JP2015213406A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To employ power cards housing three switching elements for a power converter including a voltage converter circuit and an inverter circuit, and provide a technique for effectively utilizing an internal space of the power cards.SOLUTION: A power converter 10 includes a voltage converter circuit 12 and an inverter circuit 16a. The power converter 10 comprises first to third power cards and a lamination unit as hardware. Three upper arm switching elements T1 to T3 of the inverter circuit are housed in the first power card PC1. Three lower arm switching elements T4 to T6 of the inverter circuit are housed in the second power card PC2. A step-up switching element T8, a step-down switching element T7, and a snubber capacitor 5 of the voltage converter circuit are housed in the third power card PC5. The first, second, and third power cards and a plurality of coolers alternately laminated.

Description

  The present invention relates to a power converter that converts DC power of a battery into AC power and supplies it to a traveling three-phase AC motor. In particular, a chopper-type voltage converter circuit that performs a step-up operation that boosts the battery power and a step-down operation that steps down the regenerative power generated by the traveling three-phase AC motor, and converts the power boosted by the voltage converter circuit into alternating current The present invention relates to a power converter including an inverter circuit that supplies the three-phase AC motor.

  Since the traveling motor of an electric vehicle has a large output, the power converter that converts the DC power of the battery into AC power and supplies the motor to the motor generates a large amount of heat. In particular, the amount of heat generated by a switching element for power conversion called a power transistor is large. In addition, an inverter circuit for creating a three-phase alternating current requires at least six switching elements. Some electric vehicles use a motor having a drive voltage higher than the output voltage of the battery, and such an electric vehicle includes a voltage converter circuit for voltage conversion as a front stage of the inverter circuit. The voltage converter circuit also includes a plurality of switching elements.

  As a device for efficiently cooling a large number of switching elements, a multilayer unit in which a large number of switching elements are packaged several times and a plurality of flat-plate packages (power cards) and a plurality of flat-plate coolers are alternately stacked is known. It has been. In Patent Document 1, three upper arm switching elements of an inverter circuit that generates three-phase alternating current are accommodated in one power card, and three lower arm switching elements are accommodated in another one power card. Proposed. Since six switching elements are distributed to two power cards, there is an advantage that the number of power cards may be small.

  On the other hand, the inverter circuit has a configuration in which three sets of series circuits of two switching elements are connected in parallel. As is well known, a chopper type buck-boost voltage converter also has a series circuit of a step-up switching element and a step-down switching. In other words, a power converter including a voltage converter has four sets of series circuits of two switching elements (in the case of a power converter that drives two motors, there are seven sets). Patent Document 2 provides that a series circuit of two switching elements is accommodated in one power card.

  In addition to the switching element, a technique for accommodating another element together with the switching element in a power card has also been proposed. For example, Patent Document 3 proposes that a switching element and a snubber capacitor connected in parallel to the switching element are accommodated in one power card. The snubber capacitor is a capacitor that is inserted in order to reduce a surge voltage during a switching operation.

JP 2007-006575 A JP 2012-249552 A JP 2010-153527 A

  A power converter including a voltage converter circuit and an inverter circuit requires eight switching elements. In Patent Document 2, eight switching elements are housed in a power card two by two, and a total of four power cards are stacked with a cooler. If a power card that accommodates three switching elements is applied to eight switching elements, only three power cards are required. However, only two switching elements are required for one power card. There is room in the interior. The present specification provides a technique for effectively using the internal space of a power card while adopting a power card that accommodates three switching elements for a power converter including a voltage converter circuit and an inverter circuit. In the case of a power converter that drives two motors, six additional switching elements are required for another motor drive inverter, but a total of 14 switching elements are accommodated. If it is distributed to the power cards that can be made, there will still be space in one power card.

  The technology disclosed in this specification accommodates a step-up switching element, a step-down switching element, and a snubber capacitor of a voltage converter circuit in one power card having a capacity sufficient to accommodate three switching elements. The snubber capacitor is connected in parallel to at least one of the step-up switching element and the step-down switching element (that is, the snubber capacitor may be connected in parallel to a series circuit of two switching elements). . For the inverter circuit, three upper arm switching elements are accommodated in one power card, and three lower arm switching elements are accommodated in another power card. The three power cards are stacked with a plurality of coolers to constitute a stacked unit. In addition, switching elements of inverter circuits and voltage converter circuits often involve diodes connected in antiparallel. Said power card may accommodate the diode connected antiparallel with the switching element.

