Inverter device and motor device having the inverter device

Abstract

This invention relates to an inverter device that converts power from a power source and drives a motor. The inverter device includes: an inverter circuit having switching elements; a drive circuit for switching the switching elements on and off; and a control unit for controlling the drive circuit. The control unit has a speed calculation unit that calculates the minimum speed of the motor based on the power supply voltage. After performing fail-safe control, the control unit terminates the fail-safe control when the speed of the motor is less than the minimum speed.

Description

Technical Field

[0001] The present invention relates to an inverter device and an electric motor device having the inverter device, and particularly to an inverter device including a speed calculation unit for calculating the minimum speed of the electric motor. Background Technology

[0002] In the past, when the motor was rotating and it was desired to stop the normal torque control, fail-safe control would be executed to prevent overcharging of the power supply and damage to the IGBT components caused by back electromotive force.

[0003] In existing technologies, a method for triggering fail-safe control has been disclosed that employs a set speed threshold. Specifically, in existing fail-safe control, when an abnormality occurs in the motor unit (i.e., the motor power supply voltage becomes abnormally high), fail-safe control is performed based on the motor speed at the time of the abnormality. Since other components are more likely to malfunction when the motor speed is high, fail-safe control can be performed simply by monitoring the motor speed. For example, fail-safe control is initiated when the fixed speed is above 4000 rpm, and terminated when the fixed speed is below 3000 rpm, after which normal torque control begins.

[0004] For example, Patent Document 1 discloses a technical solution for initiating fault-safe control based on the motor speed when the motor device malfunctions. Specifically, in the inverter control device of Patent Document 1, when the speed is detected to have dropped to zero, a signal is sent to the vehicle side to stop the fault-safe control. The fault-safe control includes ASC control and SD control. In the case of ASC control, the minimum ASC speed ωasc is set based on the vehicle's deceleration and the temperature of the stator coil. In the case of SD control, the maximum SD speed ωsd is set based on the magnitude of the power supply current in the relay-on state and the rise in the DC link voltage in the relay-off state (see paragraphs 0039, 0042, and 0050 of Patent Document 1).

[0005] For example, Patent Document 2 discloses a motor control device that switches between ASC control and SD control based on the rotational speed. Specifically, in the motor control device of Patent Document 2, when the rotational speed is detected to be zero, the fail-safe control is stopped, while when the rotational speed is not zero, the SD control in the fail-safe control continues (see paragraphs 0049, 0055, and 0058 of Patent Document 2).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Patent Publication No. WO2016076429A1

[0009] Patent Document 2: Japanese Patent Application Publication No. JP2005033932A Summary of the Invention

[0010] The technical problem to be solved by the present invention

[0011] In existing technologies, the rotational speed at which fail-safe control is not required is predetermined as a fixed value. Fail-safe control terminates when the motor speed falls below this predetermined fixed value. Therefore, even if fail-safe control is not actually needed, it will continue as long as the rotational speed does not fall below the predetermined fixed value.

[0012] The present invention was made in view of the above-mentioned technical problems, and its object is to provide an inverter device that can narrow the speed range of the motor for fault-safe control, thereby enabling fault-safe control to be performed without excessive execution.

[0013] In a first embodiment of the inverter device of the present invention, the inverter device converts power from a power source and drives a motor. The inverter device includes: an inverter circuit having a switching element; a drive circuit for switching the switching element on and off; and a control unit for controlling the drive circuit. The control unit has a speed calculation unit for calculating the minimum speed of the motor based on the power supply voltage. After performing fail-safe control, the control unit terminates the fail-safe control when the speed of the motor is less than the minimum speed.

[0014] According to the inverter device of the present invention, by comparing the speed of the motor with the minimum speed, the fault safety control ends when the speed of the motor is less than the minimum speed, thereby narrowing the speed range of the motor for fault safety control and thus preventing excessive execution of fault safety control.

[0015] In a second embodiment of the inverter device of the present invention, in the first embodiment, the speed calculation unit calculates the maximum speed of the motor based on the power supply voltage, and when the speed of the motor is greater than the maximum speed, the control unit performs the fault safety control.

