JP6665951B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter.

  Conventionally, hybrid vehicles and electric vehicles are equipped with a high-voltage battery and a power converter. The high-voltage battery supplies power to a power converter for driving a motor for driving a vehicle. The power converter is equipped with a DCDC converter for converting a high voltage of a high voltage battery to a low voltage. The low voltage converted by the DCDC converter supplies power to accessories such as lights and radios of automobiles.

  As described in Patent Document 1, a power converter including a power semiconductor module that converts a DC voltage into an AC voltage and a DCDC converter that converts a DC voltage into a different DC voltage is disclosed.

JP 2013-212943 A

  Devices such as power converters need to be mounted in a limited space in order to improve the comfort of automobiles, and miniaturization is required. As described in Patent Literature 1, it has been proposed to reduce the size of a power conversion device by shortening a wiring distance from a power semiconductor module and each input terminal from a DCDC converter or the like.

  However, in order to further reduce the size of the power converter, it is necessary not only to shorten the wiring distance but also to reduce the size of equipment mounted on the power converter. In order to reduce the size of the power converter, it is conceivable to reduce the size of the DCDC converter mounted on the power converter. In order to reduce the size of the DCDC converter, it is expected that the frequency of the DCDC converter will increase.

  By the way, conventionally, a Si-MOSFET (silicon metal oxide semiconductor field effect transistor) used for a DCDC converter is driven at a switching frequency of several hundred kHz. In recent years, the frequency of DCDC converters has been spurred by next-generation semiconductor devices represented by SiC and GaN, which have dramatically improved performance compared to Si semiconductor devices. Although the frequency of the DCDC converter has been increasing, the deterioration of radio noise may be considered as a factor preventing the DCDC converter from increasing the frequency.

  Even at the switching frequency of a conventional DCDC converter, there is a problem that high-order harmonic components equal to or higher than the third harmonic cause noise to be mixed into a radio mounted on an automobile. As a cause of radio noise, radiated noise caused by a common mode current flowing in wiring is superimposed on a radio antenna, thereby causing noise and the like to be mixed into a radio.

  In the future, when further increasing the frequency of the DCDC converter in order to reduce the size of the DCDC converter, the fundamental wave of the switching frequency will be close to the radio frequency, and the problem of radio noise will be more serious than the current situation.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a power conversion device that suppresses radio noise and allows a DCDC converter to be downsized.

The power converter of the present invention includes an inverter (24, 25), a DCDC converter (80), and a case (40).
The inverter converts a DC voltage supplied from the battery (20) into an AC voltage.
The DCDC converter steps up or down the DC voltage supplied from the battery (20).

  The case includes a plurality of walls (401 to 404) surrounding the inverter from six directions, an inverter input terminal (41) connected to a power line from a battery and inputting a voltage to the inverter, and a DCDC converter connected to a power line to the DCDC converter. And a converter input terminal (81) for inputting a voltage to the input terminal.

In the plurality of wall portions, when the two wall portions arranged to face each other are a reference wall portion (401) and a facing wall portion (402),
The inverter input terminal is disposed on the reference wall side with respect to a virtual plane that bisects the case between the reference wall and the opposite wall.
The converter input terminal is arranged on the opposite wall with respect to the virtual plane.

  In the power converter of the present invention, the inverter input terminal and the converter input terminal are arranged on opposite sides with respect to the virtual plane, and the inverter has a virtual line (Iv) connecting the inverter input terminal and the converter input terminal. It is provided above. With such a configuration, the impedance inside the power conversion device increases, so that the radiation noise caused by the common mode current can be suppressed.

  Radio noise can be suppressed by suppressing radiation noise. Radio noise is suppressed, and the switching frequency of the DCDC converter can be increased. Since the frequency of the DCDC converter can be increased, the size of the DCDC converter can be reduced.