  The technology disclosed in this specification can realize a space efficient power converter that effectively uses the internal space of a power card having a volume capable of accommodating three switching elements. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the drive system of the electric vehicle containing the power converter of an Example. It is a perspective view explaining the hardware constitutions of a power converter. It is a schematic diagram explaining the structure of a 1st power card. It is a schematic diagram explaining the structure of a 2nd power card. It is a schematic diagram explaining the structure of a 3rd power card. It is a schematic diagram explaining the structure of the 3rd power card of a modification. It is a schematic diagram explaining the structure of the 3rd power card of another modification. It is a schematic diagram explaining the structure of the 3rd power card of another modification.

  A power converter according to an embodiment will be described with reference to the drawings. FIG. 1 shows a block diagram of an electric power system of an electric vehicle 100 equipped with the power converter of the embodiment. The electric vehicle 100 includes two traveling motors 7a and 7b. Therefore, the power converter 10 includes two inverter circuits 16a and 16b. The outputs of the two motors 7a and 7b are appropriately combined or distributed by the power distribution mechanism 8 and transmitted to the axle 9 (that is, drive wheels).

  The power converter 10 is connected to the battery 14 via the system main relay 13. The power converter 10 includes a chopper type voltage converter circuit 12 that boosts the voltage of the battery 14, and two sets of inverter circuits 16a and 16b that convert the boosted DC power into AC. The motors 7a and 7b are driven by the electric power converted through the power converter 10. The power converter 10 can also step down the regenerative power from the motors 7 a and 7 b and store it in the battery 14. In this case, the voltage converter circuit 12 operates as a step-down circuit. That is, regenerative power (AC) from the motors 7 a and 7 b is converted into DC power by the inverter circuits 16 a and 16 b, and then stepped down by the voltage converter circuit 12 and stored in the battery 14.

  The circuit configuration of the voltage converter circuit 12 will be described. The reactor 2 and the switching element T7 are connected between the output side and the input side in the high potential side line of the voltage converter circuit 12. The low-potential line directly connects the input side and the output side of the voltage converter circuit 12. The line on the low potential side corresponds to the ground line. That is, the line directly connecting the low potential end on the input side (battery 14 side) and the low potential end on the output side (inverter circuits 16a and 16b) of the voltage converter circuit 12 corresponds to the ground line.

  One end of the reactor 2 is connected to a high potential end on the input side (battery 14 side), and a switching element T7 is connected to the other end (output side). Further, another switching element T8 is connected between the other end of the reactor 2 (low potential end of the switching element T7) and the ground line. In other words, the voltage converter circuit 12 includes a series circuit of two switching elements T7 and T8, and the reactor 2 is connected to the midpoint thereof. A snubber capacitor 5 is connected in parallel with a series circuit of two switching elements T7 and T8. The snubber capacitor 5 is inserted in order to relieve a surge voltage generated due to the switching operation of the switching elements T7 and T8. Since the purpose is to suppress surge voltage, the capacity of the snubber capacitor 5 is much smaller than that of the filter capacitor 3 and the smoothing capacitor 4 (described later).

  A filter capacitor 3 is connected between the battery side of the reactor 2 and the ground line. On the other hand, a smoothing capacitor 4 is connected between the high potential end of the voltage converter circuit 12 on the inverter circuit side and the ground line. The filter capacitor 3 is a device that temporarily stores electric energy during the step-up / step-down operation of the voltage converter circuit 12, and the smoothing capacitor 4 suppresses the pulsation of the current input to the inverter circuits 16a and 16b. It is a device.

  Diodes D7 and D8 are connected in antiparallel to the switching elements T7 and T8, respectively. Further, a pulse signal (PWM signal) is sent from the controller 15 to each switching element of the voltage converter circuit 12 to control on / off of each switching element.

  The voltage converter circuit 12 is a type called a chopper type, and the boosting operation is mainly performed by the switching element T8. The step-down operation is mainly performed by the switching element T7. Hereinafter, for convenience of explanation, the switching element T7 may be referred to as a step-down switching element, and the switching element T8 may be referred to as a step-up switching element. Since the operation of the voltage converter circuit 12 of FIG. 1 is well known, detailed description thereof is omitted.

  A circuit configuration of the inverter circuit 16a will be described. The inverter circuit 16a outputs a three-phase AC to supply power to the three-phase AC motor 7a. Therefore, the inverter circuit 16a has a configuration in which three sets of series circuits of two switching elements are connected in parallel (T1 and T4, T2 and T5, T3 and T6). A diode is connected in antiparallel to each switching element. The high potential side of the three sets of series circuits is connected to the input terminal on the high potential side of the inverter circuit 16a, and the low potential side of the three sets of series circuits is connected to the input terminal on the low potential side of the inverter circuit 16a. Three-phase alternating current (U-phase, V-phase, W-phase) is output from the midpoint of the three sets of series circuits.

