Control device

Abstract

To provide a technique for appropriately reducing vibration or sound caused by a relation between a carrier frequency used for PWM control of an inverter and a resonant frequency of circular ring vibration of a motor.SOLUTION: A control device controls an inverter by which DC power is converted into AC power and supplied to a motor. In a case where a difference between a carrier frequency used for PWM (Pulse Width Modulation) control of the inverter and a resonant frequency of circular ring 0-order vibration of the motor is smaller than a predetermined threshold, when an element temperature of the inverter is equal to or higher than a predetermined temperature or a torque variation amount of the motor is within a predetermined range, the control device sets the carrier frequency to a first frequency lower than the resonant frequency in such a manner that the difference between the carrier frequency and the resonant frequency becomes larger than the predetermined threshold. When the element temperature is lower than the predetermined temperature and the torque variation amount is out of the predetermined range, the control device sets the carrier frequency to a second frequency higher than the resonant frequency in such a manner that the difference between the carrier frequency and the resonant frequency becomes larger than the predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a control device. [Background technology]

[0002] Patent Document 1 discloses a motor that is driven by a current flowing through an inverter PWM control. It is known that this type of motor generates vibrations and noise when the resonant frequency of the circular vibration of the stator approaches the carrier frequency used for the inverter PWM control.

[0003] In the motor of Patent Document 1, a gap is formed in the stator core to reduce the rigidity of the stator and lower the resonant frequency of the circular vibration of the stator. This moves the resonant frequency of the circular vibration of the stator away from the carrier frequency used for PWM control, suppressing the generation of vibration and noise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-24366 A Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the vibration and sound are suppressed by adjusting the resonance frequency by changing the design of the stator that constitutes the motor, so the degree of freedom in motor design and material selection is low. This specification provides a technology that appropriately reduces vibration and sound that may occur due to the relationship between the carrier frequency used for PWM control of the inverter and the resonance frequency of the circular vibration of the motor. [Means for solving the problem]

[0006] This specification discloses a control device for an inverter that converts DC power into AC power and supplies it to a motor. When a difference between a carrier frequency used for PWM (Pulse Width Modulation) control of the inverter and a resonance frequency of a circular zero-order vibration of the motor is smaller than a predetermined threshold, the control device sets the carrier frequency to a first frequency lower than the resonance frequency so that the difference between the carrier frequency and the resonance frequency becomes larger than the predetermined threshold when an element temperature of the inverter is equal to or higher than a predetermined temperature or a torque fluctuation amount of the motor is within a predetermined range, and sets the carrier frequency to a second frequency higher than the resonance frequency so that the difference between the carrier frequency and the resonance frequency becomes larger than the predetermined threshold when the element temperature is lower than the predetermined temperature and the torque fluctuation amount is outside the predetermined range.

[0007] As described above, when the difference between the carrier frequency used in the PWM control and the resonance frequency of the circular zero-order vibration of the motor becomes smaller than a predetermined threshold, vibrations and noise may occur. In the above-mentioned control device, in such a case, the carrier frequency is set as follows according to the situation. That is, when the element temperature of the inverter is equal to or higher than a predetermined temperature or the torque fluctuation amount of the motor is within a predetermined range, the control device sets the carrier frequency to a value (first frequency) lower than the resonance frequency so that the difference between the carrier frequency and the resonance frequency becomes larger than a predetermined threshold. When the carrier frequency is lowered, the amount of heat generated by the elements constituting the inverter decreases. When the element temperature is equal to or higher than a predetermined temperature, the control device sets the carrier frequency to a first frequency on the low frequency side in order to prevent the elements from becoming excessively hot. In addition, the control device sets the carrier frequency to the first frequency on the low frequency side even when the torque fluctuation amount of the motor is within a predetermined range. When the torque fluctuation amount increases, vibrations and noise may occur, but when the vibrations and sounds caused by the torque fluctuation amount are within an allowable range (i.e., within a predetermined range), the control device sets the carrier frequency to the first frequency. It is known that lowering the carrier frequency in an inverter can cause noise, but since the vibrations and noise caused by torque fluctuations are small, lowering the carrier frequency has little effect on the overall vibrations and noise.