1 shows a drive system in which the power converter according to the first embodiment of the present invention is used. FIG. 2 is an equivalent circuit diagram of the noise filter according to the first embodiment of the present invention. FIG. 2 is an equivalent circuit diagram of the DCDC converter according to the first embodiment of the present invention. FIG. 3 is a top view of the case according to the first embodiment of the present invention. FIG. 11 is a top view of a case according to the second embodiment of the present invention. (A) A side view of the case as viewed from VIa-VIa in FIG. 5, and (b) a side view of the case as viewed from VIb-VIb in FIG. FIG. 13 is an equivalent circuit diagram of a power conversion device according to a third embodiment of the present invention. FIG. 13 is an equivalent circuit diagram of a power conversion device according to a fourth embodiment of the present invention. FIG. 13 is an equivalent circuit diagram of a power conversion device according to a fifth embodiment of the present invention. FIG. 14 is an equivalent circuit diagram of a power conversion device according to a sixth embodiment of the present invention. FIG. 17 is an equivalent circuit diagram of a power conversion device according to a seventh embodiment of the present invention. The top view of the case in other embodiments.

Hereinafter, a power converter according to an embodiment of the present invention will be described with reference to FIGS. In the description of the plurality of embodiments, the same components as those in the first embodiment will be denoted by the same reference numerals. Further, the “first embodiment” includes the first to seventh embodiments. The power converters of these embodiments are used, for example, in a system that drives a DCDC converter that supplies power to an inverter and auxiliary equipment.
(1st Embodiment)

The configuration of the motor drive system including the power converter 101 will be described with reference to FIG.
As shown in FIG. 1, motor generators 26 and 27 used in a motor drive system and a power converter 101 are provided.
The motor generators 26 and 27 are permanent-magnet synchronous three-phase AC motors, for example, motor generators used in a series-parallel hybrid system mounted on a hybrid vehicle. It has both a function as an electric motor that generates torque by being driven by the electric power from the battery 20 and a function as a generator that is driven and generated when the vehicle is braked.

  The power conversion device 101 includes a battery 20, a common mode capacitor 21, a filter capacitor 22, a boost converter 30, a smoothing capacitor 23, inverters 24 and 25, a noise filter 60, a DCDC converter 80, and a case 40. Hereinafter, “motor generator” is described as “MG”, and DCDC converter is described as “DDC”. In the figure, the inverter is described as “INV”.

  The battery 20 is a DC power supply connected to the inverter input terminal 41 of the case 40 and configured by a chargeable / dischargeable secondary battery such as a nickel hydride battery or a lithium ion battery. Instead of the battery 20, a power storage device such as an electric double layer capacitor may be used as the DC power supply. The voltage applied by the battery 20 is referred to as a battery voltage Vb.

  The common mode capacitor 21 is connected in parallel with the battery 20, is a series connection of two capacitors, and is a so-called “Y capacitor” in which a connection point is connected to a ground line. Further, the common mode capacitor 21 drops a common mode current conducted from the battery 20 via the high potential line Lp1 and the low potential line Lg1 to the ground line, and suppresses common mode noise.

  The filter capacitor 22 is a so-called “X capacitor” that is connected in parallel with the battery 20 and configured by one capacitor. Further, the filter capacitor 22 has a function of suppressing normal mode noise from the battery 20 and a function of smoothing fluctuations in the battery voltage Vb.

Boost converter 30 includes a reactor 31 and a booster 32. Boost converter 30 boosts battery voltage Vb to generate boosted voltage Vs. The generated boosted voltage Vs is output to inverters 24 and 25.
Reactor 31 is capable of storing and discharging electric energy due to an induced voltage generated with a change in current.
The boosting unit 32 includes two switching elements 33 and 34 connected in series, and freewheel diodes 35 and 36 connected in parallel to the switching elements 33 and 34.

  The high-potential side switching element 33 is connected between the output terminal of the reactor 31 and the high-potential line Lp1 of the inverters 24 and 25. The switching element 34 on the low potential side is connected between the output terminal of the reactor 31 and the low potential line Lg1 of the inverters 24 and 25. The return diodes 35 and 36 are provided in such a direction as to allow a current from a low potential side to a high potential side.