  In the inverter circuit, the current path from the high potential input side of DC power to the motor is called the upper arm, and the current path from the motor to the low potential input side of the DC power is called the lower arm. The upper arm of the inverter circuit 16 a is connected to the output terminal on the high potential side of the voltage converter circuit 12, and the lower arm of the inverter circuit 16 a is connected to the ground line of the voltage converter circuit 12. The switching elements T1, T2, and T3 in FIG. 1 are included in the “upper arm”, and the switching elements T4, T5, and T6 are included in the “lower arm”. Hereinafter, for convenience of explanation, the switching elements T1, T2, and T3 included in the upper arm are referred to as upper arm switching elements, and the switching elements T4, T5, and T6 included in the lower arm are referred to as lower arm switching elements. is there.

  The inverter circuit 16b outputs a three-phase AC to supply power to the three-phase AC motor 7b. Since the circuit configuration of the inverter circuit 16b is the same as that of the inverter circuit 16a, a specific circuit is not shown in FIG. Similarly to the inverter circuit 16a, the inverter circuit 16b has a configuration in which three sets of series circuits of switching elements are connected in parallel. Similarly to the voltage converter circuit 12, a pulse signal (PWM signal) is sent to each switching element of the inverter circuits 16a and 16b from the controller 15 to control on / off of each switching element. Since the operation of the inverter circuits 16a and 16b is also a well-known technique, detailed description thereof is omitted.

  Transistors are used as the switching elements T1 to T8 (and the switching elements included in the inverter circuit 16b). In this embodiment, an IGBT (Insulated Gate Bipolar Transistor) is used. However, this transistor may be another transistor, for example, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Alternatively, different types of switching elements may be used in the power converter in the future. The technology disclosed in this specification does not depend on the type of the switching element.

  A hardware configuration of the power converter 10 according to the embodiment will be described. FIG. 2 is a perspective view showing a device layout in the case of the power converter 10. In order to supply electric power to the traveling motors 7a and 7b mounted on the electric vehicle 100, a large current flows through the switching elements T1-T8 (and the switching elements included in the inverter circuit 16b) provided in the power converter 10. The calorific value is also large. In order to efficiently cool a plurality of switching elements, the power converter 10 includes a stacked unit 20 in which five power cards PC1 to PC5 and six coolers 21 are alternately stacked. Here, the power card is a package in which several switching elements are molded with resin. The package is provided with a terminal for connecting the switching element accommodated in the package to an external element. The terminals will be described later. Moreover, the broken-line rectangle shown with the code | symbol PC1-PC5 in FIG. 1 represents the components incorporated in each power card.

  Also, the filter capacitor 3, the smoothing capacitor 4, and the reactor 2 of FIG. 1 are large in size so that they can withstand a large current. 2 indicates a capacitor element group constituting the smoothing capacitor 4, and reference numeral 33 indicates a capacitor element constituting the filter capacitor 3. Moreover, the code | symbol 32 is a reactor unit equivalent to the reactor 2 of FIG. In addition, the power converter 10 includes a terminal unit 37 in which a current sensor for monitoring an output current is embedded, a control board 34 for generating a PWM signal to be applied to each switching element, and the like. The multilayer unit 20, the capacitor elements 31, 33, the reactor unit 32, the control board 34, and the terminal unit 37 are accommodated in a case 36 and covered with a cover 35 from above.

  The laminated unit 20 will be further described. Each power card is sandwiched between the coolers 21 on both sides. The inside of each cooler 21 is a cavity through which the refrigerant passes. Holes are provided on both sides of each cooler 21 in the longitudinal direction (Y-axis direction in FIG. 2), and adjacent coolers 21 are connected by a connecting pipe. A refrigerant supply pipe and a refrigerant discharge pipe are connected to the cooler 21 located at the end in the stacking direction. The refrigerant supplied from the refrigerant supply pipe is distributed to all the coolers 21 through the connection pipe. The refrigerant absorbs the heat of the adjacent power card while passing through the inside of each cooler 21 and is sent to the refrigerant discharge pipe through the other connecting pipe. The refrigerant is a liquid, for example, water or LLC (Long Life Coolant).

  As shown in FIG. 1, the power card PC1 accommodates the three upper arm switching elements T1-T3 of the inverter circuit 16a and the diodes D1-D3 connected in antiparallel thereto. FIG. 3 is a schematic diagram illustrating the internal configuration of the power card PC1. It should be noted that FIG. 3 is a schematic diagram and does not show physical hardware.

