JPH09172791A - Failure detection device for a.c. motor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device suitable to detect failure of a current sensor for a.c. motor control and so on. SOLUTION: A voltage command value to a motor 10 is inputted into a CPU 18, based on which the estimated values iuc , ivc , iwc of respective phase current of the motor 10 are calculated. The detected current value is inputted from a current sensor 30 fitted onto the motor 10 to calculate a deviation from the calculated estimated values iuc , ivc , iwc . When calculated deviation is larger than a prescribed threshold, processing against failure such as power converting operation is conducted. A current command value to the motor may be used in place of the estimated current values iuc , ivc , iwc .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting apparatus for an AC motor control circuit, for example, an apparatus for detecting an abnormality of a sensor for detecting a current flowing through an AC motor.

[0002]

2. Description of the Related Art When a direct current from a power supply is converted into an alternating current by a power circuit such as an inverter and supplied as a drive current to an alternating current motor, the current flowing through the alternating current motor or its power circuit must be detected. Various current sensors are provided in each part of the device. For example, the current flowing through the AC motor is detected by a current sensor, and the result is used to feedback control the operation of the inverter. Further, these current sensors are also useful for detecting an abnormality of the AC motor to be controlled. For example, in Japanese Unexamined Patent Publication No. 6-133591, when the direct current flowing from the power supply to the inverter is larger than the threshold value, it is determined that the peak value of the current supplied to the three-phase induction motor via the inverter is large.

[0003]

If any abnormality occurs in the current sensor used in the feedback control of the AC motor or its power circuit as described above, the AC motor and its power circuit will be affected. The operation / output cannot be made as intended. Therefore, when using such a current sensor, it is preferable to provide a device or control procedure for detecting the occurrence of an abnormality in the current sensor in order to be able to cope with the occurrence of the abnormality. However, in balanced AC, the sum of the detected values of each phase current is 0.
Therefore, it is possible to detect abnormality of the current sensor corresponding to each phase by using this, but with this method,
It is not possible to deal with the case where current anomalies occur simultaneously in multiple phases. In addition, such principle cannot be used in unbalanced alternating current.

A first object of the present invention is to propose a new principle of detecting a current abnormality so that a current sensor can be used even when current abnormalities occur in a plurality of phases at the same time or even in unbalanced AC. The purpose is to make it possible to detect abnormalities in the power circuit, wiring, and elements including the above, and thus to make the control of the AC motor to be controlled more stable and reliable. A second object of the present invention is to introduce a control adapted to the operation of the AC motor so that an abnormality of a power circuit, a wiring, and an element including a current sensor can be detected properly without error, and a countermeasure against a current abnormality is dealt with. It should be possible only when necessary.

[0005]

In order to achieve such an object, the abnormality detecting device according to the first configuration of the present invention is
(A) AC motor control circuit for controlling the AC motor via the power circuit according to a voltage command value indicating a voltage to be applied from the power circuit to the AC motor and referring to a motor current value detected by a current sensor Used in
(B) The motor current value detected by the current sensor is
If the difference between the motor current value estimated based on the voltage command value and the means for comparing and (C) the comparison result in a difference exceeding the threshold value, the current sensor or the current sensor And a unit for determining that there is an abnormality in the related circuit or wiring, or that there is an abnormality in the power circuit or the circuit or wiring related thereto.

The abnormality detecting device according to the second aspect of the present invention is (A ') the motor current value detected by the current sensor according to the current command value indicating the instantaneous current to be supplied to the AC motor from the power circuit. Used in an AC motor control circuit for controlling the AC motor via the power circuit while referencing, (B ′) means for comparing a motor current value detected by the current sensor with the current command value, (C) When it is determined that the difference between the two exceeds the threshold value as a result of comparison, the fact that there is an abnormality in the current sensor or a circuit or wiring related thereto, or the power circuit or And a means for determining that there is an abnormality in a circuit or wiring related thereto.

In the first and second configurations, the abnormality of the current sensor or the like is detected by comparing the motor current value estimated based on the voltage command value or the current command value with the current sensor output. Since the voltage command value and the current command value are amounts that can be converted into the motor current of each phase or given for each phase, the above-described abnormality detection in these configurations can be executed for each phase. Therefore, in these configurations, even when a current abnormality occurs in a plurality of phases at the same time, the abnormality of the current sensor or the like can be detected, and the control of the AC motor to be controlled becomes more stable and reliable. Particularly, in the second configuration, there is no room for the equilibrium condition because the process of estimating the motor current value from the voltage command value is not required unlike the first configuration. That is, in the second configuration, an abnormality of the current sensor or the like can be detected even with unbalanced AC.