[0016] According to the inverter device of the present invention, by comparing the speed of the motor with the maximum speed, fault safety control is only initiated when the speed of the motor is greater than the maximum speed. This narrows the speed range of the motor for which fault safety control is performed, thereby preventing excessive execution of fault safety control.

[0017] In a third embodiment of the inverter device of the present invention, which is either the first embodiment or the second embodiment, the speed calculation unit calculates the maximum speed and the minimum speed based on the power supply voltage, the correction coefficient, and the bias value.

[0018] In the third embodiment of the inverter device of the present invention, the fourth embodiment preferably includes a correction coefficient and a bias value that are fixed values ​​that vary depending on the type of motor and the power supply.

[0019] According to the inverter device of the present invention, the maximum speed and minimum speed of the motor can be calculated based on the power supply voltage, correction coefficient, and bias value. Moreover, the correction coefficient and bias value are fixed values ​​that vary depending on the type of motor and power supply. Therefore, the maximum speed and minimum speed of the motor can be obtained by storing them in a table in advance.

[0020] In a fifth embodiment of the inverter device of the present invention, which is either the first or the second embodiment, the inverter circuit includes an upper arm-side switching element group and a lower arm-side switching element group, and the control unit controls the drive circuit to switch the on / off states of the upper arm-side switching element group and the lower arm-side switching element group.

[0021] In the fifth embodiment, the sixth aspect of the electric motor device of the present invention preferably includes a fail-safe control method that enables one of the upper arm-side switch element group and the lower arm-side switch element group to be fully connected in one phase and the other to be fully disconnected in the other phase.

[0022] In the fifth embodiment, the seventh method of the electric motor device of the present invention preferably includes a fault-safe control that performs full-phase disconnection of both the upper arm-side switch element group and the lower arm-side switch element group.

[0023] When the electric motor rotates at high speed, it can overheat. When the motor speed is reduced to a low speed using ASC control, it can suddenly be subjected to braking torque. According to the inverter device of the present invention, by performing fail-safe control (ASC control or SD control) when the motor rotates at high speed, it is possible to prevent failures of switching elements and the power supply.

[0024] The eighth embodiment of the electric motor device of the present invention includes an inverter device as described in any one of the first to seventh embodiments above.

[0025] Invention Effects

[0026] First, according to the inverter device of the present invention, the speed range of the motor for which fail-safe control is performed can be narrowed, thereby preventing excessive execution of fail-safe control.

[0027] Secondly, the inverter device according to the present invention can prevent damage to the power supply and motor, and minimize the generation of braking torque. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the structure of the electric motor device with an inverter according to the present invention.

[0029] Figure 2 This is a table illustrating the control flow of the inverter device of the present invention.

[0030] Figure 3 This is a schematic diagram illustrating the overall structure of the electric motor device in the fail-safe control of the present invention.

[0031] Figure 4 This is a schematic diagram illustrating the ASC control and SD control in the fail-safe control of this invention. Detailed Implementation

[0032] The preferred embodiment of the inverter device 10 according to the present invention will now be described using the accompanying drawings. In the drawings, the same or equivalent parts are described using the same reference numerals.

[0033] <Structure of Inverter Device>

[0034] Figure 1 This is a schematic diagram illustrating the structure of the electric motor device 1 of the present invention. As an example, the electric motor device 1 of the present invention includes: a DC power supply 20, an electric motor 30, and an inverter device 10.

[0035] like Figure 1 As shown, the motor 30 has a rotor and a stator, and is a motor driven to rotate by supplying three-phase alternating current. For example, the motor 30 may be a permanent magnet synchronous motor.

[0036] like Figure 1 As shown, the DC power supply 20 is, for example, a high-voltage battery, but is not limited to a high-voltage battery; it can also be other power supply devices with DC voltage.

[0037] The electric motor 30, which drives the inverter device 10, is, for example, a rotary motor that serves as the driving force source for the wheels in vehicles such as hybrid electric vehicles and electric vehicles. In this embodiment, the example is given where the electric motor 30 is the driving force source for the wheels in such a vehicle, but the application of the electric motor 30 is not limited to this. This electric motor 30 is a rotary motor that performs three-phase alternating current operation, and can function as both an electric motor and a generator. That is, the electric motor 30 converts electricity from the DC power supply 20 into power via the inverter device 10 (power operation mode). Alternatively, the electric motor 30 converts the rotational driving force transmitted from a gas turbine (not shown) or wheels into electricity, and charges the DC power supply 20 via the inverter device 10 (regenerative mode).

