Drive device

Abstract

The present invention provides a driving device for suppressing torque fluctuations that may occur when switching from a switch pattern that suppresses LC resonance in a resonance region to a rectangular wave pulse pattern in rectangular wave control. When the voltage applied to the converter is above a threshold voltage, a first rectangular wave control mode using a rectangular wave pulse pattern is used. On the other hand, when the voltage applied to the converter is less than the threshold voltage, a second rectangular wave control mode is used, the second rectangular wave control mode being a mode in which a rectangular wave pulse pattern is used when the rotation speed of the motor is above a first specified rotation speed greater than the first resonance region and a first switch pattern that suppresses LC resonance in the first resonance region is used when the rotation speed of the motor is less than the first specified rotation speed.

Description

Technical Field

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

[0002] Conventionally, as such a driving device, the following driving device has been proposed: when switching the switching element of the inverter driving the motor is switched between pulse width modulation control and rectangular wave control by a modulation rate, when switching control is performed by rectangular wave control, when the rotation speed of the motor is greater than or equal to a first predetermined rotation speed smaller than the first resonance region, switching control is performed using a first switching pattern of a switching pattern that suppresses resonance in the first resonance region, and when the rotation speed of the motor is less than the first predetermined rotation speed, switching control is performed using a second switching pattern of a switching pattern that suppresses resonance in a second resonance region smaller than the first predetermined rotation speed (for example, refer to Patent Document 1). Here, the first switching pattern is a pattern in which one or more gaps are formed in a region where a rectangular wave pulse exists when a pulse pattern in which the first half cycle or the second half cycle of one cycle becomes a rectangular wave pulse is set as a rectangular wave pulse pattern, and a short pulse of the same width as the gap is formed in a region where a rectangular wave pulse does not exist, and the pattern is a pattern for suppressing LC resonance in the first resonance region. The second switching pattern is a pattern in which the number of gaps and the number of short pulses are greater than the first switching pattern, and the pattern is a pattern for suppressing LC resonance in the second resonance region.

[0003] In addition, it has been proposed that when switching from the first switching pattern to the rectangular wave pulse pattern, the width of the gap or the short pulse of the first switching pattern is gradually reduced (for example, refer to Patent Document 2).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-146281

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-145795 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the above-mentioned driving device, when the switching pattern for suppressing LC resonance in the resonance area is switched to the rectangular wave pulse pattern in the rectangular wave control, even if the width of the gap or short pulse of the switching pattern is gradually reduced, the width of the gap or short pulse cannot be made less than the dead time, so there is a situation where a voltage step corresponding to the width of the dead time is generated and a torque change occurs.

[0010] The main purpose of the electric vehicle control device of the present invention is to suppress torque fluctuations that may occur when switching from a switching pattern that suppresses LC resonance in a resonance region to a rectangular wave pulse pattern in rectangular wave control.

[0011] Means for solving problems

[0012] In order to achieve the above-mentioned main object, the driving device of the present invention adopts the following means.

[0013] The drive device of the present invention comprises a power storage device, a motor, a converter for driving the motor, a boost converter installed between the power storage device and the converter, and a control device for switching a switching element of the converter and controlling the boost converter, wherein:

[0014] The control device controls the switching of the switching element of the converter,

[0015] When the boost converter is controlled so that the voltage applied to the inverter becomes equal to or higher than a threshold voltage based on the current from the power storage device, the pulse width modulation control mode and the first rectangular wave control mode are switched according to the modulation degree,

[0016] When the boost converter is controlled so that the voltage applied to the inverter is less than the threshold voltage, the pulse width modulation control mode and the second rectangular wave control mode are switched according to the modulation degree,

[0017] The first rectangular wave control mode is a mode using a rectangular wave pulse pattern in which the first half cycle or the second half cycle of one cycle becomes a rectangular wave pulse.

[0018] The second rectangular wave control mode is a mode in which the rectangular wave pulse pattern is used when the rotation speed of the motor is greater than a first specified rotation speed greater than the first resonance area, and a first switching pattern is used when the rotation speed of the motor is less than the first specified rotation speed, and the first switching pattern is a pattern in which one or more gaps are formed in an area where a rectangular wave pulse exists in the rectangular wave pulse pattern and a short pulse with the same width as the gap is formed at the same timing as the gap in an area where the rectangular wave pulse does not exist, and the LC resonance in the first resonance area is suppressed.

