JP7100976B2 - Inverter abnormality diagnosis device, inverter device and electric vehicle equipped with this inverter device - Google Patents

Description

The present invention relates to an inverter abnormality diagnosis device, an inverter device, an electric vehicle equipped with the inverter device, and an in-wheel motor drive device, for example, an inverter using a semiconductor switching element such as an IGBT used in an electric vehicle or the like. Regarding the abnormality diagnosis device.

Various techniques for diagnosing an abnormality of an inverter have been proposed.
For example, a pulse signal for measurement is given to the primary side (gate side) of each switching element of the inverter, and the abnormality of each switching element is determined by the current value detected by the current sensor (Patent Document 1).

Japanese Unexamined Patent Publication No. 8-308244

In Patent Document 1, since a pulse signal for measurement is applied to each switching element to determine an abnormality, it is not possible to determine an abnormality while the inverter is in operation. When the technique of Patent Document 1 is applied to a vehicle driving inverter, it is not possible to perform an abnormality diagnosis of the inverter while the vehicle is running.

An object of the present invention is to provide an inverter abnormality diagnosis device capable of diagnosing an abnormality during operation, an inverter device, and an electric vehicle equipped with the inverter device.

The inverter abnormality diagnosis device of the present invention is a device for diagnosing an abnormality of the inverter 24 that converts the DC power of the DC power supply 32 into three-phase AC power used for driving the motor 6 by turning on and off a plurality of switching elements 27. ,
A calculation circuit unit 19 that calculates a command value of a current flowing through the motor 6 according to a given torque command, and a current sensor 29 that detects the phase current of each phase flowing through the motor 6 are provided.
A comparison means 33 that compares the phase current detected by the current sensor 29 with the threshold value at regular time intervals while the absolute value of the command value of the current calculated by the calculation circuit unit 19 exceeds the threshold value.
The comparison means 33 includes a determination means 34 for determining that the switching element 27 for driving the phase is an open abnormality when the phase current does not continuously exceed the threshold value for a predetermined number of times or more.
The threshold value, the fixed time, and the specified number of times are the threshold value, the fixed time, and the specified number of times, respectively, which are arbitrarily determined by the design and the like, and are, for example, a threshold value, a fixed time, which are more appropriate for one or both of the test and the simulation. It is determined by asking for the specified number of times.

Since the detected phase current includes errors such as offset or gain error and noise, the detected phase current does not meet the command value of the current. In particular, when the command value of the current is small, the influence of offset error and the like is large, and it is difficult to judge whether it is normal or abnormal.
Therefore, according to this configuration, the comparison means 33 compares the phase current detected by the current sensor 29 with the threshold value at regular time intervals while the absolute value of the command value of the current exceeds the threshold value. In this way, since the phase current comparison processing is performed while the absolute value of the current command value exceeds the threshold value, the influence of offset error and the like is mitigated, and it is easy to judge whether it is normal or abnormal. It can be carried out.

When the phase current falls below the threshold value continuously for a predetermined number of times or more, the determination means 34 determines that the switching element 27 for driving the phase has an open abnormality. If the number of times the phase current falls below the threshold value is continuously less than the specified number of times, the switching element 27 for driving the phase is determined to be normal. This is because even when the switching element is normal, the detected phase current may momentarily fall below the threshold value due to an error or the like. In this way, it is possible to prevent erroneous determination of normal or abnormal. Therefore, the abnormality diagnosis can be easily and accurately performed while the inverter 24 is in operation.

The inverter device of the present invention includes an abnormality diagnosis device for the inverter 24 having the above configuration of the present invention. According to this configuration, the redundancy of the inverter device 13 can be improved.

The electric vehicle of the present invention is equipped with the inverter device 13 having the above configuration of the present invention. In this case, since it is possible to confirm the opening abnormality of the switching element 27 while the electric vehicle is in operation, the electric vehicle can be safely stopped at the roadside, a parking space, or the like.

The in-wheel motor drive device of the present invention includes the inverter device of the present invention. Therefore, if an abnormality occurs in the inverter while the motor is being driven, the in-wheel motor drive device can be treated at an early stage.

