JP2013198365A - Inverter and converter control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a ripple of a DC voltage inputted into an inverter while suppressing an increase of a device size and an increase of a manufacturing cost.SOLUTION: A control device PWM-controls an inverter and a converter. The control device includes: first signal generation means for generating a first duty signal for driving inverter-side switching elements; second duty signal generation means for generating a second duty signal for driving converter-side switching elements, with a frequency of the second duty signal being three times as high as that of the first duty signal; and phase control means for controlling phases of the first duty signal and the second duty signal. At the time of a step-down operation of the converter, the phase control means performs the phase control so that a center of an ON-period of the first duty signal for driving a switching element constituting an upper arm, out of the inverter-side switching elements, and a center of an ON-period of the second dury signal for driving a high-side switching element, out of the converter-side switching elements, are aligned with each other.

Description

  Embodiments described herein relate generally to an inverter and converter control device.

  2. Description of the Related Art A motor drive device that drives a motor includes a configuration that includes an inverter, a step-up / step-down DC-DC converter, and a control device that performs PWM control on the inverter. In such a motor drive device, during power running, the converter performs a boost operation, whereby the DC voltage supplied from the battery is boosted and supplied to the inverter through a pair of DC power supply lines. Further, during regeneration, the converter performs a step-down operation, whereby the DC voltage regenerated from the motor through the inverter and the pair of DC power supply lines is stepped down and supplied to the battery (charging the battery). On the other hand, the inverter converts a DC voltage supplied through a pair of DC power supply lines into an AC voltage and supplies the AC voltage to the motor. A smoothing capacitor for smoothing the DC voltage is provided between the pair of DC power supply lines.

  In such a configuration, a ripple (pulsation) occurs in the voltage between the DC power supply lines (input voltage to the inverter) with the switching operation by the inverter and the converter. In particular, when the inverter and the converter operate simultaneously, voltage ripples resulting from the respective switching operations influence each other, and as a result, the voltage ripple may increase. When the input voltage to the inverter pulsates, the maximum value of the voltage output from the inverter is limited to the minimum value of the pulsating input voltage. Therefore, there is a possibility that the voltage used for driving the motor falls below the rated value range.

  In order to reduce such voltage ripple, it is necessary to take measures such as using a smoothing capacitor having a large capacity or connecting a large number of capacitors in parallel. However, when such measures are taken, there arises a problem that the apparatus becomes large and the manufacturing cost becomes high. Further, the voltage ripple caused by the switching operation of the converter can be reduced by increasing the capacity of the coil included in the converter. However, enlarging the coil leads to problems such as an increase in the size of the apparatus and an increase in manufacturing cost.

JP 2005-168161 A JP 2006-101675 A

  Therefore, a control device for an inverter and a converter that can reduce ripples of DC voltage input to the inverter while suppressing increase in size of the device and an increase in manufacturing cost is provided.

  The inverter and converter control device of the present embodiment steps down and outputs an inverter that converts a DC voltage applied through a pair of DC power lines into a three-phase AC voltage, and a DC voltage that is input through the pair of DC power lines. PWM control is performed on the converter configured to execute at least one of the step-down operation to be performed and the step-up operation to step up and output the input DC voltage through a pair of DC power supply lines. The inverter includes six inverter-side switching elements connected in a three-phase bridge between a pair of DC power supply lines, and a smoothing capacitor connected between the pair of DC power supply lines. The converter includes two converter-side switching elements connected in series between a pair of DC power supply lines, and a coil having one terminal connected to an interconnection point between the two converter-side switching elements.

  The control device includes a first signal generating means for generating a first duty signal for driving the inverter-side switching element, and a second signal for driving the converter-side switching element having a frequency three times that of the first duty signal. A second duty signal generating unit configured to generate a duty signal; and a phase control unit configured to control phases of the first duty signal and the second duty signal. In the step-down operation, the phase control means includes a first duty signal for driving any one of the inverter-side switching elements constituting the upper arm, and a high-side switching among the converter-side switching elements. Phase control is performed so that the centers of the ON periods of the second duty signal for driving the element are aligned. In the step-up operation, the phase control means includes a first duty signal for driving any one of the inverter-side switching elements constituting the upper arm, and a low-side switching element among the converter-side switching elements. Phase control is performed so as to align the centers of the on periods with the second duty signal for driving.

