Motor drive device

Abstract

To provide a motor drive device capable of reducing manufacturing cost.SOLUTION: The motor drive device 8 specifies the third current sensor having the current detection error larger than the current detection errors detected by the first current sensor and the second current sensor, and drives the three phase AC motor based on the current values detected by the remaining first current sensor and second current sensor.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive device. [Background technology]

[0002] The conventional technology described in Patent Document 1 sequentially performs offset learning to detect the offset error of the current sensor and corrects the sensor output value using the learned value of the offset error, thereby improving the detection accuracy of the current sensor used in motor control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-098091 [Non-patent literature]

[0004] [Non-Patent Document 1] "Current detection error correction for three-phase AC power converters" [Retrieved May 30, 2024], Internet <URL: https: / / www.meidensha.co.jp / rd / rd_01 / rd_01_02 / rd_01_02_17 / rd_01_02_17_01 / pdf / article-201502-0069.pdf> Summary of the Invention [Problem to be solved by the invention]

[0005] Current sensors contain not only offset errors but also gain errors. However, conventional technology cannot correct gain errors, so in order to keep the gain errors within the allowable variation range, a current sensor with high detection accuracy must be selected. Using such a current sensor with high detection accuracy to drive a motor can increase the manufacturing costs of the motor drive device. Thus, conventional technology leaves room for improvement in reducing the manufacturing costs of motor drive devices.

[0006] The present disclosure provides a motor drive device that can reduce manufacturing costs. [Means for solving the problem]

[0007] A motor drive device according to one aspect of the present disclosure includes a control unit that generates and outputs a control signal for converting a DC voltage into an AC voltage for driving a three-phase AC motor based on current values ​​detected by at least two of a current sensor that detects a first phase current of a three-phase AC current, a current sensor that detects a second phase current of the three-phase AC current, and a current sensor that detects a third phase current of the three-phase AC current. The control unit performs an identification process for identifying a third current sensor among the three current sensors whose current detection error is greater than the current detection errors detected by the first and second current sensors based on the absolute value of the sum of the current values ​​detected by the three current sensors, and a drive process for driving the three-phase AC motor by generating the control signal based on the current values ​​detected by the first and second current sensors. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a motor drive device that can reduce manufacturing costs. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of a vehicle 100 including a motor drive device 8 according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a hardware configuration diagram of the motor driving device 8 according to the embodiment of the present disclosure. [Figure 3] FIG. 3 is a hardware configuration diagram of the motor driving device 8 according to the embodiment of the present disclosure. [Figure 4] FIG. 4 is a functional block diagram realized by the processor 81a of the motor driving device 8. [Figure 5(A)] FIG. 5A is a diagram for explaining the current detection error of the current sensor. [Figure 5(B)]FIG. 5B is a diagram for explaining the current detection error of the current sensor. [Figure 5(C)] FIG. 5C is a diagram for explaining the current detection error of the current sensor. [Figure 6(A)] FIG. 6A is a diagram for explaining the process of identifying the third current sensor by the identification processing unit 81a2. [Figure 6(B)] FIG. 6B is a diagram for explaining the process of identifying the third current sensor by the identification processing unit 81a2. [Figure 6(C)] FIG. 6C is a diagram for explaining the process of identifying the third current sensor by the identification processing unit 81a2. [Figure 7] FIG. 7 is a flowchart for explaining the operation of the motor driving device 8. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. Note that all drawings used in the following description are schematic, and the dimensional relationships between elements, ratios of elements, etc. shown in the drawings do not necessarily correspond to the actual ones. Furthermore, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the present disclosure.

[0011] 1 is a configuration diagram of a vehicle 100 including a motor drive device 8 according to an embodiment of the present disclosure. The vehicle 100 may be interpreted as a battery electric vehicle (BEV) powered by a battery 6 that stores power for driving and a motor 7. Note that the vehicle 100 is not limited to a BEV, and may include a hybrid electric vehicle (HEV) equipped with the battery 6, a plug-in hybrid electric vehicle (PHEV), and the like.

[0012] The vehicle 100 may include a battery 6, a motor 7, and a motor drive device 8. The battery 6 may be interpreted as a power storage device including a plurality of cells. The battery 6 may store power to drive the motor 7 and may also store power regenerated from the motor 7.