In the abnormality detecting device according to the third structure of the present invention, in the first or second structure, (D) the change per unit time of the current command value indicating the instantaneous current to be supplied from the power circuit to the AC motor. Rate and / or means for detecting the number of revolutions of the AC motor, and (E) means for adaptively setting the threshold value so that it becomes large when the detected rate of change is high or when the number of revolutions is low, It is characterized by including. In this configuration, since the control adapted to the operation of the AC motor is introduced in the threshold setting procedure, the abnormality of the current sensor or the like can be detected properly without any error. Therefore, the countermeasure for the current abnormality can be performed only when necessary, and the countermeasure for the current abnormality can be rarely executed when unnecessary.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the system configuration of an AC motor control circuit according to the first embodiment of the present invention. The circuit shown in this figure is, for example, a battery 1 of 192 V DC.
When power is supplied from two to the three-phase AC motor 10, the power is supplied to the intelligent power module (IPM) 1
4 is a circuit for controlling the operation of converting DC to three-phase AC by means of 4, and can be used, for example, in a control circuit of a traveling motor of an electric vehicle.

The controller 16 for controlling the operation of the IPM 14 includes a CPU 18, a ROM 20, a RAM 22, and an I / O.
The port 24 and the A / D converter 26 are incorporated.
The ROM 20 stores a control program to be executed by the CPU 18 and fixed parameters, and the RAM 22 stores the CPU.
18 to provide a work area. I / O port 24 and A /
The D converters 26 are means for inputting digital or analog information from the outside. Here, a torque command value indicating the torque to be output from the motor 10,
An output of a resolver 28 that is attached to the motor 10 and that generates a signal in accordance with the rotation of the rotor is input from the I / O port 24. The A / D converter 26 is the motor 1
Current sensors 30u provided corresponding to each phase of 0,
The outputs ius, ivs, and iws of 30v and 30w are converted from analog to digital and input to the controller 16. C
In the PU 18, the torque corresponding to the torque command value is the motor 1
A control signal is supplied to the IPM 14 so that it is output from 0. At that time, the CPU 18 refers to the output signal of the resolver 28, that is, the number of rotations or the rotation angle of the motor 10, the outputs ius, ivs, iws of the current sensors 30u, 30v, 30w, that is, the detected value of each phase current instantaneous value.

The CPU 18 includes current sensors 30u and 30.
In order to detect the v and 30w abnormalities, the current sensor abnormality detection routine shown in FIG. 2 is executed at a predetermined frequency. Here, the routine shown in FIG. 2 uses the following principle.

First, the U, V, and W phase voltages v of the motor 10
If the voltage equation representing u, vv, vw is described for each phase,

## EQU1 ## vu = (Ra + pLa) iu-0.5pMa (iv + iw) + euvv = (Ra + pLa) iv-0.5pMa (iu + iw) + evvw = (Ra + pLa) iw-0.5pMa (i) ) + Ew. In this equation, iu, iv, and iu are induced in the armature winding by the current flowing in each phase armature winding, and eu, ev, and ew are induced in the armature winding by the field flux (in the permanent magnet field type motor, the magnetic flux from the permanent magnet). Voltage (speed electromotive force), Ra is the armature winding resistance of the motor 10, La is the armature winding self-inductance of the motor 10, Ma is the mutual inductance between the armature windings of the motor 10, and p is a differential operator. is there. The first and second terms on the right side of this equation are

Since it can be summarized by using the equilibrium condition represented by iu + iv + iw = 0, the above voltage equation is eventually

## EQU3 ## vu = (Ra + pLa + 0.5pMa) iu + eu vv = (Ra + pLa + 0.5pMa) iv + evvw = (Ra + pLa + 0.5pMa) iw + ew. Furthermore, if this equation is solved for iu, iv, and iw,

Iu = (vu-eu) / (Ra + pLa + 0.
5 pMa) iv = (vv -ev) / (Ra + pLa +0.5 pMa
) Iw = (vw-ew) / (Ra + pLa + 0.5 pMa
).

