JP2013059151A - Three-level power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-level power conversion device that uses a power conversion unit having such an element array configuration as implements a compact and inexpensive design.SOLUTION: The three-level power conversion device includes a three-level converter 12 and a three-level inverter 13, and comprises three power conversion units each having a single phase of pressure-welded semiconductor elements of the three-level converter 12 and a single level of pressure-welded semiconductor elements of the three-level inverter 13. A power conversion unit 8RU includes a tandem stack 8RU1 comprising main circuit switching elements, a tandem stack 8RU2 comprising freewheeling diodes, and a tandem stack 8RU3 comprising clamp diodes and snubber diodes. The tandem stacks 8RU1 and 8RU2 have a common N potential electrode in the middle and P potential electrodes at both ends, and have one set of intermediate electrodes between the middle and both ends as a single phase of AC input of the three-level converter 12 and the other as a single phase of AC output of the three-level inverter 13.

Description

  The present invention relates to a three-level power converter that converts alternating current into direct current and converts the direct current into alternating current again.

  In a conventional power converter that inputs alternating current and converts it to direct current, and then converts the direct current to alternating current and outputs it, normally the converter side unit that converts the three-phase alternating current input to direct current and the direct current The inverter side unit that converts to AC again is installed independently.

In general, such a power conversion device includes three converter-side power conversion units that convert each of the input AC three phases into DC, and converts the converted DC into a three-phase output AC. It is composed of a total of six power conversion units of power conversion units on the inverter side.

  In contrast to the above, the power conversion unit for one phase on the converter side and the power conversion unit for one phase on the inverter side are integrated into a new power conversion unit. With three such power conversion units, the converter and the inverter The proposal which comprises the power converter device which consists is made (for example, refer patent document 1).

JP 2002-291259 A (page 6-7, FIG. 1)

  In Patent Document 1, in a two-level power conversion device, a power conversion unit for one phase on the converter side and a power conversion unit for one phase on the inverter side are integrated to form a power conversion unit, and an element short circuit fault is detected. Is disclosed in terms of a balance between each phase, but a three-level power converter is not described. There is no disclosure about the element arrangement configuration inside each power conversion unit. With the recent increase in size of devices, it is an important issue to devise the element arrangement configuration inside the power conversion unit of the three-level power conversion device with the aim of downsizing and cost reduction.

  The present invention has been made to solve the above-described problems, and provides a three-level power conversion device using a power conversion unit having an element arrangement configuration that realizes compactness and cost reduction. Objective.

  In order to achieve the above object, a three-level power converter of the present invention comprises a three-level converter that converts alternating current into direct current of a three-level potential of P, C, and N, and a three-level inverter that converts the direct current into alternating current. And a three-level power conversion device comprising three power conversion units each having a pressure-contact type semiconductor element for one phase of the three-level converter and a pressure-contact type semiconductor element for one phase of the three-level inverter, The power conversion unit includes a first skewer stack composed of main circuit switching elements, a second skewer stack composed of flywheel diodes, and a third skewer composed of clamp diodes and snubber diodes. The first skewer stack and the second skewer stack have a common N potential pole at the center and P potential poles at both ends, respectively. One of the middle electrodes between the center and both ends is an AC input for one phase of the three-level converter, and the other is an AC output for one phase of the three-level inverter. .

  According to the present invention, it is possible to provide a three-level power conversion device using a power conversion unit having an element arrangement configuration that achieves compactness and cost reduction.

The circuit block diagram of the 3 level power converter device used as the object of the present invention. The block diagram of the power conversion unit used for the 3 level power converter device which concerns on Example 1 of this invention. The schematic structure figure of the 3 level power converter of the present invention. The block diagram of the power conversion unit used for the 3 level power converter device which concerns on Example 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, a three-level power converter according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a circuit configuration diagram of a three-level power converter that is an object of the present invention.

  In FIG. 1, an AC voltage is supplied from a power system (not shown) to a three-level converter 12 via a transformer 11. A three-level converter 12 converts the AC voltage into a three-level DC voltage and supplies it to a three-level inverter 13. The three-level inverter 13 outputs a three-phase AC voltage and drives the AC motor 14. Here, although the capacitors for smoothing the DC voltage are distributed and arranged in the three-level converter 12 and the three-level inverter 14, they may be concentrated in the DC link portion.

