Motor drive device

Abstract

To specify a faulty phase at an early stage in regard to three current sensors that detect three-phase current values, respectively.SOLUTION: A motor drive device 1 comprises a three-phase AC motor 2, a battery 4, an inverter 3 for driving the motor 2 by converting DC power fed from the battery 4 into AV power, three current sensors 11, 12, 13 for detecting respective three-phase current values fed to the motor 2 from the inverter 3; and a controller 5 for controlling the inverter 3. The controller 5 executes a voltage control by which a voltage of the battery 4 is made to be higher than a counter electromotive voltage of the motor 2, when specifying whether or not any of the three current sensors 11, 12, 13 fails.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses that in a motor drive device equipped with a three-phase AC motor, when determining that one of three current sensors that detects the current values ​​of each of the three phases has failed, the back electromotive force of the motor is used to identify the failed phase. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-110721 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a motor drive device equipped with three current sensors that detect the current values ​​of the three phases, such as the configuration described in Patent Document 1, if any of the three current sensors fails, it is desirable to identify the faulty phase early while preventing erroneous identification of the faulty phase.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a motor drive device that can quickly identify a faulty phase for three current sensors that detect three-phase current values ​​respectively. [Means for solving the problem]

[0006] The present invention is a motor drive device comprising a three-phase AC motor, a battery, an inverter that converts DC power supplied from the battery into AC power to drive the motor, three current sensors that detect each of the three-phase current values ​​supplied from the inverter to the motor, and a control device that controls the inverter, wherein the control device performs voltage control to make the battery voltage higher than the back electromotive force of the motor when determining whether any of the three current sensors is faulty. Effect of the Invention

[0007] According to the present invention, it is possible to quickly identify the faulty phase with respect to three current sensors that detect current values ​​of three phases, respectively. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a motor drive device according to an embodiment. [Diagram 2] FIG. 2 is a flow chart showing the flow of the faulty phase identification process. [Diagram 3] FIG. 3 is a diagram for explaining a method for identifying a faulty phase by diagnosis. [Figure 4] FIG. 4 is a diagram for explaining the current values ​​of the phase currents while the inverter is shut down. [Diagram 5] FIG. 5 is a diagram for explaining a method for identifying a faulty phase when a three-phase sum abnormality occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A motor drive device according to an embodiment of the present invention will be specifically described below, however, the present invention is not limited to the embodiment described below.

[0010] 1 is a diagram showing a motor drive device according to an embodiment. The motor drive device 1 is mounted on a vehicle. The motor drive device 1 includes a motor 2, an inverter 3, a boost converter 6, a battery 4, a control device 5, and current sensors 11, 12, and 13.

[0011] The motor 2 is a three-phase AC motor. The motor 2 functions as a power source for driving, and is a motor generator having the functions of an electric motor and a generator. The vehicle in which the motor 2 is mounted is an electric vehicle such as an electric car or a hybrid car. In this electric vehicle, the wheels can be driven by the power output from the motor 2. The motor 2 is a synchronous motor that includes a rotor in which a permanent magnet is embedded, and a stator around which a three-phase coil is wound. The three-phase coils (U phase, V phase, W phase) wound around the stator of the motor 2 are electrically connected to the inverter 3. When a three-phase voltage is applied to the motor 2 by the inverter 3, a three-phase current flows through the coils of the motor 2, and torque is generated in the motor 2.

[0012] The inverter 3 is a power conversion device that converts DC power from the battery 4 into AC power and supplies it to the motor 2. The inverter 3 drives the motor 2. The inverter 3 is composed of an electric circuit (inverter circuit) equipped with a plurality of switching elements so that a three-phase current can be applied to the three-phase coils of the motor 2. The inverter 3 is equipped with first to sixth switching elements SW1 to SW6. A diode is connected in inverse parallel to each of the switching elements SW1 to SW6.