[0038] like Figure 1 As shown, the inverter device 10 includes an inverter circuit 100, a drive circuit 110, and a control unit 120 that controls the drive circuit 110. It converts the DC power stored in the DC power supply 10 into three-phase AC power and supplies the converted three-phase AC power to the motor 30, thereby driving the motor 30. The control unit 120 also includes a speed calculation unit 130 that calculates the minimum speed of the motor 30 based on the power supply voltage Vdc of the DC power supply 20. After performing fail-safe control, the control unit 120 terminates the fail-safe control when the speed of the motor 30 is less than the minimum speed.

[0039] like Figure 1 As shown, the speed calculation unit 130 calculates the maximum and minimum speeds of the motor 30 using equation (1) as described below, based on the power supply voltage, correction coefficient, and bias value. This prevents overcharging of the DC power supply.

[0040] Rotational speed X,Y (rpm) = Power supply voltage (V) × Correction coefficient (rpm / V) + Offset value (rpm) ... (Equation 1)

[0041] In addition, since the DC power supply 20 will be charged when the back electromotive force is greater than the power supply voltage, in order to prevent unnecessary charging of the DC power supply 20, the correction coefficient and bias value are set to make the back electromotive force less than the power supply voltage Vdc.

[0042] Furthermore, in this invention, the speed calculation unit 130 of the control unit 120 calculates the minimum speed of the motor 30 based on the power supply voltage, and after performing fail-safe control, the control unit 120 terminates the fail-safe control when the speed of the motor 30 is less than the minimum speed. Therefore, compared to setting the minimum speed to a fixed value, the speed range of the motor for which fail-safe control is performed can be narrowed, thereby preventing excessive execution of fail-safe control.

[0043] Furthermore, the speed calculation unit 130 calculates the maximum speed of the motor based on the power supply voltage. When the speed of the motor 30 exceeds the maximum speed, the control unit 120 performs fail-safe control. This prevents damage to the power supply and the motor, and minimizes the generation of braking torque.

[0044] Furthermore, the specific actions of fail-safe control, such as the specific actions of ASC control and SD control, will be explained in detail later.

[0045] like Figure 1 As shown, the inverter circuit 10 is a power conversion device that converts power between the DC power supply 20 and the motor 30, and between DC power and three-phase AC power. The inverter circuit 10 is constructed by a series circuit of an upper arm-side switching element group 22 and a lower arm-side switching element group 23. The upper arm-side switching element group 22 includes multiple (e.g., three) switching elements, and the lower arm-side switching element group 23 also includes multiple (e.g., three) switching elements. Furthermore, a diode 5 is connected in parallel to each switching element. Generally, the switching elements are IGBT switching elements, and the diodes 5 are freewheeling diodes, but are not limited to these.

[0046] <Control Flow of Inverter Circuit>

[0047] Below, based on Figure 2 The table shown illustrates the control flow of the inverter circuit 10 of the present invention.

[0048] like Figure 2 As shown, firstly, it is determined whether the voltage state of the DC power supply 20 is in an overvoltage state. If the voltage state of the DC power supply 20 is determined to be in an overvoltage state, for example, above 540V, the inverter circuit 10 starts ASC control to put the inverter circuit 10 into an overvoltage ASC state. Then, if the voltage state of the DC power supply 20 is determined to be not in an overvoltage state, for example, returning to below 250V, or if the speed of the motor 30 is determined to be below 3000rpm, the inverter circuit 10 ends ASC control.

[0049] As described above, when the voltage state of the DC power supply 20 is determined to be an overvoltage state, the inverter circuit 10 starts ASC control. Then, in this case, it is determined whether the voltage state of the motor 30 is a battery relay state.