[0019] In the driving device of the present invention, there are provided a power storage device, a motor, a converter for driving the motor, a boost converter installed between the power storage device and the converter, and a control device for switching the switch element of the converter and controlling the boost converter. The control device switches the pulse width modulation control mode and the first rectangular wave control mode according to the modulation degree when the boost converter is controlled in such a way that the voltage acting on the converter becomes greater than the threshold voltage based on the current from the power storage device. The first rectangular wave control mode is a mode in which a rectangular wave pulse pattern is used in which the first half cycle or the second half cycle of one cycle becomes a rectangular wave pulse. In addition, when the control device is controlling the boost converter in such a way that the voltage acting on the converter is less than the threshold voltage, the pulse width modulation control mode and the second rectangular wave control mode are switched according to the modulation degree. The second rectangular wave control mode is a mode in which a rectangular wave pulse pattern is used when the rotation speed of the motor is greater than or equal to a first predetermined rotation speed greater than the first resonance region, and a first switching pattern is used when the rotation speed of the motor is less than the first predetermined rotation speed. The first switching pattern is a pattern in which one or more gaps are formed in the region where the rectangular wave pulse exists in the rectangular wave pulse pattern, and a short pulse with the same width as the gap is formed at the same timing as the gap in the region where the rectangular wave pulse does not exist, and the LC resonance in the first resonance region is suppressed. The current from the power storage device is calculated as a value obtained by multiplying the current (load current) flowing to the converter by the transfer function, and the transfer function can be obtained as the product of the transfer function of the circuit and the transfer function of the boost converter control. The transfer function of the boost converter control can adjust the characteristics by adjusting the gain (duty cycle) of the boost converter control. Therefore, if the gain is adjusted in such a way that the cutoff frequency of the transfer function of the boost converter control is smaller than the LC resonance frequency, the LC resonance can be avoided. Therefore, as the threshold voltage, a voltage greater than the voltage applied to the converter when the gain is adjusted in such a way that the cutoff frequency of the transfer function of the boost converter control is smaller than the LC resonance frequency can be used. Therefore, when the boost converter is controlled in such a way that the voltage acting on the converter becomes greater than the threshold voltage, even if the rectangular wave pulse pattern is used, the LC resonance in the first resonance region can be avoided. In addition, when the boost converter is controlled in such a way that the voltage acting on the converter becomes greater than the threshold voltage, the rectangular wave pulse pattern is used instead of the first switch pattern, so that the switching from the first switch pattern to the rectangular wave pulse pattern does not occur. As a result, the torque fluctuation that may occur when switching from the first switch pattern to the rectangular wave pulse pattern can be avoided. It should be noted that when the boost converter is controlled in such a way that the voltage acting on the converter is less than the threshold voltage, since the first switch pattern is used, the torque fluctuation occurs when switching from the first switch pattern to the rectangular wave pulse pattern, but the LC resonance in the first resonance region can be suppressed.As a result, as a whole, it is possible to suppress the torque fluctuation that may occur when switching from the first switching pattern that suppresses LC resonance in the resonance region to the rectangular wave pulse pattern in the rectangular wave control. In particular, the switching from the first switching pattern to the rectangular wave pulse pattern is only when the voltage acting on the converter is less than the threshold voltage based on the current from the power storage device, so it is only when the voltage step corresponding to the dead time width is small, and the torque fluctuation can be reduced. It should be noted that the threshold voltage is different depending on the current (especially the discharge current and the charging current) input and output to the power storage device, and is therefore set to a voltage based on the current from the power storage battery.

[0020] In the driving device of the present invention, the threshold voltage may be a voltage predetermined relative to the current from the power storage device as a voltage at which the duty ratio does not become 100% due to the amplitude of the feedback control when the boost converter is controlled by the duty ratio control accompanied by feedback control. When the duty ratio is 100%, that is, when the voltage is not boosted by the boost converter at all, the transfer function of the boost converter control becomes a value of 1, and the transfer function depends only on the transfer function of the circuit. Therefore, if the frequency of the duty ratio becoming 100% due to the amplitude of the feedback control is high, the frequency of the transfer function depending on the transfer function of the circuit becomes high, and LC resonance occurs in the resonance region. Therefore, by making the duty ratio not become 100% due to the amplitude of the feedback control, the transfer function of the boost converter control can be reflected in the transfer function, and the occurrence of LC resonance in the resonance region can be avoided. In this case, the control device may use the duty ratio at which the duty ratio does not become 100% due to the amplitude of the feedback control as the threshold voltage for control. That is, the voltage applied to the converter may be controlled by using the duty ratio instead of the voltage applied to the converter.

[0021] In addition, in the driving device of the present invention, it may be that when the control device is controlling the boost converter in such a manner that the voltage applied to the converter becomes higher than the threshold voltage, the control device switches the pulse width modulation control mode and the first rectangular wave control mode through an overmodulation area according to the modulation degree, and when the control device is controlling the boost converter in such a manner that the voltage applied to the converter becomes lower than the threshold voltage, the control device switches the pulse width modulation control mode and the second rectangular wave control mode through an intermediate area in which the width of the gap and the short pulse in the first switching pattern are changed according to the modulation degree.

[0022] In the drive device of the present invention, the second rectangular wave control mode may be a mode in which a second switching pattern is used when the rotation speed of the motor is less than a second predetermined rotation speed which is smaller than the first predetermined rotation speed, the second switching pattern being a pattern having a larger number of gaps and a larger number of short pulses than the first switching pattern and suppressing LC resonance in a second resonance region included in a rotation speed range smaller than the second predetermined rotation speed. In this way, the LC resonance in the second resonance region can also be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram showing the structure of an electric vehicle equipped with a drive device as one embodiment of the present invention.

[0024] Figure 2 : is a flowchart showing an example of the control mode setting process executed by the electronic control unit.

[0025] Figure 3 It is an explanatory diagram showing an example of a map for setting a threshold voltage.

[0026] Figure 4 1 is an explanatory diagram showing an example of the relationship between the rotation speed Nm, torque Tm and control mode of the electric motor when the second rectangular wave control mode is executed regardless of the high voltage system voltage VH.

[0027] Figure 5 : is a flowchart showing an example of rectangular wave control mode pulse pattern setting processing executed by the electronic control unit.

[0028] Figure 6 It is an explanatory diagram showing an example of a rectangular wave pulse pattern, a first switching pattern, and a second switching pattern.

[0029] Figure 7 This is a flowchart showing an example of the intermediate control mode pulse pattern setting process executed by the electronic control unit.

[0030] Figure 8 It is an explanatory diagram showing an example of an intermediate rectangular wave pulse pattern, an intermediate first switching pattern, and an intermediate second switching pattern.

[0031] Fig. 9 This is an explanatory diagram showing an example of a map for setting a gap width.

[0032] Fig.10 1 is an explanatory diagram showing an example of the relationship between the motor rotation speed Nm and the gap and short pulse width p of the first switching pattern.