When the CPU 18 controls the IPM 14, the U, V, W phase voltage command values vu *, vv *, vw * to be applied from the IPM 14 to the motor 10 are calculated based on the torque command values. Are used to generate control signals for the IPM 14. Therefore, by substituting vu *, vv *, vw * for vu, vv, vw in the above voltage equation, iu, iv, iw can be estimated. That is,

## EQU5 ## iuc = (vu * -eu) / (Ra + pLa + 0.
5 pMa) ivc = (vv * -ev) / (Ra + pLa + 0.5 pMa
) Iwc = (vw * -ew) / (Ra + pLa + 0.5 pMa
), U, V, W phase currents iu, i of the motor 10
It is possible to obtain the estimated values iuc, ivc, and iwc of v and iw. Since Ra, La, and Ma are constants, they can be obtained in advance during designing and testing, and eu, ev, and ew.
Can also be obtained by testing or measurement in advance.

In the routine shown in FIG. 2, first, the CPU 18 calculates iuc, ivc, iwc according to this principle. That is, the CPU 18 first moves from the main routine to the current sensor abnormality detection routine, vu *, vv *, vw *.
Is passed (100), and iuc, ivc, iwc are calculated using this and according to the above-mentioned principle (102). CPU1
8 then sends via the A / D converter 26 ius, iv
s and iws are input (104), and deviations of ius, ivs, and iws with respect to iuc, ivc, and iwc | iuc-ius |, | ivc-i
vs |, | iwc-iws | is calculated (106). CPU18
Is the expression

[Equation 6] | iuc-ius | ≦ ΔI1u | ivc-ivs | ≦ ΔI1v | iwc-iws | ≦ ΔI1w It is determined whether or not the condition is satisfied (10
8), if established, current sensors 30u, 30
It is determined that both v and 30w are normal, and the current sensor abnormality detection routine ends. Current sensor 30u, 30
When this condition is not satisfied for at least one of v and 30w, the CPU 18 considers that normal control cannot be continued, turns off the output of the IPM 14, and cuts off the current supply to the motor 10 (110). . As described above, according to the present embodiment, since the threshold value determination for each phase is executed, the abnormality of the current sensors 30u, 30v, 30w can be detected even when the current abnormality occurs in a plurality of phases at the same time. The control of the motor 10 becomes more stable and reliable.

FIGS. 3 to 5 are timing charts showing an outline of current abnormality detection in this embodiment. The “abnormality detection allowable range” shown in each figure is the judgment thresholds ΔI1u, ΔI1v, Δ in step 108.
The range determined by I1w and judged as current sensor = normal is shown. Further, FIGS. 4 and 5 show two types of abnormal modes of the current sensor (FIG. 4 is open, and FIG. 5 is ground short circuit mode). In the figure, "threshold value (+)" and "threshold value (-)" are examples of threshold value setting for detecting an abnormality of the current sensor by determining the peak value of its output. is there. As is apparent from FIGS. 4 and 5, according to the present embodiment, it is possible to detect a mode abnormality that cannot be detected by the abnormality determination based on the peak value detection.

FIG. 6 shows the contents of the current sensor abnormality detection routine in the second embodiment of the present invention. In this embodiment, the CPU 18 calculates the current command values iu *, iv *, iw * indicating the instantaneous value of the current to be supplied to each phase of the motor 10 based on the input torque command value (100A) (102A). ), The input ius, ivs, i
deviation of ws (104) | iu * -ius |, | iv * -ivs |,
| Iw * -iws | is calculated (106A), and the following equation is obtained.

[Equation 7] | iu * −ius | ≦ ΔI2u | iv * −ivs | ≦ ΔI2v | iw * -iws | ≦ ΔI2w It is determined whether or not the condition is satisfied (10
8A). When the condition is satisfied, the CPU 18 determines that all the current sensors 30u, 30v, 30w are normal and ends the current sensor abnormality detection routine. When this condition is not satisfied for any one or more of the current sensors 30u, 30v, 30w, the CPU 18
Considering that normal control cannot be continued, the output of the IPM 14 is turned off, and the current supply to the motor 10 is cut off (110).
Therefore, also in this embodiment, the same advantages as those of the first embodiment can be obtained. In addition, since this embodiment does not use the equilibrium condition in principle, it can be applied to unbalanced alternating current.

