Control apparatus

Abstract

To provide a technique capable of suppressing a flowing of an excess current from a motor to a battery.SOLUTION: A control apparatus includes: three upper transistors connected to a positive electrode of a battery; and three lower arm transistors connected serially to the three upper transistors, respectively, and controls an inverter supplied to a motor by converting DC power output from the battery into AC power. The control apparatus makes one of all of the three upper transistors and the three lower arm transistors to be turned on in the case where a counter electromotive voltage of the motor is higher than a voltage of the battery when an abnormality occurs in a control component in the motor, and executes three-phase ON control that makes the other all of transistors to be turned off. In the case where the counter electromotive voltage of the motor is lower than the voltage of the battery, shut-down control for turning off all of the three upper transistors and the three lower arm transistors is executed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control device, and more particularly to a control device for a motor drive device including a battery, an inverter, and a motor. [Background technology]

[0002] Inverters are known that convert DC power output from a battery into AC power and supply it to a motor. In this type of inverter, shutdown control may be performed when an abnormality occurs in the motor's control components. Shutdown control is a control that turns off all transistors that make up the inverter, thereby turning the inverter off.

[0003] If the motor's back electromotive force is high when shutdown control is executed, a large regenerative current will flow from the motor into the battery, which may cause the battery to fail due to overvoltage or overcharging. To avoid this, in Patent Document 1, when shutdown control is executed, the electrical connection between the inverter and the battery is cut off in certain cases based on the current flowing through the motor windings and the current flowing through each transistor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-21689 Summary of the Invention [Problem to be solved by the invention]

[0005] This specification provides a novel technique for suppressing overcurrent from flowing from the motor to the battery. [Means for solving the problem]

[0006] This specification discloses a control device for an inverter having three upper-arm transistors connected to a positive electrode of a battery and three lower-arm transistors connected in series corresponding to the three upper-arm transistors, which converts DC power output from the battery into AC power and supplies the AC power to a motor. When an abnormality occurs in a control component of the motor, the control device performs three-phase ON control to turn on all of one of the three upper-arm transistors and the three lower-arm transistors and turn off all of the other when a back electromotive force of the motor is higher than the voltage of the battery, and performs shutdown control to turn off all of the three upper-arm transistors and the three lower-arm transistors when the back electromotive force of the motor is lower than the voltage of the battery.

[0007] According to the above control device, when an abnormality occurs in a control component of the motor and the back electromotive force of the motor is higher than the battery voltage, three-phase ON control is executed to form a closed circuit in which a circulating current flows between the motor and the inverter, thereby short-circuiting the motor. This prevents overcurrent from flowing to the battery. Furthermore, when an abnormality occurs in a control component of the motor and the back electromotive force of the motor is lower than the battery voltage, executing shutdown control makes it difficult for current to flow from the motor to the battery. Therefore, executing shutdown control can prevent the motor from generating a large negative torque. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram of an inverter device according to an embodiment. [Figure 2] 4 is a flowchart showing a process executed by a control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Example) 1, the inverter device 1 includes a battery 2, a relay 3, a capacitor 4, an inverter 6, a motor 8, and a control device 10. The inverter device 1 is mounted on, for example, a hybrid vehicle or an electric vehicle.

[0010] The battery 2 supplies current to the motor 8 via the inverter 6. The inverter 6 is connected between the battery 2 and the motor 8, and converts the DC power output from the battery 2 into AC power and supplies it to the motor 8. The motor 8 is a three-phase AC motor, and is driven by the AC power supplied from the inverter 6.

[0011] The relays 3 are SMRs (system main relays) arranged on the high potential line 20 and the low potential line 22, respectively, and are turned on and off simultaneously. The capacitor 4 is inserted between the high potential line 20 and the low potential line 22, and smooths the potential difference between them.

[0012] The inverter 6 includes three upper-arm transistors 12A, 12B, and 12C connected to the positive electrode of the battery 2, and three lower-arm transistors 12D, 12E, and 12F connected in series to correspond to the transistors 12A, 12B, and 12C, respectively. The transistors 12D, 12E, and 12F are connected to the negative electrode of the battery 2. A free-wheeling diode 14 is connected in anti-parallel to each of the transistors 12A to 12F. When the control device 10 appropriately turns the transistors 12A to 12F on and off, an AC current is output from the midpoint of the series connection of the three sets of transistors.

[0013] The inverter device 1 further includes a current sensor 30, a motor rotation speed sensor 32, and a tire rotation speed sensor 34. The current sensor 30 is provided on each power line between the inverter 6 and the motor 8, and measures the current of each phase of the three-phase AC. The control device 10 controls the operation of the transistors 12A to 12F while monitoring the current of each phase with the current sensor 30. The motor rotation speed sensor 32 is provided on the motor 8, and measures the rotation speed of the motor 8. The tire rotation speed sensor 34 is provided on the tire axle (not shown), and measures the rotation speed of the tire. The outputs of the current sensor 30, the motor rotation speed sensor 32, and the tire rotation speed sensor 34 are input to the control device 10.

