JP2022112557A - Failure detection device and failure detection method for three-phase current detector - Google Patents

Abstract

To improve fault detection accuracy when a three-phase current detection gain deviation occurs during motor rotation.SOLUTION: A current control system that controls a current flowing in a three-phase AC motor driven by an inverter includes: a current sensor 101 that detects a three-phase current flowing through a motor; a subtractor 102 that calculates a current difference between the detected three-phase currents; a zero-cross detection unit 103 that outputs a zero-cross trigger signal at the timing when any of the current differences becomes zero; and a failure determination unit 105 that determines that a current detection gain deviation has occurred when Tdet<Tref-ΔT or Tdet>Tref+ΔT is satisfied on the basis of a reference value Tref corresponding to a time interval between zero-cross trigger signals when there is no current detection gain deviation, calculated from a rotation speed detection value ω detected by a rotation speed sensor 104, a set margin time ΔT, and a time interval Tdet between the output zero-crossing trigger signals.SELECTED DRAWING: Figure 1

Description

The present invention relates to failure detection of a three-phase current detector for controlling a three-phase AC motor driven by an inverter, for example, a vehicle-mounted motor.

FIG. 2 shows a conventional configuration example in which a three-phase AC motor is driven by an inverter. FIG. 2 shows a motor control device described in FIG. 1 of Patent Document 1, which detects a three-phase current for controlling the current of the motor, detects the rotation speed ω for controlling the rotation speed of the motor, and switches in the inverter. The rotation speed and torque of the motor are controlled by controlling the current flowing through the motor by turning on and off the elements.

In FIG. 2, 50 is a motor control device, which has an inverter 50a and a control section 50b. A storage battery 51 is connected to the DC side of the motor control device 50, and a motor 52 (for example, a PM motor (Permanent Magnet Motor)) is connected to the AC side.

A DC voltage detection sensor 53 for detecting a DC voltage detection value is applied to the DC bus of the inverter 50a, and AC current detection values (Iu, Iv, Iw) are applied to the U-phase, V-phase, and W-phase of the AC bus of the inverter 50a. Alternating current detection sensors 54 a , 54 b , 54 c for detection, and the motor 52 are provided with a magnetic pole position sensor 55 (for example, a resolver) for detecting the rotational speed detection value (ω) of the motor 52 .

The control unit 50b receives a rotation speed command value from the outside of the apparatus, a DC voltage detection value from the DC voltage detection sensor 53, an AC current detection value from the AC current detection sensors 54a, 54b, and 54c, and a rotation speed detection value from the magnetic pole position sensor 55. input.

The control unit 50b generates a desired voltage command value through vector control based on these rotation speed command values and detection values from various sensors (DC voltage detection sensor 53, AC current detection sensors 54a, 54b, 54c, and magnetic pole position sensor 55). is output to a gate drive circuit (not shown).

The gate drive circuit outputs a gate signal based on the input voltage command value to the inverter 50a to turn on/off the switching element (eg, IGBT).

The motor control device 50 performs motor control by converting the DC voltage of the storage battery 51 into a desired AC voltage and outputting it to the motor 52 using an inverter 50a having a switching element.

JP 2018-174655 A JP 2013-055796 A JP 2011-050214 A

In the current control section (50b) of a three-phase AC motor as shown in FIG. Fault detection methods have been implemented to monitor the summation value and detect faults.

This failure detection method detects a failure when the total value of the three-phase current deviates from 0 for a certain period of time. , three-phase currents Iu, Iv, and Iw and the current waveforms of the total values, near the zero crossing of the faulty phase (U-phase current Iu), the total value of the detected three-phase currents ("I total" in the drawing) is Since it becomes close to 0, the time is reset in the vicinity of the zero crossing where "failure detection is performed when the total value deviates from 0 continuously for a certain period of time", and failure detection becomes impossible.

Therefore, in order to see through the gain shift with this failure detection method, it is necessary to detect failures based on the accumulated time. There is a problem that it takes a long time from the occurrence of the failure to the detection due to the detection.

