JP2014171362A - Power conversion apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion apparatus capable of reducing switching loss.SOLUTION: A first inverter part 20 includes SW elements 21 to 26 connected to one ends of coils 11 to 13 and is driven by a first power supply source 41. A second inverter part 30 includes SW elements 31 to 36 connected to the other ends of the coils 11 to 13 and is driven by a second power supply source 42. A first control signal generation part 61 controls an on/off operation of the SW elements 21 to 26 through PWM control based on a carrier wave and a first fundamental wave F1. A second control signal generation part 62 controls, on the basis of a second fundamental wave F2 whose phase is shifted by 180° with respect to the first fundamental wave F1, an on/off operation of the SW elements 31 to 36 so that the number of times of switching of the SW elements 31 to 36 is smaller than that of the SW elements 21 to 26. This makes it possible to reduce switching loss.

Description

  The present invention relates to a power conversion device.

  Conventionally, an inverter drive system that converts electric power of a rotating electrical machine by two inverters is known. For example, in Patent Document 1, the phase of the fundamental wave component of the pulse width modulation signal (hereinafter referred to as “PWM”) of the first inverter system and the second inverter system is shifted by 180 ° at high voltage. Thus, the two power supplies are electrically connected in series, and the rotating electrical machine is driven by the sum of the two power supply voltages. Further, in Patent Document 1, at the time of a low voltage, either one of the upper arm or the lower arm of the first inverter system or the second inverter system is simultaneously turned on for three phases and the other is PWM driven.

JP 2006-238686 A

In Patent Document 1, PWM driving is performed in the first inverter system and the second inverter system. Therefore, for example, compared to the case where the electric power of the rotating electrical machine is converted by one inverter system, the switching loss as a whole is large, so that the switching loss is relatively large.
This invention is made | formed in view of the above-mentioned subject, The objective is to provide the power converter device which can reduce switching loss.

  The present invention is a power conversion device that converts electric power of a rotating electrical machine having a winding, and includes a first power supply source, a second power supply source, a first inverter unit, a second inverter unit, and a control unit. And comprising. The first inverter unit has a first switching element connected to one end of the winding, and is driven by a first power supply source. The second inverter unit has a second switching element connected to the other end of the winding, and is driven by a second power supply source.

The control unit includes first control signal generation means and second control signal generation means.
The first control signal generating means controls the on / off operation of the first switching element by PWM control based on the first carrier wave and the first fundamental wave relating to the current passed through the winding.
The second control signal generating means generates a second control signal based on a second fundamental wave that is 180 degrees out of phase with the first fundamental wave so that the number of times of switching of the second switching element is less than the number of times of switching of the first switching element. The on / off operation of the switching element is controlled.
Here, when the on / off operation of the second switching element is controlled based on the second fundamental wave, the state in which the switching frequency of the second switching element is the smallest is the so-called rectangular shape that switches on / off every half cycle of the second fundamental wave. This is the case of wave control.

  In the present invention, the first inverter unit and the second inverter unit are controlled based on the fundamental wave whose phase is shifted by 180 °, so that the first power supply source and the second power supply source are connected in series. To drive the rotating electrical machine. As a result, the rotating electrical machine can be driven with a high voltage, and thus high rotation and high torque can be output.

  The number of switching times of the second switching element is less than the number of switching times of the first switching element that is PWM-controlled based on the carrier wave and the first fundamental wave. Thereby, compared with the case where PWM control similar to the 1st inverter part is performed, since the frequency | count of switching in a 2nd inverter part can be reduced, the switching loss in a 2nd inverter part can be reduced. As a result, the loss of the entire apparatus is reduced and the efficiency is improved. Since the switching loss increases as the drive voltage increases, when the voltage of the second power supply source is higher than the voltage of the first power supply source, the effect of reducing the switching loss by reducing the number of times of switching of the second inverter unit is great.

It is a schematic block diagram which shows the structure of the power converter device by one Embodiment of this invention. It is explanatory drawing explaining switching of the control mode of one Embodiment of this invention. It is a time chart explaining the high voltage mode in one Embodiment of this invention. It is explanatory drawing explaining the high voltage mode in one Embodiment of this invention. It is explanatory drawing explaining the inverter loss in the high voltage mode of one Embodiment of this invention. It is explanatory drawing explaining the low voltage mode in one Embodiment of this invention. It is a time chart explaining the line voltage at the time of neutralizing the 2nd inverter part in one Embodiment of this invention. It is a time chart explaining the line voltage at the time of neutralizing the 1st inverter part in one Embodiment of this invention. It is explanatory drawing explaining the efficiency in each control mode of one Embodiment of this invention. It is explanatory drawing explaining the relationship between the switching speed and switching loss in one Embodiment of this invention. It is explanatory drawing explaining the relationship between the switching speed and inverter loss in one Embodiment of this invention. It is explanatory drawing explaining the relationship between the switching speed in the 1st inverter part of one Embodiment of this invention, wiring length, and a surge voltage. It is explanatory drawing explaining the relationship between the switching speed in the 2nd inverter part of one Embodiment of this invention, wiring length, and a surge voltage. It is explanatory drawing explaining the relationship between the switching speed and wiring length in one Embodiment of this invention, and a surge voltage peak value. It is explanatory drawing explaining the surge maximum voltage ratio by one Embodiment of this invention.

Hereinafter, a power converter according to the present invention will be described with reference to the drawings.
(One embodiment)
As shown in FIG. 1, the power converter device 1 by one Embodiment of this invention converts the electric power of the motor 10. As shown in FIG.