[0008] On the other hand, when the element temperature of the inverter is below a predetermined temperature and the torque fluctuation of the motor is outside a predetermined range, the control device sets the carrier frequency to a value (second frequency) higher than the resonant frequency so that the difference between the carrier frequency and the resonant frequency is greater than a predetermined threshold. Increasing the carrier frequency increases the amount of heat generated by the elements that make up the inverter. However, since the element temperature is below the predetermined temperature, the effect on the elements is small even if the amount of heat generated by the elements increases. Also, when the torque fluctuation is outside the predetermined range, vibrations and noise caused by the torque fluctuation may become large. In such a case, the control device can reduce the overall vibrations and noise by increasing the carrier frequency.

[0009] As described above, according to the above control device, when the difference between the carrier frequency and the resonant frequency is smaller than a predetermined threshold value (i.e., when vibrations or noise may occur), the carrier frequency used for PWM control is shifted to a higher or lower frequency depending on the element temperature of the inverter and the amount of torque fluctuation of the motor, thereby reducing the thermal effects on the elements that make up the inverter and the effects on fuel efficiency, while reducing the vibrations and noise caused by the relationship between the carrier frequency and the resonant frequency without changing the design of the motor, etc. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit diagram of an inverter device according to an embodiment. [Diagram 2] 4 is a flowchart showing a process executed by a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Example) 1, the inverter device 1 includes a battery 2, a relay 3, a capacitor 4, a converter 5, a capacitor 6, an inverter 7, a motor 8, and a control device 10. The inverter device 1 is mounted on, for example, a hybrid vehicle or an electric vehicle.

[0012] The battery 2 is connected to a converter 5 via a relay 3. The converter 5 boosts the voltage of the battery 2 (e.g., 300 V) to a voltage (e.g., 600 V) suitable for driving a motor 8 and supplies the boosted voltage to an inverter 7. The inverter 7 converts the DC power supplied from the converter 5 into AC power and supplies the AC power to the motor 8. The motor 8 is a three-phase AC motor, and is driven by the AC power supplied from the inverter 7 to rotate the drive shaft of the wheels.

[0013] Capacitor 4 is provided between battery 2 and converter 5, and smoothes the input / output voltages between battery 2 and converter 5. Capacitor 6 is provided between converter 5 and inverter 7, and smoothes the input / output voltages between converter 5 and inverter 7.

[0014] The converter 5 and the inverter 7 are each configured with a plurality of switching elements (not shown), and the control device 10 controls the driving of the converter 5 and the inverter 7 by controlling the on / off of these switching elements.

[0015] The inverter device 1 further includes a temperature sensor 30, a rotation speed sensor 32, and a torque sensor 34. The temperature sensor 30 detects the temperature of each switching element constituting the inverter 7. The rotation speed sensor 32 detects the rotation speed of the motor 8. The torque sensor 34 detects fluctuations in the torque of the motor. The outputs of the temperature sensor 30, the rotation speed sensor 32, and the torque sensor 34 are input to the control device 10.

[0016] The control device 10 has a function of controlling the operation of each element constituting the inverter device 1 as a whole, but in this embodiment, the operation of the inverter 7 will be particularly described. As shown in FIG. 1, the control device 10 has a storage unit 40, a voltage command calculation unit 42, a switching signal generation unit 44, and a carrier frequency setting unit 46.

[0017] The storage unit 40 stores a carrier frequency map 50, resonance frequency information 52, and torque fluctuation information 54. The carrier frequency map 50 is a map in which values ​​of carrier frequencies of PWM control corresponding to the torque and rotation speed of the motor 8 are described. The resonance frequency information 52 is information indicating the resonance frequency of the circular zeroth vibration of the stator of the motor 8. The torque fluctuation information 54 is information that specifies the range of torque fluctuation in which vibrations and sounds corresponding to the torque fluctuation are tolerable.