[0014] In the inverter device 1 described above, an abnormality may occur in the control components of the motor 8. For example, if an abnormality occurs in the current sensor 30, the control device 10 cannot output an appropriate command. When the control device 10 of this embodiment detects that an abnormality has occurred in the control components of the motor 8, it executes the following process shown in FIG. 2.

[0015] 2, the control device 10 determines whether or not the output of the motor rotation speed sensor 32 is normal. If the output of the motor rotation speed sensor 32 is normal (YES in S12), the control device 10 acquires the rotation speed of the motor 8 based on the output of the motor rotation speed sensor 32 in S14.

[0016] On the other hand, if the output of the motor rotation speed sensor 32 is abnormal (NO in S12), in S16 the control device 10 acquires the rotation speed of the tire based on the output of the tire rotation speed sensor 34. Next, in S18, the control device 10 calculates the rotation speed of the motor 8 based on the rotation speed of the tire.

[0017] In S20, the control device 10 calculates the back electromotive force of the motor 8 based on the rotation speed of the motor 8 acquired in S14 or S18.

[0018] Next, in S22, the control device 10 determines whether the calculated back electromotive force voltage of the motor 8 is higher than the voltage of the battery 2. If the control device 10 determines that the back electromotive force voltage is lower than the voltage of the battery 2 (NO in S22), the control device 10 executes shutdown control in S24. The shutdown control is control that turns off all of the upper arm transistors 12A, 12B, and 12C and the lower arm transistors 12D, 12E, and 12F. In this case, since the voltage of the battery 2 is higher than the back electromotive force voltage of the motor 8, even if the shutdown control is executed, the freewheel diodes 14 of the upper arm transistors 12A, 12B, and 12C do not turn on. Therefore, no current flows from the motor 8 to the positive electrode of the battery 2. After executing S24, the control device 10 ends the series of processes.

[0019] On the other hand, when the control device 10 determines that the back electromotive force of the motor 8 is higher than the voltage of the battery 2 (NO in S22), the control device 10 executes three-phase ON control in S26. The three-phase ON control is a control in which all of the upper arm transistors 12A, 12B, and 12C and all of the lower arm transistors 12D, 12E, and 12F are turned ON and all of the other transistors are turned OFF. When the three-phase ON control is executed, a closed circuit through which a circulating current flows is formed between the inverter 6 and the motor 8, and the motor 8 is short-circuited. This generates a braking torque due to the back electromotive force of the motor 8, and the motor 8 decelerates. The control device 10 ends the series of processes after executing S26. Note that when S26 is executed, the motor 8 decelerates, and the back electromotive force gradually decreases. Therefore, the control device 10 may execute shutdown control if the back electromotive force of the motor 8 becomes smaller than the voltage of the battery 2 after executing S26.

[0020] As described above, in the inverter device 1 of this embodiment, when an abnormality occurs in the control components of the motor 8, either shutdown control or three-phase ON control is selected and executed depending on the magnitude relationship between the back electromotive force of the motor 8 and the voltage of the battery 2. When the back electromotive force of the motor 8 is higher than the voltage of the battery 2, three-phase ON control is executed, forming a closed circuit in which a circulating current flows between the motor 8 and the inverter 6, and the motor 8 is short-circuited. This prevents overcurrent from flowing to the battery 2. Furthermore, when an abnormality occurs in the control components of the motor 8, if the back electromotive force of the motor 8 is lower than the voltage of the battery 2, current is unlikely to flow from the motor 8 to the battery 2 even if shutdown control is executed. Therefore, executing shutdown control can prevent the motor 8 from generating a large negative torque.

[0021] The technology disclosed in this specification is particularly useful in a device that does not have a boost converter between the battery 2 and the inverter 6, i.e., a device that does not have a unit for stepping down the voltage of regenerative power. [Explanation of symbols]

[0022] 1: inverter device, 2: battery, 6: inverter, 8: motor, 10: control device, 12A, 12B, 12C: upper arm transistors, 12D, 12E, 12F: lower arm transistors, 30: current sensor, 32: motor rotation speed sensor, 34: tire rotation speed sensor

Claims

[Claim 1] A control device for an inverter having three upper arm transistors connected to a positive electrode of a battery and three lower arm transistors connected in series corresponding to the three upper arm transistors, the control device converting DC power output from the battery into AC power and supplying the AC power to a motor, When an abnormality occurs in a control part of the motor, the control device when a back electromotive voltage of the motor is higher than a voltage of the battery, a three-phase ON control is executed in which one of the three upper arm transistors and the three lower arm transistors is all turned on and the other of the three upper arm transistors and the three lower arm transistors is all turned off; when the back electromotive voltage of the motor is lower than the voltage of the battery, a shutdown control is executed to turn off all of the three upper arm transistors and the three lower arm transistors. Control device.

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