  Hereinafter, the internal configuration of the three-level converter 12 and the three-level inverter 13 will be described.

  The three-level converter 12 is composed of a parallel circuit of switching legs constituting each of the three phases of R phase, S phase, and T phase. Since the configuration of each switching leg is the same, the configuration of the R-phase switching leg will be described below.

  The basic circuit of the R-phase switching leg is a series circuit composed of switching elements 1R1, 1R2, 1R3, and 1R4. Flywheel diodes 2R1, 2R2, 2R3, and 2R4 are connected in antiparallel to each switching element 1R1, 1R2, 1R3, and 1R4, respectively. Switching elements 1R1, 1R2 constitute a positive arm, and switching elements 1R3, 1R4 constitute a negative arm. The R-phase secondary output of the transformer 11 is connected as an AC input to an intermediate point between the two arms, that is, a connection point between the switching elements 1R2 and 1R3.

  The positive electrode of the switching element 1R1 is connected to the positive electrode of the DC capacitor 7R1 through the fuse 6R1. The negative electrode of the switching element 1R4 is connected to the negative electrode of the DC capacitor 7R2 via the fuse 6R2. The DC capacitor 7R1 and the DC capacitor 7R2 are connected in series, and the connection point between them forms a neutral point. The positive clamp diode 3R1 is connected from the neutral point to the midpoint of the positive arm, that is, the connection point of the switching elements 1R1 and 1R2. Similarly, a negative clamp diode 3R2 is connected from the midpoint of the negative arm, that is, from the connection point of the switching elements 1R3 and 1R4 to the neutral point.

  Further, a positive snubber diode 4R1 for absorbing surge voltage and a snubber capacitor 5R1 are connected between the positive electrode and the negative electrode of the switching element 1R1, and between the negative electrode and positive electrode of the switching element 1R4, A negative snubber diode 4R2 and a snubber capacitor 5R2 are connected. These form a snubber circuit, but the illustration of the S phase and the T phase is omitted.

  Next, the main circuit configuration of the three-level inverter 13 will be described. The three-level inverter 13U is composed of a parallel circuit of switching legs constituting each of the three phases of the U phase, the V phase, and the W phase. Since the configuration of each switching leg is the same, the configuration of the U-phase switching leg will be described below.

  The basic circuit of the U-phase switching leg is a series circuit composed of switching elements 1U1, 1U2, 1U3 and 1U4. Flywheel diodes 2U1, 2U2, 2U3, and 2U4 are connected in antiparallel to the switching elements 1U1, 1U2, 1U3, and 1U4, respectively. The switching elements 1U1, 1U2 constitute a positive arm, and the switching elements 1U3, 1U4 constitute a negative arm. A U-phase AC output is obtained from an intermediate point between the two arms, that is, a connection point between the switching elements 1U2 and 1U3, and is connected to the U-phase terminal of the AC motor 15.

  The positive electrode of the switching element 1U1 is connected to the positive electrode of the DC capacitor 7U1 through the fuse 6U1. The negative electrode of the switching element 1U4 is connected to the negative electrode of the DC capacitor 7U2 via the fuse 6U2. The direct current capacitor 7U1 and the direct current capacitor 7U2 are connected in series, and the connection point between them forms a neutral point. The DC capacitor 7U1 is supplied with the positive DC output from the three-level converter circuit 13, and the DC capacitor 7U2 is supplied with the negative DC output from the three-level converter circuit 13. A positive clamp diode 3U1 is connected from the neutral point to the midpoint of the positive arm, that is, the connection point of the switching elements 1U1 and 1U2. Similarly, a negative clamp diode 3U2 is connected from the midpoint of the negative arm, that is, from the connection point of the switching elements 1U3 and 1U4 to the neutral point.

  Further, a positive snubber diode 4U1 for absorbing surge voltage and a snubber capacitor 5U1 are connected between the positive electrode and the negative electrode of the switching element 1U1, and the surge voltage absorbing element is connected between the negative electrode and the positive electrode of the switching element 1U4. A negative snubber diode 4U2 and a snubber capacitor 5U2 are connected. Although these form a snubber circuit, illustration of the V phase and the W phase is omitted.