In addition, when the divergence of the current values is detected not by the three-phase current values but by the current effective values, the abnormality of the current itself can also be detected by the means for detecting failures by the cumulative time. However, three-phase current detection values are required for control and the like, and it is necessary to check whether the detection values are abnormal.

An object of the present invention is to solve the above-described problems, and to provide a failure detection device and failure detection method for a three-phase current detection unit that improves the accuracy of failure detection when a three-phase current detection gain shift occurs during motor rotation. is to provide

A failure detection device for a three-phase current detection unit according to claim 1 for solving the above problems,
In a current control system that controls current flowing in a three-phase AC motor driven by an inverter,
a current detection unit that detects a three-phase current flowing through the three-phase AC motor;
a current difference calculation unit that calculates a current difference between each phase of the three-phase current detected by the current detection unit;
a zero-cross detection unit that outputs a zero-cross trigger signal when any of the current differences calculated by the current difference calculation unit becomes zero;
a reference value Tref corresponding to the time interval between zero-cross trigger signals when there is no current detection gain shift, calculated from a rotation speed detection value obtained by detecting the rotation speed of the three-phase AC motor or a motor rotation speed command value; Based on the set margin time ΔT and the time interval Tdet between the zero-cross trigger signals output from the zero-cross detection unit, a current detection gain shift occurs when Tdet<Tref−ΔT or Tdet>Tref+ΔT. an abnormality determination unit that determines that
characterized by comprising

The failure detection device for a three-phase current detection unit according to claim 2 is characterized in that, in claim 1,
The current detection unit includes two current sensors for detecting two phase currents out of the three phases, and a function for calculating the remaining one phase current from the detected currents of the two current sensors. It is characterized by having

A failure detection method for a three-phase current detection unit according to claim 3,
In a current control system that controls current flowing in a three-phase AC motor driven by an inverter,
a step in which a current detection unit detects a three-phase current flowing through the three-phase AC motor;
a step in which a current difference calculation unit calculates a current difference of each phase of the three-phase currents detected by the current detection unit;
a step in which the zero-cross detection unit outputs a zero-cross trigger signal at the timing when any of the current differences calculated by the current difference calculation unit becomes zero;
A reference value corresponding to the time interval between zero-cross trigger signals when there is no current detection gain deviation from the rotation speed detection value or motor rotation speed command value with which the abnormality determination unit detects the rotation speed of the three-phase AC motor. computing Tref;
The abnormality determination unit determines Tdet<Tref−ΔT or Tdet> based on the calculated reference value Tref, the set margin time ΔT, and the time interval Tdet between the zero-cross trigger signals output from the zero-cross detection unit. a step of determining that a current detection gain shift occurs when Tref+ΔT;
characterized by comprising

(1) According to the inventions described in claims 1 to 3, it is possible to detect unbalance of the three-phase current due to the gain deviation of the three-phase current detection, and to Improves detection accuracy.

In addition, since the timing at which any of the current differences becomes zero is used to determine the occurrence of gain deviation in current detection, it is resistant to erroneous detection due to noise and ripples in the detected current at the zero-cross timing.
(2) According to the second aspect of the present invention, it is possible to determine the occurrence of gain deviation in current detection even when only two phases out of three phases of current sensors are provided.

1 is a block diagram of a failure detection device according to an example embodiment of the present invention; FIG. FIG. 2 is a configuration diagram showing an example of a motor drive configuration using a conventional inverter; FIG. 10 is a current waveform diagram in a conventional method of detecting a failure by monitoring the total value of three-phase currents. FIG. 3 is a current waveform diagram when there is no gain deviation of three-phase currents for explaining an embodiment of the present invention; FIG. 4 is a current waveform diagram when there is a gain deviation of the U-phase current for explaining the embodiment of the present invention; FIG. 10 is a current waveform diagram when an offset deviation occurs in a conventional method of detecting a failure by monitoring the total value of three-phase currents;

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiment examples. In this embodiment, in order to detect a gain deviation in current detection during rotation, a failure of the current control system is detected by comparing the intersection point of the three-phase currents and the rotation speed.

