ° is extended to a plurality of cycles of the electrical angle, and an average value is obtained to obtain an offset value.
The offset value thus obtained is subtracted from the current detection value as shown in FIG. 4 or added to the current command as shown in FIG. 5, thereby simplifying the sampling process and reducing the load of the process related to the speed control cycle. The accuracy of the offset adjustment can be improved while reducing the amount and calculation processing time to avoid a situation where the integrated value overflows.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a current control block diagram of an AC motor according to a first embodiment of the present invention. FIG. 3 is a diagram showing a relationship between a current command for a plurality of cycles of the electrical angle shown in FIG. 1 and an offset error. In FIG. 1, 1
00 is a speed controller that outputs a current value from a speed command, 10
1 is a current command calculator that outputs a U-phase and V-phase two-phase current command based on a multiplication value of a torque command and an electrical angle, 102 is a current controller that outputs a three-phase voltage command, and 103 is based on a three-phase voltage command. A power converter (PWM inverter) for applying and driving a three-phase current to the three-phase AC motor 104, a current detector 105 such as a Hall CT, and a position detector 106 by an encoder. Reference numeral 10 denotes an integrator that samples the current command from the current command calculation unit 101 for a period set according to an electrical angle number setting command from a control unit (not shown), and counts the number of samples n. 11 is a divider that divides the integrated value by the number of samples n, 12 is a new offset value created by an offset update request from the control unit,
This is an offset setting unit that performs offset compensation by subtracting from the current detection value by the subtractor 13.

Next, the operation will be described. In the current control unit of the three-phase AC motor shown in FIG. 1, there is a phase difference of 120 degrees between the two output from current command calculation unit 101.
Assuming that the phase current commands are a U-phase current command IrefU and a V-phase current command IrefV, respectively, IrefU and IrefV
Is represented by the following equation. IrefU = U-phase command component + U-phase offset component (ΔU) (1) IrefV = V-phase command component + V-phase offset component (ΔV) (2) In equations (1) and (2), The phase command component and the V-phase command component are current commands obtained by multiplying a torque command obtained by multiplying a required torque by a torque multiplier without an offset and an electric angle of the electric motor 104 at that time.
Current command IrefU, I including fixed offset components ΔU, ΔV of the U-phase and V-phase,
refV is output to the electric motor 104. Therefore, when the offset components ΔU and ΔV in both equations are obtained and subtracted from the current detection value, offset removal and compensation from the current commands IrefU and IreV can be performed. The offset components ΔU and ΔV can be obtained from the following equations by sampling IrefU and IrefV n times.

(Equation 1) Here, i: 1, 2, 3,..., Nn: Number of samples n is the total number of samples of the current command, but actually passed the electrical angle of 0 degree as shown in FIGS. From the moment, sampling and integration of the current command are started, and immediately before passing the electrical angle of 0 degree after moving through a plurality of cycles of the electrical angle set in advance (n =
12 and 13, or between 37 and 38), the sampling and the integration are terminated, and the integrated value is divided by the number of samples n. The sample time and the electrical angle period based on the speed control cycle and the like are completely Since they do not match, the integrated value includes an error Er as shown in FIG. The value of this error Er is not a constant value because it differs depending on the sampling timing of the current command. Therefore, the offset components ΔU and ΔV include an error ΔEr represented by the following equation. ΔEr = Er / n (5) Since the magnitude of this Er is limited by the amount of change in the current command between one sample, the number of samples n must be increased in order to reduce ΔEr in equation (5). For this purpose, the sampling time of the current command may be increased from one electrical angle cycle as shown in FIG. 9 to a plurality of electrical angle cycles as shown in FIG. FIG. 3 shows an example in which a plurality of cycles of the electrical angle are expanded to three cycles (not limited). By setting the electrical angle to a plurality of cycles, for example, if the electrical angle is set to three cycles as shown in FIG. 3, the number of samples n is increased from n = 12 in the case of one electrical angle cycle of FIG. 9 to n = 37. Assuming that the error in the offset value obtained by dividing the integrated value of the current command by the number of samples n is the same as the error in FIG. 9 and the error in FIG. 3, the error finally obtained is as shown in FIG. 1/3 of 9
And an offset value with a small error can be obtained.