[0013] The first switching element SW1 and the second switching element SW2 are connected in series to form a U-phase arm. In the U-phase arm, the first switching element SW1 is the upper arm, and the second switching element SW2 is the lower arm. The third switching element SW3 and the fourth switching element SW4 are connected in series to form a V-phase arm. In the V-phase arm, the third switching element SW3 is the upper arm, and the fourth switching element SW4 is the lower arm. The fifth switching element SW5 and the sixth switching element SW6 are connected in series to form a W-phase arm. In the W-phase arm, the fifth switching element SW5 is the upper arm, and the sixth switching element SW6 is the lower arm. The U-phase arm consisting of the first switching element SW1 and the second switching element SW2, the V-phase arm consisting of the third switching element SW3 and the fourth switching element SW4, and the W-phase arm consisting of the fifth switching element SW5 and the sixth switching element SW6 are connected in parallel. In the inverter 3, each of the three-phase coils of the motor 2 is connected to each of the connection points between the paired switching elements. Each of the switching elements SW1 to SW6 of the inverter 3 is configured by an IGBT, a MOSFET, or the like, and performs a switching operation in response to a control signal from the control device 5.

[0014] The boost converter 6 boosts the power supplied from the battery 4 and supplies the boosted power to the inverter 3. The boost converter 6 is provided between the inverter 3 and the battery 4. The boost converter 6 includes a capacitor 61, a reactor 62, a first switching element SW61, and a second switching element SW62.

[0015] The capacitor 61 is connected to a parallel line connecting between the positive and negative pole lines on the lower voltage side of the reactor 62. The reactor 62 is provided on the positive pole line. The first switching element SW61 and the second switching element SW62 are connected in series. The first switching element SW61 serves as an upper arm, and the second switching element SW62 serves as a lower arm. The reactor 62 is connected to the connection point between the first switching element SW1 and the second switching element SW2. Each of the switching elements SW61 to SW62 of the boost converter 6 is composed of an IGBT, a MOSFET, or the like, and performs a switching operation in response to a control signal from the control device 5.

[0016] The battery 4 is a DC power supply capable of being charged and discharged, and is constituted by, for example, a secondary battery such as a nickel metal hydride battery or a lithium ion battery. The battery 4 discharges power to the inverter 3 side, or charges with power supplied from the inverter 3 side.

[0017] The control device 5 is an electronic control device that controls the inverter 3 and the boost converter 6. The control device 5 includes a processor and a memory. The control device 5 loads a program stored in a storage unit into a working area of ​​the memory (main storage device) and executes it, and realizes a function that matches a predetermined purpose by controlling each component through the execution of the program. Signals from various sensors are input to the control device 5. A signal from a current sensor 11, a signal from a current sensor 12, and a signal from a current sensor 13 are input to the control device 5. The control device 5 executes inverter control based on the signals input from each current sensor, and outputs a command signal to the inverter 3. The control device 5 also outputs a command signal to the boost converter 6, and executes voltage control that controls the boost operation in the boost converter 6.

[0018] The current sensor 11 is provided between the inverter 3 and the motor 2, and detects a U-phase current value Iu. The current sensor 11 is provided on a wiring that connects a connection point between the first switching element SW1 and the second switching element SW2 of the inverter 3 and one end of the U-phase coil of the motor 2. The current sensor 11 detects the U-phase current flowing between the inverter 3 and the motor 2, and outputs the U-phase current value Iu, which is the sensor value, to the control device 5. The control device 5 can monitor the sensor value of the current sensor 11 based on a signal input from the current sensor 11.

[0019] Current sensor 12 is provided between inverter 3 and motor 2, and detects a V-phase current value Iv. Current sensor 12 is provided on a wiring that connects a connection point between the third switching element SW3 and the fourth switching element SW4 of inverter 3 and one end of a V-phase coil of motor 2. Current sensor 12 detects a V-phase current flowing between inverter 3 and motor 2, and outputs a sensor value, that is, a V-phase current value Iv, to control device 5. Control device 5 can monitor the sensor value of current sensor 12 based on a signal input from current sensor 12.

[0020] The current sensor 13 is provided between the inverter 3 and the motor 2, and detects a W-phase current value Iw. The current sensor 13 is provided on a wiring that connects a connection point between the fifth switching element SW5 and the sixth switching element SW6 of the inverter 3 and one end of the W-phase coil of the motor 2. The current sensor 13 detects the W-phase current flowing between the inverter 3 and the motor 2, and outputs the W-phase current value Iw, which is the sensor value, to the control device 5. The control device 5 can monitor the sensor value of the current sensor 13 based on a signal input from the current sensor 13.