The motor 10 is applied to, for example, an electric vehicle and generates torque for driving drive wheels (not shown). The motor 10 of the present embodiment has a function as an electric motor for driving drive wheels and a so-called motor generator having a function as a generator that can be driven by kinetic energy transmitted from an engine or drive wheels (not shown) to generate electric power. (MG). In the present embodiment, the case of functioning mainly as an electric motor will be described, so it is referred to as “motor 10”.
The motor 10 of this embodiment is a three-phase AC rotating electric machine, and includes a U-phase coil 11, a V-phase coil 12, and a W-phase coil 13. In the present embodiment, the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 correspond to “windings”.

  The power conversion apparatus 1 includes a first inverter unit 20, a second inverter unit 30, a first power supply source 41, a second power supply source 42, a first capacitor 51, a second capacitor 52, a control unit 60, and the like. .

  The first inverter unit 20 is a three-phase inverter and has six switching elements (hereinafter referred to as “SW elements”) 21 to 26 in order to switch energization to the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13. Are bridged. The SW elements 21 to 26 of the present embodiment are IGBTs (Insulated Gate Bipolar Transistors).

The SW element 21 is connected to the high potential side of the SW element 24. A connection point 27 between the SW element 21 and the SW element 24 is connected to one end 111 of the U-phase coil 11. The connection point 27 and one end 111 of the U-phase coil 11 are connected by a wiring 151.
The SW element 22 is connected to the high potential side of the SW element 25. A connection point 28 between the SW element 22 and the SW element 25 is connected to one end 121 of the V-phase coil 12. The connection point 28 and one end 121 of the V-phase coil 12 are connected by a wiring 152.
The SW element 23 is connected to the high potential side of the SW element 26. A connection point 29 between the SW element 23 and the SW element 26 is connected to one end 131 of the W-phase coil 13. The connection point 29 and one end 131 of the W-phase coil 13 are connected by a wiring 153.
The wirings 151, 152, and 153 are cables or bus bars, for example. In the present embodiment, the wirings 151, 152, and 153 that connect the connection points 26 to 29 and the coils 11 to 13 are “wirings that connect the first inverter unit 20 and the motor 10”. This is the first wiring length L1.

  The second inverter unit 30 is a three-phase inverter, similar to the first inverter unit 20, and is a three-phase inverter, and six switches are provided to switch energization to the U-phase coil 11, the V-phase coil 12 and the W-phase coil 13. SW elements 31 to 36 are bridge-connected. The SW elements 31 to 36 of the present embodiment are IGBTs, like the SW elements 21 to 26.

The SW element 31 is connected to the high potential side of the SW element 34. A connection point 37 between the SW element 31 and the SW element 34 is connected to the other end 112 of the U-phase coil 11. The connection point 37 and the other end 112 of the U-phase coil 11 are connected by a wiring 161.
The SW element 32 is connected to the high potential side of the SW element 35. A connection point 38 between the SW element 32 and the SW element 35 is connected to the other end 122 of the V-phase coil 12. The connection point 38 and the other end 122 of the V-phase coil 12 are connected by a wiring 162.
The SW element 33 is connected to the high potential side of the SW element 36. A connection point 39 between the SW element 33 and the SW element 36 is connected to the other end 132 of the W-phase coil 13. The connection point 39 and the other end 132 of the W-phase coil 13 are connected by a wiring 163.
The wirings 161, 162, and 163 are, for example, cables or bus bars. In the present embodiment, the wirings 161, 162, and 163 that connect the connection points 36 to 39 and the coils 11 to 13 are “wirings that connect the second inverter unit 30 and the motor 10”, and the length of the wirings This is the second wiring length L2.

  Hereinafter, the SW elements 21 to 23 and 31 to 33 connected to the high potential side are referred to as “upper arm elements”, and the SW elements 24 to 26 and 34 to 36 connected to the low potential side are appropriately referred to as “lower arm elements”. That's it. In the present embodiment, the SW elements 21 to 26 correspond to “first switching elements”, and the SW elements 31 to 36 correspond to “second switching elements”.

The first power supply source 41 is a DC power source connected in parallel to the first inverter unit 20, and supplies power to the motor 10 via the first inverter unit 20.
The second power supply source 42 is a DC power source connected in parallel to the second inverter unit 30, and supplies power to the motor 10 via the second inverter unit 30.

In the present embodiment, the second voltage value E2 applied by the second power supply source 42 is larger than the first voltage value E1 applied by the first power supply source 41. That is, E2> E1. In the present embodiment, the second voltage value E2 is twice the first voltage value E1. That is, E2 = 2 × E1.
Hereinafter, the first voltage value E1 that is a voltage related to driving of the first inverter unit 20 and the second voltage value E2 that is a voltage related to driving of the second inverter unit 30 are referred to as “drive voltage” as appropriate.

The first capacitor 51 is a smoothing capacitor that is connected in parallel to the first power supply source 41 and smoothes the current supplied from the first power supply source 41 to the first inverter unit 20.
The second capacitor 52 is connected to the second power supply source 42 in parallel and is a smoothing capacitor that smoothes the current supplied from the second power supply source 42 to the second inverter unit 30.

  The combination of the first inverter unit 20, the first power supply source 41 and the first capacitor 51 is the first system 100, and the combination of the second inverter unit 30, the second power supply source 42 and the second capacitor 52 is the second system 200. In this embodiment, it can be said that the first system 100 and the second system 200 are connected to both sides of the motor 10.

The control unit 60 is configured as a normal computer, and includes a CPU, a ROM, an I / O, a bus line that connects these configurations, and the like.
The control unit 60 includes a first control signal generation unit 61 and a second control signal generation unit 62.
The first control signal generation unit 61 outputs a first control signal for controlling the on / off operation of the SW elements 21 to 26 of the first inverter unit 20 to the first inverter unit 20. The second control signal generation unit 62 outputs a second control signal for controlling the on / off operation of the SW elements 31 to 36 of the second inverter unit 30 to the second inverter unit 30.