The 1st Embodiment is a figure showing the schematic structure of a motor drive device Waveform diagram of each part when on-duty of inverter and converter are both 50% FIG. 2 equivalent diagram showing an example when the on-duty of the inverter and the converter is different FIG. 2 equivalent diagram showing another example when the on-duty of the inverter and the converter are different from each other A diagram for explaining a method of generating a drive signal using a single-phase triangular wave (part 1) Diagram for explaining a method of generating a drive signal using a single-phase triangular wave (part 2) FIG. 3 is a diagram for explaining a method of generating a drive signal using a single-phase triangular wave (No. 3). The figure for demonstrating the production | generation method of the drive signal using the sawtooth wave of a single phase FIG. 1 equivalent diagram showing the second embodiment

Hereinafter, a plurality of embodiments of a motor drive device will be described with reference to the drawings. In each embodiment, substantially the same components are denoted by the same reference numerals and description thereof is omitted.
(First embodiment)
Hereinafter, a first embodiment will be described with reference to FIGS.
As shown in FIG. 1, the motor drive device 1 includes a battery 2, an inverter 3, a converter 4, and a control device 5. The motor drive device 1 drives, for example, a three-phase motor M mounted on a vehicle with electric power supplied from a battery 2 that outputs a DC voltage Vd1.

  The inverter 3 includes six switching elements Tuh to Twl connected in a three-phase bridge shape between the pair of DC power supply lines 6 and 7 and a smoothing capacitor C1 connected between the DC power supply lines 6 and 7. Yes. The switching elements Tuh to Twl (corresponding to inverter-side switching elements) are, for example, NPN-type bipolar transistors. Although not shown, a reflux diode having an emitter on the anode side is connected between the collector and emitter of the switching elements Tuh to Twl.

  The interconnection node Nu of the switching elements Tuh and Tul is connected to the U-phase terminal of the motor M. The interconnection node Nv of the switching elements Tvh and Tvl is connected to the V-phase terminal of the motor M. The interconnection node Nw of the switching elements Twh and Twl is connected to the W phase terminal of the motor M. Drive signals Suh to Swl output from the control device 5 are respectively supplied to the bases of the switching elements Tuh to Twl. The switching elements Tuh, Tvh, Twh constituting the upper arm and the switching elements Tul, Tvl, Twl constituting the lower arm are driven in a complementary manner, so that a DC voltage applied through the DC power supply lines 6, 7 is obtained. Is converted into a three-phase AC voltage and supplied to the motor M.

  The converter 4 is a step-up / step-down DC-DC converter. The converter 4 includes switching elements Tdh and Tdl, a coil L1, and a capacitor C2. The switching elements Tdh and Tdl (corresponding to converter-side switching elements) are, for example, NPN bipolar transistors. The switching elements Tdh and Tdl are connected in series between the DC power supply lines 6 and 7. One terminal of the coil L1 is connected to the interconnection node Nd of the switching elements Tdh and Tdl. The other terminal of the coil L1 is connected to the high potential side terminal of the battery 2. The low potential side terminal of the battery 2 is connected to the DC power supply line 7 (emitter of the switching element Tdl). The capacitor C <b> 2 is connected between the terminals of the battery 2. Drive signals Sdh and Sdl output from the control device 5 are applied to the bases of the switching elements Tdh and Tdl, respectively. The high-side switching element Tdh and the low-side switching element Tdl are driven in a complementary manner, thereby realizing a step-up operation and a step-down operation.

  In the boosting operation, the DC voltage supplied from the battery 2 is boosted and output through the DC power supply lines 6 and 7. Such a boosting operation is performed when the inverter 3 is powered. Therefore, during power running, the DC voltage output from the battery 2 is boosted and supplied to the inverter 3 through the DC power supply lines 6 and 7. On the other hand, in the step-down operation, a DC voltage input through the DC power supply lines 6 and 7 is stepped down and output. Such a step-down operation is performed during regeneration of the inverter 3. Therefore, during regeneration, the DC voltage regenerated from the motor M through the inverter 3 and the DC power supply lines 6 and 7 is stepped down and supplied to the battery 2 (charging of the battery 2).