[0013] The motor 7 may be construed as a main motor for driving the vehicle, a three-phase AC motor, or the like. The motor 7 may be rotated by AC power from the motor drive device 8 to provide driving torque to the driving wheels 1 of the vehicle 100, thereby causing the vehicle 100 to run. Hereinafter, the motor 7 may also be referred to as an MG (Motor Generator).

[0014] The motor drive device 8 may be considered as a device that controls the current, voltage, power, etc. that drives the MG using a torque command, speed command, position command, etc. of the MG based on information from the sensor group. Specifically, the motor drive device 8 may convert the DC voltage discharged from the battery 6 into a three-phase AC voltage and apply the three-phase AC voltage to the MG to drive the MG. The motor drive device 8 may also have a function of converting AC power regenerated from the MG into DC power and supplying the DC power to the battery 6, thereby charging the battery 6.

[0015] The sensor group may include an accelerator sensor 2, a steering angle sensor 3, a rotation sensor 4, a current sensor group 5, etc. The accelerator sensor 2 may detect the amount of depression of the accelerator pedal (accelerator opening) and output a signal corresponding to the detected accelerator opening. The steering angle sensor 3 may detect the steering angle of the steering wheel (handle) and output a signal voltage corresponding to the detected steering angle. The rotation sensor 4 may detect the rotation angle of the MG and output a signal corresponding to the detected rotation angle.

[0016] The current sensor group 5 may include a current sensor that detects a first phase current of the three-phase AC, a current sensor that detects a second phase current of the three-phase AC, and a current sensor that detects a third phase current of the three-phase AC. The first phase may be interpreted as the U phase, the second phase as the V phase, and the third phase as the W phase. Each current sensor may be interpreted as a sensor that converts the phase current detected by a shunt resistor into a voltage and outputs a voltage corresponding to the current value. The shunt resistor may detect a current in a three-phase wiring provided between the motor drive device 8 and the MG.

[0017] Next, a configuration example of the motor driving device 8 will be described with reference to Figures 2 and 3. Figures 2 and 3 are hardware configuration diagrams of the motor driving device 8 according to an embodiment of the present disclosure.

[0018] As shown in FIG. 2, the motor drive device 8 may include a control unit 82 and an inverter 81. The inverter 81 may include a plurality of switching elements. Specifically, it may include three upper-arm switching elements and three lower-arm switching elements. The inverter 81 converts a control signal (which may be interpreted as a gate signal, a PWM signal, or the like) output from the control unit 82 into a signal (gate drive signal) of a voltage capable of driving these switching elements, and inputs the converted gate drive signal to the gate of each switching element. As a result, the upper-arm switching elements and the lower-arm switching elements perform complementary switching operations, so that a DC voltage formed by the output voltage of the battery 6 is converted into a three-phase AC voltage and supplied to the MG. At this time, a U-phase current (U-phase AC current), a V-phase current (V-phase AC current), and a W-phase current (W-phase AC current) flow through three wirings connected to the output of the inverter 81, respectively.

[0019] The current sensor group 5 may include a U-phase current sensor 51 that detects a U-phase current, a V-phase current sensor 52 that detects a V-phase current, and a W-phase current sensor 53 that detects a W-phase current. The U-phase current sensor 51 may be interpreted as a current sensor that detects a first-phase current of a three-phase AC. The V-phase current sensor 52 may be interpreted as a current sensor that detects a second-phase current of the three-phase AC. The W-phase current sensor 53 may be interpreted as a current sensor that detects a third-phase current of the three-phase AC. Hereinafter, when there is no need to distinguish between the U-phase current sensor 51, the V-phase current sensor 52, and the W-phase current sensor 53, they may be simply referred to as "current sensors." The current value output by each current sensor is a voltage corresponding to the detected current, and therefore may be interpreted as a sensor output voltage.

[0020] The control unit 82 may generate a signal (corresponding to the control signal described above) for converting a DC voltage into an AC voltage based on the sensor output voltages of at least two of these three current sensors, and output the signal to the inverter 81. That is, the control unit 82 may use the sensor output voltages from two current sensors that detect the currents of any two of the three phases as the detected currents, and may calculate the current of the remaining phase from the sensor output voltages of these two current sensors, and use the calculated current as the detected current of the remaining phase.

[0021] 3, the control unit 82 may include a processor 81a, a memory 81b, a communication I / F 81c, and an input / output I / F 81d, which may be communicably connected to each other via a bus 81e.