[0033] Fig.11 It is an explanatory diagram showing an example of the relationship between the high voltage system voltage VH, the rotation speed Nm of the motor, the torque Tm, and the control mode.

[0034] Fig.12 This is an explanatory diagram showing an example of a Bode diagram when the transfer function C(s) is changed.

[0035] Fig.13 This is an explanatory diagram showing an example of a time change of an actual duty ratio when the duty ratio as a command value is slightly smaller than 100% and a diagram in which a part thereof is enlarged. DETAILED DESCRIPTION

[0036] Next, the mode for carrying out the present invention will be described using examples. Figure 1 1 is a schematic structural diagram showing the structure of an electric vehicle 20 equipped with a drive device as an embodiment of the present invention. As shown in the figure, the electric vehicle 20 of the embodiment includes a motor 32, an inverter 34, a battery 36 as a power source, a boost converter 40, and an electronic control unit 50.

[0037] The electric motor 32 is configured as a synchronous generator motor and includes a rotor having permanent magnets embedded therein and a stator having three-phase coils wound thereon. The rotor of the electric motor 32 is connected to a drive shaft 26 connected to drive wheels 22a and 22b via a differential gear 24 .

[0038] The inverter 34 is used to drive the motor 32. The inverter 34 is connected to the boost converter 40 via the high-voltage side power line 42, and has six transistors T11 to T16 as switching elements and six diodes D11 to D16 connected in parallel with each of the six transistors T11 to T16. The transistors T11 to T16 are arranged in pairs of two each so as to become the source side and the drain side with respect to the positive side line and the negative side line of the high-voltage side power line 42. In addition, each of the three-phase coils (U-phase, V-phase, and W-phase coils) of the motor 32 is connected to each of the connection points between the paired transistors T11 to T16. Therefore, when a voltage is applied to the inverter 34, the ratio of the on-time of the paired transistors T11 to T16 is adjusted by the electronic control unit 50, and a rotating magnetic field is formed in the three-phase coils, and the motor 32 is driven to rotate. The capacitor 46 for smoothing is installed on the positive side line and the negative side line of the high-voltage side power line 42.

[0039] Battery 36 is configured as, for example, a lithium ion secondary battery or a nickel-metal hydride secondary battery, and is connected to boost converter 40 via low voltage power line 44. Low voltage power line 44 has capacitors 48 for smoothing installed on the positive and negative lines.

[0040] The boost converter 40 is connected to the high-voltage power line 42 and the low-voltage power line 44, and includes two transistors T31 and T32, two diodes D31 and D32 connected in parallel to the two transistors T31 and T32, and a reactor L. The transistor T31 is connected to the positive electrode side line of the high-voltage power line 42. The transistor T32 is connected to the transistor T31 and the high-voltage power line 42 and the negative electrode side line of the low-voltage power line 44. The reactor L is connected to the connection point between the transistors T31 and T32 and the positive electrode side line of the low-voltage power line 44. By adjusting the ratio of the on-time of the transistors T31 and T32 by the electronic control unit 50, the boost converter 40 boosts the power of the low-voltage power line 44 and supplies it to the high-voltage power line 42, or steps down the power of the high-voltage power line 42 and supplies it to the low-voltage power line 44.

[0041] The electronic control unit 50 is configured as a microprocessor centered around a CPU 52, and in addition to the CPU 52, it also includes a ROM 54 for storing a processing program, a RAM 56 for temporarily storing data, and an input / output port. Signals from various sensors are input to the electronic control unit 50 via the input port. As signals input to the electronic control unit 50, for example, the rotation position θm from a rotation position detection sensor (e.g., a rotary transformer) 32a for detecting the rotation position of the rotor of the motor 32, and the phase currents Iu and Iv from current sensors 32u and 32v for detecting the phase currents of each phase of the motor 32 can be cited. In addition, the voltage (battery voltage) Vb from a voltage sensor 36a installed between the terminals of the battery 36 and the current (battery current) Ib from a current sensor 36b installed at the output terminal of the battery 36 can be cited. Furthermore, the current IL from the current sensor 40a installed in series with the reactor L, the voltage (high voltage system voltage) VH of the capacitor 46 (high voltage side power line 42) from the voltage sensor 46a installed between the terminals of the capacitor 46, and the voltage (low voltage system voltage) VL of the capacitor 48 (low voltage side power line 44) from the voltage sensor 48a installed between the terminals of the capacitor 48 can also be cited. In addition, the ignition signal from the ignition switch 60 and the shift position SP from the shift position sensor 62 that detects the operation position of the shift lever 61 can also be cited. In addition, the accelerator opening Acc from the accelerator pedal position sensor 64 that detects the amount of depression of the accelerator pedal 63, the brake pedal position BP from the brake pedal position sensor 66 that detects the amount of depression of the brake pedal 65, and the vehicle speed V from the vehicle speed sensor 68 can also be cited. The electronic control unit 50 calculates the rotation speed Nm of the motor 32 based on the rotation position θm from the rotation position detection sensor 32a, and calculates the power storage ratio SOC of the battery 36 based on the integrated value of the current Ib of the battery 36 from the current sensor 36b. Here, the power storage ratio SOC is the ratio of the power storage amount (the amount of power that can be discharged) of the battery 36 to the total capacity of the battery 36.

[0042] Various control signals are outputted from the electronic control unit 50 via the output port. Examples of the signals outputted from the electronic control unit 50 include switching control signals to the transistors T11 to T16 of the inverter 34 and switching control signals to the transistors T31 and T32 of the boost converter 40.