  The control device 5 includes an inverter control unit 8, a converter control unit 9, and a phase control unit 10. The control device 5 performs PWM (Pulse Width Modulation) control on the inverter 3 and the converter 4. The inverter control unit 8 (corresponding to the first signal generation means) compares the carrier wave and the signal wave corresponding to the command voltage of each phase, and based on the comparison result, the drive signals Suh to Swl (to the first duty signal) Equivalent). As the carrier wave, a triangular wave, a sawtooth wave or the like can be used.

  First, the case where a three-phase triangular wave is used as a carrier wave will be described with reference to FIGS. In this case, the cycle of the carrier wave used by the inverter control unit 8 is three times the cycle T of the carrier wave used by the converter control unit 9 described later. As shown in FIG. 2 to FIG. 4A, the three-phase (U-phase, V-phase, and W-phase) triangular waves have the same period 3T (frequency) and have a phase of 120 degrees with respect to each other. It is different (deviation). Based on the comparison result between the triangular wave and the signal wave, the drive signals Suh to Swl are generated. 2 to 4B show drive signals Suh, Svh, Swh for driving the switching elements Tuh, Tvh, Twh constituting the upper arm. The drive signals Sul, Svl, Swl for driving the switching elements Tul, Tvl, Twl constituting the lower arm are signals whose levels are inverted with respect to the drive signals Suh, Svh, Swh, respectively (not shown).

  Specifically, the drive signals Suh, Svh, and Swh are at the H level (the level at which the switching elements Tuh, Tvh, and Twh are turned on) during the period in which the signal wave level is higher than the triangular wave level. In addition, the drive signals Suh, Svh, and Swh are at the L level (the level at which the switching elements Tuh, Tvh, and Twh are turned off) during the period in which the signal wave level is lower than the triangular wave level. That is, the drive signals Suh to Swl are signals having a duty corresponding to a period during which the switching elements Tuh to Twl are turned on (or a period during which the switching elements Tuh to Twl are turned off).

  FIG. 2 shows an example in which the on-duty of the drive signals Suh, Svh, and Swh is 50%. Therefore, in FIG. 2, the duty of energizing each phase of the motor M is 50%. 3 and 4 show examples in which the on-duties of the drive signals Suh, Svh, and Swh are 70%, 50%, and 30%, respectively. Therefore, in FIGS. 3 and 4, the duty of energizing each phase of the motor M is 70% (U phase), 50% (V phase), and 30% (W phase), respectively.

  Next, a case where a single-phase triangular wave is used as the carrier wave will be described with reference to FIGS. 5 and 7 show examples in which the on-duty of the drive signals Suh, Svh, and Swh is 50%. FIG. 6 shows an example in which the on-duty of one drive signal is 60%. In this case, as indicated by a solid line in FIGS. 5A and 6A, the period of the carrier wave (single-phase triangular wave) used by the inverter control unit 8 is the period T of the carrier wave used by the converter control unit 9. Is the same. That is, the period T of the single-phase triangular wave is 1/3 of the period 3T of the three-phase triangular wave described above. The amplitude of the single-phase triangular wave is 1/3 of the amplitude of the three-phase triangular wave described above. In this case, not the original signal wave (shown by a solid line in FIGS. 5A and 6A), but a comparison signal wave (FIG. A) and a triangular wave are compared with each other (shown by a dotted line in FIG. 6A).

  The above-described comparison signal wave is calculated as follows. That is, in the first period (one period of the triangular wave) from the minimum value of the triangular wave to the minimum value of the next triangular wave, the comparison signal wave is the same value (“100%” or “1” as the maximum value of the triangular wave). Equivalent). In the second period (1/2 period of the triangular wave) from the first period to the maximum value of the next triangular wave, the comparative signal wave is set to the center value (“50%” or “0” of the triangular wave). Is set to a value three times the original signal wave.

  When a drive signal having an on-duty of 50% is generated (FIG. 5), the value of the comparison signal wave in the second period is 50% ((the original signal wave value is 50% -50%) × 3 + 50%) or 0 ((original signal wave value 0-0) × 3 + 0). When a drive signal having an on-duty of 60% is generated (FIG. 6), the value of the comparison signal wave in the second period is 80% ((the original signal wave value is 60% -50%). ) * 3 + 50%) or 0.6 ((original signal wave value 0.2-0) * 3 + 0).