FIG. 7 shows the contents of the threshold value setting routine in the third embodiment of the present invention. In this embodiment, the determination threshold Δ in the first and second embodiments is used.
This is an improvement in the method of setting I1u etc. or ΔI2u etc. That is, in this embodiment, the CPU 18 uses the resolver 28.
The number of rotations of the motor 10 is obtained based on the output of (200),
Further, the threshold value setting table 300 that associates the rotation speed with the determination threshold value is referred to by the obtained rotation speed (202), and the determination threshold value ΔI1u or the like or ΔI2u or the like is set. Further, FIG. 8 shows the contents of the threshold value setting routine in the fourth embodiment of the present invention. This embodiment is also an improvement of the method of setting the determination threshold value ΔI1u or the like or ΔI2u or the like in the first and second embodiments. That is, in this embodiment, the CPU 18 obtains the time change rate (200B) based on the current command value (200A) delivered from the main routine, and further associates the time change rate with the determination threshold. The value setting table 300A is referred to by the obtained time change rate (2
02A), the determination threshold value ΔI1u or the like or ΔI2u or the like is set. Further, the current command value input in step 200A is stored in the RAM 22 for the next execution of this routine.
Store it above (204).

According to these embodiments, the judgment threshold value ΔI1u or the like or ΔI2u or the like can be adapted to the current command value. For example, when a slight abnormality should not occur in the current sensor 30u or the like (that is, when the "abnormality detection allowable range" in FIGS. 3 to 5 is narrow), the determination threshold value ΔI2u or the like in the second embodiment is fixed. If it is set, the delay in following the current of the motor 10 with respect to the current command value may be erroneously detected as an abnormality of the current sensor 30u or the like.
If the adaptive control of the determination threshold value is executed as in the third and fourth embodiments, the determination threshold value is decreased when the rotation speed of the motor 10 is high, or the rate of change of the current command value is reduced. Since it is possible to reduce the determination threshold value when it is low, it is possible to realize accurate abnormality detection while not performing step 110 unnecessarily.

Although the determination threshold value ΔI1u and the like are set for each phase in each of the above-described embodiments, the same value may be set for all phases. Further, in each of the above-described embodiments, the output of the IPM 14 is turned off when any one of the current sensors 30u, 30v, and 30w is abnormal. If it remains (that is, if two or more are not abnormal at the same time), the current detection values for all the phases can be obtained from the outputs of the remaining two current sensors.
It is also possible to keep the output of 14 on. Furthermore, in the above description, the abnormality detection of the current sensor is taken as an example, but the present invention can also be applied to the detection of current abnormality of various control circuits and wirings related to AC motor control.

[0021]

According to the first aspect of the present invention, the motor current value detected by the current sensor is compared with the motor current value estimated based on the voltage command value that can be converted into the motor current of each phase, As a result, when it is determined that the difference between the two exceeds the threshold value, it is determined that the current sensor or the like has an abnormality, so that the abnormality can be detected for each phase. Therefore, even when the current abnormality occurs in a plurality of phases at the same time, the abnormality of the current sensor or the like can be detected, and the control of the AC motor to be controlled becomes more stable and reliable.

According to the second configuration of the present invention, the motor current value detected by the current sensor is compared with the current command value given for each phase, and as a result, the difference between the two exceeds the threshold value. If it is determined that they are different, it is determined that an abnormality has occurred in the current sensor or the like, so that abnormality detection can be performed for each phase. Therefore, even when the current abnormality occurs in a plurality of phases at the same time, the abnormality of the current sensor or the like can be detected, and the control of the AC motor to be controlled becomes more stable and reliable.
Furthermore, since the equilibrium condition is not necessary for the abnormality detection operation,
Even with unbalanced AC, it is possible to detect an abnormality in the current sensor or the like.

According to the third aspect of the present invention, the rate of change per unit time of the current command value indicating the instantaneous current to be supplied from the power circuit to the AC motor and / or the rotational speed of the AC motor is detected and detected. Since the threshold value in the first or second configuration is adaptively set so as to increase when the change rate is high or the rotational speed is low, the threshold value setting is adapted to the operation of the AC motor. be able to. As a result, an abnormality of the current sensor or the like can be detected without error and appropriately, so that the countermeasure for the current abnormality can be performed only when necessary, and the countermeasure for the current abnormality when unnecessary is reduced.

[0024]

[Addendum] The present invention can be understood as the following configuration.

