Inverter device and motor device equipped therewith

Abstract

To provide an inverter device in which excessive fail-safe control is not executed.SOLUTION: The present invention relates to an inverter device that converts power from a power supply to drive a motor and includes: an inverter circuit having a switching element; a drive circuit for switching on and off of the switching element; and a control unit for controlling the drive circuit. The control unit has a rotation number calculation unit for calculating the minimum number of rotations of the motor based on a power supply voltage. After executing fail-safe control, the control unit terminates the fail-safe control when the number of rotations of the motor becomes less than the minimum number of rotations.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inverter device and a motor device including the same, and more particularly to an inverter device including a rotation speed calculation unit that calculates the minimum rotation speed of a motor.

Background Art

[0002] Conventionally, when it is desired to stop normal torque control while the motor is rotating, fail-safe control is executed to prevent overcharging of the power supply due to back electromotive force and damage to IGBT elements.

[0003] Conventionally, a method of setting a rotation speed threshold has been disclosed as a trigger for performing fail-safe control.

[0004] Specifically, in conventional fail-safe control, when an abnormality occurs in the motor device (that is, when the motor power supply voltage becomes abnormally high), fail-safe control is performed based on the rotation speed of the motor at the time of the abnormality.

[0005] When the rotation speed of the motor is high, there is a high possibility that an abnormality will occur in other components, so fail-safe control can be executed simply by monitoring the rotation speed of the motor.

[0006] For example, if the fixed rotation speed is 4000 rpm or more, fail-safe control is started, and if the fixed rotation speed is 3000 rpm or less, fail-safe control is terminated and normal torque control is started.

[0007] For example, Patent Document 1 discloses starting fail-safe control according to the motor rotation speed when an abnormality occurs in the motor device.

[0008] Specifically, in the inverter control device of Patent Document 1, when it is detected that the rotation speed has become 0, a signal for stopping the fail-safe control is notified to the vehicle side.

[0009] Here, the fail-safe control includes ASC control and SD control, in which case the minimum ASC rotational speed ωasc is set based on the vehicle's deceleration and the stator coil temperature, and in which case the maximum SD rotational speed ωsd is set based on the magnitude of the power supply current when the relay is ON and the rise in the DC link voltage when the relay is OFF (see paragraphs 0039, 0042, and 0050 of Patent Document 1).

[0010] For example, Patent Document 2 discloses a motor control device that switches between ASC control and SD control depending on the rotational speed.

[0011] Specifically, in the motor control device of Patent Document 2, when it is detected that the rotational speed has become 0, the fail-safe control is stopped, and if the rotational speed is not 0, the SD control in the fail-safe control is continued (see paragraphs 0049, 0055, and 0058 of Patent Document 2). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] International Patent Publication WO2016076429A1

[0013] [Patent Document 2] Japanese Patent Publication No. 2005-033932 [Overview of the project] [Problems that the invention aims to solve]

[0014] In conventional technology, a fixed value is set in advance for the rotational speed at which fail-safe control is not required, and the fail-safe control is terminated when the motor's rotational speed falls below this predetermined fixed value. Therefore, even if there is no actual need to perform fail-safe control, the fail-safe control continues as long as the rotational speed does not fall below the predetermined fixed value. The present invention has been made in view of the above problems, and aims to provide an inverter device that can shorten the rotational speed interval for which fail-safe control is performed on the motor and does not perform fail-safe control excessively.

[0015] A first embodiment of the inverter device according to the present invention is an inverter device that converts power from a power source to drive a motor, comprising: an inverter circuit having a switching element; a drive circuit that switches the switching element on and off; and a control unit that controls the drive circuit, wherein the control unit has a rotation speed calculation unit that calculates the minimum rotation speed of the motor based on the power supply voltage, and after executing fail-safe control, the control unit terminates the fail-safe control when the rotation speed of the motor becomes less than the minimum rotation speed.

[0016] According to the inverter device of the present invention, the motor rotation speed is compared with the minimum rotation speed, and the fail-safe control is terminated when the motor rotation speed is less than the minimum rotation speed. This shortens the rotation speed interval during which fail-safe control is performed on the motor, and prevents excessive execution of fail-safe control.