The inverter abnormality diagnosis device of the present invention is a device for diagnosing an abnormality of an inverter that converts the DC power of a DC power supply into three-phase AC power used for driving a motor by turning on and off a plurality of switching elements, and is a given torque. A calculation circuit unit that calculates a command value of the current flowing through the motor according to a command and a current sensor that detects the phase current of each phase flowing through the motor are provided, and the current command calculated by the calculation circuit unit is provided. While the absolute value of the value exceeds the threshold value, the phase current detected by the current sensor is compared with the threshold value at regular time intervals, and the comparison means continuously changes the phase current to the threshold value more than a specified number of times. If the current does not exceed, the switching element for driving the phase is determined to have an open abnormality. Therefore, it is possible to diagnose an abnormality during the operation of the inverter.

Since the inverter device of the present invention includes the abnormality diagnosis device for the inverter having the above configuration of the present invention, it is possible to diagnose an abnormality during the operation of the inverter. This makes it possible to improve the redundancy of the inverter device.

Since the electric vehicle of the present invention is equipped with the inverter device having the above configuration of the present invention, it is possible to diagnose an abnormality during the operation of the inverter. As a result, it is possible to confirm an open abnormality of the switching element while the electric vehicle is in operation, so that the electric vehicle can be safely stopped at the roadside, a parking space, or the like.

Since the in-wheel motor drive device of the present invention includes the inverter device of the present invention,
If an abnormality occurs in the inverter while driving the motor, early treatment of the in-wheel motor drive device can be performed.

It is a block diagram of the conceptual structure which shows the electric vehicle equipped with the abnormality diagnosis apparatus of the inverter which concerns on embodiment of this invention in the plan view. It is sectional drawing of the in-wheel motor drive device in the electric vehicle. It is a block diagram which shows the main part of the inverter. It is a figure which shows the current waveform at the time of normality determination in the abnormality diagnosis apparatus. It is a figure which shows the current waveform at the time of abnormality determination in the abnormality diagnosis apparatus. It is a flowchart which shows the abnormality judgment flow in the abnormality diagnosis apparatus. It is a block diagram of the conceptual structure which shows the electric vehicle equipped with the abnormality diagnosis apparatus of the other inverter of this invention in the plan view.

An embodiment of the present invention will be described with reference to FIGS. 1 to 6.
The inverter abnormality diagnosis device according to this embodiment is mounted on an electric vehicle.
<About the conceptual structure of this electric vehicle>
FIG. 1 is a block diagram of a conceptual configuration showing a plan view of an electric vehicle equipped with an abnormality diagnosis device for an inverter according to this embodiment. This electric vehicle is a four-wheel electric vehicle in which the left and right rear wheels 2 of the vehicle body 1 are used as driving wheels and the left and right front wheels 3 are used as driven wheels. The wheel 3 serving as the front wheel is a steering wheel. The left and right wheels 2 and 2, which are the driving wheels, are driven by independent motors 6 for traveling. Each motor 6 constitutes an in-wheel motor drive device IWM, which will be described later. Brake is provided on each of the wheels 2 and 3. The wheels 3 and 3, which are the steering wheels that are the left and right front wheels, can be steered via a steering mechanism (not shown), and are steered by a steering means 15 such as a steering wheel.

<About the outline configuration of the in-wheel motor drive device IWM>
As shown in FIG. 2, the left and right in-wheel motor drive devices IWM each have a motor 6, a speed reducer 7, and a wheel bearing 4, and a part or all of them are arranged in the wheel. The rotation of the motor 6 is transmitted to the wheel 2 which is a drive wheel via the speed reducer 7 and the wheel bearing 4. A brake rotor 5 constituting the brake is fixed to the flange portion of the hub wheel 4a of the wheel bearing 4, and the brake rotor 5 rotates integrally with the wheel 2.

The motor 6 is a three-phase motor, for example, an embedded magnet type synchronous motor in which a permanent magnet is built in the core portion of the rotor 6a. The motor 6 is a motor provided with a radial gap between the stator 6b fixed to the housing 8 and the rotor 6a attached to the rotary output shaft 9.