(1) In the AC motor control method according to the fourth aspect of the present invention, the step of inputting a voltage command value indicating the voltage to be applied to the AC motor from the power circuit, and the motor current value based on the voltage command value. The step of estimating the motor current value supplied to the AC motor from the power circuit with the current sensor, the step of comparing the detected motor current value with the estimated motor current value, and the result of the comparison. If the difference between the two exceeds the threshold value, it means that there is an abnormality in the current sensor or the circuit or wiring related thereto, or the power circuit or the circuit or wiring related thereto. That something is wrong with
A step of determining and a step of controlling the AC motor via the power circuit while referring to the detected motor current value according to the input voltage command value, except when it is determined that the abnormality has occurred, It is characterized by having. According to this configuration, the same advantages as the first configuration can be obtained.

(2) In the AC motor control method according to the fifth aspect of the present invention, a step of inputting a current command value indicating an instantaneous current to be supplied to the AC motor from the power circuit, and a method of supplying the AC motor from the power circuit. It is said that the difference between the detected motor current value with the current sensor, the step of comparing the detected motor current value and the current command value, and the difference between the two exceed the threshold value. In the event of a malfunction, the current sensor or a circuit or wiring related thereto has an abnormality, or the power circuit or a circuit or wiring related thereto has an abnormality; Except when it is determined that the AC current is generated, the step of controlling the AC motor via the power circuit is performed according to the input current command value and referring to the detected motor current value. And having a flop, a.
According to this configuration, the same advantages as the second configuration can be obtained.

(3) In the AC motor control method according to the sixth aspect of the present invention, in the fourth or fifth aspect, per unit time of a current command value indicating an instantaneous current to be supplied from the power circuit to the AC motor. A step of detecting the rate of change and / or the number of revolutions of the AC motor, and a step of adaptively setting the threshold value so as to increase when the detected rate of change is high or the number of revolutions is low. It is characterized by According to this structure, the same advantages as the third structure can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a flow of a current sensor abnormality detection routine in this embodiment.

FIG. 3 is a timing chart showing an abnormality detection allowable range in this embodiment.

FIG. 4 is a timing chart showing an output waveform of the current sensor when an abnormality in the open mode occurs in the current sensor.

FIG. 5 is a timing chart showing current sensor output waveforms when a short-circuit mode abnormality occurs in the current sensor.

FIG. 6 is a flowchart showing a flow of a current sensor abnormality detection routine according to the second embodiment of the present invention.

FIG. 7 is a flowchart showing the flow of a threshold value setting routine in the third embodiment of the present invention.

FIG. 8 is a flowchart showing a flow of a threshold value setting routine in the fourth embodiment of the present invention.

[Explanation of symbols]

1 motor, 12 battery, 14 IPM (intelligent power module), 16 controller, 1
8 CPU, 28 resolver, 30u, 30v, 30w
Current sensor, ius, ivs, iws U, V, W phase detected value (instantaneous value), iuc, ivc, iwc U, V, W phase current estimated value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H02P 7/63 302 H02P 7/63 302S

Claims (3)

[Claims] 1. An AC motor for controlling the AC motor via the power circuit according to a voltage command value indicating a voltage to be applied from the power circuit to the AC motor and referring to a motor current value detected by a current sensor. A means used to compare the motor current value detected by the current sensor detected by the current sensor with the motor current value estimated based on the voltage command value, and the difference between the two exceeds the threshold value as a result of comparison. If there is a difference, it means that there is an abnormality in the current sensor or circuits or wiring related thereto, or that there is an abnormality in the power circuit or circuits or wiring related thereto, An abnormality detection device comprising: a determination unit. 2. An AC for controlling the AC motor via the power circuit according to a current command value indicating an instantaneous current to be supplied from the power circuit to the AC motor and referring to a motor current value detected by a current sensor. It is said that the means for comparing the motor current value detected by the current sensor with the current command value used in the motor control circuit and the difference between the two as a result of comparison exceed the threshold value. In this case, there is provided means for determining that there is an abnormality in the current sensor or a circuit or wiring related thereto or that there is an abnormality in the power circuit or a circuit or wiring related thereto. Anomaly detection device characterized by. 3. The abnormality detection device according to claim 1, wherein the rate of change of a current command value indicating an instantaneous current to be supplied from the power circuit to the AC motor per unit time and / or the rotational speed of the AC motor is detected. And a means for adaptively setting the above-mentioned threshold value so as to increase when the detected rate of change is high or the number of revolutions is low.