Next, the offset compensation performed using the offset value thus obtained will be described. First, FIG.
The number of electrical angles N representing the number of multiple electrical angle periods is set in the integrator 10 (3 in FIG. 3), and an integration start request is issued while the AC motor 104 is moving by a constant speed command. , The integrator 10 starts to sample and integrate the current command output from the current command calculation unit 101,
The V-phase current command is integrated. The offset values ΔU and ΔV are calculated by dividing the current command integrated by the equations (3) and (4) by the number of samples n. Subsequently, when an offset update request is input, the calculated and estimated offset values ΔU, Δ
V is set in the offset setting unit 12, and the set new offset value is subtracted from the current detection value detected by the current detector 105 using the subtractor 13 to perform offset compensation of the current command. As described above, according to the present embodiment, by increasing the number of electrical angle periods for sampling the current command and increasing the number of times of sampling n, the offset error value can be reduced and highly accurate offset compensation can be performed.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a current control block diagram of an AC motor according to a second embodiment of the present invention. FIG.
1 is different from that of FIG. 1 in that the offset value calculated / estimated by the integrator 10 and the divider 11 is set in the offset setting device 12, and the offset value is added to the current command by the adder 15 to perform offset compensation. This is a configuration in which an adder 15 for performing the above is added. The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.
Next, the operation will be described. The number N of the plurality of cycles of the electrical angle is set in the integrator 10, and the current command from the current command calculation unit 101 is integrated by the integration start request, and the equations (3) and (4) are obtained.
The procedure for estimating the offset values ΔU and ΔV of the U and V phases is the same as that in the first embodiment. The offset compensation method performed using the offset value thus obtained is different from the previous embodiment, and when the offset update request is issued, the offset value obtained is set to the offset setting unit 12.
The offset compensation is performed by adding the current command output from the current command calculation unit 101 to the current command via the adder 15. As described above, according to the second embodiment, the offset value error can be reduced by increasing the number of samples n as in the first embodiment, and in general, the current detection value In many cases, the resolution of the current command value is higher than that of the current command value. Therefore, the second embodiment using the offset value addition method shown in FIG. 2 has an advantage that the accuracy of the offset adjustment can be easily increased. .

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a current control block diagram of an AC motor according to a third embodiment of the present invention. FIG.
5 is a diagram showing a sample of the current command shown in FIG. FIG.
FIG. 5 is a diagram showing a relationship between a current command for a plurality of cycles of an electrical angle shown in FIG. 4 and an offset error. 4 is different from FIG. 1 in that an integrator 16 that performs two-point sampling at electrical angles of 90 degrees and 270 degrees and a divider 17 that performs a division of 1 / 2N (where N is the number of electrical angular periods). Configuration. The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.
Next, the operation will be described. This embodiment simplifies the sample processing in the previous embodiment, improves the speed control processing load, and enables high-speed processing. In the current control of the three-phase AC motor, the U-phase current command IrefU and the V-phase current command IrefV are as described in the following (1) and (2).
It is expressed by an equation. IrefU = U-phase command component + ΔU (1) IrefV = V-phase command component + ΔV (2) During the current command, U at an electrical angle of 90 degrees as shown in FIG.
The phase and V-phase current command components become the maximum value of the current command in one cycle of the electrical angle, and the current command not including the offset at this time is defined as IrefMAX, and Iremax at the electrical angle of 90 degrees.
The values of fU and IrefV are changed to IrefU90 and IrefU, respectively.
If it is refV90, IrefU90 and IrefV9
0 is represented by the following equations (6) and (7). IrefU90 = IrefMAX + ΔU (6) IrefV90 = IrefMAX + ΔV (7) On the other hand, the U-phase and V-phase current command components at an electrical angle of 270 degrees are:
It becomes the minimum value of the current command in one cycle of the electrical angle, and the current command not including the offset at this time is -IrefMAX
And IrefU and IrefV at an electrical angle of 270 degrees
Are set to IrefU270 and IrefV270, respectively.
Then, IrefU270 and IrefV270 are expressed by the following equations (8) and (9). IrefU270 = −IrefMAX + ΔU (8) IrefV270 = −IrefMAX + ΔV (9) Accordingly, the offset values ΔU and ΔV are obtained from the equations (6) to (9) by the following equations (10) and (11). . ΔU = (IrefU90 + IrefU270) / 2 (10) ΔV = (IrefV90 + IrefV270) / 2 (11) As described above, the speed control processing is simplified by the sample calculation processing simplified from the first and second embodiments. The load can be reduced and high-speed offset estimation can be performed. However, in a case where the speed command cycle is long and the current command generation interval is coarse, the electrical angle 90
Since it is difficult to sample the current command at the timing of degrees and 270 degrees, the offset values ΔU and ΔV obtained by the equations (10) and (11) are likely to include the error ΔEr,
The accuracy of the offset adjustment deteriorates. As a countermeasure, the current command samples of 90 degrees and 270 degrees performed during one electrical angle cycle in FIG.
As shown in (1), a method is used in which the error is reduced by extending the electric angle to a plurality of cycles N, obtaining the average value, and using the average value as the offset value.