[0017] A second aspect of the inverter device according to the present invention is that, in the first aspect described above, the rotational speed calculation unit calculates the maximum rotational speed of the motor based on the power supply voltage, and the control unit executes the fail-safe control when the rotational speed of the motor is greater than the maximum rotational speed.

[0018] According to the inverter device of the present invention, the motor's rotational speed is compared with the maximum rotational speed, and fail-safe control is initiated when the motor's rotational speed is greater than the maximum rotational speed. This allows for a narrower range of motor rotational speeds under fail-safe control, preventing excessive execution of fail-safe control.

[0019] A third aspect of the inverter device according to the present invention is characterized in that, in the first or second aspect, the rotational speed calculation unit calculates the maximum rotational speed and the minimum rotational speed based on the power supply voltage, a correction coefficient, and an offset value.

[0020] A fourth aspect of the inverter device according to the present invention is characterized in that, in the third aspect, the correction coefficient and the offset value are fixed values ​​that differ depending on the type of motor and the power supply.

[0021] According to the inverter device of the present invention, the maximum and minimum rotational speeds of a motor can be calculated based on the power supply voltage, correction coefficient, and offset value. Moreover, since these correction coefficient and offset value are fixed values ​​that differ depending on the type of motor and power supply, the maximum and minimum rotational speeds of the motor can be obtained by storing them in a table in advance.

[0022] A fifth aspect of the inverter device according to the present invention is that, in the first or second embodiment, the inverter circuit comprises 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 upper arm side switching element group and the lower arm side switching element group on and off.

[0023] A sixth aspect of the motor device according to the present invention is, in the fifth aspect, characterized in that the fail-safe control is ASC control which turns on all phases of one of the upper arm side switching element group and the lower arm side switching element group and turns off all phases of the other.

[0024] The seventh aspect of the motor device according to the present invention is that, in the fifth aspect, the fail-safe control is SD control that completely shuts off both the upper arm side switching element group and the lower arm side switching element group.

[0025] When the motor rotates at high speed, the motor overheats. When the rotation speed of the motor is decreased by ASC control to rotate the motor at low speed, a sudden braking torque is applied to the motor.

[0026] According to the inverter device of the present invention, by performing fail-safe control (ASC control or SD control) during high-speed rotation of the motor, failures of the switching elements and the power supply can be prevented.

[0027] The eighth aspect of the motor device according to the present invention includes the inverter device according to any one of the first aspect to the seventh aspect.

Advantages of the Invention

[0028] First, according to the inverter device of the present invention, the rotational speed range of the motor that performs fail-safe control can be reduced, and the fail-safe control can be prevented from being executed excessively. Next, according to the inverter device of the present invention, while preventing damage to the power supply and the motor, it is possible to prevent the generation of braking torque as much as possible.

Brief Description of the Drawings

[0029] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a motor device including an inverter device according to the present invention. [Figure 2] FIG. 2 is a table showing the control flow of the inverter device according to the present invention. [Figure 3] FIG. 3 is a schematic diagram for explaining the overall configuration of the motor device in the fail-safe control of the present invention. [Figure 4] FIG. 4 is a schematic diagram for explaining ASC control and SD control in the fail-safe control of the present invention. [Modes for carrying out the invention]

[0030] Hereinafter, preferred embodiments of the inverter device 10 according to the present invention will be described with reference to the drawings.

[0031] In each figure, the same or corresponding parts are denoted by the same reference numerals and described accordingly. Figure 1 is a schematic diagram showing the configuration of the motor device 1 according to the present invention.

[0032] As an example, the motor device 1 according to the present invention comprises a DC power supply 20, a motor 30, and an inverter device 10.

[0033] As shown in Figure 1, the motor 30 has a rotor and a stator, and is driven to rotate by the supply of three-phase AC power.

[0034] For example, a permanent magnet synchronous motor can be used as the motor 30.

[0035] As shown in Figure 1, the DC power supply 20 is, for example, a high-voltage battery, but is not limited to a high-voltage battery; it may be any other power supply device having a DC voltage.

[0036] The motor 30, which is the object driven by the inverter device 10, is, for example, a rotating electric machine that serves as a driving force source for the wheels of a vehicle such as a hybrid car or an electric vehicle.