By the way, when the motor 10 is driven, there are a rotation limit and a torque limit depending on the drive voltage, and if the drive voltage is high, output at high rotation and high torque is possible. On the other hand, when the drive voltage is large, the switching loss increases.
Therefore, in the present embodiment, the control mode is switched according to the rotation speed of the motor 10 and the torque of the motor 10. As shown in FIG. 2, in the present embodiment, the rotation speed and torque are smaller than the solid line T1 in the region A and the rotation speed and torque are between the solid lines T1 and T2 in accordance with the rotation speed and torque of the motor 10. In B, the control mode is the low voltage mode as the “second control mode”, and in the region C where the rotation speed and the torque are between the solid lines T2 and T3, the control mode is the high voltage as the “first control mode”. Set to voltage mode. Further, hereinafter, the control mode in the region A is referred to as control mode A, the control mode in the region B is referred to as control mode B, and the control mode in the region C is referred to as control mode C.

Hereinafter, each control mode will be described.
First, the high voltage mode will be described with reference to FIGS. In FIG. 3, the U phase will be described as an example. In FIG. 4, the SW element that is turned on is indicated by a solid line, the SW element that is turned off is indicated by a broken line, and the description of the control unit 60 is omitted. Further, in order to avoid complication, the numbers of the wirings 151 to 153 and 161 to 163 are omitted (the same applies to FIG. 6).
In the high voltage mode, the on / off operation of the SW elements 21 to 26 of the first inverter unit 20 is controlled based on the first fundamental wave F1 shown in FIG. 3A, and the SW elements 31 to 36 of the second inverter unit 30 are controlled. The on / off operation is controlled based on the second fundamental wave F2 whose phase is shifted by 180 ° from the fundamental wave F1.

  As shown in FIGS. 3B and 3C, the first control signal generator 61 compares the first fundamental wave F1 and a carrier wave (not shown), and outputs a PWM control signal as the first control signal. The on / off operation of the SW elements 21 and 24 is controlled. Here, the PWM control includes “sine wave PWM control” in which the amplitude of the first fundamental wave F1 is equal to or less than the amplitude of the carrier wave, and “overmodulation PWM in which the amplitude of the first fundamental wave F1 is larger than the amplitude of the carrier wave Control ". The carrier wave of this embodiment corresponds to the “first carrier wave”. When the amplitude of the fundamental wave with respect to the amplitude of the carrier wave is a modulation rate, the modulation rate of sine wave PWM control is 1 or less, and the modulation rate of overmodulation PWM control is greater than 1.

  Further, as shown in FIGS. 3D and 3E, the second control signal generator 62 is based on the second fundamental wave F2, and when the second fundamental wave F2 is positive, the SW element that is an upper arm element. When the second fundamental wave F2 is negative, the SW element 31 that is the upper arm element is turned off, and the SW element 34 that is the lower arm element is turned on when the second fundamental wave F2 is negative. The wave control signal is output as the second control signal.

That is, in this embodiment, in the high voltage mode, the first inverter unit 20 is set to PWM control, and the second inverter unit 30 is set to rectangular wave control. Therefore, as shown in FIGS. 3B to 3E, the switching frequency of the SW elements 31 and 34 of the second inverter unit 30 is smaller than the switching frequency of the SW elements 21 and 24 of the first inverter unit 20.
The same applies to the V phase and the W phase.

  In the high voltage mode, the phase of the first fundamental wave F1 and the phase of the second fundamental wave F2 are shifted by 180 °. Therefore, as in the example shown in FIG. 4, in the first inverter unit 20, the SW element 21 that is the upper arm element is turned on in the U phase, and the SW elements 35 and 36 that are lower arm elements are turned on in the V phase and W phase. In the second inverter section 30, if the SW element 24, which is a lower arm element, is on in the U phase, and the SW elements 32, 33, which are upper arm elements, are on in the V phase and the W phase, As indicated by an arrow Y, the motor 10 can be driven with the first power supply source 41 and the second power supply source 42 connected in series.

  Therefore, as shown in FIGS. 3 (f) and 3 (g), in the high voltage mode, the U-V line voltage and the U-W line voltage have a pulse height of the first power supply source 41. E1 + E2, which is the sum of the first voltage value E1 and the second voltage value E2 of the second power supply source 42. Although not shown, the same applies to the line voltage between V and W.

  In the present embodiment, since the second inverter unit 30 is controlled by the rectangular wave control, the number of times of switching can be reduced compared to the case where the same PWM control as that of the first inverter unit 20 is performed. Specifically, the number of times of switching in the second inverter unit 30 can be reduced by (number of times of switching by PWM control) − (number of times of switching by rectangular wave control). Thereby, since the switching loss in the second inverter unit 30 can be reduced, as shown in FIG. 5, the inverter is compared with the reference example 1 in which the second inverter unit 30 is driven by the same PWM control as that of the first inverter unit 20. Loss can be reduced.

Next, the low voltage mode will be described with reference to FIGS. In FIG. 6, as in FIG. 4, the SW elements that are turned on are indicated by solid lines, and the SW elements that are turned off are indicated by broken lines, and the description of the control unit 60 is omitted.
As shown in FIG. 6, in the low voltage mode, one of the first inverter unit 20 or the second inverter unit 30 is neutralized, and the other one of the first inverter unit 20 or the second inverter unit that is not neutralized is used. Single-sided power drive.

FIG. 6A shows an example in which the second inverter unit 30 is neutralized. In the example shown in FIG. 6A, the upper arm elements 31 to 33 are turned on simultaneously for three phases, and the lower arm elements 34 to 36 are turned off simultaneously for three phases. Further, the first inverter unit 20 performs PWM control based on the first fundamental wave F1 and the carrier wave. Accordingly, the second inverter unit 30 side can be regarded as a neutral point, and the motor 10 can be driven by the first power supply source 41 and the first inverter unit 20.
When the second inverter unit 30 is neutralized, as shown in FIG. 7, the line voltage between U and V and the line voltage between U and W have a pulse height of the first power supply source 41. The first voltage value E1 is obtained. Although not shown, the same applies to the line voltage between V and W.