<About the control system>
As shown in FIG. 1, the control device 16 that controls each motor 6 controls the ECU 14 which is an electric control unit that controls the entire automobile, and the left and right motors 6 and 6 for traveling according to the command of the ECU 14. It has a two-axis integrated inverter unit IU. The inverter unit IU has inverter devices 13 and 13 that control the left and right motors 6 and 6, respectively. In the case of an electric vehicle, the ECU 14 is also referred to as a VCU (vehicle control unit).

FIG. 3 shows the basic structure of an inverter system for one axis. In FIG. 1, two sets of this basic structure are used. As shown in FIG. 3, the inverter device 13 has a power circuit unit 17 provided for each motor 6 and a motor control unit 18 for controlling each power circuit unit 17. The motor control unit 18 includes an arithmetic circuit unit 19 corresponding to each motor 6, a current monitoring unit 22, and an abnormality reporting unit 23, which will be described later. The motor control unit 18 has a function of outputting information such as detection values and control values of the in-wheel motor drive device IWM (FIG. 1) of the motor control unit 18 to the ECU 14.

The power circuit unit 17 has an inverter 24 that converts the current of the DC power supply 32 into three-phase AC power used for driving the motor 6, and a gate drive circuit 25 that drives the inverter 24. The inverter 24 has a smoothing capacitor 26 that stabilizes electric power, and a U-phase, V-phase, and W-phase switching element 27. Each phase has switching elements UP, VP, WP connected to the high side side of the DC power supply 32 and switching elements UN, VN, WN connected to the low side, from between both the high side and low side switching elements. The phase current output units Uout, Vout, and Wout of each of the U, V, and W phases are drawn out.

As each switching element 27, for example, an insulated gate bipolar transistor (abbreviation: IGBT) is applied. The gate drive circuit 25 drives each switching element 27 based on the input on / off command. In each switching element 27, the fast recovery diode 28 is attached for protection of the switching element 27 and return from the motor 6. As each switching element 27, another switching element such as a field effect transistor (abbreviation: FET) or a transistor may be used instead of the IGBT.

The motor control unit 18 is composed of a computer, a program executed by the computer, and an electronic circuit, and has an arithmetic circuit unit 19 as a basic control unit thereof.
As shown in FIGS. 1 and 3, the ECU 14 receives an accelerator opening signal (acceleration command) output by the accelerator operation unit 20 and a deceleration command output by the brake operation unit 21, or an acceleration command and a deceleration command. From the turning command output by the steering means 15, acceleration / deceleration commands given to the motors 6 and 6 of the left and right rear wheels 2 and 2 are generated as torque commands and output to each inverter device 13.

The arithmetic circuit unit 19 converts a torque command given from the ECU 14, which is a higher-level control means, into a current command value (current command value). The current monitoring means 22 obtains the phase current of each phase flowing from each phase of the inverter 24 to the motor 6 from the current sensors 29, 29, 29, and determines whether the current is appropriate for the current command value. This determination result is given to the arithmetic circuit unit 19. The number of current sensors 29 is usually two, but in this example, three are provided including a spare.

The arithmetic circuit unit 19 further increases the current command value if the measured current is smaller than the calculated current command value, and further decreases the current command value if the measured current is larger than the calculated current command value. By doing so, the motor current is feedback-controlled. The arithmetic circuit unit 19 calculates a command voltage by feedback control, converts this command voltage into a pulse width modulation signal, and gives an on / off command to the gate drive circuit 25.

As shown in FIG. 3, for example, when it is desired to pass a current from the U phase of the motor 6 to the V phase, a switching element on the high side side of the U phase among the plurality of switching elements 27 is instructed by the gate drive circuit 25. The UP and the switching element VN on the low side of the V phase are turned on, and the others are turned off. A voltage Vbat is supplied from the DC power supply 32, whereby the current flows from the U phase of the motor 6 to the V phase through the switching element UP, the U phase phase current output unit Uout, and the U phase. Further, the current passes through the switching element VN and returns to the ground GND of the DC power supply 32.