  In operation, when the high-potential side switching element 33 is off and the low-potential side switching element 34 is on, current flows from the battery 20 to the reactor 31 to store energy. When the switching element 33 on the high potential side is on and the switching element 34 on the low potential side is off, the energy accumulated in the reactor 31 is released, and the boost voltage in which the induced voltage is superimposed on the battery voltage Vb is boosted. The voltage Vs is output to the inverters 24 and 25.

The smoothing capacitor 23 is connected between the boost converter 30 and the inverter 24 in parallel with the inverter 24, and smoothes the fluctuation of the boosted voltage Vs output to the inverters 24 and 25.
Each of the inverters 24 and 25 includes six switching elements connected in a bridge, and receives a boosted voltage Vs. Inverters 24 and 25 convert the DC voltage into three-phase AC voltages and supply them to MGs 26 and 27 by switching on and off the switching elements of each phase by PWM control or phase control.

The noise filter 60 is arranged between the converter input terminal 81 and the inverter input terminal 41 and is connected in parallel with the filter capacitor 22 to suppress normal mode noise and common mode noise.
As shown in FIG. 2, the noise filter 60 has a filter input terminal 61, a filter output terminal 62, common mode capacitors 63 and 64, line capacitors 65 and 66, a normal mode choke coil 67, and a common mode choke coil 68. .

The filter input terminal 61 includes a first filter input terminal 611 and a second filter input terminal 612. The filter output terminal 62 includes a first filter output terminal 621 and a second filter output terminal 622.
The common mode capacitors 63 and 64 are Y capacitors, and drop a common mode current conducted via the high potential line Lp2 and the low potential line Lg2 to the ground line to suppress common mode noise.
The line capacitors 65 and 66 suppress normal mode noise transmitted through the high potential line Lp2 and the low potential line Lg2.

  The normal mode choke coil 67 has a structure in which one conductor is wound around one core, and is connected in series between the first filter input terminal 611 and the common mode choke coil 68. The normal mode choke coil 67 generates a magnetic flux in the normal mode choke coil 67 when a normal mode current flows through the normal mode choke coil 67. When a magnetic flux is generated in the normal mode choke coil 67, it acts as an inductor and suppresses normal mode noise.

  The common mode choke coil 68 includes a first coil 681 and a second coil 682 and has a structure in which two cores are wound around one core. The winding directions of the conductive wires of the first coil 681 and the second coil 682 are opposite to each other. In the common mode choke coil 68, when a common mode current flows through the first coil 681 and the second coil 682, the generated magnetic flux reinforces each other. Since the magnetic fluxes reinforce each other, the common mode choke coil 68 functions as an inductor that generates a large impedance, and suppresses common mode noise.

The DDC 80 is surrounded by a cover 99 and is connected to a converter input terminal 81 of the case 40. The DDC 80 reduces the voltage of the battery voltage Vb applied from the battery 20 via the inverter input terminal 41 to generate a reduced voltage Vd.
As shown in FIG. 3, the DDC 80 is a full-bridge DCDC converter, and includes a case connection terminal 92, a converter output terminal 82, switching elements 93 to 96, a transformer 83, synchronous rectification elements 84 and 85, a reactor 86, and a smoothing. It has capacitors 90 and 91.

The case connection terminal 92 includes a first case connection terminal 921 and a second case connection terminal 922, and is connected to the converter input terminal 81 of the case 40.
Converter output terminal 82 includes a first converter output terminal 821 and a second converter output terminal 822, and is connected to an auxiliary device such as a light or a radio of an automobile.

The switching elements 93 to 96 are arranged on two pairs of high and low potential lines to form a full bridge circuit. The switching element 93 and the switching element 95 are connected to the high potential line Lp3, and the switching element 94 and the switching element 96 are connected to the low potential line Lg3.
One diagonal switching elements 93 and 96 and the other diagonal switching elements 94 and 95 of the full bridge circuit alternately turn on and off at high speed, and positive and negative voltages are alternately applied to the primary coil 87 of the transformer 83.

  Transformer 83 converts a voltage between a primary side connected to case connection terminal 92 and a secondary side connected to converter output terminal 82. The transformer 83 includes a primary coil 87 and secondary coils 88 and 89. When positive and negative voltages are alternately applied to the primary coil 87, the voltages are output to the secondary coils 88 and 89 to convert the voltage.

