JP5040249B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter, and more particularly to a power converter having a reduced ripple current.

Each inverter that constitutes the motor drive power conversion device has a problem that it has a large loss in the wiring portion because it has a long connection distance to each winding of the motor, and it is easy to generate radiation noise and conduction noise. Therefore, the present applicant, when the unit inverters (power drivers) are dispersedly arranged in the motor, connect the DC terminals and capacitors of the individual unit inverters in a short distance, and disperse the capacitors for each phase. Technology has been developed (see Patent Document 1).
Japanese Patent No. 3559909 (paragraphs [0005-0006], [FIG. 1])

  However, since the conventional configuration described above includes an inverter and a capacitor for each phase, the ripple current cannot be canceled between the phases, and a large capacity capacitor is required for each phase. It was difficult to make it. Moreover, even if it arrange | positions by the structure which shares a capacitor | condenser between adjacent phases, since the phase of a mutual phase current has shifted | deviated 120 degrees, a ripple current cannot be canceled. FIG. 8 is a diagram showing the timing of each switch and phase current of the unit inverter constituting the power conversion device according to the prior art, but the timing of switch on and switch off is shifted between phases as shown in the figure. As a result, the ripple current cannot be effectively canceled out. The phase current of the first inverter shown in FIG. 8A and the phase current of the second inverter shown in FIG. 8B have a phase difference of 120 ° (degrees). The second group of switches is turned off and the second group of switches is turned on, but the third group and the fourth group of switches SW are not turned on at a timing that cancels this. The same applies to time t2. Therefore, since the conventional technology has a configuration that cannot effectively cancel the ripple current, a smoothing capacitor having a larger capacity and a larger size is required to smooth the ripple current.

In addition, when the phase current phase difference is configured to be 180 °, the switch-on and switch-off timings of the switch elements (power elements) included in the inverter are the same, and the ripple current can be offset. However, a phase with a phase difference of 180 ° does not always exist, and even if a phase with a phase difference of 180 ° exists, in the above-described conventional configuration, capacitors that are far away from each other share a capacitor. In some cases, the routing of the bus bar wiring becomes longer (that is, the inductance becomes larger), the members, terminals, or bus bars need to be overlapped in a complicated manner, and there is no difference in impedance between the bus bar wirings ( There were many design and manufacturing problems such as the need for equal-length wiring and current balance.
In view of the above-described problems, an object of the present invention is to provide a power conversion device with a reduced ripple current.

In order to solve the above-described problems, a power conversion device according to the present invention includes:
A power conversion device that converts a DC output of a DC power source into an AC output by an inverter of each phase,
(Smoothing) capacitor shared by a pair of inverters (each inverter is an individual power converter / motor drive circuit comprising at least one switch element) having a phase difference of 180 ° between each other. . Preferably, all the inverter pairs share one capacitor for each inverter pair.

  According to the present invention, by sharing a capacitor among unit inverters having a phase difference of 180 °, it becomes possible to effectively cancel a ripple current, and a capacitor having a small capacitance can be used. For example, in the case of an electromechanical integrated system configuration, a smaller capacitor can be used by reducing the capacitor capacity, and the electromechanical integrated drive device can be further miniaturized.

In the first embodiment of the power conversion device according to the present invention,
Both inverters included in a pair of inverters sharing the capacitor are disposed adjacent to each other,
It is characterized by that.

In the second embodiment of the power converter according to the present invention,
The number of inverters is an even number (ie, set to the number of inverters divisible by 2 to form an “inverter pair” without taking out the remaining inverters)
It is characterized by that.

Moreover, in the 3rd embodiment of the power converter device by this invention,
The inverter is connected to each winding (stator winding) included in the motor driven by the power converter,
A first imaginary line (radial line) connecting the rotating shaft of the motor and a winding installation position (ie, the center position of the winding), and an inverter connected to the winding (ie, its center position) ) And a second imaginary line (radial line) connecting the rotation axis of the motor is 90 ° or less,
It is characterized by that.

Moreover, in the 4th embodiment of the power converter device by this invention,
The P terminal of the shared capacitor is connected to each P terminal of both inverters included in the pair of inverters sharing the capacitor (via a P bus bar);
The N terminal of the shared capacitor is connected to each N terminal of both inverters included in the pair of inverters (via an N bus bar).
It is characterized by that.

Moreover, in the 5th embodiment of the power converter device by this invention,
The P terminal of the shared capacitor is connected to each P terminal of both inverters included in the pair of inverters sharing the capacitor via a P bus bar,
The P bus bar branches between the P terminal of the shared capacitor and the P terminal of one inverter included in the pair of inverters;
The N terminal of the shared capacitor is connected to each N terminal of both inverters included in the pair of inverters via an N bus bar,
The N bus bar is branched between the N terminal of the shared capacitor and the N terminal of the other inverter included in the pair of inverters;
It is characterized by this.
As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method substantially equivalent to these, and it is understood that these are also included in the scope of the present invention. I want to be.