FIG. 6B is an example when the first inverter unit 20 is neutralized. In the example shown in FIG. 6B, the upper arm elements 21 to 23 are turned on simultaneously for three phases, and the lower arm elements 34 to 36 are turned off simultaneously for three phases. The second inverter unit 30 performs PWM control based on the first fundamental wave F1 and the carrier wave. Accordingly, the first inverter unit 20 side can be regarded as a neutral point, and the motor 10 can be driven by the second power supply source 42 and the second inverter unit 30.
When the first inverter unit 20 is neutralized, as shown in FIG. 8, the line voltage between U and V and the line voltage between U and W have a pulse height of the second power supply source 42. The second voltage E2. Although not shown, the same applies to the line voltage between V and W.

In FIG. 6A, the upper arm elements 31 to 33 are simultaneously turned on and the lower arm elements 34 to 36 are simultaneously turned off. However, the upper arm elements 31 to 33 are simultaneously turned off and the lower arm elements 34 to 36 are turned off. Even if the switches are simultaneously turned on, the second inverter unit 30 can be neutralized.
Similarly, in FIG. 6B, the upper arm elements 21 to 23 are simultaneously turned on and the lower arm elements 34 to 36 are simultaneously turned off. However, the upper arm elements 21 to 23 are simultaneously turned off and the lower arm element 24 is turned off. Even if .about.26 are turned on simultaneously, the first inverter unit 20 can be neutralized.

Therefore, in this embodiment, when the second inverter unit 30 is neutralized, the upper arm elements 31 to 33 are on, the lower arm elements 34 to 36 are off, and the upper arm elements 31 to 33 are off. The state where the lower arm elements 34 to 36 are turned on is switched every predetermined period. Similarly, when the first inverter unit 20 is neutralized, the upper arm elements 21 to 23 are on, the lower arm elements 24 to 26 are off, the upper arm elements 21 to 23 are off, and the lower arm elements are off. The state in which 24-26 is on is switched every predetermined period.
As a result, it is possible to reduce heat generation due to the continued ON state of a specific element and unevenness of heat loss between elements.

  In addition, it is desirable that the predetermined period for switching is a period (for example, several seconds) that is sufficiently longer than one cycle of the first fundamental wave F1. Further, the predetermined period may be variable according to the rotation speed, torque, or the like of the motor 10. Furthermore, the predetermined period may be different in length between the first inverter unit 20 and the second inverter unit 30.

In the present embodiment, the first voltage value E1 of the first power supply source 41 and the second voltage value E2 of the second power supply source 42 are different values. Therefore, in the low voltage mode, it is possible to select whether the second inverter unit 30 is neutralized or whether the first inverter unit 20 is neutralized.
That is, in this embodiment, the low voltage mode is set to a neutral point on the second inverter unit 30 side and driven by the first voltage value E1 of the first power supply source 41, and the first inverter unit It can be divided into “control mode B” in which the 20 side is neutralized and driven by the second voltage value E 2 of the second power supply source 42. Further, three “control mode C (high voltage mode)” that is driven by the sum E1 + E2 of the first voltage value E1 of the first power supply source 41 and the second voltage value E2 of the second power supply source 42 is added. A control mode can be selected.

Here, FIG. 9 shows inverter efficiency, MG efficiency, and overall efficiency in the three control modes. In FIG. 9, the case of driving in the control mode A is indicated by a solid line, the case of driving in the control mode B is indicated by a broken line, and the case of driving in the control mode C is indicated by a one-dot chain line.
FIG. 9 shows a case where the torques P1 to P4 in FIG. The control mode A can output the rotation speed and torque below the solid line T1 in FIG. 2, the control mode B can output the rotation speed and torque below the solid line T2, and the control mode C is below the solid line T3. The rotation speed and torque can be output. That is, P1 and P2 can be output in all control modes, P3 can be output in control modes B and C, and P4 can be output in control mode C. In other words, P3 and P4 torque cannot be output in the control mode A, and P4 torque cannot be output in the control mode B.

Since the switching loss is smaller as the drive voltage is lower, as shown in FIG. 9A, the inverter efficiency is highest in the control mode A where the drive voltage is low, and then in the order of the control modes B and C.
Further, as shown in FIG. 9B, the MG efficiency is approximately the same regardless of the control mode, that is, regardless of the drive voltage.
Therefore, as shown in FIG. 9C, the overall efficiency is highest in the control mode A where the drive voltage is low, and then in the order of the control modes B and C.

  Therefore, in the present embodiment, in order to increase the overall efficiency, the area A below the solid line T1 in FIG. 2 drives the motor 10 in the control mode A with the lowest driving voltage, and the area B between the solid line T1 and the solid line T2. Next, the motor 10 is driven in the control mode B with the low driving voltage, and the region C between the solid line T2 and the solid line T3 is controlled so as to drive the motor 10 in the control mode C with the highest driving voltage. The mode is switched.

  Here, the switching loss due to the difference in switching speed will be described with reference to FIGS. The switching speed is a speed related to switching of the SW elements 21 to 26 and 31 to 36 from on to off or from off to on, and FIGS. 12A and 12B and FIGS. This corresponds to the rising slope of the inverter output voltage in b).

10, (a) is the relationship between current and voltage when the switching speed is slow, (b) is the switching loss when switching speed is slow, (c) is the relationship between current and voltage when switching speed is fast, ( d) shows the switching loss when the switching speed is high. Note that the switching loss corresponds to the area of the hatched area shown in FIGS. 10B and 10D, and when the switching loss is P, the switching loss is based on the current i and the voltage v. It is expressed as
P = ∫ (i × v) dt (1)

  As shown in FIG. 10, the higher the switching speed, the smaller the switching loss. Therefore, as shown in FIG. 11, the higher the switching speed, the smaller the inverter loss. In FIG. 11, the horizontal axis represents the switching speed ratio and the vertical axis represents the inverter loss ratio.