  The power card PC1 is a device in which three upper arm switching elements T1-T3 and three diodes D1-D3 are molded in a resin mold package 41. Four power terminals 43a-43d are exposed at the lower end of the power card PC1, and three control terminals 42a-43a are exposed at the upper end. The power terminal 43a is a terminal to which the high potential output line of the voltage converter circuit 12 is connected, and is electrically connected to the high potential side electrodes (collector electrodes) of the three upper arm switching elements T1-T3 inside the power card. . The three power terminals 43b-43c are electrically connected to the low potential side electrodes (emitter electrodes) of the three upper arm switching elements, respectively. Inside the mold package 41, diodes D1-D3 are connected in antiparallel to the switching elements.

  The three types of control terminals 42a-42c are electrically connected to the gates of the switching elements T1-T3, respectively. The control terminals 42a-42c are connected to the control board 34, and a PWM signal is supplied from the control board 34 to each switching element via the control terminals 42a-42c.

  The power card PC2 accommodates three lower arm switching elements T4-T6 of the inverter circuit 16a and diodes D4-D6 connected in antiparallel to them (see FIG. 1). FIG. 4 is a schematic diagram illustrating the internal configuration of the power card PC2. It should be noted that FIG. 4 is also a schematic diagram and does not show physical hardware.

  The power card PC2 is a device in which three lower arm switching elements T4-T6 and three diodes D4-D6 are molded in a resin mold package 41. Four power terminals 43a-43d are exposed at the lower end of the power card PC2, and three control terminals 42a-43a are exposed at the upper end. The power terminal 43a is a terminal to which the ground line of the voltage converter circuit 12 is connected, and is electrically connected to the low potential side electrodes (emitter electrodes) of the three upper arm switching elements T1-T3 inside the power card. The three power terminals 43b-43c are electrically connected to the high potential side electrodes (collector electrodes) of the three lower arm switching elements T4-T6, respectively. Inside the mold package 41, diodes D4-D6 are connected in antiparallel to the switching elements. The three types of control terminals 42a-42c of the power card PC2 are the same as the control terminals of the power card PC1.

  The power terminal 43b of the power card PC1 and the power terminal 43b of the power card PC2 are connected to construct a series circuit of the upper arm switching element T1 and the lower arm switching element T4. Similarly, another series circuit is constructed by connecting the power terminals 43c and 43d of the power card PC1 and the power terminals 43c and 43d of the power card PC2, respectively.

  Since the power cards PC3 and PC4 of the second inverter circuit 16b have the same configuration as the PC1 and PC2 of the first inverter circuit 16a, description thereof is omitted.

  The power card PC5 will be described. As described above, the power cards PC1 to PC4 accommodate three switching elements. However, as shown in FIG. 1, the power card PC5 includes two switching elements T7 and T8 and vice versa. The diodes D7 and D8 connected in parallel and the snubber capacitor 5 are accommodated. FIG. 5 is a schematic diagram for explaining the internal layout of the power card PC5. As understood from comparison with the schematic diagram of the power card PC1 (FIG. 3), in the power card PC5, the snubber capacitor 5 is arranged at the position of the switching element in the center of the power card PC1.

  The power terminal 43d is electrically connected to the high potential electrode (collector electrode) of the step-down switching element T7, and the power terminal 43b is electrically connected to the low potential side electrode (emitter electrode) of the step-up switching element T8. The step-down switching element T7 and the step-up switching element T8 are connected in series inside the mold package 41, and the middle point thereof is electrically connected to the power terminal 43a. The power terminal 43c is not used.

  The control terminals 42a and 42c are electrically connected to the gates of the step-up switching element T8 and the step-down switching element T7, respectively. The control terminal 42b is not used.

  The advantages of the power converter 10 will be described. As described above, the power converter 10 includes the power cards PC1 and PC3 that accommodate the three upper arm switching elements T1-T3 of the inverter circuit, and the power card PC2 that accommodates the three lower arm switching elements T4-T6. In addition to PC4, a power card PC5 containing a step-down switching element T7, a step-up switching element T8, and a snubber capacitor 5 is provided. These power cards PC1 to PC5 are alternately stacked with a plurality of coolers 21 to form a stacked unit 20.