  According to the first embodiment, it is possible to enhance the ripple current canceling effect by adjoining inverters that are 180 ° out of phase. Further, according to the second embodiment, by setting the number of unit inverters to an even number, the phase is shifted by 180 ° in any combination, so that all phases can be combined, and the inverter is not left out of the combination. , Ripple current can be canceled in all phases.

  Further, according to the third embodiment, the first imaginary line (radial line) connecting the motor rotation shaft and the winding installation position, the inverter connected to the winding, and the rotation of the motor The angle formed by the second imaginary line (radial line) connecting the shaft is 90 ° or less, that is, the circumferential misalignment angle between the inverter distribution module (unit inverter) and the corresponding motor winding is 90 °. By setting the angle below, the wiring length of the motor winding can be minimized.

  In addition, according to the fourth embodiment, the wiring bus bars can be made equidistant and shortest by connecting the PN terminals of the capacitors between the PN terminals of the inverter distribution modules (unit inverters) forming a pair. Inductance can be reduced, current balance is good, and surge voltage can be reduced. Further, according to the fifth embodiment, the P bus bar connecting the inverter and the capacitor branches between one inverter P terminal and the capacitor P terminal, and the N bus bar is connected between the other inverter N terminal and the capacitor N terminal. By branching, a “shared capacitor” can be interposed in the power supply path, so that noise leakage can be prevented.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a basic circuit configuration of a power converter according to the present invention. As shown in the figure, the present power conversion device includes an inverter 10 that is an individual power converter / motor drive circuit that supplies AC power to a motor winding L10 as a load, and a motor winding L20 as a load. And an inverter 20 which is a separate power converter / motor driving circuit for supplying AC power. The inverter 10 includes switch elements (power elements such as IGBTs) SW11-14. By turning on and off each switch element, the DC output of the DC power source is converted into an AC output, and the AC power is converted into the winding L10 of the motor of the load. To drive a motor (not shown). Similarly, the inverter 20 includes switch elements SW21-24, and by turning each switch element on and off, the inverter 20 converts the DC output of the DC power source into an AC output, and supplies AC power to the winding L20 of the load motor. Drive the motor. In the two inverters 10 and 20, the P terminal 10 </ b> P of the inverter 10 and the P terminal 20 </ b> P of the inverter 20 are connected to the P terminal 30 </ b> P of the smoothing capacitor 30 via the P bus bar 40. Similarly, the N terminal 10N of the inverter 10 and the N terminal 20N of the inverter 20 are connected to the N terminal 30N of the capacitor 30 via the N bus bar 50. That is, the inverters 10 and 20 constitute an inverter pair sharing the capacitor 30. The P bus bar 40 and the N bus bar 50 are connected to a DC power source (not shown). In the circuit diagram shown in FIG. 1, the configuration in which the inverter and the motor are integrated is not illustrated, and the phase current of the inverter 10 and the phase current of the inverter 20 are 180 ° between the phase currents. The ripple current can be offset, which will be described in detail with reference to FIG.

  FIG. 2 is an explanatory diagram showing the phase current of each inverter of FIG. 1 and the on / off timing of the switch element. FIG. 2A shows an on / off timing chart of each switch element SW11-14 constituting the inverter 10 and a waveform diagram of the phase current iL10 supplied to the motor winding L10 generated by the on / off of these switch elements. It is shown. The set of switch elements SW11, 12 (first set) is turned on / off at the same timing, the set of switch elements SW13, 14 (second set) is also turned on / off at the same timing, and the second set of switch elements is They are turned on and off at the opposite timing to those of one set.

  FIG. 2B shows an on / off timing chart of each switch element SW21-24 constituting the inverter 20 and a waveform diagram of the phase current iL20 supplied to the motor winding L20 generated by the on / off of these switch elements. It is shown. The set of switch elements SW21, 22 (third set) is turned on / off at the same timing, the set of switch elements SW23, 24 (fourth set) is also turned on / off at the same timing, and the fourth set of switch elements is They are turned on and off at the opposite timing to those of the third set.