[0050] If the voltage state of the motor 30 is determined to be in battery relay state, and a fault safety control command is sent from the vehicle control unit (VCU) and there is an abnormality in the high-voltage battery, when the speed of the motor 30 is, for example, above 4000 rpm, the inverter circuit 10 starts fault safety control to make the inverter circuit 10 enter ASC state or SD state.

[0051] If the voltage state of motor 30 is determined to be non-battery relay state, normal torque control continues when a torque control command is sent from VCU.

[0052] If the voltage status of motor 30 is determined to be non-battery relay state, when a fault safety control command is sent from VCU, further determination is made as to what fault state has occurred.

[0053] In the first scenario, if a rotary transformer failure occurs, the forced inverter unit 10 will continuously perform ASC control.

[0054] In the second scenario, if the high-voltage power supply 13 malfunctions, the inverter device 10 will begin fault safety control when the speed of the motor 30 is above 4000 rpm, and will terminate fault safety control when the speed of the motor 30 is below 30000 rpm.

[0055] In the third scenario, if a fault occurs other than a rotary transformer fault or a BECM CAN abnormality, such as a CPU abnormality, an IGBT component abnormality, a power IC abnormality, or a current sensor abnormality, the inverter device 10 switches to start fault safety control when the speed of the motor 30 is above the judgment condition 1 described below, and switches to end fault safety control when the speed of the motor 30 is below the judgment condition 2 described below.

[0056] Furthermore, when no torque control command or fault safety control command is sent from the VCU of the motor 30, if the speed of the motor 30 is above the judgment condition 1 described below, the inverter device 10 switches to start fault safety control, and if the speed of the motor 30 is below the judgment condition 2 described below, the inverter device 10 switches to end fault safety control.

[0057] The following explains judgment conditions 1 and 2 related to the speed of the motor.

[0058] Judgment condition 1 corresponds to the "minimum speed" recorded in the claims of this invention. The threshold speed ωa of the motor that satisfies judgment condition 1 is calculated according to formula 1.

[0059] As described above, after the control unit 120 performs fail-safe control, the speed calculation unit 130 in the control unit 120 calculates the minimum speed of the motor 30. When the speed of the motor 30 is less than the minimum speed, the fail-safe control ends.

[0060] Furthermore, judgment condition 2 corresponds to the "maximum speed" recorded in the claims of this invention, and the threshold speed ωb of the motor that satisfies judgment condition 2 is calculated according to Equation 1.

[0061] As described above, the speed calculation unit 130 in the control unit 120 calculates the maximum speed of the motor 30, and when the speed of the motor 30 is greater than the maximum speed, fail-safe control is started.

[0062] Therefore, the inverter device according to the present invention can not only narrow the speed range of the motor 30 for fault-safe control and avoid excessive fault-safe control, but also prevent damage to the DC power supply 20 and the motor 30, and minimize the generation of braking torque.

[0063] <Specific Actions of Fail-Safe Control>

[0064] Figure 3 This is a schematic diagram illustrating the overall structure of the electric motor device in the fail-safe control of the present invention. Figure 4 This is a schematic diagram illustrating the ASC control and SD control in the fail-safe control of this invention.

[0065] like Figure 3 As shown, the inverter circuit 200 has an upper arm-side switching element group 22 and a lower arm-side switching element group 23. A DC power supply 13 (e.g., the high-voltage battery shown) provides a high voltage to the inverter circuit 200, and a low-voltage power supply 14 (e.g., the low-voltage battery shown) provides a low voltage to the control unit 120. The drive circuit 110 is powered by a control circuit that includes the control unit 120. The control unit 120 controls the drive circuit 110. Here, the switching elements in the upper arm-side switching element group 22 and the lower arm-side switching element group 23 are IGBTs, but the invention is not limited to this.

[0066] The control unit 120 controls the switching elements included in the upper arm-side switching element group 22 and the lower arm-side switching element group 23 via the drive circuit 110. According to the control flow described above, when the speed of the motor 300 does not exceed the threshold, the control unit 120 performs normal torque control, that is, controls the on / off state of the six switching elements in the upper arm-side switching element group 22 and the lower arm-side switching element group 23 in the inverter circuit 200, so that the inverter circuit 200 converts the DC power stored in the high-voltage battery 13 into three-phase AC power and supplies the converted three-phase AC power to the motor 300.