For example, in the motor drive device of FIG. 2, FIG. 4 shows the three-phase current waveforms when there is no gain deviation, and FIG. 5 shows the three-phase current waveforms when there is a gain deviation of the U-phase current. The current waveforms in FIGS. 4 and 5 use the values derived using the detected values of the other two phases for one phase (V phase) of the three phase current values, and the current values of each of the three phases are It is written as Iu, Iw, Iv (calculated).

During normal driving, three-phase currents intersect every 1/6 cycle as indicated by crossing times t1, t2, t3, t4, t5, and t6 in FIG. When unbalanced, the intervals between intersections deviate from the 1/6 period as indicated by intersection times t1', t2', t3', t4', t5', and t6' in FIG.

Therefore, the deviation of the three-phase current (Iu-Iv, Iv-Iw, Iw-Iu) is calculated, and the interval of the sign inversion (zero cross) point (=intersection of the three-phase current) of the three-phase current deviation and the rotation speed A comparison of the derived 1/6 periods is made.

When the reference value Tref derived from the 1/6 cycle (interval between current intersections in FIGS. 4 and 5) Tdet and the number of revolutions is Tdet<Tref−ΔT or Tdet>Tref+ΔT (ΔT: allowance time) Then, it is determined that there is a gain deviation in current detection, and an alarm is issued or the inverter that controls the motor is stopped due to failure.

FIG. 1 shows a control block for abnormality detection according to this embodiment, which is applied to the motor drive device shown in FIG. 2, for example. Reference numeral 101 denotes a current sensor (current detection unit) provided on each phase cable connecting between the inverter (50a) and the motor (52) to detect currents Iu, Iw and Iv of each phase.

The current sensor 101 is provided with two current sensors for detecting any two phase currents out of the three phases, and the remaining one phase current is calculated from the detected currents of the two current sensors. may be configured.

Reference numeral 102 denotes a subtractor (current difference calculation unit) that calculates a current difference (Iu-Iv, Iv-Iw, Iw-Iu) of each phase of the three-phase current detected by the current sensor 101 .

Reference numeral 103 denotes a zero-cross detector that outputs a zero-cross trigger signal when any of the current differences (Iu-Iv, Iv-Iw, Iw-Iu) calculated by the subtractor 102 becomes zero.

A rotational speed sensor 104 detects the rotational speed ω of the motor (52).

A reference value Tref is calculated based on the time interval Tdet between the zero-cross trigger signals output from the zero-cross detection unit 103 and the rotation speed detection value ω detected by the rotation speed sensor 104, and a margin time ΔT. and an abnormality determination function that compares the time interval Tdet with the reference value Tref and the margin time ΔT to determine whether or not there is a gain shift in current detection. .

The reference value Tref is a value corresponding to the time interval between zero-cross trigger signals when there is no current detection gain shift, and the abnormality determination function has a comparison result of Tdet<Tref−ΔT or Tdet>Tref+ΔT. It has a function of judging that a current detection gain deviation has occurred and generating an alarm (abnormal signal) or stopping the inverter that controls the motor due to failure.

Incidentally, the rotational speed detection value ω for deriving the reference value Tref may be replaced with a rotational speed command value to be input to the inverter.

According to the configuration of FIG. 1, when the motor is normally driven, the three-phase currents intersect at equal intervals (every 1/6 cycle). Unbalance can be detected.

Also, if one of the detected three-phase currents deviates from the actual current due to an offset deviation, the three-phase total value does not become 0 near the zero crossing as shown in FIG. It can be detected by the conventional failure detection method.

Therefore, by using the present invention in combination with the conventional method of monitoring the total value of three-phase currents, it is possible to more accurately identify failure states in both cases of gain deviation and offset deviation of current detection values. can.