[0021] In the motor drive device 1 configured as above, when a failure occurs in a current sensor that detects a phase current, it identifies which of the three current sensors 11, 12, 13 has failed, and continues driving the motor 2. After identifying the failed phase, it switches to the remaining two normal phases and performs evacuation driving. At that time, it is desirable to identify the failed phase as soon as possible. Therefore, the motor drive device 1 is configured to be able to shorten the time until shifting to evacuation driving when the failed phase cannot be identified by diagnosis. Specifically, the control device 5 identifies the failed phase based on the phase current detected in the driving region where the battery voltage is greater than the back electromotive voltage of the motor 2.

[0022] 2 is a flow chart showing a faulty phase identification process flow. The control shown in FIG.

[0023] The control device 5 detects (step S1) the diagnostics of the current sensors that detect the three-phase currents of the motor 2. In step S1, the diagnostics of the current sensor 11 that detects the U-phase current, the diagnostics of the current sensor 12 that detects the V-phase current, and the diagnostics of the current sensor 13 that detects the W-phase current are detected.

[0024] The control device 5 identifies the faulty phase by diagnosis (step S2). In step S2, a process is performed to identify which of the three current sensors 11, 12, and 13 has failed, based on the diagnosis of the current sensor detected in step S1.

[0025] In step S2, the control device 5 can identify the faulty phase based on the diagnosis of each phase, as shown in FIG. 3. When the diagnosis state indicates an abnormality in only one of the three phases, as in patterns 1, 2, and 3 shown in FIG. 3, the faulty phase can be identified. In this case, the control device 5 judges that the faulty phase can be identified, and identifies the phase indicating the abnormality as the faulty phase. In contrast, when the diagnosis state is normal for each of the three phases and the sum of the currents of the three phases indicates an abnormality, as in pattern 4 shown in FIG. 3, the faulty phase cannot be identified. In this case, the control device 5 judges that the faulty phase cannot be identified. Also, when the diagnosis state is other than patterns 1 to 4, as in pattern 5 shown in FIG. 3, the faulty part cannot be isolated.

[0026] The control device 5 judges whether or not the faulty phase can be identified by the diagnosis (step S3). In step S3, it is judged whether or not the faulty phase has been identified by the identification process in step S2. The control device 5 judges whether or not the faulty phase has been identified by the process in step S2.

[0027] When it is determined that the faulty phase can be identified by the diagnosis (step S3: Yes), the control device 5 executes a process of returning from the diagnosis (step S4). After the process of step S4 is executed, the process proceeds to step S5.

[0028] The control device 5 switches to the normal phase and performs evacuation running (step S5). In step S5, the vehicle transitions to evacuation running using the remaining two normal phases. The control device 5 controls the switching of the switching elements of the inverter 3 for those two phases to cause the vehicle to run evacuation. When step S5 is performed, the faulty phase is identified and the transition to evacuation running is performed in a short time. After the processing of step S5 is performed, this control routine ends.

[0029] If it is determined that the faulty phase cannot be identified by the diagnosis (step S3: No), the control device 5 detects the current values ​​of the three-phase currents while the inverter 3 is shut down, and identifies the faulty phase based on the current values ​​of each phase (step S6). In step S6, an identification process is performed to identify which of the three current sensors 11, 12, and 13 has failed, based on the current values ​​detected by the current sensors 11, 12, and 13 while the inverter 3 is shut down. At that time, the control device 5 executes voltage control to make the voltage of the battery 4 higher than the back electromotive force of the motor 2. When the motor drive device 1 is mounted on an electric vehicle, the voltage (battery voltage) VB of the battery 4 is high in the electric vehicle, so that the battery voltage VB is often in a region higher than the back electromotive force of the motor 2. When the battery voltage VB is higher than the back electromotive force of the motor 2, the phase current becomes 0A.

[0030] In step S6, the control device 5 judges whether the current value during shutdown of the inverter 3 is equal to or lower than the normal current threshold value as shown in FIG. 4. When the battery voltage VB is higher than the back electromotive voltage of the motor 2, the phase current becomes 0 A. However, since the current sensors 11, 12, and 13 have errors, the normal current threshold value is set in consideration of these current sensor errors and the phase current that becomes 0 A. The normal current threshold value is a preset value. The sensor variation value includes variation due to temperature characteristics and variation of the main body. The control device 5 identifies the current sensor whose sensor value exceeds the normal current threshold value as the faulty phase. Specifically, when only one of the sensor values ​​of the three current sensors 11, 12, and 13 exceeds the normal current threshold value, the control device 5 identifies that phase as the faulty phase and judges that the remaining two phases are normal.