[0043] In the electric vehicle 20 of the embodiment thus constructed, the electronic control unit 50 performs the following driving control. In the driving control, the required torque Td* required for the drive shaft 26 is set based on the accelerator opening Acc and the vehicle speed V, and the set required torque Td* is set as the torque command Tm* of the motor 32, and the switching control of the transistors T11 to T16 of the converter 34 is performed in a manner such that the motor 32 is driven by the torque command Tm*. In addition, in the driving control, the target voltage VH* of the high-voltage side power line 42 is set in a manner such that the motor 32 can be driven by the torque command Tm*, and the switching control of the transistors T31 and T32 of the boost converter 40 is performed in a manner such that the voltage VH of the high-voltage side power line 42 becomes the target voltage VH*.

[0044] Next, the control in the control device mounted on the electric vehicle 20 of the embodiment, particularly the switching control of the switching elements of the inverter 34 will be described. Figure 2 2 is a flowchart showing an example of the control mode setting process executed by the electronic control unit 50. This process is repeatedly executed at predetermined time intervals.

[0045] When the control mode setting process is executed, the electronic control unit 50 first performs a process of inputting the high voltage system voltage VH from the voltage sensor 46a, the battery current Ib from the current sensor 36b, the rotation speed Nm of the motor 32, the modulation degree M, etc. (step S100). Regarding the rotation speed Nm of the motor 32, a value calculated based on the rotation position θm from the rotation position detection sensor 32a can be input. Regarding the modulation degree M, it can be obtained by dividing the square root of the sum of the squares of the d-axis component Vd and the q-axis component Vq in the voltage vector by the voltage VH of the high voltage side power line 42.

[0046] Next, the input rotation speed Nm of the motor 32 is compared with the threshold value Nref1 and the threshold value Nref2 (step S110). The threshold values ​​Nref1 and Nref2 will be described later. When the rotation speed Nm of the motor 32 is less than the threshold value Nref1, the threshold value Mref2 is set to a value Mset1 (step S120). When the rotation speed Nm of the motor 32 is greater than the threshold value Nref1 and less than the threshold value Nref2, the threshold value Mref2 is set to a value Mset2 (step S130). When the rotation speed Nm of the motor 32 is greater than the threshold value Nref2, the threshold value Mset3 is set to the threshold value Mref2 (step S140). The threshold value Mref2, the value Mset1, the value Mset2, and the value Mset3 will be described later.

[0047] Next, the modulation index M is compared with the threshold value Mref1 (step S150). When it is determined that the modulation index M is less than the threshold value Mref1, the PWM control mode is set (step S160). The PWM control mode is a control mode for controlling the converter 34 in such a way that a simulated three-phase AC voltage is applied (supplied) to the motor 32. When it is determined that the modulation index M is greater than the threshold value Mref1, the threshold voltage Vref is set based on the battery current Ib (step S170), and it is determined whether the high voltage system voltage VH is greater than the threshold voltage Vref (step S180). The threshold voltage Vref is predetermined as a voltage at which the duty ratio of the voltage (high voltage system voltage VH) acting on the converter 34 does not become 100% (the upper arm (transistor T31) does not become turned on) due to the amplitude of the feedback control amount in the boost control of the boost converter 40. In the embodiment, the threshold voltage Vref is set by "preliminarily finding the relationship between the battery current Ib and the threshold voltage Vref through experiments or the like and storing it as a map for setting the threshold voltage, and deriving the corresponding threshold voltage Vref from the map when the battery current Ib is given." Further details on the threshold voltage Vref will be described later.

[0048] When it is determined in step S180 that the high voltage system voltage VH is less than the threshold voltage Vref, it is determined whether the modulation degree M is less than the threshold value Mref2 (step S190). When it is determined that the modulation degree M is less than the threshold value Mref2, the intermediate control mode is set (step S200), and when it is determined that the modulation degree M is greater than the threshold value Mref2, the second rectangular wave control mode is set (step S210), and the present process is terminated. The threshold value Mref1 is the modulation degree for distinguishing between the pulse width modulation control mode (hereinafter referred to as the PWM control mode) and the intermediate control mode, and the threshold value Mref2 is the modulation degree for distinguishing between the intermediate control mode and the second rectangular wave control mode. The second rectangular wave control mode is a control mode for controlling the converter 34 in such a manner that a rectangular wave voltage is applied to the motor 32. The intermediate control mode is a control performed when switching between the PWM control mode and the second rectangular wave control mode. The details will be described later. It is a control mode for controlling the converter 34 in such a manner that a voltage of a pulse pattern having a gap or a short pulse is applied to the motor 32 at the timing of the zero crossing of the phase current crossing the value 0 in the pulse pattern in the second rectangular wave control mode. An example of the relationship between the rotation speed Nm and the torque Tm of the motor 32 and the control mode when the second rectangular wave control mode is executed regardless of the high voltage system voltage VH is shown in FIG. Figure 4 In the figure, the lower left area is the PWM control mode, the hatched area is the middle control mode, and the upper right area is the second rectangular wave control mode.

[0049] The control in the PWM control mode uses a pulse pattern formed by the well-known pulse width modulation, and since it does not constitute the core of the present invention, its detailed description is omitted. In addition, for ease of description, the pulse pattern in the second rectangular wave control mode is first described, and then the pulse pattern in the intermediate control mode is described.