  In the third period (one period of the triangular wave) after the second period until the maximum value of the next triangular wave, the comparison signal wave corresponds to the minimum value of the triangular wave ("0%" or "-1"). ) Is set to the same value. In the fourth period from the third period to the minimum value of the next triangular wave, the comparison signal wave is set to a value three times the original signal wave with the center value of the triangular wave as a reference. That is, the value of the comparison signal wave in the fourth period is the same as the value of the comparison signal wave in the second period.

  A drive signal (for example, refer to FIG. 5B) generated based on a comparison between such a comparison signal wave and a single-phase triangular wave having a period T is a triangular wave having a period 3T and an original signal wave. And a signal having a duty equivalent to that of the drive signal generated based on the comparison result (for example, see FIG. 2B). The generated drive signal becomes L level during a period when the level of the triangular wave is higher than the level of the comparison signal wave, and becomes H level when the level of the triangular wave is lower than the level of the comparison signal wave. In FIGS. 5 and 6, a triangular wave having a period of 3T (a pseudo-generated triangular wave) is indicated by a one-dot chain line.

  However, the duty of the drive signal that can be set by the above method is limited to the range of 33.3% (100/3) to 66.6% (200/3). That is, the settable duty range is 1/3 compared to the method using the three-phase triangular wave described above. The reason for this is that if the duty of less than 33.3% is set, the value of the calculated comparison signal wave is less than “0%” or “−1” and the duty exceeds 66.6%. This is because the calculated value of the comparison signal wave exceeds “100%” or “1”.

  Then, three comparative signal waves (shown by dotted lines in FIG. 7A) whose timing is shifted by a period T (one period of a single-phase triangular wave) and a single-phase triangular wave having a period T (FIG. 7A) Drive signals Suh, Svh, and Swh for driving the switching elements Tuh, Tvh, and Twh constituting the upper arm are generated (see FIG. 7B). The drive signals Sul, Svl, Swl for driving the switching elements Tul, Tvl, Twl constituting the lower arm are signals whose levels are inverted with respect to the drive signals Suh, Svh, Swh, respectively (not shown). . In this way, a drive signal equivalent to a technique using a three-phase triangular wave with a period 3T is generated even by a technique using a single-phase triangular wave with a period T.

  Next, a case where a single-phase sawtooth wave is used as a carrier wave will be described with reference to FIG. In this case, the period of the carrier wave (single-phase sawtooth wave) used by the inverter control unit 8 is three times the period T of the carrier wave used by the converter control unit 9. That is, the period of the single-phase sawtooth wave is the same as the period 3T of the three-phase triangular wave described above. Based on the comparison result of the sawtooth wave and the signal wave, the drive signals Suh to Swl are generated. FIG. 8B shows drive signals Suh, Svh, Swh for driving the switching elements Tuh, Tvh, Twh constituting the upper arm. The drive signals Sul, Svl, Swl for driving the switching elements Tul, Tvl, Twl constituting the lower arm are signals whose levels are inverted with respect to the drive signals Suh, Svh, Swh, respectively (not shown).

  Specifically, the drive signals Suh, Svh, Swh are changed from the H level to the L level when the sawtooth wave level reaches the signal wave level ("U reset", "V reset", "W reset" in FIG. 8). Turn to. Thereafter, when the level of the sawtooth wave reaches the set value of the signal wave of each phase (“U set”, “V set”, “W set” in FIG. 8), the level changes from the L level to the H level. The set value is set to a different value for each phase signal wave. Note that when the sawtooth wave is reset to the lowest (minimum value), it crosses each signal wave (crosses each signal wave), but at this time, the drive signal does not change. In this way, a drive signal equivalent to a method using a three-phase triangular wave with a period of 3T is also generated by a method using a single-phase sawtooth wave with a period of 3T.