FIG. 7 shows a case where a plurality of cycles of electrical angle are performed for three cycles (N =
FIG. 4 is a diagram showing an example of a U-phase current command set as 3), and a current command Ir having an electrical angle of 90 degrees and an electrical angle of 270 degrees during three cycles.
efU 90 degrees, IrefU 270 degrees and offset value Δ
It shows the relationship of U. In this case, “N” represents the number of multiple periods of the electrical angle. In FIG. 7, N = 3 because it is an example of three periods (a plurality of periods and not limited to three periods). Further, in this case, the number of samples per electrical angle cycle = 2, so that the total number of samples n = 2 × N = 6 in a plurality of cycles in FIG. (Of course, n = 2 × 1 = 2 for one electrical angle period, and n = 2 × 2 = for two electrical angle periods.
4). Therefore, the equation for calculating the offset value for a plurality of cycles of the electrical angle (in this case, N = 3) shown in FIG.
It is expressed by the following equations (12) and (13).

(Equation 2) However, i: 1, 2, 3,..., Nn: the number of samples N: the number of multiple periods of the electrical angle When offset compensation is performed using the offset value thus obtained, as shown in FIG. The number of electrical angles representing the number N of the plurality of cycles of the electrical angle is set in advance in the integrator 16, the number of samples n is increased, and when an integration start request is issued during movement by a constant speed command, the integration is started. The sampler 16 samples and integrates the current command only when the electrical angle is 90 degrees and 270 degrees, and calculates the offset value by dividing the integrated current command by the number of samples n as shown in equations (12) and (13). I do. Next, when an offset update request is issued, the calculated offset value is set in the offset setting device 12, and the offset setting device 12 subtracts the newly set offset value from the current detection value via the subtractor 13 to obtain the current command. Perform offset compensation. As described above, according to the third embodiment, the sampling and integration of the current command are simplified, so that the processing speed is increased, the load of the speed control cycle is reduced, and the torque ripple is improved.

Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram of current control of an AC motor according to a fourth embodiment of the present invention. 5 differs from FIG. 4 in that the integrator 16 and the divider 17
An adder 15 for adding the offset values obtained by the two-point sampling of the electrical angles of 90 degrees and 270 degrees to the current command to perform offset compensation is added. The same components as those in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted. Next, the operation will be described. The offset values ΔU and ΔV are calculated by the equations (12) and (1) as in the previous embodiment.
3) Or, if it is determined by equations (10) and (11),
The offset values ΔU and ΔV calculated as soon as the offset update request is input are set in the offset setting unit 12 and added to the current command via the adder 15 to perform offset compensation. As described above, according to the fourth embodiment, similar to the third embodiment, by simplifying the sample integration process,
In this embodiment, the offset of the current command value is higher than the resolution of the current detection value at the same time as the load of the speed control process can be reduced to speed up the offset value calculation process. There is an advantage that the accuracy of adjustment is easily increased.

[0012]

As described above, according to the present invention,
In the control of the AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is integrated for each sampling cycle for a plurality of electrical angles and divided by the number of samples. The value is used as an offset value to estimate the offset of the current detection system, and the current offset is adjusted by subtracting the estimated offset value from the current detection value or adding it to the current command value. There is an effect that the error included in the offset value is reduced, the accuracy of the offset adjustment is improved, and the torque ripple can be reduced.
Further, in the control of the AC motor, a current command value which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electric angle is applied at positions of 90 degrees and 270 degrees in the electric angle during one cycle of the electric angle. The current offset is estimated by subtracting the estimated offset value from the current detection value or adding the estimated offset value to the current command value by estimating the offset of the current detection system as an offset value using the averaged value obtained by performing the sample for a plurality of cycles of the electrical angle. Because it was configured as
The calculation process of the offset value is simplified, the influence of the offset value calculation process on the load of the speed control process can be reduced, and the accuracy of the calculated offset value can be improved, which has the effect of improving the torque ripple.