Next, the surge voltage due to the difference in switching speed will be described with reference to FIGS. FIG. 12 shows an example of the first inverter unit 20 (that is, low voltage driving), and FIG. 13 shows an example of the second inverter unit 30 (that is, high voltage driving).
12 and 13, (a) is the inverter output voltage when the switching speed is low, (b) is the inverter output voltage when the switching speed is high, (c) is the motor input voltage when the switching speed is low, ( d) shows the motor input voltage when the switching speed is fast. In (c) and (d), the case where the first wiring length L1 or the second wiring length L2 is relatively short is indicated by a solid line, and the case where it is long is indicated by a broken line.

As shown in FIGS. 12A and 12B and FIGS. 13A and 13B, if the drive voltage is the same, the inverter output voltage is equal regardless of the switching speed. On the other hand, when the switching speed is fast, the rising slope of the inverter output voltage is larger than when the switching speed is slow.
12 is compared with FIG. 13, the inverter output voltage Vout1 of the first inverter unit 20 shown in FIG. 12 is smaller than the inverter output voltage Vout2 of the second inverter unit 30 shown in FIG.

Next, the motor input voltage will be described. As described with reference to FIGS. 10 and 11, in order to reduce the switching loss, it is effective to increase the switching speed. On the other hand, when a steep voltage pulse is input by switching, a surge voltage is generated.
Here, regarding the peak value of the surge voltage when the first inverter unit 20 is driven, Vcs1 is set when the switching speed is slow and the wiring length is short, and Vcl1 is set when the wiring length is long (see FIG. 12C). Vds1 is when the speed is high and the wiring length is short, and Vdl1 is when the wiring length is long (see FIG. 12D). Further, regarding the peak value of the surge voltage when the second inverter unit 30 is driven, Vcs2 is set when the switching speed is slow and the wiring length is short, and Vcl2 is set when the wiring length is long (see FIG. 13C). Vds2 when the wiring length is short and the wiring length is short, and Vdl2 when the wiring length is long (see FIG. 13D).

As shown in FIGS. 12, 13C, and 13D, if the drive voltage and the switching speed are the same, the peak value of the surge voltage increases as the wiring length increases. That is, Vcl1> Vcs1 and Vdl1> Vds1. Further, Vcl2> Vcs2, and Vdl2> Vds2.
Further, if the drive voltage and the wiring length are the same, the peak value of the surge voltage becomes larger as the switching speed is faster. That is, Vds1> Vcs1 and Vdl1> Vcl1. Further, Vds2> Vcs2 and Vdl2> Vcl2.
Furthermore, if the switching speed and the wiring length are the same, the peak value of the surge voltage increases as the drive voltage increases. That is, Vcs2> Vcs1 and Vcl2> Vcl1. Further, Vds2> Vds1 and Vdl2> Vdl1.

FIG. 14 shows the relationship between the switching speed and wiring length and the peak value of the surge voltage. In FIG. 14, the horizontal axis represents the switching speed ratio, and the vertical axis represents the surge voltage peak value. The wiring length is Lx>Ly> Lz.
As shown in FIG. 14, the higher the switching speed, the greater the peak value of the surge voltage. Further, the longer the wiring length, the larger the peak value of the surge voltage.

  By the way, when the peak value of the surge voltage exceeds the partial discharge start voltage between the coils of the motor 10, partial discharge occurs inside the motor 10, and the insulating coating may be deteriorated, which may cause dielectric breakdown. Therefore, in order to ensure insulation performance, it is necessary to suppress the peak value of the surge voltage below the partial discharge start voltage.

Therefore, in the present embodiment, in order to suppress the peak value of the surge voltage below the partial discharge start voltage, the second driving speed is the second switching speed of the SW elements 31 to 36 of the second inverter unit 30 having a large surge voltage peak value. The switching speed S2 is made slower than the first switching speed S1, which is the switching speed of the first inverter unit 20. That is, S2 <S1.
In addition, the first inverter unit 20 and the second inverter unit 30 are preferably arranged as close to the motor 10 as possible. However, when there is a restriction such as a mounting space, the second inverter unit 30 is given priority in the vicinity of the motor 10. The second wiring length L2 that is the wiring length between the second inverter unit 30 and the motor 10 is shortened. That is, L2 <L1.

  FIG. 15 shows the effect when the wiring length on the second inverter unit 30 side is shortened and the switching speed is slowed. FIG. 15 shows a surge maximum voltage ratio that is a ratio of peak values of surge voltages. In the present embodiment, the total wiring length is the same as in Reference Example 2, and the second wiring length L2 is shortened. Therefore, the first wiring length L1 is longer than that of the reference example 2. In the present embodiment, the switching speed of the second inverter unit 30 is set slower than that of the reference example 2.

  As shown in FIG. 15, in the present embodiment, the first wiring length L1 is made longer than the reference example 2 in order to shorten the second wiring length L2, so that the first inverter unit 20 that is driven at a low voltage is used. The peak value of the surge voltage is larger than that in Reference Example 2. However, since it is smaller than the peak value of the surge voltage by the second inverter unit 30 that is driven at a high voltage and is equal to or lower than the partial discharge start voltage, it does not cause deterioration of the insulating coating.

  On the other hand, in the present embodiment, the second wiring length L2 is shortened and the second switching speed S2 is slowed down. Therefore, the peak value of the surge voltage by the second inverter unit 30 that is driven at high voltage is Small compared. Therefore, when viewed as the whole power converter 1, the peak value of the surge voltage in this embodiment is smaller than that in Reference Example 2. Therefore, it is possible to suppress the deterioration of the insulating film due to the peak value of the surge voltage exceeding the partial discharge start voltage.