  Converter control unit 9 (corresponding to the second signal generating means) compares the carrier wave with a signal wave corresponding to the command voltage (the target value of the output voltage in the step-up operation or step-down operation), and based on the comparison result Drive signals Sdh and Sdl (corresponding to the second duty signal) are generated. As the carrier wave, a triangular wave or a sawtooth wave can be used. Here, a case where a single-phase triangular wave is used as the carrier wave will be described. The period T of the single-phase triangular wave used by the converter control unit 9 (see FIG. 2 to FIG. 4C) is the period 3T of the three-phase triangular wave used by the inverter control unit 8 (FIG. 2A to FIG. 4A). 1). That is, the PWM frequency on the converter 4 side is three times the PWM frequency on the inverter 3 side.

  Based on the comparison result of the single-phase triangular wave and the signal wave, the drive signals Sdh and Sdl are generated. 2 to 4D show a drive signal Sdh for driving the high-side switching element Tdh during the step-down operation, or a drive signal for driving the low-side switching element Tdl during the step-up operation. Sdl is shown. The drive signal Sdl for driving the switching element Tdl on the low side during the step-down operation is a signal whose level is inverted with respect to the drive signal shown in FIG. Further, the drive signal Sdh for driving the switching element Tdh on the high side during the boosting operation is a signal whose level is inverted with respect to the drive signal shown in FIG.

  Specifically, the drive signal Sdh during the step-down operation or the drive signal Sdl during the step-up operation is at the H level (the switching element Tdh or Tdl is turned on) during the period when the signal wave level is higher than the triangular wave level. Level). Further, the drive signal Sdh during the step-down operation or the drive signal Sdl during the step-up operation is at the L level (the level at which the switching element Tdh or Tdl is turned off) during the period in which the signal wave level is lower than the triangular wave level. It becomes. That is, the drive signals Sdh and Sdl are signals having a duty corresponding to a period during which the switching elements Tdh and Tdl are turned on (or a period during which the switching elements Tdl and Tdl are turned off).

  FIG. 2 shows an example in which the on-duty of the drive signal Sdh during the step-down operation or the drive signal Sdl during the step-up operation is 50%. FIG. 3 shows an example in which the on-duty of the drive signal Sdh during the step-down operation or the drive signal Sdl during the step-up operation is 80%. FIG. 4 shows an example in which the on-duty of the drive signal Sdh during the step-down operation or the drive signal Sdl during the step-up operation is 20%.

  The phase control unit 10 (corresponding to the phase control means) has a phase relationship between the drive signals Suh to Swl given to the switching elements Tuh to Twl and the drive signals Sdh and Sdl given to the switching elements Tdh and Tdl. The phase control is performed so that the relationship shown in FIG. Specifically, when the converter 4 performs a step-down operation, the phase control unit 10 performs a period (on period) in which at least one of the drive signals Suh, Svh, and Swh generated by the inverter control unit 8 is at the H level. Phase control is performed so that the center and the center of the period in which the drive signal Sdh generated by the converter control unit 9 is at the H level are aligned. On the other hand, when the converter 4 performs a boost operation, the phase control unit 10 determines the center of the period in which at least one of the drive signals Suh, Svh, Swh is at the H level and the center of the period in which the drive signal Sdl is at the H level. Phase control is performed so that

  When the drive signals Suh to Swl are generated by the three-phase triangular wave technique, the phase control unit 10 can also perform phase control of the drive signals Suh to Swl and the drive signals Sdh and Sdl as follows. is there. That is, the phase control unit 10 is configured such that, of the three-phase triangular waves used by the inverter control unit 8, the converter control unit 9 determines when any one of the triangular waves has a maximum value (peak) or a minimum value (valley). It is also possible to perform phase control so that the time point (crest) at which the single-phase triangular wave to be used becomes the maximum value or the time point (valley) at which the single-phase triangular wave becomes the minimum value are aligned. Further, the above-mentioned “perform phase control so that the centers of the respective periods are aligned” does not mean that the centers of the respective periods are completely matched, but within a range in which a voltage ripple reducing action described later can be obtained. If there is, there may be some deviation.