[0067] If the speed of the motor 300 exceeds the threshold, the control unit 120 terminates the normal torque control and begins to execute fail-safe control.

[0068] The above-mentioned fail-safe controls can be as follows: Figure 4The left side of the diagram shows ASC control, which enables one of the upper arm-side switching element group 22 and the lower arm-side switching element group 23 to be fully turned on and the other to be fully turned off. By employing ASC control, the back electromotive force generated in the motor can be returned, preventing overcharging of the power supply and preventing failure of the switching elements and the power supply.

[0069] In addition, the above-mentioned fail-safe controls can also be implemented as follows: Figure 4 The right side of the diagram shows SD control, which enables both the upper arm-side switching element group 22 and the lower arm-side switching element group 23 to be fully disconnected. By employing SD control, it is possible to prevent failure of the switching elements and the power supply.

[0070] When the electric motor rotates at high speed, it can overheat. When the motor speed is reduced to a low speed using ASC control, it can suddenly be subjected to braking torque. To prevent this, in this invention, fail-safe control ends when the speed returns to a low level. According to the inverter device of this invention, by performing fail-safe control (ASC control or SD control) when the motor is rotating at high speed, failures in switching elements and the power supply can be prevented.

[0071] It should be understood that within the scope of this invention, the components in the embodiments can be freely combined, or the components in the embodiments can be appropriately modified or omitted.

[0072] As described above, the invention has been described in detail, but the above description is merely illustrative of all aspects, and the invention is not limited thereto. Numerous variations not illustrated are to be understood and are not departed from the scope of the invention.

[0073] Industrial practicality

[0074] The inverter device and the motor device including the inverter device involved in this invention can be widely used in fields such as motors for EVs (electric vehicles).

[0075] Label Explanation

[0076] 1. Electric motor assembly;

[0077] 10. Inverter unit;

[0078] 20 DC power supply;

[0079] 30 Electric motors;

[0080] 100 Inverter Circuit;

[0081] 110 Drive circuit;

[0082] 120 Control Department;

[0083] 130 RPM Calculation Unit;

[0084] 13. High-voltage power supply;

[0085] 14. Low-voltage power supply;

[0086] 22 Upper arm side switch element group;

[0087] 23. Lower arm side switch element group;

[0088] 5. Diodes.

Claims

1. An inverter device that converts power from a power source and drives a motor, characterized in that, The inverter device includes: Inverter circuit with switching elements; A drive circuit that switches the on / off state of the switching element; and The control unit that controls the drive circuit. The control unit includes a speed calculation unit that calculates the minimum speed of the motor based on the power supply voltage. After executing fail-safe control, the control unit terminates the fail-safe control and begins normal torque control when the motor speed is lower than the minimum speed. The speed calculation unit calculates the maximum speed and the minimum speed based on the power supply voltage, correction coefficient, and bias value. The correction coefficient and the bias value are set such that the back electromotive force generated by the motor is less than the power supply voltage.

2. The inverter device as described in claim 1, characterized in that, The speed calculation unit calculates the maximum speed of the motor based on the power supply voltage. When the speed of the motor is greater than the maximum speed, the control unit executes the fail-safe control.

3. The inverter device as described in claim 1, characterized in that, The correction coefficient and the bias value are fixed values ​​that vary depending on the type of motor and the power supply.

4. The inverter device as described in claim 1 or 2, characterized in that, The inverter circuit includes an upper arm-side switching element group and a lower arm-side switching element group. The control unit controls the drive circuit to switch the upper arm side switch element group and the lower arm side switch element group on and off.

5. The inverter device as described in claim 4, characterized in that, The fault-safe control is an ASC control that enables one of the upper arm-side switch element group and the lower arm-side switch element group to be fully connected in one phase and fully disconnected in the other phase.

6. The inverter device as claimed in claim 4, characterized in that, The fault-safe control is a SD control that causes both the upper arm-side switch element group and the lower arm-side switch element group to be completely disconnected.

7. An electric motor device, characterized in that, The inverter device includes any one of claims 1 to 6.

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