For the synchronous rectifiers 84 and 85, for example, MOSFETs are used. The synchronous rectifier 84 is connected to a secondary coil 88, and the synchronous rectifier 85 is connected to a secondary coil 89. When the synchronous rectifiers 84 and 85 are alternately turned on and off, the secondary-side current is synchronously rectified.
The reactor 86 is capable of storing and discharging magnetic energy due to an induced voltage generated with a change in current.
Smoothing capacitors 90 and 91 smooth the voltage between case connection terminals 92 and between converter output terminals 82.
(Action)

Before describing the characteristic configuration of the present embodiment, the operation of the power converter 101 will be described.
For example, a battery voltage Vb of 100 to 300 V is applied from the battery 20 to the inverter input terminal 41. When battery voltage Vb is applied, boost converter 30 boosts battery voltage Vb to about 900 V to generate boosted voltage Vs. When the boosted voltage Vs is applied to the inverters 24 and 25, the inverters 24 and 25 convert the DC voltage into a three-phase AC voltage and supply the converted voltages to the MGs 26 and 27 during power running. In addition, inverters 24 and 25 convert the alternating current generated by MGs 26 and 27 into a direct current so that battery 20 can be charged during regeneration.

  When the battery voltage Vb is applied, the DDC 80 reduces the battery voltage Vb to 10 to 20 V by the high-speed switching of the switching elements 93 to 96 formed of the full bridge circuit, and the reduced voltage Vd is generated. The generated step-down voltage Vd is supplied to an auxiliary device such as a light or a radio of an automobile. At this time, radio noise is generated by superimposing radiated noise caused by a common mode current flowing through the wiring on the radio antenna. Since this radio noise is generated, the frequency of the DDC 80 cannot be increased, and the DDC 80 cannot be miniaturized conventionally.

  Therefore, in order to suppress radio noise and reduce the size of the DDC 80, the arrangement of the inverter input terminal 41 and the converter input terminal 81 in the case 40 is "developed". Specifically, the inverter input terminal 41 and the converter input terminal 81 in the case 40 are disposed on opposite sides of a virtual plane Sv that bisects the case 40. Hereinafter, the case 40 will be described in detail.

  As shown in FIG. 4, the case 40 is formed in a rectangular parallelepiped shape, is a three-dimensional body having a polygonal cross section in the height direction, has a plurality of wall portions surrounding from six directions, and has a reference wall portion 401 and a facing wall portion 402. Having. The case has an inverter input terminal 41 and a converter input terminal 81.

The reference wall 401 faces the opposing wall 402, and the opposing wall 402 includes a range Sp where the inverter input terminal 41 is projected.
The range Sp is a virtual plane Sa formed from the first inverter input terminal 411 toward the opposing wall 402, a virtual plane Sb directed from the second inverter input terminal 412 toward the opposing wall 402, and a projection plane formed by the surface of the opposing wall 402. It is. In the facing wall portion 402, a wall surface outside the range Sp is defined as Sr.
A virtual plane bisected between the reference wall 401 and the opposing wall in the longitudinal direction of the case 40 is defined as Sv. The virtual surface Sv is a virtual surface that bisects the outermost surface among the projection surfaces on which the case 40 is projected from six directions. The opposing wall 402 is disposed on the opposite side of the reference wall 401 with respect to the virtual surface Sv.

  Inverter input terminal 41 is connected to battery 20 and includes a first inverter input terminal 411 and a second inverter input terminal 412. The inverter input terminal 41 is connected to a power line from the battery 20, and inputs a voltage to the inverters 24 and 25 via the boost converter 30.

  Converter input terminal 81 is connected to case connection terminal 92 of DDC 80, and includes first converter input terminal 811 and second converter input terminal 812. The converter input terminal 81 is connected to the power line to the DDC 80 and inputs the voltage via the noise filter 60 to the DDC 80.

  The inverter input terminal 41 and the converter input terminal 81 are arranged on opposite sides with respect to the virtual plane Sv. The inverter input terminal 41 is provided on the reference wall 401, and the converter input terminal 81 is provided on the opposing wall 402. The converter input terminal 81 is provided outside the range Sp, that is, on the wall surface Sr in the opposing wall portion 402.