  As shown in the figure, the phase current iL10 on the first inverter 10 side and the phase current iL20 on the second inverter 10 side have a phase difference of 180 °, that is, the phase currents are opposite to each other. It is possible to effectively cancel the ripple current. For example, at time t1, the switch elements SW13 and 14 (second set) on the inverter 10 side are turned on, and a ripple current is generated. On the other hand, at time t1, the switching elements SW21 and 22 (third set) on the inverter 20 side are turned on at the same time, and a ripple current that is opposite to and substantially the same amplitude as the “ripple current” on the first inverter side is generated. To do. Therefore, it is possible to effectively cancel the ripple current in the shared capacitor 30 into which the ripple current flows. Similarly, at time t2, the switch elements SW11 and 12 (first set) on the inverter 10 side are turned on, and a ripple current is generated. On the other hand, at the time t2, the switching elements SW23 and SW24 (third set) on the inverter 20 side are turned on at the same time, and a ripple current that is opposite to the “ripple current” on the first inverter side and has substantially the same amplitude is generated. To do. Even at the time t2, the ripple current can be effectively canceled by the shared capacitor 30 into which the ripple current flows. For convenience of drawing and explanation, only a pair of inverters composed of the first inverter 10 and the second inverter 20 is given. However, this power conversion device includes a plurality of inverter pairs and generates a ripple current with the same configuration and principle. Can be effectively offset. Therefore, it is possible to use a smoothing capacitor having a lower capacity and a smaller size.

  FIG. 3 is a diagram showing an embodiment in which three-phase inverters are arranged in a distributed manner. A total of 12 windings L1 to L3 and L1 (−) to L3 (−) are arranged on a stator ST of a motor (not shown), and inverter distribution modules M1 to M3 and M1 are arranged on each motor winding. (−) To M3 (−) are provided and controlled independently in each phase. In the three-phase inverter, the phase difference between the phases is 120 °, and a phase current of L1 (0 °) → L2 (120 °) → L3 (240 °) → L1 (−) (0 °) is required. Here, the motor windings are reversely connected (reversely wound) between L1 and L1 (−). That is, in M1 and M1 (−), the phase current phase difference is 180 °, and the M1 inverter and M1 (−) inverter are connected to the common capacitor C via the wiring B1-4 to cancel the ripple current. ing. In this example, capacitors can be similarly connected to M2 and M2 (−), and M3 and M3 (−), but are omitted for convenience of drawing. In addition, the capacitor C is illustrated in order to conceptually indicate that it is shared, and a rotor (not illustrated) is installed at the location.

  FIG. 4 is a diagram showing another embodiment in which three-phase inverters are dispersedly arranged. Inverters having a phase current phase difference of 180 ° are arranged adjacent to each other, and the inverters PA1 ( M1 and M1 (−)), an inverter pair PA2 (M2 and M2 (−)), and an inverter pair PA3 (M3 and M3 (−)) are configured. In this example, there are a total of six inverter pairs PA1-PA6. That is, the bus bar wiring W can be shortened in the inverters constituting each inverter pair (M1 and M1 (−), M2 and M2 (−), M3 and M3 (−)), and the ripple current of each other can be effectively obtained. Can be offset. A first imaginary line (radial line) VL1 that connects the rotation axis CTR of the motor and the winding (L1 (−)) installation position (that is, the center position of the winding), and a bus bar wiring W to the winding. The angle formed by the second imaginary line (radial line) VL2 connecting the inverter connected via the motor (that is, the center position of M1 (-)) and the rotation axis CTR of the motor is configured to be 90 ° or less. . The imaginary line is orthogonal to the rotation axis CTR.

  5 and 6 are diagrams showing an embodiment in which multiphase inverters are distributedly arranged. In FIGS. 5 and 6, since the number of inverters is an even number, the inverter pair PA can be configured without much, and in any combination, the phase difference of the phase current is shifted by 180 °, so that all the phases can be reduced. Can be combined. Therefore, the ripple current can be effectively canceled in all phases. Depending on the number of phases, inverter distribution modules M1 to M7, M1 (−) to M7 (−), and windings L1 to L7 are mounted. Further, in order to arrange them adjacent to each other, in FIG. 5, the positions of the inverter distribution modules in the circumferential direction are different from the positions of the motor windings connected to the respective inverter distribution modules, and they are connected via the bus bar wirings W1-W6. However, the deviation angle in the circumferential direction can be arranged within 90 °, and the wiring length of the motor winding can be minimized, and the extra length of the motor winding can be sufficiently routed. It is. As shown in FIGS. 5 and 6, even in a motor with various numbers of phases, when the number of motor windings is an even number, a phase difference of 180 ° is given to at least the facing (facing) motor windings. Therefore, the inverter distribution module can be arranged at a circumferential intermediate position (position where the deviation angle is 90 °) from the facing motor winding. The first imaginary line (radial direction line) VL1 and the second imaginary line (radial direction line) VL2 indicate the deviation angle in the circumferential direction.