[0037] In this embodiment, the motor 30 is described as being a driving force source for the vehicle's wheels, but the use of the motor 30 is not limited to this.

[0038] This motor 30 is a rotating electric machine that operates on three-phase AC power and can function as both a motor and a generator.

[0039] In other words, the motor 30 converts power from the DC power supply 20 into motor power via the inverter device 10 (motor mode).

[0040] Alternatively, the motor 30 converts the rotational driving force transmitted from an engine or wheels (not shown) into electricity and charges the DC power supply 20 via the inverter device 10 (regenerative mode).

[0041] As shown in Figure 1, the inverter device 10 comprises 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 20 into three-phase AC power and drives the motor 30 by supplying the converted three-phase AC power to the motor 30.

[0042] The control unit 120 further includes a rotation speed calculation unit 130 that calculates the minimum rotation speed of the motor 30 based on the power supply voltage Vdc of the DC power supply 20. After executing fail-safe control, the control unit 120 terminates the fail-safe control when the rotation speed of the motor 30 falls below the minimum rotation speed.

[0043] As shown in Figure 1, the rotation speed calculation unit 130 calculates the maximum and minimum rotation speeds of the motor 30 based on the power supply voltage, correction coefficient, and offset value using the following equation (1).

[0044] This prevents overcharging of the DC power supply.

[0045] Rotational speed X,Y (rpm) = Power supply voltage (V) × Correction coefficient (rpm / V) + Offset value (rpm) ... (Equation 1)

[0046] Furthermore, if the back electromotive force is greater than the power supply voltage, the DC power supply 20 will be charged. Therefore, in this invention, in order to prevent unnecessary charging of the DC power supply 20, the correction coefficient and bias value are set so that the back electromotive force is less than the power supply voltage Vdc.

[0047] Furthermore, in this invention, the rotational speed calculation unit 130 of the control unit 120 calculates the minimum rotational speed of the motor 30 based on the power supply voltage, and after executing fail-safe control, the control unit 120 terminates the fail-safe control if the rotational speed of the motor 30 is less than the minimum rotational speed.

[0048] This allows for a smaller rotational speed interval for the motor during fail-safe control compared to setting a fixed minimum rotational speed, thus preventing excessive execution of fail-safe control.

[0049] Furthermore, the rotation speed calculation unit 130 calculates the maximum rotation speed of the motor based on the power supply voltage, and the control unit 120 executes fail-safe control if the rotation speed of the motor 30 is greater than the maximum rotation speed.

[0050] This makes it possible to minimize the generation of braking torque while preventing damage to the power supply and motor.

[0051] The specific operations of fail-safe control, such as ASC control and SD control, will be described in detail later.

[0052] As shown in Figure 1, the inverter circuit 10 is a power conversion device installed between the DC power supply 20 and the motor 30, which performs power conversion between DC power and three-phase AC power.

[0053] The inverter circuit 10 is composed of a series circuit of the upper arm side switching element group 22 and the lower arm side switching element group 23.

[0054] The upper arm side switching element group 22 includes multiple (for example, three) switching elements, and the lower arm side switching element group 23 also includes multiple (for example, three) switching elements.

[0055] Furthermore, a diode 5 is connected in parallel to each switching element.

[0056] Generally, the switching element is an IGBT switching element and diode 5 is a freewheeling diode, but neither is limited to these.

[0057] Next, the control flow of the inverter circuit 10 of the present invention will be explained based on the table shown in Figure 2.

[0058] As shown in Figure 2, first, it is determined whether the voltage state of the DC power supply 20 is in an overvoltage state.

[0059] If the inverter circuit 10 determines that the voltage state of the DC power supply 20 is an overvoltage state, for example, 540 V or higher, the inverter circuit 10 starts ASC control so that it enters an overvoltage ASC state.

[0060] Then, the inverter circuit 10 terminates ASC control when it determines that the voltage state of the DC power supply 20 has returned to a non-overvoltage state, for example, 250 V or less, or when it determines that the rotational speed of the motor 30 is 3000 rpm or less.