For example, when it is desired to pass a current from the V phase of the motor 6 to the U phase, the switching element UN on the low side of the U phase and the high side of the V phase among the plurality of switching elements 27 are commanded by the gate drive circuit 25. The switching element VP on the side is turned on, and the others are turned off. A voltage Vbat is supplied from the DC power supply 32, whereby the current flows from the V phase of the motor 6 to the U phase through the switching element VP and the phase current output unit Vout of the V phase. Further, the current passes through the switching element UN and returns to the ground GND of the DC power supply 32. The same applies to the other four operation patterns. Further, when changing the current, it is realized by changing the pulse width by the PWM operation.

<About the abnormality diagnosis device>
This abnormality diagnosis device is a device for diagnosing an abnormality of the inverter 24, and is provided in the inverter device 13 in this example. To diagnose the abnormality of the inverter 24 is to determine whether or not the secondary side (load side) of the switching element 27 is operating properly according to the drive command. This abnormality diagnosis device has a comparison means 33 and a determination means 34.

The comparison means 33 compares the phase current detected by the current sensor 29 with the threshold value at regular time intervals while the absolute value of the current command value calculated by the calculation circuit unit 19 exceeds the threshold value. When the phase current does not exceed the threshold value continuously for a predetermined number of times or more by the comparison means 33, the determination means 34 determines that the switching element 27 for driving the phase has an open abnormality. The comparison means 33 and the determination means 34 are provided in the arithmetic circuit unit 19.

When the abnormality reporting means 23 determines that the switching element 27 is an open abnormality, the abnormality reporting means 23 outputs the abnormality occurrence information to the ECU 14. The ECU 14 receives the abnormality occurrence information output from the abnormality reporting means 23, and controls, for example, to display a display device for the driver's seat (not shown) to notify the abnormality. Instead of the display device or together with the display device, an output device for notifying an abnormality by an alarm or the like may be provided. As a result, the driver can confirm the abnormality of the inverter 24 and safely stop the electric vehicle at the roadside, the parking space, or the like.

<Current waveform at the time of normal judgment>
FIG. 4 is a diagram showing a current waveform at the time of normality determination in the abnormality diagnosis device. Hereinafter, it will be described together with FIG. FIG. 4 shows, for example, the relationship between the command current (current command value) of the U phase of the motor 6, the measured current actually detected by the current sensor 29 (phase current of the U phase), and the threshold value for determination. The measured current does not follow the command current because it includes errors such as offset or gain error and noise. Especially when the current command value is small, the influence of offset error etc. is large and it is difficult to judge whether it is normal or abnormal. Therefore, this abnormality diagnosis device sets a threshold value equal to the absolute value on the plus side and the minus side, and the command current is If it is in the meantime, it is not judged whether it is normal or abnormal.
As the threshold value, different values may be used for the determination and the pass / fail determination. Further, the value may be changed between the plus side and the minus side.

Specifically, the abnormality diagnosis device compares the value of the command current and the value of the measured current at each sampling time interval (at the fixed time) of the inverter 24. The sampling time interval is usually from several tens of μs to several hundreds of μs. The judgment criterion is that when the absolute value of the command current exceeds the threshold value, the sign of the measurement current is the same as the sign of the command current, and if the absolute value of the measurement current exceeds the threshold value, it passes, and in other cases. Is a failure. If the failure continues for a predetermined number of times or more, it is determined that the switching element 27 driving the phase (U phase in this example) is open abnormality.

In FIG. 4, an example in which the switching element is determined to be normal will be described. The order of sampling is (1) to (11). In the sampling order (1), (6), (7), (11), since the command current is within the threshold value, it is not judged whether the product passes or fails. In the sampling order (2), the command current exceeds the threshold value and the measurement current is within the threshold value, so the test is rejected. The sampling order (3), (4), and (5) is acceptable because the command current exceeds the + side threshold value and the measurement current also exceeds the + side threshold value. Further, in the sampling order (8), (9), and (10), the command current exceeds the − side threshold value and the measurement current also exceeds the − side threshold value, so that the test is passed. As a whole, the switching element of the target phase is normal because the rejection is not continuous more than the specified number of times.