[0050] In the control device mounted on electric vehicle 20 of the embodiment, the second rectangular wave control mode controls inverter 34 using three pulse patterns, namely, a first switching pattern, a second switching pattern, and a rectangular wave pulse pattern. Figure 5 1 is a flowchart showing an example of the second rectangular wave control mode pulse pattern setting process executed by the electronic control unit 50. In the second rectangular wave control mode pulse pattern setting process, first, the rotation speed Nm of the motor 32 is input (step S300), and the input rotation speed Nm of the motor 32 is compared with the threshold value Nref1 and the threshold value Nref2 (step S310). The threshold value Nref2 is a rotation speed greater than the upper limit value of the first resonance region after the region where the LC resonance is generated due to the electric sixth-order frequency variation of the motor 32 is converted to the rotation speed of the motor 32, and the threshold value Nref1 is a rotation speed greater than the upper limit value of the second resonance region after the region where the LC resonance is generated due to the electric twelfth-order frequency variation of the motor 32 is converted to the rotation speed of the motor 32 and smaller than the lower limit value of the first resonance region. When it is determined that the rotational speed Nm of the motor 32 is less than the threshold value Nref1, the second switch pattern is set (step S320). When it is determined that the rotational speed Nm of the motor 32 is greater than the threshold value Nref1 and less than the threshold value Nref2, the first switch pattern is set (step S330). When it is determined that the rotational speed Nm of the motor 32 is greater than the threshold value Nref2, the rectangular wave pulse pattern is set (step S340), and the present processing is terminated.

[0051] Figure 6This is an explanatory diagram showing an example of a rectangular wave pulse pattern, a first switch pattern, and a second switch pattern. As shown in the figure, the rectangular wave pulse pattern is a pulse pattern in which the first half of a cycle of time T1 to T2 forms a single pulse (rectangular wave pulse) as a whole, and no pulse is formed in the second half (a pulse pattern in a normal rectangular wave control). The first switch pattern is a pulse pattern in which a gap is formed in the area where the rectangular wave pulse of the rectangular wave pulse pattern exists in the first half of a cycle of time T1 to T2, and a short pulse is formed at the same timing as the gap in the second half, and is a switch pattern for converting the sixth-order electrical frequency component to a high frequency. As a switch pattern for converting the sixth-order electrical frequency component to a high frequency, not only a pulse pattern having three pulses in one cycle as shown in the figure, but also a pulse pattern having four or more pulses in one cycle is effective, but in the first embodiment, a pulse pattern with the least number of pulses in one cycle is used as the first switch pattern. The second switch pattern is a pulse pattern that further forms one gap (a total of two gaps) and one short pulse (a total of two short pulses) on the basis of the first switch pattern. It is a switch pattern that converts the electrical twelfth-order frequency component to a high frequency in addition to the electrical sixth-order frequency component. Regarding the switch pattern that converts the electrical twelfth-order frequency component to a high frequency in addition to the electrical sixth-order frequency component, not only a pulse pattern with four pulses in one cycle as shown in the figure but also a pulse pattern with five or more pulses in one cycle is effective. However, in the first embodiment, a pulse pattern with the least number of pulses in one cycle is used as the second switch pattern. Figure 4 In the rectangular wave control mode in the upper right region of FIG. 1 , the second switching pattern, the first switching pattern, and the rectangular wave pulse pattern are shown in order from the left by the regions separated by the threshold values ​​Nref1 and Nref2 .

[0052] According to the above description, in the second rectangular wave control mode pulse pattern setting process, when it is determined in step S310 that the rotation speed Nm of the motor 32 is less than the threshold value Nref1, the second switch pattern is set to suppress the LC resonance caused by the 12th-order electrical frequency change of the motor 32. When the rotation speed Nm of the motor 32 is greater than the threshold value Nref1 and less than the threshold value Nref2, the first switch pattern is set to suppress the LC resonance caused by the 6th-order electrical frequency change. When the rotation speed Nm of the motor 32 is greater than the threshold value Nref2, no LC resonance occurs, so the rectangular wave pulse pattern is set. Thus, vibration that may be generated due to LC resonance caused by the 6th-order electrical frequency change and the 12th-order electrical frequency change can be suppressed.

[0053] Here, Figure 2The meanings of the values ​​Mset1, Mset2, and Mset3 set for the threshold value Mref2 in steps S110 to S140 are explained. The value Mset1 is the modulation degree when the second switching pattern is used in the second rectangular wave control mode, and 0.75 is used in the first embodiment. The value Mset2 is the modulation degree when the first switching pattern is used, and a value larger than the value Mset1 is used (0.756 in the embodiment). The value Mset3 is the modulation degree when the second rectangular wave pulse pattern is used, and a value larger than the value Mset2 is used (0.78 in the embodiment). As shown Figure 4 As shown, since the modulation degree in the second rectangular wave control mode is used for the threshold value Mref2 of the upper limit value of the modulation degree M of the intermediate control mode, when the rotational speed Nm of the motor 32 is less than the threshold value Nref1, it becomes the modulation degree when the second switching pattern is used (value Mset1); when the rotational speed Nm is greater than the threshold value Nref1 and less than the threshold value Nref2, it becomes the modulation degree when the first switching pattern is used (value Mset2); and when the rotational speed Nm is greater than the threshold value Nref2, it becomes the modulation degree when the rectangular wave pulse pattern is used (value Mset3). Figure 2 The processing of steps S110 to S140 in the control mode setting processing takes this into consideration and sets the threshold value Mref2.