  FIG. 7 is a diagram in which inverters having a phase difference of phase current of 180 ° are connected to a capacitor. As shown in FIG. 7A, the inverter pair PA1-PA6 and capacitors C10-C60 are provided in the inverter pair. As shown in FIGS. 7B and 7C, the P terminal C60P of the capacitor C60 is connected between the P terminal M3P of the inverter distribution module M3 and the P terminal M3 (−) P of the inverter distribution module M3 (−). The N terminal C60N of the capacitor C60 is connected between the N terminal M3N of the inverter distribution module M3 and the N terminal M3 (−) N of the inverter distribution module M3 (−). Since the capacitors C60 are placed at equal distances from each inverter distribution module, the current balance is good, and the length of the bus bar wiring W can be shortened, so that the surge voltage can be reduced.

  In FIG. 7C, since there are the branch portions 50BR and 60BR of the P bus bar 40 and the N bus bar 50 between the inverter distribution module M3 and the capacitor C60, a power supply path without a capacitor from the power supply source of the inverter distribution module M3 is provided. Since it exists, it causes noise leakage. Therefore, as shown in FIG. 7 (b), a branching section 40BR of the P bus bar 40 to the power supply source is provided between the P terminal M3P of the inverter distribution module M3 and the P terminal C60P of the capacitor C60, and the split inverter module M3 A branch portion 50BR of the N bus bar 50 to the power supply source (DC power supply not shown) is provided between the N terminal M3 (-) N of the (-) module and the N terminal C60N of the capacitor C60. A capacitor is interposed in the power supply path. This can effectively prevent noise leakage.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each member, each means, and the like can be rearranged so that there is no logical contradiction, and a plurality of members, means, etc. can be combined into one or divided. In the embodiments, description has been made mainly with reference to a three-phase inverter, but it should be noted that the present invention can be applied to multi-phase inverters such as four-phase and six-phase.

It is a figure which shows the basic circuit structure of the power converter device by this invention. It is explanatory drawing which shows the phase current of each inverter of FIG. 1, and the on-off timing of a switch element. It is a figure which shows the Example which distributedly arranged the three-phase inverter. It is a figure which shows another Example which distributedly arranged the three-phase inverter. It is a figure which shows the Example which distributedly arranged the polyphase inverter. It is a figure which shows the Example which distributedly arranged the polyphase inverter. It is the figure which connected the inverter and capacitor | condenser with which the phase difference of a phase current becomes 180 degrees. It is a figure which shows the timing of each switch and phase current of a unit inverter which comprise the power converter device by a prior art.

Explanation of symbols

10, 20 Inverter 10N N terminal 10P P terminal 20N N terminal 20P P terminal 30 Capacitor 30N N terminal 30P P terminal 40 P Bus bar 50 N Bus bar 40BR, 50BR Branch B1-B4 Wiring C Capacitor C10-C60 Capacitor C60N N terminal C60P P Terminal CTR Rotating shaft iL10, iL20 Phase current L1-L7 Winding L10, L20 Winding M1-M7 Inverter distribution module M1 (-) to M7 (-) Inverter distribution module M3N N terminal M3P P terminal PA, PA1-PA6 Inverter pair ST Stator SW11-SW14, SW21-SW24 Switch element t1 Time t2 Time W, W1-W6 Bus bar wiring

Claims (4)

A power conversion device that converts a DC output of a DC power source into an AC output by an inverter of each phase,
A capacitor shared by a pair of inverters having a phase difference of 180 ° between each other ,
The number of inverters is an even number;
The inverter is connected to each winding included in the motor driven by the power converter,
An angle formed by a first imaginary line connecting the rotation axis of the motor and the winding installation position, and a second imaginary line connecting the inverter connected to the winding and the rotation axis of the motor is 90 °. Is
The power converter characterized by the above-mentioned. The power conversion device according to claim 1,
Both inverters included in a pair of inverters sharing the capacitor are disposed adjacent to each other,
The power converter characterized by the above-mentioned. The power conversion device according to claim 1 ,
The P terminal of the shared capacitor is connected to the P terminals of both inverters included in the pair of inverters sharing the capacitor;
The N terminal of the shared capacitor is connected to each N terminal of both inverters included in the pair of inverters.
The power converter characterized by the above-mentioned. The power converter of placing serial to claim 1,
The P terminal of the shared capacitor is connected to each P terminal of both inverters included in the pair of inverters sharing the capacitor via a P bus bar,
The P bus bar branches between the P terminal of the shared capacitor and the P terminal of one inverter included in the pair of inverters;
The N terminal of the shared capacitor is connected to each N terminal of both inverters included in the pair of inverters via an N bus bar,
The N bus bar is branched between the N terminal of the shared capacitor and the N terminal of the other inverter included in the pair of inverters;
Power converter, wherein the this.

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