<Current waveform at the time of abnormality judgment>
In FIG. 5, an example in which the switching element is determined to be abnormal will be described. The order of sampling is (1) to (11). In the sampling order (1), (6), (7), (11), since the command current is within the threshold value, it is not judged whether the product passes or fails. In the sampling order (2), (3), (4), (5), the command current exceeds the threshold value and the measurement current is within the threshold value, so that the test fails.

Further, in the sampling order (8), (9), and (10), the command current exceeds the − side threshold value and the measurement current also exceeds the − side threshold value, so that the test is passed. As a whole, when the number of times of failure is set to be 4 or less, it is determined that the switching element of the target phase is abnormal because the failure is repeated 4 times. However, when the set number of failures is more than that, the switching element is determined to be abnormal after the set number of failures is continuously generated after the sample (12) (not shown).

The failing state, which is regarded as abnormal in the determination means 34, is counted separately for each sign (+ or −) of the command current, and is determined separately. The set number of failures may be changed depending on the rotation speed of the motor 6.
As the threshold value, a different value may be used between the threshold value used for comparison with the command current and the threshold value used for comparison with the measured current. Further, the threshold value may be changed between the plus side and the minus side.
Since the total of the three-phase currents is zero, two current sensors may be used to detect the phase currents of any two of the U-phase, V-phase, and W-phase. In this case, the number of parts can be reduced and the cost of the inverter device 13 can be reduced.

If both the + side and the-side become abnormal in each phase, it is possible that both the high-side side and low-side switching elements 27 and 27 become open abnormal at the same time, but the motor 6 is out of phase. Alternatively, the phase may be defective, such as a wiring defect.
Even if the switching element 27 becomes abnormal while the motor 6 is rotating at high speed and is in regenerative operation, it may be erroneously detected as normal by the recirculation by the fast recovery diode 28. Therefore, switching is performed while the motor 6 is in high speed regenerative operation. It may be necessary to take measures such as not determining the abnormality of the element 27.

<Abnormal judgment flow>
FIG. 6 shows an abnormality judgment flow for one phase, and the processing procedure will be described below.
This determination is started at the same time as the motor is started to be driven (step S1). Next, the abnormality diagnosis device clears the high-side counter and the low-side counter, which are the fail error counters (step S2). Next, the abnormality diagnosis device determines whether or not the command current is equal to or greater than the + side threshold value (step S3). Upon determining that the command current is equal to or greater than the + side threshold value (step S3: Yes), the abnormality diagnosis device determines whether or not the measured current is equal to or greater than the + side threshold value (step S4). When it is determined that the measured current is equal to or greater than the + side threshold value (step S4: Yes), the high side counter is cleared (step S5).

The abnormality diagnostic device determines that the measured current is not equal to or greater than the + side threshold value (step S4: No), increments the high-side counter (step S6), and determines whether the high-side counter is at least a specified number of consecutive set values or more. Judgment (step S7). If it is determined that the value is equal to or higher than the set value (step S7: Yes), error processing is performed as an abnormality of the switching element on the high side side (step S8).

In step S3, if it is determined that the command current is not equal to or greater than the + side threshold value (step S3: No) and the command current is equal to or less than the − side threshold value (step S9: Yes), the abnormality diagnostic apparatus measures the current on the − side. It is determined whether or not it is equal to or less than the threshold value (step S10). When it is determined that the measured current is equal to or less than the − side threshold value (step S10: Yes), the low side counter is cleared (step S11).

The abnormality diagnosis device increments the low-side counter (step S12) on the determination that the measured current is not equal to or less than the minus-side threshold value (step S10: No), and determines whether the low-side counter is equal to or more than the specified continuous set value. (Step S13). If it is determined that the value is equal to or higher than the set value (step S13: Yes), error processing is performed as an abnormality of the switching element on the low side side (step S14).
If steps S4 and S10 are Yes, and steps S7, S9, and S13 are No, the process returns to step S3 after a certain period of time, and a series of determinations are performed again. These judgments are made in the same way for the other two phases.