[Brief description of the drawings]

FIG. 1 is a current control block diagram of an AC motor according to a first embodiment of the present invention.

FIG. 2 is a current control block diagram of an AC motor according to a second embodiment of the present invention.

3 is a diagram showing a relationship between a current command and an offset error for a plurality of cycles of the electrical angle shown in FIG. 1;

FIG. 4 is a current control block diagram of an AC motor according to a third embodiment of the present invention.

FIG. 5 is a current control block diagram of an AC motor according to a fourth embodiment of the present invention.

FIG. 6 is a diagram showing a sample of the current command shown in FIG. 4;

FIG. 7 is a diagram showing a relationship between a current command and an offset error for a plurality of cycles of the electrical angle shown in FIG. 4;

FIG. 8 is a current control block diagram of a conventional AC motor.

9 is a diagram showing a relationship between a current command and an offset error shown in FIG.

[Explanation of symbols]

 10, 16 Integrator 11 1 / n divider 12 Offset setting unit 13 Subtractor 15 Adder 17 Divider 100 Speed controller 101 Current command operation unit 102 Current controller 103 Power converter 104 AC motor 105 Current detector 106 Position Detector

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (9)

[Claims] In an AC motor control, a current command value, which is a product of a torque command in a constant speed control state and a value corresponding to an electrical angle, is integrated for a plurality of cycles of an electrical angle for each sampling period. A current offset estimating method for an AC motor, comprising estimating an offset of a current detection system using a value divided by the number of times of sampling as an offset value. 2. In the control of an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is integrated for a plurality of cycles in an electrical angle for each sampling period. Estimate the offset of the current detection system using the value divided by the sample period as the offset value,
A current offset adjusting method for an AC motor, wherein a current offset is adjusted by subtracting an estimated offset value from a current detection value. 3. In the control of an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is integrated for a plurality of cycles of the electrical angle for each sampling period. Estimate the offset of the current detection system using the value divided by the number of samples as the offset value,
A current offset adjustment method for an AC motor, wherein a current offset is adjusted by adding an estimated offset value to a current command value. 4. In the control of an AC motor, a current command value, which is a product of a torque command in a constant speed control state and a value corresponding to an electrical angle, is converted into an electrical angle of 90 degrees and 270 degrees in one cycle of the electrical angle. A current offset estimating method for an AC motor characterized by estimating an offset of a current detection system by using a value sampled and averaged at a position of (i) as an offset value. 5. In the control of an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electric angle, is converted into an electric angle of 90 degrees and 270 degrees in one cycle of the electric angle. And estimating the offset of the current detection system using the averaged value as an offset value by performing sampling over a plurality of cycles of the electrical angle. 6. In controlling an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is used to control an electrical angle of 90 degrees and 270 degrees during one cycle of the electrical angle. A current offset adjustment method for an AC motor, comprising: estimating an offset of a current detection system using a sampled and averaged value at a position as an offset value, and adjusting the current offset by subtracting the estimated offset value from the detected current value. . 7. In controlling an AC motor, a current command value, which is a multiplication value of a torque command in a constant speed control state and a value corresponding to an electrical angle, is used to control the electrical angle of 90 degrees and 270 degrees during one electrical angle cycle. A current offset adjustment for an AC motor, characterized by estimating an offset of a current detection system using a value sampled and averaged at a position as an offset value, and adding the estimated offset value to a current command value. Method. 8. In the control of the AC motor, the torque command and the electrical angle in the constant speed control state are 90 degrees and 27 degrees.
A sample is taken at a position of 0 degrees, the sample is taken over a plurality of cycles of the electrical angle, an average value is used as an offset value to estimate an offset of the current detection system, and the estimated offset value is subtracted from the current detection value to obtain a current value. A method for adjusting a current offset of an AC motor, comprising adjusting an offset. 9. In the control of the AC motor, the torque command and the electrical angle in the constant speed control state are 90 degrees and 27 degrees.
A sample is taken at a position of 0 degree, the sample is performed over a plurality of cycles of the electrical angle, an average value is estimated as an offset value, an offset of the current detection system is estimated, and the estimated offset value is added to a current command value. A current offset adjusting method for an AC motor, comprising adjusting a current offset.