[0022] The processor 81a may be considered a central processing unit. The processor 81a may execute various programs and control each part. The processor 81a may read a motor control program 81b1 from the memory 81b and execute specific processing by deploying the motor control program 81b1. The functions realized by the motor control program 81b1 will be described later.

[0023] The communication I / F 81c may be considered as an interface for the motor drive device 8 to communicate with other devices. The communication I / F 81c may use standards such as CAN (Controller Area Network), Ethernet (registered trademark), or Wi-Fi (registered trademark). The input / output I / F 81d may input information detected by the accelerator sensor 2, steering angle sensor 3, rotation sensor 4, current sensor group 5, etc. shown in FIG. 1.

[0024] Next, the function of the motor driving device 8 will be described with reference to FIGS. 4, 5(A), 5(B), 5(C), 6(A), 6(B), and 6(C).

[0025] 4 is a functional block diagram realized by processor 81a of motor drive device 8. Processor 81a may include an information input unit 81a1, a specific processing unit 81a2, and a drive processing unit 81a3. The information input unit 81a1, the specific processing unit 81a2, and the drive processing unit 81a3 may be realized by processor 81a executing a motor control program 81b1.

[0026] (Information input unit 81a1) The information input unit 81a1 may input information detected by the accelerator sensor 2, the steering angle sensor 3, the rotation sensor 4, the current sensor group 5, and the like.

[0027] (Specific processing unit 81a2) The identification processing unit 81a2 may identify one current sensor among the three current sensors that has the largest current detection error based on the current detection information (current values) of each of the three current sensors input to the information input unit 81a1. Specifically, the identification processing unit 81a2 may perform an identification process to identify one current sensor (third current sensor) among the three current sensors that has a current detection error larger than the current detection errors detected by two predetermined current sensors (first current sensor and second current sensor) based on the absolute value of the sum of the current values ​​detected by the three current sensors. The identification processing unit 81a2 may output identification information of the identified one current sensor (here, for example, the third current sensor) to the drive processing unit 81a3.

[0028] 6A, 6B, and 6C are diagrams illustrating the process performed by the identification processing unit 81a2 to identify the third current sensor. The vertical axis of each of FIGS. 6A, 6B, and 6C represents the detected current, and the horizontal axis represents time. Each of these diagrams shows the waveforms of the detected currents for the U, V, and W phases, with the solid line representing the U phase, the thin solid line representing the V phase, and the dashed line representing the W phase.

[0029] In Figure 6(A), the maximum positive values ​​of these currents (I) are equal to each other, and the maximum negative values ​​of these currents (-I) are also equal to each other, so the absolute value of the sum of these currents is 0 over time.

[0030] Figures 6(B) and 6(C) show the current waveforms of each phase when the current detection error of the W-phase current sensor (corresponding to the third current sensor) is larger than the current detection errors of the U-phase and V-phase current sensors (corresponding to the first and second current sensors).

[0031] At time t1 in FIG. 6B, the maximum negative value of the W-phase current is greater than the maximum negative value (-I) of each of the remaining U-phase and V-phase currents. Therefore, the absolute value of the sum of these currents is the most negative. At time t2 in FIG. 6B, the maximum positive value of the W-phase current is greater than the maximum positive value (I) of each of the remaining U-phase and V-phase currents. Therefore, the absolute value of the sum of these currents is the most positive.

[0032] At time t1 in FIG. 6C, the maximum negative value of the W-phase current is smaller than the maximum negative value (-I) of the remaining U-phase and V-phase currents. Therefore, the absolute value of the sum of these currents is the maximum positive value. At time t2 in FIG. 6C, the maximum positive value of the W-phase current is smaller than the maximum positive value (I) of the remaining U-phase and V-phase currents. Therefore, the absolute value of the sum of these currents is the maximum negative value.

[0033] In this way, when the current detection error of the W-phase current sensor is larger than the current detection errors of the U-phase and V-phase current sensors, the current waveform (current pattern) of the W-phase is different from the current waveforms of the other two phases, and the identification processing unit 81a2 utilizes this difference in current waveforms to identify the third current sensor with the largest current detection error.

[0034] Here, the mechanism by which torque ripple occurs due to current detection errors will be explained by quoting equations (1) to (3) disclosed in Non-Patent Document 1.