[0061] As described above, if it is determined that the voltage state of the DC power supply 20 is in an overvoltage state, the inverter circuit 10 is instructed to start ASC control, and then, in this case, it is determined whether or not the voltage state of the motor 30 is in a battery relay state.

[0062] If the voltage state of the motor 30 is determined to be in a battery relay state, and a fail-safe control command is sent from the vehicle control unit (VCU) indicating an abnormality in the high-voltage battery, then when the rotational speed of the motor 30 exceeds, for example, 4000 rpm, the inverter circuit 10 starts fail-safe control to enter the ASC state or SD state.

[0063] If the voltage state of motor 30 is determined to be in a non-battery relay state, normal torque control will continue when a torque control command is sent from the VCU.

[0064] If the voltage state of motor 30 is determined to be in a non-battery relay state, the VCU will send a fail-safe control command and then determine what kind of failure condition has occurred.

[0065] In the first case, if a resolver failure occurs, the inverter device 10 is instructed to continue ASC control.

[0066] The second case is when, in the event of a malfunction in the high-voltage battery 13, the inverter device 10 starts fail-safe control when the rotational speed of the motor 30 exceeds 4000 rpm, and the inverter device 10 terminates fail-safe control when the rotational speed of the motor 30 falls below 30000 rpm.

[0067] The third case is when a failure other than resolver failure or BECM CAN abnormality occurs, such as a CPU abnormality, IGBT element abnormality, power supply IC abnormality, or current sensor abnormality, and the inverter device 10 switches to start fail-safe control when the rotational speed of the motor 30 is equal to or greater than the judgment condition 1 described later, and switches to terminate fail-safe control when the rotational speed of the motor 30 is less than or equal to the judgment condition 2 described later.

[0068] Furthermore, if the inverter device 10 has not received a torque control command or fail-safe control command from the VCU of the motor 30, it will start fail-safe control if the rotational speed of the motor 30 is equal to or greater than the determination condition 1 described later, and will end fail-safe control if the rotational speed of the motor 30 is equal to or less than the determination condition 2 described later.

[0069] Next, we will explain the determination conditions 1 and 2 regarding the motor's rotational speed.

[0070] Judgment condition 1 corresponds to the "minimum rotational speed" described in the claims of the present invention, and the threshold rotational speed ωa of a motor that satisfies judgment condition 1 is calculated according to equation 1.

[0071] As described above, after the control unit 120 performs fail-safe control, the rotation speed calculation unit 130 in the control unit 120 calculates the minimum rotation speed of the motor 30, and when the rotation speed of the motor 30 becomes less than the minimum rotation speed, the fail-safe control is terminated.

[0072] Furthermore, determination condition 2 corresponds to the "maximum rotational speed" described in the claims of the present invention, and the threshold rotational speed ωb of a motor that satisfies determination condition 2 is calculated according to Equation 1.

[0073] As described above, the rotational speed calculation unit 130 of the control unit 120 calculates the maximum rotational speed of the motor 30, and when the rotational speed of the motor 30 exceeds the maximum rotational speed, it starts executing fail-safe control.

[0074] As a result, the inverter device of the present invention makes it possible to narrow the rotational speed range of the motor 30 that performs fail-safe control, thereby preventing excessive execution of fail-safe control, and also prevents damage to the DC power supply 20 and the motor 30 while minimizing the generation of braking torque.

[0075] Figure 3 is a schematic diagram illustrating the overall configuration of the motor device in the fail-safe control of the present invention.

[0076] Figure 4 is a schematic diagram illustrating the ASC control and SD control in the fail-safe control of the present invention.

[0077] As shown in Figure 3, the inverter circuit 200 includes an upper arm-side switching element group 22 and a lower arm-side switching element group 23.

[0078] The DC power supply 13 (for example, the high-voltage battery shown in the figure) supplies high voltage to the inverter circuit 200, and the low-voltage power supply 14 (for example, the low-voltage battery shown in the figure) supplies low voltage to the control unit 120.

[0079] The drive circuit 110 is powered by a control circuit that includes a control unit 120.

[0080] The control unit 120 controls the drive circuit 110.

[0081] Here, IGBTs were used as the switching elements for the upper arm switching element group 22 and the lower arm switching element group 23, but the invention is not limited to these.