  The power cards PC1 to PC5 are made to have the same outer shape in order to share the manufacturing process. In addition, it is advantageous also on the load balance at the time of laminating | stacking alternately with the several cooler 21 that the external shape of all the power cards is the same. Since all the power cards have the same outer shape, the power card PC5 only needs to accommodate two switching elements compared to the power cards PC1 to PC4 that accommodate three switching elements, so there is room in the internal space. There is. In the power converter 10 of the embodiment, the snubber capacitor 5 is disposed in the marginal space. The snubber capacitor 5 is connected in parallel to a series circuit of a step-down switching element T7 and a step-up switching element T8. The snubber capacitor 5 reduces the surge voltage generated due to the step-down switching element T7 or the step-up switching element T8. The power converter 10 employs a power card of a size that can accommodate three switching elements, and the power card that accommodates the switching elements T7 and T8 for the voltage converter accommodates the snubber capacitor 5, thereby providing a power card. To effectively use the internal space.

  A modification of the internal layout of the power card PC5 that accommodates the step-down switching element T7 and the step-up switching element T8 will be described. FIG. 6 is a schematic diagram of a power card PC5a of the first modification. In the power card PC5a, the switching elements on the left side of the three switching elements arranged in the power card PC1 are discarded, and the snubber capacitor 5 is inserted therein. The power terminal 43d is electrically connected to the high potential side electrode (collector electrode) of the step-down switching element T7, and the power terminal 43c is electrically connected to the low potential side electrode (emitter electrode) of the step-up switching element T8. The power terminal 43a is electrically connected to the midpoint of the series circuit of the switching elements T7 and T8. The power terminal 43b is not used. The control terminals 42b and 42c are electrically connected to the gate electrodes of the step-up switching element T8 and the step-down switching element T7, respectively. The control terminal 42a is not used.

  Another modification of the power card PC5 is shown in FIG. The power card PC5b in FIG. 7 is an example in which snubber capacitors 5a and 5b are connected in parallel to the step-down switching element T7 and the step-up switching element T8, respectively. FIG. 8 is a schematic diagram of a power card PC5c of still another modification. The power card PC5c is an example in which the snubber capacitor 5a is connected in parallel to the step-down switching element T7, but the step-up switching element T8 is not provided with a snubber capacitor.

  Points to be noted regarding the technology described in the embodiments will be described. In the embodiment, the power cards PC1 and PC3 containing the three upper arm switching elements correspond to an example of the first power card. The power cards PC2 and PC4 that house three lower arm switching elements correspond to an example of a second power card. A power card that houses the step-down switching element T7 and step-up switching element T8 of the voltage converter circuit, and the snubber capacitor 5 (5a, 5b) corresponds to an example of a third power card.

  The power converter 10 according to the embodiment includes two inverter circuits 16a and 16b in order to supply power to two traveling motors. The technology disclosed in this specification is also preferably applied to an electric vehicle including one voltage converter circuit and one inverter circuit. The technology disclosed in the present specification is also preferably applied to a hybrid vehicle in which an engine is mounted together with a motor for traveling.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Reactor 3: Filter capacitor 4: Smoothing capacitor 5, 5a, 5b: Snubber capacitor 7a, 7b: Three-phase AC motor (traveling motor)
10: Power converter 12: Voltage converter circuit 13: System main relay 14: Battery 15: Controllers 16a, 16b: Inverter circuit 20: Multilayer unit 21: Cooler 31, 33: Capacitor element 32: Reactor unit 33: Smoothing capacitor 34: Control board 36: Case 37: Terminal unit 41: Mold packages 42a, 42b, 42c: Control terminals 43a, 43b, 43c, 43d: Power terminal 100: Electric vehicle D1-D8: Diode T1-T8: Switching element PC1, PC3: Power card (first power card)
PC2, PC4: Power card (second power card)
PC5, PC5a, PC5b, PC5c: Power card (third power card)
T1-T3: Upper arm switching element T4-T6: Lower arm switching element T7: Step-down switching element T8: Step-up switching element

Claims (1)

A chopper type voltage converter circuit that performs a step-up operation that boosts the power of the battery and a step-down operation that steps down the regenerative power generated by the traveling three-phase AC motor, and converts the power boosted by the voltage converter circuit into alternating current And an inverter circuit that supplies the three-phase AC motor to the power converter,
A first power card containing three upper arm switching elements of the inverter circuit;
A second power card containing three lower arm switching elements of the inverter circuit;
The voltage converter circuit houses a step-up switching element and a step-down switching element and a snubber capacitor connected in parallel to at least one of the step-up switching element and the step-down switching element. 3 power cards,
A laminated unit in which the first, second, and third power cards and a plurality of coolers are alternately laminated;
A power converter comprising:

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