[0035] Inverter 81 output current i u , i v , i w is defined as in equation (1), where θ is the motor reference phase, φ is the phase difference from θ, and I is the current amplitude.

[0036]

number

[0037] three phase current i u sense , i v sense , i w sense is defined as in equation (2). Three-phase current i u sense , i v sense , i w sense includes the sensor error of the current detection value. The sensor error includes the offset error (Δi u , Δi v , Δi w ) and gain errors (α, β, δ).

[0038]

number

[0039] Here, we will explain current detection errors (offset error and gain error) with reference to Figures 5(A), 5(B), and 5(C). Figures 5(A), 5(B), and 5(C) are diagrams for explaining current detection errors of current sensors. In Figures 5(A), 5(B), and 5(C), the vertical axis represents the sensor output voltage, and the horizontal axis represents the detected current. The sensor output voltage may be interpreted as the voltage value corresponding to the current value detected by each current sensor, and the detected current may be interpreted as the current value detected by each current sensor. Figure 5(A) shows the current detected by the current sensor without current detection error, i.e., the sensor output voltage. Figure 5(B) shows the voltage-current relationship when the current sensor includes an offset error. Figure 5(C) shows the voltage-current relationship when the current sensor includes a gain error. The offset error may be interpreted as an error in which the detected value is detected as a constant value other than zero when the true value is zero, and the gain error may be interpreted as an error in which the change in the true value and the change in the detected value no longer match.

[0040] For equations (1) and (2), a rotational coordinate transformation (dq transformation) synchronized with the motor phase θ is performed. The d-axis current id when offset error and gain error occur sense and q-axis current iq sense is expressed in equation (3). d-axis current id sense is the d-axis current detection value when no error occurs, and the q-axis current iq sense is the detected q-axis current value when no error occurs.

[0041]

number

[0042] From equation (3), the offset error (Δi u , Δi v , Δi w ) is a factor in the oscillation of the primary electrical frequency component, and the gain error (α, β, δ) is a factor in the oscillation of the secondary electrical frequency component. In other words, these errors can be factors in the generation of torque ripple due to current detection errors.

[0043] The conventional technology disclosed in the aforementioned Patent Document 1 can correct offset errors but cannot correct gain errors. Therefore, in order to keep the gain error within the allowable variation range, a current sensor with high detection accuracy must be selected, and the use of such a current sensor can increase the manufacturing costs of the device.

[0044] According to the present disclosure, it is possible to identify one of three current sensors that may contain a gain error, and then use the remaining two current sensors excluding the identified current sensor to perform motor drive control. In other words, it is possible to perform motor drive control using two current sensors with negligible gain error, or two current sensors with gain error that falls within an allowable variation range. Therefore, it is possible to use inexpensive current sensors instead of specialized current sensors with high detection accuracy, thereby reducing the manufacturing cost of the motor drive device 8.

[0045] (Drive processing unit 81a3) Based on the identification information received from the specific processing unit 81a2 and the current detection information input to the information input unit 81a1 from the remaining two current sensors (first current sensor and second current sensor) excluding the third current sensor, the drive processing unit 81a3 may generate a control signal (gate signal) that converts the DC voltage into an AC voltage that drives the MG, and output it to the inverter 81.

[0046] (Another configuration example 1 of the control unit 82) The control unit 82 may execute the above-described identification process, for example, while the vehicle 100 is traveling. Specifically, the control unit 82 may constantly calculate and monitor the three-phase currents that flow when the MG mounted on the vehicle 100 is rotating, and determine the phase in which the current detection error is high or low based on the value of the phase current when these currents exceed a specific current threshold.

[0047] For example, if the command current, MG rotation speed, etc. fluctuate while the vehicle 100 is traveling, these fluctuations may cause the maximum value of each phase current to fluctuate, potentially resulting in erroneous determination of a current sensor with a large current detection error. Therefore, the control unit 82 may execute the aforementioned identification process as a precondition for determination, for example, if the command current is equal to or less than a certain value, or if the fluctuation in the MG rotation speed is equal to or less than a certain value. This makes it possible to avoid erroneous determination of a current sensor with a large current detection error even when the aforementioned identification process is executed while the vehicle 100 is traveling.