The midpoint of the inverter input terminal 41 is Pi, the midpoint of the converter input terminal 81 is Pc, and the virtual line connecting the midpoint Pi and the midpoint Pc is Iv. The midpoint Pi and the midpoint Pc are arranged on opposite sides of the virtual plane Sv. The midpoint Pi is adjacent to the reference wall 401, and the midpoint Pc is adjacent to the opposing wall 402. Inverters 24 and 25 are arranged on virtual line Iv in case 40.
(effect)

  (1) In the present embodiment, the inverter input terminal 41 and the converter input terminal 81 are arranged on opposite sides with respect to the virtual plane Sv. The inverter input terminal 41 is provided on the reference wall 401, and the converter input terminal 81 is provided on the opposite wall 402. With such a configuration, the inductance or capacitance in power conversion device 101 is utilized between inverter input terminal 41 and converter input terminal 81.

  Since the inductance or the capacitance is used, the impedance inside the power conversion device 101 increases, and radiation noise caused by the common mode current can be suppressed. Since radiation noise can be suppressed, radio noise can be suppressed, and the switching frequency of the DDC 80 can be increased. Since the frequency of the DDC 80 can be increased, the size of the DDC 80 can be reduced.

  (2) In addition, since the inverters 24 and 25 are on the virtual line Iv, the inductance or the capacitance parasitic on the inverter can be used, so that the impedance inside the power converter increases. For this reason, the radiation noise caused by the common mode current can be further suppressed.

(2nd Embodiment)
The configuration of the second embodiment is the same as the configuration of the first embodiment, except for the form of the wall of the case.
As illustrated in FIG. 5, the case 42 of the power conversion device 102 includes a reference wall 403, which is two walls adjacent to each other on the common side EC, and an adjacent wall 404.

As shown in FIG. 6A, the outer shape of the reference wall portion 403 is configured by a plurality of sides E11 to E14. The sides E11 and E14 face each other, and the sides E12 and E13 face each other.
As shown in FIG. 6B, the outer shape of the adjacent wall portion 404 is constituted by a plurality of sides E21 to E24. The sides E21 and E24 face each other, and the sides E22 and E23 face each other. The side E11 and the side E24, which are sides common to the reference wall 403 and the adjacent wall 404, are defined as a common side Ec.

  The inverter input terminal 41 is adjacent to the side E14 farthest from the common side Ec in the reference wall portion 403. The converter input terminal 81 is adjacent to the side E21 farthest from the common side Ec in the adjacent wall portion 404. The second embodiment has the same advantages as the first embodiment.

(Third embodiment)
The configuration of the third embodiment is the same as the configuration of the first embodiment except for the arrangement of the noise filter of the power conversion device.
As shown in FIG. 7, the noise filter 160 of the power conversion device 103 is arranged between the common mode capacitor 21 and the filter capacitor 22 in parallel. As described above, even in a mode in which the distance from the inverter input terminal 41 to the noise filter 160 is short, the same effect as in the first embodiment can be obtained.

(Fourth embodiment)
The configuration of the fourth embodiment is the same as the configuration of the first embodiment except for the arrangement of the filter capacitor and the boost converter.
As shown in FIG. 8, the filter capacitor 122 of the power converter 104 is arranged between the boost converter 130 and the noise filter 60 on the converter input terminal 81 side, and is arranged in parallel with the noise filter 60.

  Boost converter 130 is arranged between inverters 24 and 25 and filter capacitor 122 on converter input terminal 81 side. The distance from inverter input terminal 41 to filter capacitor 122 is large, and the distance from inverter input terminal 41 to boost converter 130 is large. Also in the fourth embodiment, the same effects as in the first embodiment can be obtained.

(Fifth embodiment)
The configuration of the fifth embodiment is the same as the configuration of the first embodiment except for the arrangement of the filter capacitors.
As shown in FIG. 9, the filter capacitor 222 of the power converter 105 is arranged between the inverters 24 and 25 and the noise filter 60, and is arranged in parallel with the noise filter 60. As described above, the same effect as that of the first embodiment can be obtained even in a mode in which the distance from the inverter input terminal 41 to the filter capacitor 122 is large.