As described in detail above, the power conversion device 1 that converts the power of the motor 10 having the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 includes the first power supply source 41 and the second power supply source 42. And a first inverter unit 20, a second inverter unit 30, and a control unit 60.
The first inverter unit 20 includes SW elements 21 to 26 connected to one end 111 of the U-phase coil 11, one end 121 of the V-phase coil 12, and one end 131 of the W-phase coil 13. Driven.
The second inverter unit 30 includes SW elements 31 to 36 connected to the other end 112 of the U-phase coil 11, the other end 122 of the V-phase coil 12, and the other end 132 of the W-phase coil 13, and the second power supply Driven by source 42.

The control unit 60 includes a first control signal generation unit 61 and a second control signal generation unit 62.
The first control signal generation unit 61 controls the on / off operation of the SW elements 21 to 26 by PWM control based on the carrier wave and the first fundamental wave F1 related to the current passed through the coils 11 to 13.
The second control signal generator 62 has a second fundamental wave that is 180 ° out of phase with the first fundamental wave F1 so that the switching frequency of the SW elements 31 to 36 is smaller than the switching frequency of the SW elements 21 to 26. Based on F2, the on / off operation of the SW elements 31 to 36 is controlled.
When the on / off operation of the SW elements 31 to 36 is controlled based on the second fundamental wave F2, the state in which the switching frequency of the SW elements 31 to 36 is the smallest is a rectangle that switches on / off every half cycle of the second fundamental wave. This is the case of wave control.

  In the present embodiment, the first power supply source 41 and the second power supply source 42 are controlled by controlling the first inverter unit 20 and the second inverter unit 30 based on a fundamental wave whose phase is shifted by 180 °. The motor 10 is driven in a state of being connected in series. Thereby, since the motor 10 can be driven with a high voltage, a high rotation and a high torque can be output.

  Moreover, in the 2nd inverter part 30 of this embodiment, it is set as the rectangular wave control which switches on / off of SW element 31-36 for every half cycle of the 2nd fundamental wave F2. Therefore, the switching frequency of the SW elements 31 to 36 of the present embodiment is less than the switching frequency of the SW elements 21 to 26 that are PWM-controlled based on the carrier wave and the first fundamental wave F1. Thereby, compared with the case where PWM control similar to the 1st inverter part 20 is performed, since the frequency | count of switching in the 2nd inverter part 30 can be reduced, the switching loss in the 2nd inverter part 30 can be reduced. . As a result, the loss of the entire apparatus is reduced and the efficiency is improved.

  Further, the first voltage value E1 of the first power supply source 41 that is the power supply source of the first inverter unit 20 and the second voltage value E2 of the second power supply source 42 that is the power supply source of the second inverter unit 30. Is a different value. In particular, in the present embodiment, the second voltage value is larger than the first voltage value and is twice the first voltage value. Further, the switching loss is larger when the driving voltage is larger. In the present embodiment, since the number of times of switching of the second inverter unit 30 having a large drive voltage is controlled, switching loss can be further reduced.

As described above, by driving the motor 10 with a high voltage, high rotation and high torque can be output. However, the higher the voltage, the greater the switching loss in the first inverter unit 20 and the second inverter unit 30. .
Therefore, the control unit 60 of the present embodiment switches between the high voltage mode and the low voltage mode according to the rotation speed and torque of the motor 10.
In the high voltage mode when the rotation speed and torque are large, the first control signal generator 61 controls the on / off operation of the SW elements 21 to 26 by PWM control based on the carrier wave and the first fundamental wave F1. Further, the second control signal generation unit 62 performs the on / off operation of the SW elements 31 to 36 based on the second fundamental wave F2 so that the number of switching times of the SW elements 31 to 36 is smaller than the number of switching times of the SW elements 21 to 26. To control.

  In the low voltage mode when the rotation speed and torque are small, one of the first control signal generation unit 61 or the second control signal generation unit 62 is on the high potential side of the SW elements 21 to 26 or the SW elements 31 to 36. The upper arm elements 21 to 23, 31 to 33 connected in all phases or the lower arm elements 24 to 26 and 34 to 36 connected in all phases to the low potential side are turned on, and the first control signal generator 61 or the first The other of the two control signal generators 62 controls the on / off operation of the SW elements 21 to 26 and 31 to 36 by PWM control based on the first fundamental wave F1.

  In the low voltage mode, the upper arm elements 21 to 23 of the first inverter unit 20 are turned on simultaneously for all phases, or the lower arm elements 24 to 26 are turned on simultaneously for all phases. The motor 10 is driven by the PWM control of the second inverter unit 30 driven by the second voltage value E2. Further, the upper arm elements 31 to 33 of the second inverter unit 30 are turned on at the same time for all phases, or all the phases of the lower arm elements 34 to 36 are turned on at the same time, thereby neutralizing the second inverter unit 30 side. The motor 10 is driven by PWM control of the first inverter unit 20 driven by the first voltage value E1.

  Thus, in the high voltage mode, high rotation and high torque can be output in a state where the first power supply source 41 and the second power supply source 42 are connected in series. In the low rotation and low torque regions, the low voltage mode is set, and the first inverter unit 20 side or the second inverter unit 30 side is neutralized. In the low-voltage mode, the first inverter unit 20 side or the second inverter unit 30 side is neutralized, and the one-side power source drive by one of the first power supply source 41 or the second power supply source 42 is performed. Compared with the mode, switching loss in a low rotation and low torque region can be reduced, and the efficiency of the entire apparatus can be increased.