[0048] (Another configuration example 2 of the control unit 82) The control unit 82 may identify a current sensor having a current detection error only when the absolute value of the sum of the phase currents exceeds a predetermined value, i.e., only when the current detection error is large. Specifically, in the identification process, the control unit 82 may not identify a current sensor having a large current detection error if the absolute value of the sum of the phase currents does not exceed a predetermined value, but may identify a current sensor having a large current detection error if the absolute value exceeds the predetermined value. This makes it possible to prevent erroneous determination of a current sensor having a large current detection error in a region where the absolute value of the sum of the phase currents does not exceed a certain value.

[0049] Furthermore, when the error of the first current sensor or the second current sensor is larger than the value of the current sensor with the smaller error by a predetermined value or more, the motor is driven and controlled using only the first current sensor and the second current sensor. When the error of the first sensor with the smaller error is "small" and the error of the second sensor with the larger error is "large," the third sensor is not used. If the error is larger, the first sensor error is small, and the second sensor error is large, the third sensor may be used.

[0050] (Another configuration example 3 of the control unit 82) When the vehicle 100 is stopped, the control unit 82 may identify a current sensor with a large current detection error by sending a control signal (gate signal) that controls the inverter 81 so that direct currents of different values ​​flow multiple times in the first phase, second phase, and third phase during the identification process.

[0051] Specifically, in the identification process, the control unit 82 may identify a current sensor with a large current detection error by generating a control signal for controlling the inverter 81 to pass a reactive current corresponding to the rotational position of the MG when the vehicle 100 equipped with the motor drive device 8 is stopped. Because a reactive current is a current that does not contribute to torque, selecting the reactive current as a DC current makes it possible to identify a current sensor with a large current detection error when the vehicle 100 is stopped. Note that, when the vehicle 100 is stopped, the rotational angle of the tires (MG) is restricted, so the patterns of DC current that can be passed are limited. For this reason, it is preferable to control the inverter 81 so that DC currents with different values ​​flow multiple times when the vehicle 100 is stopped. In this way, by using a DC current to identify a current sensor with a large current detection error, it is possible to avoid erroneous determination of a current sensor with a large current detection error due to fluctuations in the indicated current, etc., and improve the accuracy of identifying a current sensor with a large current detection error.

[0052] (Another configuration example 4 of the control unit 82) The control unit 82 may generate a control signal (gate signal) that controls the inverter 81 to pass a reactive current in order to discharge the charge in a capacitor (e.g., a smoothing capacitor) included in the inverter 81. This makes it possible to reduce the control time required to generate a reactive current by using a direct current from the battery 6 to pass the reactive current, for example.

[0053] (Another configuration example 5 of the control unit 82) Motor drive device 8 alone, that is, motor drive device 8 connected to a motor dummy load with a neutral point connected instead of an MG as a load mounted on vehicle 100, can pass any DC current without depending on the MG mounted on vehicle 100. The motor dummy load may be interpreted as a dummy load created by, for example, a resistor. By using the motor dummy load in this way, motor drive device 8 can identify current sensors with large current detection errors before mounting motor drive device 8 on vehicle 100. This avoids the need to rewrite software or otherwise troublesome tasks to identify current sensors with large current detection errors after motor drive device 8 is mounted on vehicle 100, and can reduce the costs associated with recovering motor drive devices 8.

[0054] 7 is a flowchart illustrating the operation of motor drive device 8. In step S1, control unit 82 receives current detection information detected by a current sensor that detects a first phase current of three-phase AC, a current sensor that detects a second phase current of three-phase AC, and a current sensor that detects a third phase current of three-phase AC.

[0055] In step S2, the control unit 82 performs an identification process to identify the third current sensor among the three current sensors whose current detection error is greater than the current detection errors detected by the first and second current sensors, based on the absolute value of the sum of the current values ​​detected by each of the three current sensors.

[0056] In step S3, the control unit 82 generates a control signal based on the current values ​​detected by the first current sensor and the second current sensor, thereby executing a drive process for driving the three-phase AC motor.

[0057] As described above, the motor drive device 8 of the present disclosure identifies a third current sensor whose current detection error is larger than the current detection errors detected by the first and second current sensors, and drives the three-phase AC motor based on the current values ​​detected by the remaining first and second current sensors. This makes it possible to exclude current sensors containing large current detection errors (offset error, gain error) that could cause periodic oscillations in the motor torque and motor current from sensors used to drive the three-phase AC motor. Therefore, inexpensive current sensors can be used instead of specialized current sensors with high detection accuracy, thereby reducing the manufacturing cost of the motor drive device 8.