In motor drive device 1 having the above-described configuration, voltage ripples generated between DC power supply lines 6 and 7 when inverter 3 and converter 4 operate simultaneously are reduced. Hereinafter, the effect of reducing the voltage ripple will be described.
First, the switching elements Tuh, Tvh, Twh of the inverter 3 are all driven with an on-duty of 50%, and the switching elements Tdh, Tdl of the converter 4 are driven with an on-duty of 50%, see FIG. To explain. In this case, a voltage ripple component Vri indicated by a dotted line in FIG. 2E is generated between the DC power supply lines 6 and 7 by the switching operation of the inverter 3. As shown in FIG. 2, the frequency of the voltage ripple component Vri resulting from the switching operation of the inverter 3 is three times the PWM frequency of the inverter 3.

  On the other hand, a voltage ripple component Vrc indicated by a one-dot chain line in FIG. 2E is generated between the DC power supply lines 6 and 7 by the switching operation of the converter 4. As shown in FIG. 2, the voltage ripple component Vrc resulting from the switching operation of the converter 4 is the same as the PWM frequency of the converter 4. That is, the frequencies of the voltage ripple component Vri and the voltage ripple component Vrc are the same.

  Furthermore, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship that cancels each other. Specifically, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship in which the time point at which the voltage ripple component Vri and the voltage ripple component Vrc become the maximum coincide with each other. That is, the phases of the voltage ripple component Vri and the voltage ripple component Vrc are 180 degrees different from each other. This is a result of the phase control unit 10 controlling the phase relationship between the drive signals Suh to Swl and the drive signals Sdh and Sdl as described above.

  The voltage ripple Vr actually generated between the DC power supply lines 6 and 7 is a combination of the voltage ripple components Vri and Vrc. Therefore, the amplitude of the voltage ripple Vr generated between the DC power supply lines 6 and 7 is very small as compared with the amplitude of the voltage ripple components Vri and Vrc, as shown by the solid line in FIG.

  In this way, when the switching elements Tuh, Tvh, Twh of the inverter 3 are all driven with an on-duty of 50% and the switching element Tdh of the converter 4 is driven with an on-duty of 50%, this embodiment This is an ideal state where the voltage ripple reduction effect due to can be maximized. Actually, the motor driving device 1 does not always operate in such an ideal state. Therefore, next, the switching elements Tuh, Tvh, Twh of the inverter 3 are driven with an on-duty of 70%, 50%, 30%, and the switching element of the converter 4 (Tdh in the case of the step-down operation, which is boosted) In the case of operation, the case where Tdl) is driven with an on-duty of 80% will be described with reference to FIG.

  In this case, a voltage ripple component Vri indicated by a dotted line in FIG. 3E is generated between the DC power supply lines 6 and 7 by the switching operation of the inverter 3. As shown in FIG. 3, the frequency of the voltage ripple component Vri resulting from the switching operation of the inverter 3 is the same as the PWM frequency of the inverter 3. However, the peak value interval (peak or valley interval) in the voltage ripple component Vri is approximately ３ of the PWM period of the inverter 3.

  On the other hand, a voltage ripple component Vrc indicated by a one-dot chain line in FIG. 3E is generated between the DC power supply lines 6 and 7 by the switching operation of the converter 4. As shown in FIG. 3, the voltage ripple component Vrc resulting from the switching operation of the converter 4 is the same as the PWM frequency of the converter 4. That is, the cycle of the peak value of the voltage ripple component Vri and the cycle of the voltage ripple component Vrc are similar to each other.

  Furthermore, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship that cancels each other. Specifically, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship such that a relatively high portion and a relatively low portion substantially coincide with each other. This is a result of the phase control unit 10 controlling the phase relationship between the drive signals Suh to Swl and the drive signals Sdh and Sdl as described above.

  The voltage ripple Vr actually generated between the DC power supply lines 6 and 7 is a combination of the voltage ripple components Vri and Vrc. Therefore, the amplitude of the voltage ripple Vr generated between the DC power supply lines 6 and 7 is very small as compared with the amplitude of the voltage ripple components Vri and Vrc, as shown by the solid line in FIG. Thus, even when the on-duty in the inverter 3 and the converter 4 is different, according to the present embodiment, the voltage ripple reduction effect can be obtained.