(Sixth embodiment)
The configuration of the sixth embodiment is the same as the configuration of the fourth embodiment except for the wiring path from the inverter input terminal of the power converter to the converter input terminal.
As shown in FIG. 10, the high-potential line Lp4 and the low-potential line Lg4 from the first inverter input terminal 411 of the power converter 106 to the noise filter 60 are each directly connected by one conductor. A high-potential line Lp4 from the first inverter input terminal 411 to the input terminal of the noise filter 60 and a low-potential line Lg4 from the output terminal of the noise filter 60 to the second inverter input terminal 412 are arranged side by side on the wall 405 side of the case 40. I'm running. The sixth embodiment has the same advantages as the first embodiment.

(Seventh embodiment)
The configuration of the seventh embodiment is the same as the configuration of the fifth embodiment except for the wiring path from the inverter input terminal of the power converter to the converter input terminal.
As shown in FIG. 11, the high potential line Lp5 and the low potential line Lg5 from the first inverter input terminal 411 of the power conversion device 107 to the filter capacitor 222 are directly connected by one conductor. The high-potential line Lp5 and the low-potential line Lg5 from the first inverter input terminal 411 to the input terminal of the filter capacitor 222 run in parallel on the wall 406 side of the case 40. Also in the seventh embodiment, the same effects as in the first embodiment can be obtained.

(Other embodiments)
(I) The DDC is a step-down converter that steps down the voltage applied from the battery in the present embodiment, but may function as a step-up converter that steps up the voltage applied from the battery. The same effects as those of the first embodiment can be obtained.
(Ii) As shown in FIG. 12, the DDC 80 may be housed inside a case. Also, the battery may be housed in the case similarly. The same effects as those of the first embodiment can be obtained.

(Iii) In order to cool the inverter or the DDC, a cooling flow path through which a cooling medium such as cooling water or a cooling gas can flow may be provided inside the power converter.
(Iv) The DDC may use a push-bull type DCDC converter. Regardless of the type of the DCDC converter, the same effects as in the first embodiment can be obtained.
(V) The case need not be a rectangular parallelepiped that surrounds the case from six directions. It may have a columnar body having a polygonal bottom surface such as a stepped or trapezoidal shape, or a curved surface having a semicircular column or a sectoral column.
As described above, the present invention is not limited to such an embodiment, and can be implemented in various forms without departing from the spirit of the invention.

20 ... battery,
24, 25 ... inverter,
40 ... case, 401 to 404 ... wall,
41 ... inverter input terminal
80 DC-DC converter,
81 ··· Converter input terminal.

Claims (2)

Inverters (24, 25) for converting a DC voltage supplied from the battery (20) to an AC voltage;
A DCDC converter (80) for increasing or decreasing the DC voltage supplied from the battery;
A plurality of walls (401 to 404) surrounding the inverter from six directions, an inverter input terminal (41) connected to a power line from the battery and inputting a voltage to the inverter, and a power line to the DCDC converter are connected. A case (40) having a converter input terminal (81) for inputting a voltage to the DCDC converter;
With
In the plurality of wall portions, when the two wall portions that are arranged to face each other are a reference wall portion (401) and a facing wall portion (402),
The inverter input terminal is arranged on the reference wall side with respect to a virtual plane (Sv) that bisects the case between the reference wall and the opposing wall,
The converter input terminal is disposed on the opposite wall portion side with respect to the virtual surface,
The power converter wherein the inverter is provided on a virtual line (Iv) connecting the inverter input terminal and the converter input terminal. A boost converter (30) between the battery and the inverter, which boosts a DC voltage supplied from the battery and outputs the boosted DC voltage to the inverter;
The boost converter includes a reactor (31) capable of storing and discharging electric energy and a booster (32) including switching elements (33, 34) connected in series,
The power converter according to claim 1, wherein the booster is provided on a virtual line (Iv) connecting the inverter input terminal and the converter input terminal.

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