[0054] Next, the pulse pattern in the intermediate control mode will be described. Figure 7 : is a flowchart showing an example of the intermediate control mode pulse pattern setting process performed by the electronic control unit 50. In the intermediate control mode pulse pattern setting process, first, the rotation speed Nm of the motor 32 is input (step S400), and the input rotation speed Nm of the motor 32 is compared with the threshold value Nref1 and the threshold value Nref2 (step S410). When it is determined that the rotation speed Nm of the motor 32 is less than the threshold value Nref1, the intermediate second switch pattern is set (step S420), and when it is determined that the rotation speed Nm of the motor 32 is greater than the threshold value Nref1 and less than the threshold value Nref2, the intermediate first switch pattern is set (step S430), and when it is determined that the rotation speed Nm of the motor 32 is greater than the threshold value Nref2, the intermediate rectangular wave pulse pattern is set (step S440). An example of an intermediate rectangular wave pulse pattern, an intermediate first switch pattern, and an intermediate second switch pattern is shown in Figure 8 The middle rectangular wave pulse pattern is relative to the rectangular wave pulse pattern (refer to Figure 6) In the first half of a cycle of time T1 to T2, a gap is formed in a rectangular wave pulse at the timing T1(1) when the phase current crosses the value 0, and a short pulse of the same width as the gap is formed at the timing T1(2) when the phase current crosses the value 0 in the second half of the cycle. That is, the intermediate rectangular wave pulse pattern becomes a switching pattern in which, relative to the rectangular wave pulse pattern, a gap is formed when a pulse exists at the timing when the phase current crosses the value 0, and a short pulse of the same width as the gap is formed when the pulse does not exist. The intermediate first switching pattern and the intermediate second switching pattern are similar to the intermediate rectangular wave pulse pattern in that they are relative to the first switching pattern and the second switching pattern (see Figure 6 ) In the first half of the cycle, a gap is formed in the rectangular wave pulse at the timing T1(1) of the zero crossing, and in the second half of the cycle, a short pulse of the same width as the gap is formed at the timing T1(2) of the zero crossing. That is, the intermediate first switching pattern and the intermediate second switching pattern become switching patterns in which, relative to the first switching pattern and the second switching pattern, a gap is formed when a pulse exists at the timing of the phase current crossing zero, and a short pulse of the same width as the gap is formed when the pulse does not exist. Figure 4 In the intermediate control mode in the hatched area, the intermediate second switching pattern, the intermediate first switching pattern, and the intermediate rectangular wave pulse pattern are shown in order from the left by the areas separated by the threshold values ​​Nref1 and Nref2.

[0055] Then, the gap width p is set based on the modulation degree M (step S450), and the present process is terminated. As described above, since the short pulse has the same width as the gap, the setting of the gap width p in step S450 is synonymous with the setting of the short pulse width p. In the embodiment, the gap width p is set by "pre-storing the relationship between the pulse width p and the modulation degree M obtained by experiments, etc. in each pulse pattern so as to change the modulation degree M from the threshold value Mref1 to the threshold value Mref2 as a mapping for gap width setting, and if the modulation degree M is given, deriving the corresponding gap width from the mapping." An example of a mapping for gap width setting is shown in FIG. Fig. 9 As shown in the figure, the larger the modulation index M is, the smaller the gap width p is. If the modulation index M reaches the threshold value Mref2, the gap width p becomes 0. That is, if the modulation index M reaches the threshold value Mref2, the intermediate control mode is switched to the rectangular wave control mode, so the intermediate rectangular wave pulse pattern, the intermediate first switch pattern, and the intermediate second switch pattern are switched to the rectangular wave pulse pattern, the first switch pattern, and the second switch pattern. At this time, since the gap width p gradually decreases and becomes 0 as the modulation index M increases, no torque variation occurs when switching from the intermediate control mode to the rectangular wave control mode. It should be noted that it is believed that the formation of gaps and short pulses at the timing of the zero crossing of the phase current is to reduce the influence on the waveform of the phase current.

[0056] Next, the operation when switching from the first switching pattern to the rectangular wave pulse pattern, that is, Figure 4 The operation when the motor speed Nm exceeds the threshold value Nref2 and increases is described below. When the motor speed Nm reaches the vicinity of the threshold value Nref2, it gradually decreases. Figure 6 An example of the relationship between the motor speed Nm and the gap of the first switching pattern and the width p of the short pulse is shown in FIG. Fig.10 As shown in . If the motor speed Nm reaches the threshold value Nref2, the width p of the gap and the short pulse becomes 0, and the first switching pattern is switched to the rectangular wave pulse pattern. However, in fact, due to the existence of dead time, the width p of the gap and the short pulse will not change linearly, but will suddenly change by the amount of dead time width. Therefore, when switching from the first switching pattern to the rectangular wave pulse pattern, a voltage level difference corresponding to the amount of dead time width will be generated, and a slight torque change will occur. In addition, the same torque change will occur when switching from the second switching pattern to the first switching pattern. The switch from the second switching pattern to the first switching pattern is achieved by "gradually reducing if the motor speed Nm reaches the vicinity of the threshold value Nref2." Figure 6 Therefore, when the width of the gap and the short pulse is set to a value of 0, a voltage step difference corresponding to the dead time width will be generated, and a slight torque variation will occur.

[0057] return Figure 2 Description of the control mode setting process. When it is determined in step S180 that the high voltage system voltage VH is greater than the threshold voltage VH, it is determined whether the modulation degree M is less than the threshold value Mref2 (step S220). When it is determined that the modulation degree M is less than the threshold value Mref2, the overmodulation control mode is set (step S230), and when it is determined that the modulation degree M is greater than the threshold value Mref2, the first rectangular wave control mode is set (step S240), and the present process is terminated. In this case, the threshold value Mref1 becomes the modulation degree for distinguishing the PWM control mode from the overmodulation control mode, and the threshold value Mref2 becomes the modulation degree for distinguishing the overmodulation control mode from the first rectangular wave control mode. The first rectangular wave control mode is a control mode that uses a rectangular wave pulse pattern. The overmodulation control mode is a control mode that uses a triangular wave to set the on and off of the switching element in the same way as the PWM control with respect to the modulation degree M exceeding the PWM control area. In Fig.11An example of the relationship between the high voltage system voltage VH, the rotation speed Nm of the motor 32, the torque Tm and the control mode is shown in FIG. In the figure, in the area above VH=Vref, the area on the left is the PWM control mode, the hatched area is the overmodulation control mode, and the area on the right of the overmodulation control mode is the first rectangular wave control mode. In the area below VH=Vref, the PWM control mode, the intermediate control mode and the second rectangular wave control mode are switched as described above. Comparison Fig.11 and Figure 4 It is known that in Fig.11 In the second rectangular wave control mode, the first switching pattern and the rectangular wave pulse pattern exist, and the second switching pattern does not exist, but the second switching pattern also exists due to the position of the curve of VH=Vref. The position of the curve of VH=Vref is determined by the design of the feedback control in the circuit and duty cycle control.