<About action and effect>
Since the detected phase current includes errors such as offset or gain error and noise, the detected phase current does not meet the command value of the current. In particular, when the command value of the current is small, the influence of offset error and the like is large, and it is difficult to judge whether it is normal or abnormal.
Therefore, according to the above-described inverter abnormality diagnosis device, the comparison means 33 sets the phase current and the threshold value detected by the current sensor 29 at regular time intervals while the absolute value of the command value of the current exceeds the threshold value. Compare to. In this way, since the phase current comparison processing is performed while the absolute value of the current command value exceeds the threshold value, the influence of offset error and the like is mitigated, and it is easy to judge whether it is normal or abnormal. It can be carried out.

When the phase current falls below the threshold value continuously for a predetermined number of times or more, the determination means 34 determines that the switching element 27 for driving the phase has an open abnormality. If the number of times the phase current falls below the threshold value is continuously less than the specified number of times, the switching element 27 for driving the phase is determined to be normal. This is because even when the switching element is normal, the detected phase current may momentarily fall below the threshold value due to an error or the like. In this way, it is possible to prevent erroneous determination of normal or abnormal. Therefore, the abnormality diagnosis can be easily and accurately performed while the inverter 24 is in operation.

Since the inverter device 13 includes the inverter abnormality diagnosis device having the above configuration, the redundancy of the inverter device 13 can be improved.
This electric vehicle is equipped with an inverter device having the above configuration. In this case, since it is possible to confirm the open abnormality of the switching element while the electric vehicle is in operation, the electric vehicle can be safely stopped at the roadside, a parking space, or the like.

<About other embodiments>
In the following description, the same reference numerals will be given to the parts corresponding to the matters described in advance in each embodiment, and duplicate description will be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described above unless otherwise specified. It has the same action and effect from the same configuration. Not only the combination of the parts specifically described in each embodiment, but also the combinations of the embodiments can be partially combined as long as the combination does not cause any trouble.

In the in-wheel motor drive device, a cycloid type speed reducer, a planetary speed reducer, a two-axis parallel speed reducer, and other speed reducers can be applied. Further, in the in-wheel motor drive device of the above-described embodiment, the rear wheel drive is shown, but the front wheel drive or the four-wheel drive may be used.

In the above embodiment, an example in which the abnormality diagnosis device is applied to an electric vehicle provided with an in-wheel motor drive device has been described, but as shown in FIG. 7, two motors 6 and 6 and each motor are attached to the vehicle body 1. A two-motor on-board type electric vehicle in which speed reducers 7 and 7 corresponding to 6 are provided and the left and right wheels 3 and 3 are driven by these motors 6 and 6 may be equipped with an abnormality diagnosis device. In FIG. 7, the left and right wheels driven by the motor 6 may be any of the front and rear wheels 3 and 2. It may also be a four-wheel drive.

Although the embodiments for carrying out the present invention have been described above based on the embodiments, the embodiments disclosed this time are exemplary in all respects and are not limiting. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

6 ... Motor 13 ... Inverter device 19 ... Calculation circuit unit 24 ... Inverter 27 ... Switching element 29 ... Current sensor 32 ... DC power supply 33 ... Comparison means
34 ... Judgment means

Claims (4)

It is a device that diagnoses abnormalities in the inverter that converts the DC power of the DC power supply into the three-phase AC power used to drive the motor by turning on and off multiple switching elements.
It is equipped with an arithmetic circuit unit that calculates a command value of the phase current flowing through the motor according to a given torque command, and a current sensor that detects the phase current of each phase flowing through the motor.
In the diagnosis section where abnormality diagnosis is performed while the absolute value of the command value of the phase current calculated by the calculation circuit unit exceeds the threshold value, the phase current and the threshold value detected by the current sensor of the corresponding phase are set. A comparison method that compares at regular intervals,
An inverter abnormality diagnostic device comprising a determination means for determining that the switching element driving the phase is an open abnormality when the phase current does not exceed the threshold value continuously for a predetermined number of times or more by this comparison means. An inverter device including the inverter abnormality diagnosis device according to claim 1. An electric vehicle equipped with the inverter device according to claim 2. An in-wheel motor drive device including the inverter device according to claim 2.

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