  In particular, in the present embodiment, the second voltage value E2 of the second power supply source 42 is twice the first voltage value E1 of the first battery E1 of the first power supply source 41, and the first voltage value E1 and the second voltage The value E2 is unbalanced. Thereby, the low voltage mode can be further divided into two, control mode A driven by the first inverter unit 20 having a low drive voltage and control mode B driven by the second inverter unit 30 having a high drive voltage, Switching loss in a low rotation and low torque region can be further reduced.

  In addition, when the first inverter unit 20 side is neutralized in the low voltage mode, the first control signal generation unit 61 is in a state where the upper arm elements 21 to 23 of all phases are turned on and The state where the arm elements 24 to 26 are turned on is switched every predetermined period. When neutralizing the second inverter unit 30 side, the second control signal generation unit 62 is in a state where the upper arm elements 31 to 33 of all phases are on and the lower arm elements 34 to 36 of all phases are on. Are switched at predetermined intervals. As a result, it is possible to reduce heat generation due to a specific element being kept on and bias of heat loss for each element.

  Furthermore, in this embodiment, 2nd switching speed S2 which concerns on on / off switching of SW element 31-36 is below 1st switching speed S1 which concerns on on / off switching of SW element 21-26. Particularly in the present embodiment, the second switching speed S2 is slower than the first switching speed S1. By reducing the switching speed in the second inverter unit 30 having a high drive voltage, the peak value of the surge voltage in the second inverter unit 30 can be reduced.

  Furthermore, the second wiring length L2 that is the wiring length of the wiring that connects the second inverter unit 30 and the motor 10 is the second wiring length that is the wiring length of the wiring that connects the first inverter unit 20 and the motor 10. Shorter than L1. Accordingly, when the total wiring length is equal, the peak value of the surge voltage in the second inverter unit 30 having a high drive voltage is reduced as compared with the case where the first wiring length L1 and the second wiring length L2 are the same. Therefore, the peak value of the surge voltage as the whole power converter 1 can be reduced.

By reducing the peak value of the surge voltage, it is possible to suppress the surge voltage from exceeding the partial discharge start voltage, so that partial discharge is generated inside the motor 10 and deterioration of the insulating film can be suppressed. it can.
In the present embodiment, the wiring connecting the first inverter unit 20 and the motor 10 and the wiring connecting the second inverter unit 30 and the motor 10 are cables or bus bars.

  In the present embodiment, the control unit 60 corresponds to a “first control signal generation unit” and a “second control signal generation unit”. Specifically, the first control signal generator 61 corresponds to “first control signal generator”, and the second control signal generator 62 corresponds to “second control signal generator”.

(Other embodiments)
(A) Switching frequency In the above embodiment, in the high voltage mode, the first inverter unit is PWM-controlled and the second inverter unit is rectangular-wave controlled. In another embodiment, if the number of times of switching of the second switching element is less than the number of times of switching of the first switching element and control is performed based on the second fundamental wave that is 180 ° out of phase with the first fundamental wave, The inverter unit and the second inverter unit may be controlled in any way.
For example, if the modulation factor is (the amplitude of the fundamental wave / the amplitude of the carrier wave), if the carrier wave is the same, the larger the modulation rate, the smaller the number of switchings. It may be larger than the modulation factor of one fundamental wave. If it is assumed that the case where the modulation factor is infinite is rectangular wave control, the modulation factor of the second fundamental wave can also be regarded as the modulation factor of the first fundamental wave being large in the above embodiment. . Thereby, the frequency | count of switching of a 2nd switching element becomes smaller than the frequency | count of switching of a 1st switching element.
Note that the modulation rate may be increased stepwise when switching from the low voltage mode to the high voltage mode. With this configuration, hunting associated with switching from the low voltage mode to the high voltage mode can be suppressed.

Also, for example, in the high voltage mode, when both the first inverter unit and the second inverter unit are PWM controlled, the second control signal generation unit has a longer cycle than the first carrier wave related to driving the first inverter unit. The on / off operation of the second switching element may be controlled based on the two-carrier wave and the second fundamental wave. By making the period of the second carrier wave longer than the period of the first carrier wave, even if the modulation factor of the first fundamental wave and the modulation factor of the second fundamental wave are the same, the number of switching times of the first switching element As a result, the number of times of switching of the second switching element is reduced. Thereby, the switching loss in a 2nd inverter part can be reduced.
Note that the modulation factor and the period of the carrier wave can be set as appropriate so that the number of times of switching of the second switching element is less than the number of times of switching of the first switching element.

(A) Voltage value of power supply source In the above embodiment, the first voltage value and the second voltage value are different values. In other embodiments, the first voltage value and the second voltage value may be the same value. In the above embodiment, the second voltage value is twice the first voltage value. In other embodiments, the second voltage value may be smaller than the first voltage value, smaller than twice the first voltage value, or larger than twice the first voltage value.
In another embodiment, the first power supply source and the second power supply source may include a configuration such as a boost converter.

(C) Switching speed In the said embodiment, in order to reduce the peak value of a surge voltage, a 2nd switching speed is slower than a 1st switching speed. In other embodiments, the second switching speed may be the same as the first switching speed.
Further, as described in the above embodiment, the peak value of the surge voltage is larger as the drive voltage is higher. Here, considering the partial discharge start voltage and the peak value of the surge voltage, it is important to reduce the peak value of the surge voltage in the high voltage mode. In terms of switching loss, a higher switching speed is preferable.

  Therefore, in another embodiment, in the high voltage mode, the second switching speed is made slower than the first switching speed to reduce the peak value of the surge voltage, and in the low voltage mode, the first switching speed is reduced to reduce the switching loss. 2 The switching speed may be increased to be the same as the first switching speed. That is, in view of switching between the high-voltage mode and the low-voltage mode according to the rotation speed and torque of the rotating electrical machine, “the second switching speed is variable according to the rotation speed and torque of the rotating electrical machine”. is there. The switching speed can be changed by adjusting the gate resistance related to switching of the switching element. For example, if the switching speed is switched between the low voltage mode and the high voltage mode, two gate resistors having different resistance values are connected in parallel, and the switch is switched so that one gate resistor is connected to the switching element. Can be configured. Thereby, switching loss can be further reduced and efficiency can be improved.