  Next, the switching elements Tuh, Tvh, Twh of the inverter 3 are driven with an on-duty of 70%, 50%, 30%, and the switching element of the converter 4 (Tdh in the case of step-down operation, In this case, the case where Tdl) is driven with an on-duty of 20% will be described with reference to FIG.

  In this case, a voltage ripple component Vri indicated by a dotted line in FIG. 4E is generated between the DC power supply lines 6 and 7 by the switching operation of the inverter 3. As shown in FIG. 4, the frequency of the voltage ripple component Vri resulting from the switching operation of the inverter 3 is the same as the PWM frequency of the inverter 3. However, the peak value (interval between peaks or valleys) in the voltage ripple component Vri is approximately 1/3 of the PWM period of the inverter 3.

  On the other hand, a voltage ripple component Vrc indicated by a one-dot chain line in FIG. 4E is generated between the DC power supply lines 6 and 7 by the switching operation of the converter 4. As shown in FIG. 4, the voltage ripple component Vrc resulting from the switching operation of the converter 4 is the same as the PWM frequency of the converter 4. That is, the cycle of the peak value of the voltage ripple component Vri and the cycle of the voltage ripple component Vrc are similar to each other.

  Furthermore, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship that cancels each other. Specifically, the voltage ripple component Vri and the voltage ripple component Vrc have a phase relationship such that a relatively high portion and a relatively low portion substantially coincide with each other. This is a result of the phase control unit 10 controlling the phase relationship between the drive signals Suh to Swl and the drive signals Sdh and Sdl as described above.

  The voltage ripple Vr actually generated between the DC power supply lines 6 and 7 is a combination of the voltage ripple components Vri and Vrc. Therefore, the amplitude of the voltage ripple Vr generated between the DC power supply lines 6 and 7 is very small as compared with the amplitudes of the voltage ripple components Vri and Vrc, as shown by the solid line in FIG. Thus, even when the on-duty in the inverter 3 and the converter 4 is different, according to the present embodiment, the voltage ripple reduction effect can be obtained.

  As described above, according to the motor drive device 1 of the present embodiment, the voltage ripple component Vri generated due to the switching operation of the inverter 3 and the voltage ripple component Vrc generated arbitrarily in the switching operation of the converter 4 cancel each other. Accordingly, an effect of reducing the amplitude of the voltage ripple Vr actually generated between the DC power supply lines 6 and 7 can be obtained. Therefore, a capacitor having a small capacity can be used as the capacitor C1. Further, the PWM frequency of the converter 4 is set to three times the PWM frequency of the inverter 3. As described above, the PWM frequency of the converter 4 is increased, so that the coil L1 of the converter 4 having a small capacity can be used. Therefore, according to the present embodiment, it is possible to reduce the ripple of the DC voltage input to the inverter 3 while suppressing the increase in size and manufacturing cost of the motor drive device 1.

(Second Embodiment)
The second embodiment will be described below with reference to FIG.
The motor drive device 21 of this embodiment shown in FIG. 9 is different from the motor drive device 1 of the first embodiment shown in FIG. 1 in that a battery 22 is provided. The terminals of the battery 22 are connected to the DC power supply lines 6 and 7, respectively. The motor drive device 21 having such a configuration drives the motor M with electric power supplied from the battery 2 or electric power supplied from the battery 22. The battery 22 outputs a DC voltage Vd2 that is higher than the DC voltage Vd1 output from the battery 2.

  Converter 4 of this embodiment operates as follows. That is, when the inverter 3 is powered, the converter 4 does not perform any step-up operation or step-down operation. Therefore, the inverter 3 is supplied with the DC voltage Vd2 output from the battery 22. However, in the event of an emergency, the converter 4 performs a boosting operation as in the first embodiment. Therefore, in an emergency, the DC voltage Vd1 output from the battery 2 is boosted and supplied to the inverter 3 through the DC power supply lines 6 and 7. The emergency is, for example, when the output of the battery 22 is insufficient or when the battery 22 cannot be used completely.