[0031] The control device 5 determines whether or not the faulty phase can be identified by the current value during shutdown of the inverter 3 (step S7). In step S7, it is determined whether or not the faulty phase has been identified by the identification process in step S6. The control device 5 determines whether or not the faulty phase has been identified by the process in step S6.

[0032] If it is determined that the faulty phase can be identified from the current value while the inverter 3 is shut down (step S7: Yes), the control device 5 switches to a normal phase and performs evacuation running (step S8). In step S8, evacuation running is transitioned to using the remaining two normal phases, as in step S5. When step S8 is performed, the faulty phase is identified and the transition to evacuation running is performed in a short time. When the faulty phase can be identified by the processing of step S6, there is no need to wait for the rotation fluctuation of the motor 2 to subside, so the time required for the recovery processing can be shortened. When the processing of step S8 is performed, this control routine ends.

[0033] If it is determined that the faulty phase cannot be identified based on the current value during shutdown of the inverter 3 (step S7: No), the control device 5 executes a recovery process from the diagnosis and waits until the rotation fluctuation of the motor 2 settles down (step S9). In step S9, the control device 5 waits for the fluctuation in the rotation speed of the motor 2 to settle down. When the rotation fluctuation of the motor 2 settles down, the process proceeds from step S9 to step S10.

[0034] The control device 5 identifies the faulty phase based on the sum of squares of the three-phase current values ​​(step S10). In step S10, the sum of squares of the three-phase currents is calculated, and a process of identifying which phase of the three current sensors 11, 12, and 13 has failed is performed based on the sum of squares. As shown in FIG. 5, the control device 5 calculates the sum of squares of the three-phase currents, and identifies the faulty phase based on the fluctuation of the sum of squares. Since the sum of squares including the faulty phase fluctuates, it is possible to identify the faulty phase. For example, when the sum of squares including the U-phase current value Iu and the V-phase current value Iv is normal, if the sum of squares including the V-phase current value Iv and the W-phase current value Iw fluctuates greatly, the W-phase can be identified as the faulty phase.

[0035] The control device 5 determines whether or not the faulty phase can be identified by the sum of squares of the three-phase current values ​​(step S11). In step S11, it is determined whether or not the faulty phase has been identified by the identification process in step S10. The control device 5 determines whether or not the faulty phase has been identified by the process in step S10.

[0036] When it is determined that the faulty phase can be identified by the sum of squares of the three-phase current values ​​(step S11: Yes), the control device 5 switches to a normal phase and performs evacuation running (step S12). In step S12, evacuation running is transitioned to using the remaining two normal phases, as in step S5. When step S12 is performed, the time required to identify the faulty phase and transition to evacuation running becomes longer. The control device 5 only needs to extend the transition time when detailed identification of the faulty phase is required, such as by calculating the sum of squares of the three-phase currents. Therefore, by being able to perform step S8, the transition time to evacuation running can be shortened, while by being able to perform step S12, erroneous identification of the faulty phase can be prevented. When the process of step S12 is performed, this control routine ends.

[0037] When it is determined that the faulty phase cannot be identified by the sum of squares of the three-phase current values ​​(step S11: No), the control device 5 determines that evacuation travel is not possible (step S13). After performing the process of step S13, this control routine ends.

[0038] As described above, according to the embodiment, when the faulty phase can be identified from the current values ​​of each phase while the inverter 3 is shut down, it is not necessary to wait for the rotation fluctuation of the motor 2 to subside, thereby shortening the time required for the recovery process. In addition, since it is only necessary to extend the transition time only when detailed identification of the faulty phase is required based on the sum of the squares of the three-phase current values, it is possible to prevent erroneous identification of the faulty phase while shortening the transition time to evacuation running. [Explanation of symbols]

[0039] 1 Motor drive unit 2 Motors 3 Inverter 4 Battery 5. Control device 6 Boost Converter 11,12,13 Current sensors

Claims

[Claim 1] A three-phase motor, A battery; an inverter that converts DC power supplied from the battery into AC power to drive the motor; three current sensors each detecting a three-phase current value supplied from the inverter to the motor; A control device for controlling the inverter; A motor drive device comprising: When determining whether any one of the three current sensors is faulty, the control device executes voltage control to make the voltage of the battery higher than the back electromotive voltage of the motor. A motor drive device comprising:

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