[0082] The control unit 120 controls the on / off state of the switching elements included in the upper arm switching element group 22 and the lower arm switching element group 23 via the drive circuit 110.

[0083] According to the control flow described above, if the rotational speed of the motor 300 does not exceed a threshold, the control unit 120 performs normal torque control by controlling the on / off state of the six switching elements of 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.

[0084] If the rotational speed of the motor 300 exceeds a threshold, the control unit 120 terminates normal torque control and starts executing fail-safe control.

[0085] Fail-safe control may also be ASC control, as shown on the left side of Figure 4, in which one of the upper arm switching element group 22 and the lower arm switching element group 23 is turned on in all phases, and the other is turned off in all phases.

[0086] By employing ASC control, the back electromotive force generated in the motor can be recirculated to prevent overcharging of the power supply, thereby preventing failure of switching elements and the power supply.

[0087] Furthermore, the above fail-safe control may also be SD control, which turns off all phases of both the upper arm switching element group 22 and the lower arm switching element group 23, as shown in the right-hand portion of Figure 4.

[0088] By employing SD control, failures of switching elements and power supplies can be prevented.

[0089] When a motor rotates at high speed, it overheats.

[0090] When the motor's rotational speed is reduced by ASC control, a sudden braking torque is applied to the motor.

[0091] To prevent this, in this invention, the fail-safe control is terminated when the engine speed returns to a low speed.

[0092] According to the inverter device of the present invention, failures of switching elements and power supplies can be prevented by performing fail-safe control (ASC control or SD control) when the motor rotates at high speed.

[0093] It goes without saying that, within the scope of the present invention, it is possible to freely combine, modify, or omit each component in the embodiments.

[0094] Although the present invention has been described in detail above, the above description is in all respects illustrative and the present invention is not limited thereto.

[0095] Numerous modifications not shown in the illustrations should be interpreted as being conceivable without departing from the scope of the present invention. [Industrial applicability]

[0096] The inverter device and motor device equipped therewith according to the present invention can be widely applied to fields such as motors for electric vehicles (EVs). [Explanation of symbols]

[0097] 1. Motor device 10 Inverter device 20 DC power supply 30 motors 100 Inverter Circuit 110 Drive Circuit 120 Control Unit 130 Rotational Speed ​​Calculation Unit 13 High-voltage battery 14 Low-voltage power supply 22 Upper arm side switching element group 23 Lower arm side switching element group 5 diodes

Claims

1. An inverter device that converts power from a power source to drive a motor, An inverter circuit having a switching element, A drive circuit that switches the switching element on and off, A control unit that controls the drive circuit, The control unit has a rotation speed calculation unit that calculates the minimum rotation speed and the maximum rotation speed of the motor based on the power supply voltage. The control unit terminates torque control and performs fail-safe control, and if the motor's rotational speed is less than the minimum rotational speed, it terminates the fail-safe control, and after terminating the fail-safe control, it resumes torque control. The rotation speed calculation unit calculates the maximum rotation speed and the minimum rotation speed based on the power supply voltage, correction coefficient, and offset value, and sets the correction coefficient and the offset value so that the back electromotive force generated in the motor is smaller than the power supply voltage. An inverter device characterized by the following features.

2. An inverter device according to claim 1, The control unit executes the fail-safe control when the rotational speed of the motor is greater than the maximum rotational speed. An inverter device characterized by the following features.

3. An inverter device according to claim 1, The correction coefficient and the offset value are fixed values ​​that differ depending on the type of motor and power supply. An inverter device characterized by the following features.

4. An inverter device according to claim 1, 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 switching element group and the lower arm side switching element group on and off. An inverter device characterized by the following features.

5. An inverter device according to claim 4, The fail-safe control is an ASC control that turns on all phases of one of the upper arm-side switching element group and the lower arm-side switching element group, and turns off all phases of the other. An inverter device characterized by the following features.

6. An inverter device according to claim 4, The fail-safe control is SD control that turns off all phases of both the upper arm side switching element group and the lower arm side switching element group. An inverter device characterized by the following features.

7. A motor device comprising an inverter device according to any one of claims 1 to 6.

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