[0058] In the first rectangular wave control mode, the rectangular wave pulse pattern is used in all regions of the rectangular wave where the modulation index M is greater than the threshold value Mref2, so switching from the first switching pattern to the rectangular wave pulse pattern and switching from the second switching pattern to the first switching pattern are not performed. Therefore, in the first rectangular wave control mode, torque fluctuations caused by voltage step differences corresponding to the dead time width amount when switching from the first switching pattern to the rectangular wave pulse pattern and switching from the second switching pattern to the first switching pattern are not generated. Since the first switching pattern and the second switching pattern suppress the LC resonance in the first resonance region and the second resonance region, LC resonance may occur in the first rectangular wave control mode. However, in the first rectangular wave control mode, by setting the high voltage system voltage VH to a range greater than the threshold voltage Vref, LC resonance does not occur. The reason why LC resonance does not occur is explained below.

[0059] If the transfer function of the circuit composed of an inductor and a capacitor is G(s), and the transfer function of the control of the boost converter 40 is C(s), the battery current Ib and the current Iload flowing into the converter 40 are expressed by the following equation (1). The transfer function C(s) can adjust the characteristics by adjusting the control gain of the boost converter 40. Therefore, if the gain is designed so that the cutoff frequency of the transfer function C(s) is smaller than the LC resonance frequency, the LC resonance can be avoided. The transfer function C(s) becomes 1 when the voltage is not boosted by the boost converter 40 at all, that is, when the transistor T31 (upper arm) of the boost converter 40 is always turned on (the duty ratio is 100%), and the battery current Ib depends only on the transfer function G(s) with respect to the current Iload. The duty ratio is expressed by equation (2), and becomes 100% when the voltage is not boosted by the boost converter 40 at all (when the upper arm is always turned on), and the high voltage system voltage VH becomes higher as the duty ratio decreases. It should be noted that in equation (2), Vb is the battery voltage, Rb is the internal resistance of the battery 36, Ib is the battery current, and VH is the high voltage system voltage. An example of a Bode plot when the transfer function C(s) is changed is shown in Fig.12 In the figure, the thick solid line curve A represents the case where the duty cycle is 100% (when the transfer function C(s) is 1), the solid line curve B represents the case where the duty cycle is smaller than 100%, the thin solid line curve C represents the case where the duty cycle is smaller than curve B, and the single-point dashed line curve D represents the case where the duty cycle is smaller than curve C. The peak of curve A is the LC resonant frequency (1 / {2π(LC) 1 / 2}). The reason why LC resonance occurs even when the duty cycle is smaller than 100% is that feedback control is performed during duty cycle control, and the frequency of the duty cycle becoming 100% increases due to the amplitude of feedback control. The time variation of the actual duty cycle when the duty cycle as the command value is smaller than 100% and a part of it are magnified in the figure. Fig.13 As shown in the enlarged part, during the period when the duty cycle is 100%, the effect of feedback control does not work, so the upper arm becomes the same as being always on. In the embodiment, by setting the high voltage system voltage VH when the duty cycle does not become 100% due to the amplitude of feedback control to the threshold voltage Vref, the cutoff frequency of the transfer function C(s) is made smaller than the LC resonance frequency, thereby avoiding LC resonance. It should be noted that, Figure 3 As shown, the threshold voltage Vref becomes a constant value when the battery current Ib is a positive value (when the motor 32 is being driven and controlled), and becomes a value higher than when it is a positive value when the battery current Ib is a negative value (when the motor 32 is regeneratively controlled and the battery 36 is being charged).

[0060] Ib=G(s)·C(s)·Iload (1)

[0061] Duty cycle = (Vb-Rb·Ib) / VH (2)

[0062] In the driving device mounted on the electric vehicle 20 of the embodiment described above, when the boost converter 40 is controlled in such a manner that the high voltage system voltage VH becomes higher than the threshold voltage Vref, the first rectangular wave control mode using the rectangular wave pulse pattern is used, and the pulse width modulation control mode, the overmodulation control mode and the first rectangular wave control mode are switched according to the modulation degree. In the first rectangular wave control mode, only the rectangular wave pulse pattern is used, so the first switch pattern and the rectangular wave pulse pattern are not switched as in the second rectangular wave control mode. Therefore, the torque fluctuation caused by the voltage step corresponding to the dead time width when switching from the first switch pattern to the rectangular wave pulse pattern does not occur. In addition, since the high voltage system voltage VH when the duty ratio does not become 100% due to the amplitude of the feedback control is set to the threshold voltage Vref, the cutoff frequency of the transfer function C(s) can be made smaller than the LC resonance frequency, and the LC resonance can be avoided. Of course, when the boost converter 40 is controlled so that the high voltage system voltage VH is less than the threshold voltage Vref, the second rectangular wave control mode using the first switching pattern, the second switching pattern and the rectangular wave pulse pattern is used, and the pulse width modulation control mode, the intermediate control mode and the second rectangular wave control mode are switched according to the modulation degree. Therefore, when switching from the first switching pattern to the rectangular wave pulse pattern, a slight torque variation occurs, but the LC resonance can be suppressed. As a result, as a whole, the torque variation that may occur when switching from the switching pattern that suppresses the LC resonance in the resonance region to the rectangular wave pulse pattern in the rectangular wave control can be suppressed.