[0058] (Variation) Note that the motor control logic may be configured using all the current information from the three current sensors.Alternatively, the motor is normally controlled using the values ​​from the three current sensors, and if it is detected that the detection error of one specific current sensor is equal to or greater than a predetermined value, the motor may be controlled using the remaining two current sensors.

[0059] (Addendum) The following additional notes are provided regarding the above-described embodiment.

[0060] (Appendix 1) a control unit that generates and outputs a control signal for converting a DC voltage into an AC voltage for driving a three-phase AC motor, based on current values ​​detected by at least two of a current sensor that detects a first phase current of a three-phase AC, a current sensor that detects a second phase current of the three-phase AC, and a current sensor that detects a third phase current of the three-phase AC; The control unit an identification process for identifying a third current sensor among the three current sensors, the third current sensor having a current detection error greater than the current detection errors detected by the first current sensor and the second current sensor, based on the absolute value of the sum of the current values ​​detected by the three current sensors; a driving process for driving the three-phase AC motor by generating the control signal based on the current values ​​detected by the first current sensor and the second current sensor; A motor drive device that performs the above.

[0061] (Appendix 2) 2. The motor drive device according to claim 1, wherein the control unit, in the identification process, identifies the third current sensor by passing direct currents of different values ​​through the first phase, the second phase, and the third phase multiple times.

[0062] (Appendix 3) The motor drive device described in Appendix 2, wherein, in the identification process, the control unit identifies the third current sensor by generating the control signal that controls an inverter to flow a reactive current corresponding to the rotational position of the three-phase AC motor when a vehicle on which the motor drive device is mounted is stopped.

[0063] (Appendix 4) 4. The motor drive device according to claim 3, wherein the control unit generates the control signal to control the inverter to flow the reactive current in order to discharge an electric charge in a capacitor included in the inverter.

[0064] (Appendix 5) The motor drive device described in Appendix 1, wherein, in the identification process, the control unit does not identify the third current sensor if the absolute value does not exceed a predetermined value, and identifies the third current sensor if the absolute value exceeds the predetermined value.

[0065] The controller and method described herein may be implemented by a special-purpose computer having a processor programmed to perform one or more functions embodied in a computer program. Alternatively, the apparatus and method described herein may be implemented by a special-purpose computer having a processor configured with dedicated hardware logic circuits. Alternatively, the apparatus and method described herein may be implemented by one or more special-purpose computers configured by a combination of a processor executing a computer program and one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium. [Explanation of symbols]

[0066] 1 drive wheel 2 Accelerator sensor 3 Steering angle sensor 4 Rotation Sensor 5 Current sensors 6 Battery 7 Motor 8 Motor drive unit 51 Phase Current Sensor 52 Phase Current Sensor 53 Phase Current Sensor 81 Inverter 81a processor 81a1 Information input section 81a2 Specific processing department 81a3 Drive processing unit 81b memory 81b1 Motor control program 81e Bus 82 Control Unit 100 vehicles

Claims

1. a control unit that generates and outputs a control signal for converting a DC voltage into an AC voltage for driving a three-phase AC motor based on current values ​​detected by at least two of a current sensor that detects a first phase current of a three-phase AC, a current sensor that detects a second phase current of the three-phase AC, and a current sensor that detects a third phase current of the three-phase AC, The control unit an identification process for identifying a third current sensor among the three current sensors, the third current sensor having a current detection error greater than the current detection errors detected by the first current sensor and the second current sensor, based on the absolute value of the sum of the current values ​​detected by the three current sensors; a driving process for driving the three-phase AC motor by generating the control signal based on the current values ​​detected by the first current sensor and the second current sensor; A motor drive device that performs the above.

2. 2. The motor drive device according to claim 1, wherein the control unit, in the identification process, identifies the third current sensor by passing direct currents of different values ​​through the first phase, the second phase, and the third phase a plurality of times.

3. 3. The motor drive device according to claim 2, wherein, in the identification process, the control unit identifies the third current sensor by generating the control signal that controls an inverter to flow a reactive current corresponding to a rotational position of the three-phase AC motor when a vehicle on which the motor drive device is mounted is stopped.

4. 4. The motor drive device according to claim 3, wherein the control unit generates the control signal for controlling the inverter to flow the reactive current in order to discharge an electric charge in a capacitor included in the inverter.

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