[0018] The voltage command calculation unit 42 has a function of calculating a voltage command for the inverter 7 in order to convert the AC power from the battery 2 into DC power by the operation of the inverter 7. The switching signal generation unit 44 has a function of generating a drive signal for each switching element constituting the inverter 7 based on the voltage command input from the voltage command calculation unit 42.

[0019] The control device 10 operates the inverter 7 by selecting a control mode for the inverter 7 from among a plurality of modes based on the torque, rotation speed, and calculated voltage command of the motor 8. For example, the control device 10 switches between PWM control and square wave control as the control mode when driving the inverter 7. The carrier frequency setting unit 46 has a function of setting a carrier frequency used when generating a drive signal for each switching element in PWM control.

[0020] In the above-mentioned inverter device 1, a process for suppressing vibrations and noises that may occur due to the relationship between the carrier frequency used for PWM control of the inverter 7 and the resonance frequency of the circular zero-order vibration of the motor 8 will be described. When the vehicle starts traveling, the control device 10 of this embodiment executes the process shown in FIG.

[0021] 2, the control device 10 determines whether the control mode for driving the motor 8 is PWM control or not based on the information input from each unit. The control device 10 determines whether the control mode for the motor 8 is PWM control or not based on the torque of the motor 8 input from the torque sensor 34, the rotation speed of the motor 8 input from the rotation speed sensor 32, and the voltage command input from the voltage command calculation unit. When the control device 10 determines that the control mode of the motor 8 is not PWM control (NO in S12), it ends the series of processes.

[0022] When the control mode of the motor 8 is PWM control (YES in S12), the control device 10 determines the carrier frequency used for the PWM control in S14. The control device 10 refers to a carrier frequency map stored in the storage unit and determines the carrier frequency used for the PWM control based on the input torque and rotation speed.

[0023] Next, in S16, the control device determines whether the difference between the carrier frequency determined in S14 and the resonant frequency of the circular zero-order vibration of the motor 8 is smaller than a predetermined threshold. The control device compares the carrier frequency with the resonant frequency based on the resonant frequency information stored in the storage unit. If the difference between them is larger than the threshold (NO in S16), the control device 10 ends the series of processes.

[0024] If the difference between the carrier frequency and the resonant frequency is smaller than the threshold value (YES in S16), the control device 10 determines in S18 whether the element temperature of the inverter 7 is equal to or higher than a predetermined temperature. If the element temperature is equal to or higher than a predetermined temperature based on the temperature of each switching element input from the temperature sensor 30 (YES in S18), the control device 10 proceeds to S22.

[0025] On the other hand, if the element temperature is lower than the predetermined temperature (NO in S18), the control device 10 determines in S20 whether the torque fluctuation amount of the motor 8 is within a predetermined range. If the torque fluctuation amount is within the predetermined range based on the torque fluctuation amount input from the torque sensor 34 (YES in S20), the control device 10 proceeds to S22.

[0026] If the element temperature is equal to or higher than a predetermined temperature (YES in S18) or if the torque fluctuation amount is within a predetermined range (YES in S20), the control device 10 sets the carrier frequency used for PWM control to a first frequency in S22. The first frequency is a frequency that is lower than the resonance frequency and is set so that the difference between the first frequency and the resonance frequency is greater than a predetermined threshold. That is, in S22, the control device 10 shifts the carrier frequency to the lower frequency side so that the difference between the first frequency and the resonance frequency is greater than the predetermined threshold.

[0027] On the other hand, when the element temperature is below the predetermined temperature (NO in S18) and the torque fluctuation amount is outside the predetermined range (NO in S20), the control device 10 sets the carrier frequency used for PWM control to a second frequency in S24. The second frequency is a frequency that is higher than the resonant frequency and is set so that the difference from the resonant frequency is greater than a predetermined threshold. That is, in S24, the control device 10 shifts the carrier frequency to the higher frequency side so that the difference from the resonant frequency is greater than the predetermined threshold. After executing S22 or S24, the control device 10 ends the series of processes.