[0063] In the driving device mounted on the electric vehicle 20 of the embodiment, the first rectangular wave control mode is used when the boost converter 40 is controlled so that the high voltage system voltage VH becomes equal to or higher than the threshold voltage Vref, and the second rectangular wave control mode is used when the boost converter 40 is controlled so that the high voltage system voltage VH becomes lower than the threshold voltage Vref. However, the first rectangular wave control mode may be used when the duty ratio of the boost converter 40 is lower than the threshold duty ratio, and the second rectangular wave control mode may be used when the duty ratio of the boost converter 40 is equal to or higher than the threshold duty ratio. In this case, as the threshold duty ratio, a duty ratio when the duty ratio does not become 100% due to the amplitude of the feedback control in the duty ratio control can be used.

[0064] In the driving device mounted on the electric vehicle 20 of the embodiment, in the intermediate first switching pattern and the intermediate second switching pattern, a gap is formed when a pulse is present at the timing of the phase current crossing zero, and a short pulse having the same width as the gap is formed when a pulse is not present, and the width of the gap and the short pulse at the timing of the zero crossing are changed by the modulation degree M. However, the switching pattern in which the width of the gap and the short pulse in the first switching pattern and the second switching pattern is changed by the modulation degree M may be set to the intermediate first switching pattern and the intermediate second switching pattern.

[0065] In the driving device mounted on the electric vehicle 20 of the embodiment, the first switching pattern and the second switching pattern are used in the second rectangular wave control mode, but only the first switching pattern or only the second switching pattern may be used.

[0066] In the embodiment, the driving device is described as being mounted on the electric vehicle 20 , but the driving device may be mounted on a hybrid vehicle or a moving object other than an automobile.

[0067] The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is explained. In the embodiment, the battery 36 corresponds to the "power storage device", the motor 32 corresponds to the "motor", the inverter 34 corresponds to the "inverter", the boost converter 40 corresponds to the "boost converter", and the electronic control unit 50 corresponds to the "control device".

[0068] It should be noted that since the embodiment is an example of a method for implementing the invention recorded in the column of means for solving the problem, the correspondence between the main elements of the embodiment and the main elements of the invention recorded in the column of means for solving the problem does not limit the elements of the invention recorded in the column of means for solving the problem. That is, the interpretation of the invention recorded in the column of means for solving the problem should be based on the description in this column, and the embodiment is only a specific example of the invention recorded in the column of means for solving the problem.

[0069] Although the modes for carrying out the present invention have been described above using the embodiments, the present invention is not limited to the embodiments and can be carried out in various forms without departing from the gist of the present invention.

[0070] Industrial Applicability

[0071] The present invention can be utilized in the manufacturing industry of drive devices and the like.

Claims

1. A drive device comprising a power storage device, a motor, a converter for driving the motor, a boost converter installed between the power storage device and the converter, and a control device for switching a switching element of the converter and controlling the boost converter, wherein: The control device controls the switching of the switching element of the converter, When the boost converter is controlled so that the voltage applied to the inverter becomes equal to or higher than a threshold voltage based on the current from the power storage device, the pulse width modulation control mode and the first rectangular wave control mode are switched according to the modulation degree, When the boost converter is controlled so that the voltage applied to the inverter is less than the threshold voltage, the pulse width modulation control mode and the second rectangular wave control mode are switched according to the modulation degree, The first rectangular wave control mode is a mode using a rectangular wave pulse pattern in which the first half cycle or the second half cycle of one cycle becomes a rectangular wave pulse. The second rectangular wave control mode is a mode in which the rectangular wave pulse pattern is used when the rotation speed of the motor is greater than a first specified rotation speed greater than the first resonance region, and the first switching pattern is used when the rotation speed of the motor is less than the first specified rotation speed, the first switching pattern is a pattern in which one or more gaps are formed in a region where a rectangular wave pulse exists in the rectangular wave pulse pattern, and short pulses of the same width as the gap are formed at the same timing as the gap in a region where a rectangular wave pulse does not exist, and LC resonance in the first resonance region is suppressed, The threshold voltage is a voltage predetermined with respect to the current from the power storage device as a voltage at which the duty ratio does not become 100% due to the amplitude of the feedback control when the boost converter is controlled by duty ratio control accompanying feedback control.

2. The driving device according to claim 1, The control device performs control using a duty ratio at which the duty ratio does not become 100% due to the amplitude of the feedback control as the threshold voltage.

3. The driving device according to claim 1 or 2, The control device switches the pulse width modulation control mode and the first rectangular wave control mode via an overmodulation region according to the modulation degree while controlling the boost converter so that the voltage applied to the inverter becomes equal to or higher than the threshold voltage. When the control device is controlling the boost converter in such a manner that the voltage applied to the converter is less than the threshold voltage, the control device switches the pulse width modulation control mode and the second rectangular wave control mode according to the modulation degree via an intermediate region in which the width of the gap and the short pulse in the first switching pattern are changed.

4. The driving device according to claim 1 or 2, The second rectangular wave control mode is a mode that uses a second switching pattern when the rotational speed of the motor is less than a second specified rotational speed that is smaller than the first specified rotational speed. The second switching pattern is a pattern that has more gaps and short pulses than the first switching pattern and suppresses the LC resonance in the second resonance area included in the rotational speed range that is smaller than the second specified rotational speed.

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