It should be noted that the actual current abnormality can also be detected by another means for detecting the current effective value, so if the other means detects no abnormality, it is possible to identify the three-phase current gain deviation. .

In this embodiment, the current sensor has only two phases and the current in the remaining one phase is obtained by calculation (eg, the current sensor detects Iu and Iv and calculates Iw = -Iu - Iv. ) can also be applied.

According to this embodiment, there are the following advantages over the conventional failure diagnosis methods disclosed in Patent Documents 2 and 3, for example.

That is, in Patent Document 2, failure diagnosis is performed by comparing the currents of the other two phases at the time of current zero crossing, but in the present embodiment, failure diagnosis is performed at the timing of zero crossing detection, and (from the viewpoint of current detection system failure ) can also be detected as a value obtained by detecting two phases of the three-phase current and calculating the remaining one phase.

In addition, since the detection timing itself is compared instead of each detection value of the zero-cross timing, it is also resistant to erroneous detection due to noise and ripples at the zero-cross timing. Furthermore, from the viewpoint of diagnosing current detection system failures, there is an advantage that current can be detected even if only two phases out of three phases are detected.

In addition, in Patent Document 3, the current value after dq conversion is used, but the current after dq conversion causes an abnormality even when the phase (rotation angle) detection fails. Since it is based on the phase current value that does not use the phase (rotation angle) instead of the current value, it is not affected by the failure of the phase detector.

DESCRIPTION OF SYMBOLS 50... Motor control apparatus 50a... Inverter 50b... Control part 51... Storage battery 52... Motor 53... DC voltage detection sensor 54a-54c... AC current detection sensor 55... Magnetic pole position sensor 101... Current sensor 102... Subtractor 103... Zero cross detection part 104... RPM sensor 105... Abnormality determination unit

Claims (3)

In a current control system that controls current flowing in a three-phase AC motor driven by an inverter,
a current detection unit that detects a three-phase current flowing through the three-phase AC motor;
a current difference calculation unit that calculates a current difference between each phase of the three-phase current detected by the current detection unit;
a zero-cross detection unit that outputs a zero-cross trigger signal when any of the current differences calculated by the current difference calculation unit becomes zero;
a reference value Tref corresponding to the time interval between zero-cross trigger signals when there is no current detection gain shift, calculated from a rotation speed detection value obtained by detecting the rotation speed of the three-phase AC motor or a motor rotation speed command value; Based on the set margin time ΔT and the time interval Tdet between the zero-cross trigger signals output from the zero-cross detection unit, a current detection gain shift occurs when Tdet<Tref−ΔT or Tdet>Tref+ΔT. an abnormality determination unit that determines that
A failure detection device for a three-phase current detection unit, comprising: The current detection unit includes two current sensors for detecting currents of any two phases out of three phases, and a function of calculating the current of the remaining one phase from the detected currents of the two current sensors. 2. The failure detection device for a three-phase current detection unit according to claim 1, further comprising: In a current control system that controls the current flowing in a three-phase AC motor driven by an inverter,
a step in which a current detection unit detects a three-phase current flowing through the three-phase AC motor;
a step in which a current difference calculation unit calculates a current difference of each phase of the three-phase currents detected by the current detection unit;
a step in which the zero-cross detection unit outputs a zero-cross trigger signal at the timing when any of the current differences calculated by the current difference calculation unit becomes zero;
A reference value corresponding to the time interval between zero-cross trigger signals when there is no current detection gain deviation from the rotation speed detection value or motor rotation speed command value with which the abnormality determination unit detects the rotation speed of the three-phase AC motor. computing Tref;
The abnormality determination unit determines Tdet<Tref−ΔT or Tdet> based on the calculated reference value Tref, the set margin time ΔT, and the time interval Tdet between the zero-cross trigger signals output from the zero-cross detection unit. a step of determining that a current detection gain shift occurs when Tref+ΔT;
A failure detection method for a three-phase current detection unit, comprising:

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