[0028] As described above, in the inverter device 1 of this embodiment, when the difference between the carrier frequency used for PWM control of the inverter 7 and the resonant frequency of the circular zeroth vibration of the motor 8 becomes smaller than a predetermined threshold (YES in S16), the control device 10 sets the carrier frequency as follows depending on the situation. That is, when the element temperature of the inverter 7 is equal to or higher than a predetermined temperature (YES in S18) or the torque fluctuation amount of the motor 8 is within a predetermined range (YES in S20), the control device 10 sets the carrier frequency to a value (first frequency) lower than the resonant frequency so that the difference between the carrier frequency and the resonant frequency becomes larger than a predetermined threshold (S22).

[0029] When the carrier frequency is lowered, the amount of heat generated by the elements constituting the inverter 7 is reduced. When the element temperature is equal to or higher than a predetermined temperature, the control device 10 sets the carrier frequency to a first frequency on the low frequency side in order to prevent the elements from becoming excessively hot. The control device 10 also sets the carrier frequency to the first frequency on the low frequency side when the torque fluctuation amount of the motor 8 is within a predetermined range. When the torque fluctuation amount increases, vibrations and noise may occur, but since the vibrations and noise caused by the torque fluctuation amount are within an allowable range (i.e., within a predetermined range), lowering the carrier frequency has little effect on the overall vibrations and noise.

[0030] On the other hand, when the element temperature of the inverter 7 is below a predetermined temperature (NO in S18) and the torque fluctuation amount of the motor 8 is outside a predetermined range (NO in S20), the control device 10 sets the carrier frequency to a value higher than the resonant frequency (a second frequency) so that the difference between the carrier frequency and the resonant frequency is greater than a predetermined threshold value (S24).

[0031] Increasing the carrier frequency increases the amount of heat generated by the elements constituting the inverter 7. However, since the element temperature is below a predetermined temperature, the increase in the amount of heat generated by the elements has little effect on the elements. Also, when the torque fluctuation amount is outside a predetermined range, the vibration and noise caused by the torque fluctuation amount may become large. In such a case, the control device 10 can reduce the overall vibration and noise by increasing the carrier frequency.

[0032] As described above, according to the control device 10 of this embodiment, when the difference between the carrier frequency and the resonant frequency is smaller than a predetermined threshold (i.e., when vibration or sound may occur), the carrier frequency used for PWM control is shifted to a higher or lower frequency depending on the element temperature of the inverter 7 and the torque fluctuation amount of the motor 8, thereby making it possible to reduce vibration and sound caused by the relationship between the carrier frequency and the resonant frequency without changing the design of the motor 8 while suppressing the thermal effect on the elements constituting the inverter 7 and the effect on fuel consumption. Furthermore, in the inverter device 1 of this embodiment, when vibration or sound may occur due to the relationship between the carrier frequency and the resonant frequency, the switching loss can be reduced by limiting the conditions for shifting the carrier frequency to the higher frequency side. [Explanation of symbols]

[0033] 1: inverter device, 2: battery, 3: relay, 4: capacitor, 5: converter, 6: capacitor, 7: inverter, 8: motor, 10: control device, 30: temperature sensor, 32: rotation speed sensor, 34: torque sensor

Claims

[Claim 1] A control device for an inverter that converts DC power into AC power and supplies the AC power to a motor, When a difference between a carrier frequency used for PWM (Pulse Width Modulation) control of the inverter and a resonance frequency of a circular zero-order vibration of the motor is smaller than a predetermined threshold value, the control device when an element temperature of the inverter is equal to or higher than a predetermined temperature or a torque fluctuation amount of the motor is within a predetermined range, the carrier frequency is set to a first frequency that is lower than the resonance frequency so that a difference between the carrier frequency and the resonance frequency is greater than the predetermined threshold value; when the element temperature is lower than the predetermined temperature and the torque fluctuation amount is outside the predetermined range, the carrier frequency is set to a second frequency higher than the resonance frequency so that a difference between the carrier frequency and the resonance frequency becomes larger than the predetermined threshold value. Control device.

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