(D) In the above embodiment, in the low voltage mode, in the inverter portion that is neutralized, the state where the upper arm element of all phases is on and the state where the lower arm element of all phases are on are predetermined. It changed every period. In another embodiment, it is not necessary to switch between a state in which the upper arm elements of all phases are turned on and a state in which the lower arm elements of all phases are turned on in the inverter section that is neutralized.
Further, temperature detecting means such as a thermistor for detecting the temperature of the switching element is provided, and based on the temperature of the switching element, all phases of the upper arm element are on and all phases of the lower arm element are off, and the upper arm element May be switched between a state in which all phases are off and a state in which all phases of the lower arm element are on. As a result, the heat generation of the switching element can be suppressed and appropriately controlled without exceeding the heat resistance limit.

  (E) In the above embodiment, the high voltage mode and the low voltage mode are switched according to the rotation speed and torque of the rotating electrical machine. In other embodiments, the high voltage mode may be used regardless of the rotation speed and torque of the rotating electrical machine.

(F) In the above embodiment, the switching element is an IGBT. In another embodiment, a MOS (Metal Oxide Semiconductor) transistor, a bipolar transistor, or the like can be used as the switching element.
(G) The rotating electrical machine of the above embodiment is a so-called motor generator having both a function as an electric motor and a function as a generator. However, in other embodiments, the electric motor may not have a function as a generator. However, the generator may not have a function as an electric motor.
(H) In the above embodiment, the rotating electrical machine is applied to a main vehicle of an electric vehicle. In other embodiments, the rotating electrical machine may be applied to a vehicle auxiliary machine or may be applied to other devices.
As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

DESCRIPTION OF SYMBOLS 1 ... Power converter 10 ... Motor (rotary electric machine)
11-13 ... Coil (winding)
20 ... 1st inverter part 21-26 ... SW element (1st switching element)
30 ... 2nd inverter part 31-36 ... SW element (2nd switching element)
41 ... 1st power supply source 42 ... 2nd power supply source 60 ... Control part (1st control signal production | generation means, 2nd control signal production | generation means)

Claims (13)

A power converter (1) for converting electric power of a rotating electrical machine (10) having windings (11-13),
A first power supply source (41);
A second power supply source (42);
A first inverter unit (20) having a first switching element (21-26) connected to one end (111, 121, 131) of the winding and driven by the first power supply source;
A second inverter unit (30) having a second switching element (31 to 36) connected to the other end (112, 122, 132) of the winding and driven by the second power supply source;
First control signal generating means (61) for controlling on / off operation of the first switching element by PWM control based on a first carrier wave and a first fundamental wave relating to a current passed through the winding; and The on / off operation of the second switching element is controlled based on a second fundamental wave that is 180 degrees out of phase with the first fundamental wave so that the number of switching times of the second switching element is less than the number of switching times of one switching element. A control unit (60) having second control signal generating means (62) for performing,
A power conversion device comprising:   The power conversion device according to claim 1, wherein a modulation rate of the second fundamental wave is larger than a modulation rate of the first fundamental wave.   The power converter according to claim 1 or 2, wherein the first voltage value applied by the first power supply source and the second voltage value applied by the second power supply source are different. .   The power converter according to claim 3, wherein the second voltage value is larger than the first voltage value.   The power converter according to claim 4, wherein the second voltage value is greater than twice the first voltage value.   6. The power conversion according to claim 4, wherein a second switching speed related to on / off switching of the second switching element is equal to or lower than a first switching speed related to on / off switching of the first switching element. apparatus.   The power conversion device according to claim 6, wherein the second switching speed is variable according to a rotation speed and torque of the rotating electrical machine.   The wiring length of the wiring (161, 162, 163) connecting the second inverter unit and the rotating electrical machine is the wiring length of the wiring (151, 152, 153) connecting the first inverter unit and the rotating electrical machine. It is shorter than this, The power converter device as described in any one of Claims 1-7 characterized by the above-mentioned.   The said wiring (151-153, 161-163) is a cable or a bus bar, The power converter device of Claim 8 characterized by the above-mentioned.   The second control signal generating means controls an on / off operation of the second switching element based on a second carrier wave having a longer period than the first carrier wave and the second fundamental wave. Item 10. The power conversion device according to any one of Items 1 to 9. The controller is
The first control signal generating means controls the on / off operation of the first switching element by PWM control based on the first carrier wave and the first fundamental wave, and the second control signal generating means is the first switching element. A first control mode for controlling the on / off operation of the second switching element based on the second fundamental wave so that the switching frequency of the second switching element is less than the switching frequency of
One of the first control signal generation means or the second control signal generation means is an upper arm element or a low potential side of all phases connected to the high potential side of the first switching element or the second switching element. The lower arm elements of all the phases connected to the first control signal generating means or the second control signal generating means are turned on by the PWM control based on the first fundamental wave. A second control mode for controlling the on / off operation of the second switching element;
The power conversion device according to any one of claims 1 to 10, wherein the power is switched according to a rotational speed and torque of the rotating electrical machine.   In the second control mode, the one of the first control signal generation unit or the second control signal generation unit is configured such that the upper arm element of all phases is on and the lower arm element of all phases The power conversion device according to claim 11, wherein a state in which all phases are on is switched every predetermined period.   In the second control mode, the one of the first control signal generation unit or the second control signal generation unit is configured to change the upper arm of all phases based on the temperature of the first switching element or the second switching element. The power conversion device according to claim 11, wherein a state in which an element is on and a state in which the lower arm element for all phases is off are switched.

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