  On the other hand, during regeneration of the inverter 3, the converter 4 performs a step-down operation in the same manner as in the first embodiment. Accordingly, during regeneration, the DC voltage regenerated from the motor M side through the DC power supply lines 6 and 7 is stepped down and supplied to the battery 2 (charging of the battery 2). Thus, in the motor drive device 21, the battery 22 is a main power supply source (main battery), and the battery 2 is an auxiliary power supply source (auxiliary battery). Also with the motor drive device 21 having such a configuration, an effect of reducing voltage ripple generated between the DC power supply lines 6 and 7 when the inverter 3 and the converter 4 operate simultaneously can be obtained.

(Other embodiments)
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.
The six switching elements Tuh to Twl included in the inverter 3 and the two switching elements Tdh and Tdl included in the converter 4 are not limited to bipolar transistors. For example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and IGBTs (Insulateds). Various types of switching elements such as a gate bipolar transistor can be used.

  The converter 4 is not limited to a configuration capable of performing both the step-up operation and the step-down operation (step-up / step-down DC-DC converter). For example, a configuration capable of executing either a step-up operation or a step-down operation, such as a step-up DC-DC converter or a step-down DC-DC converter, may be used. Further, in the case of a configuration capable of executing either the step-up operation or the step-down operation, the configuration is not limited to the synchronous rectification method and may be a diode rectification method. That is, in the case of the step-up DC-DC converter, a diode can be used instead of the high-side switching element (Tdh). In the case of a step-down DC-DC converter, a diode can be used in place of the low-side switching element (Tdl).

Further, the control device 5 is not limited to the use (in-vehicle use) for controlling the inverter 3 and the converter 4 constituting the motor drive device 1 for driving the motor M mounted on the vehicle, and is a motor used for various uses. Can be used for controlling inverters and converters for driving the inverter.
These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawing, 3 is an inverter, 4 is a converter, 5 is a control device, 6 and 7 are direct-current power lines, 8 is an inverter control unit (first signal generating means), and 9 is a converter control unit (second duty signal generating means). Reference numeral 10 denotes a phase control unit (phase control means), C1 denotes a capacitor, L1 denotes a coil, Tdh and Tdl denote switching elements (converter side switching elements), and Tuh to Twl denote switching elements (inverter side switching elements).

Claims (4)

An inverter that converts a DC voltage applied through a pair of DC power supply lines into a three-phase AC voltage, a step-down operation that steps down and outputs a DC voltage that is input through the pair of DC power supply lines, and a boost of the input DC voltage A converter configured to perform PWM control of a converter configured to be capable of executing at least one of the boosting operations output through the pair of DC power supply lines,
The inverter includes six inverter-side switching elements connected in a three-phase bridge between the pair of DC power supply lines, and a smoothing capacitor connected between the pair of DC power supply lines. And
The converter includes two converter-side switching elements connected in series between the pair of DC power supply lines, and a coil having one terminal connected to an interconnection point of the two converter-side switching elements. And
First signal generating means for generating a first duty signal for driving the inverter-side switching element;
Second duty signal generating means for generating a second duty signal for driving the converter-side switching element, and having a frequency three times that of the first duty signal;
Phase control means for controlling the phases of the first duty signal and the second duty signal,
The phase control means includes
During the step-down operation, the first duty signal for driving any one of the inverter-side switching elements constituting the upper arm, and the high-side switching element among the converter-side switching elements Phase control so as to align the centers of the on periods with the second duty signal for driving
During the step-up operation, the first duty signal for driving any one of the inverter-side switching elements constituting the upper arm and the low-side switching element of the converter-side switching element are provided. A control apparatus for an inverter and a converter, wherein phase control is performed so that the centers of the on periods of the second duty signal for driving are aligned.   The first signal generation means compares a single-phase triangular wave having a frequency three times that of the first duty signal with a signal wave corresponding to the command voltage of each phase, and based on the comparison result, the first duty cycle 2. The inverter and converter control device according to claim 1, wherein the control device generates a signal.   The first signal generating means compares a single-phase sawtooth wave having the same frequency as the first duty signal with a signal wave corresponding to a command voltage of each phase, and based on the comparison result, the first duty signal 2. The inverter and converter control device according to claim 1, wherein the control device generates a signal.   The first signal generating means compares a three-phase triangular wave having the same frequency as the first duty signal and a signal wave corresponding to the command voltage of each phase, and based on the comparison result, the first duty 2. The inverter and converter control device according to claim 1, wherein the control device generates a signal.

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