  Appropriate gate pulses are supplied to the switching elements of the three-level converter 12 and the three-level inverter 13 described above from a converter control circuit and an inverter control circuit (not shown), respectively. In the normal power running mode, the three-level converter 12 is controlled to obtain a desired three-level potential DC output of P, C, and N, and the three-level inverter 13 receives a desired three-level DC input. The AC motor 14 is controlled to be converted into a three-level three-phase AC output. In the regenerative operation mode, the control is reverse to the above.

  FIG. 2 is a configuration diagram of a power conversion unit used in the three-level power conversion device according to the first embodiment of the present invention.

  This power conversion unit 8PU is configured by a semiconductor element portion 12R of the R-phase switching leg of converter 12 and a semiconductor element portion 12U of the U-phase switching leg of inverter 13 in FIG. Note that any semiconductor element is a pressure contact type semiconductor element.

  As shown in FIG. 2, the power conversion unit 8PU is composed of three stacks of skewered stacks 8RU1, 8RU2, and 8RU3. In the first skewer stack 8RU1 illustrated in the middle stage, the switching elements 1R1, 1R2, 1R3, and 1R4 are sequentially arranged from the left end toward the central portion in the semiconductor element portion 12R of the R-phase switching leg. In the U-phase switching leg semiconductor element portion 12U, the switching elements 1U1, 1U2, 1U3, and 1U4 are sequentially arranged from the right end toward the center. As described above, the first skew stack 8RU1 is configured by eight switching elements, and the electrode at the left end is the anode of the switching element 1R1, that is, the electrode of the P potential. Similarly, the electrode at the right end is also an anode of the switching element 1U1, that is, an electrode of P potential. The central electrode serves as a common N-potential electrode because it serves as the cathode of the switching element 1R4 and the cathode of the switching element 1U4.

  In the second skewer stack 8RU2 illustrated in the upper stage, flywheel diodes 2R1, 2R2, 2R3, and 2R4 are sequentially arranged from the left end toward the center in the semiconductor element portion 12R of the R-phase switching leg. In the U-phase switching leg semiconductor element portion 12U, flywheel diodes 2U1, 2U2, 2U3, and 2U4 are sequentially arranged from the right end toward the center. Thus, the second skewer stack 8RU2 is composed of eight flywheel diodes, and the left end electrode is the anode of the flywheel diode 2R1, that is, the electrode of P potential. Similarly, the electrode at the right end is also the anode of the flywheel diode 2U1, that is, the electrode of P potential. The central electrode serves as a common N-potential electrode because it serves as the cathode of the flywheel diode 2R4 and the cathode of the flywheel diode 2U4. By arranging in this way, the electrode arrangement of the second skewer stack 8RU2 is exactly the same as the electrode arrangement of the first skewer stack 8RU1, so that the electrodes adjacent to each other are connected by a conductor as shown in the figure. It becomes possible to connect easily.

  In the third skewer stack 8RU3 shown in the lower stage, the snubber diode 4R1, the clamp diodes 3R1, 3R2, and the snubber diode 4R2 are sequentially arranged from the left end toward the central portion in the semiconductor element portion 12R of the R-phase switching leg. ing. Then, in the semiconductor element portion 12U of the U-phase switching leg, the snubber diode 4U1, the clamp diodes 3U1, 3U2, and the snubber diode 4U2 are arranged in order from the right end toward the center. As described above, the third skewer stack 8RU3 includes four clamp diodes and four snubber diodes. Since the leftmost electrode is the anode of the snubber diode 4R1, that is, the electrode of P potential, it is connected to the leftmost P electrode of the first skewer stack 8RU1 as shown. A snubber capacitor 5R1 is connected to the cathode electrode of the snubber diode 4R1, but the third skewer stack 8RU3 does not include a snubber capacitor, so that the cathode electrode is floated by the insulator 91. Similarly, the right end electrode is also the anode of the snubber diode 4U1, that is, an electrode having a P potential, and is therefore connected to the right end P electrode of the first skewer stack 8RU1 as shown. The snubber capacitor 5U1 is connected to the cathode electrode of the snubber diode 4U1, but the third skewer stack 8RU3 does not include the snubber capacitor, so that the cathode electrode is floated by the insulator 92. The central electrode is a common N-potential electrode in accordance with the first and second skewer stacks 8RU1 and 8RU2, and is connected to the N-potential electrode at the center of the first skewer stack 8RU1 as shown. A snubber diode 4R2 is disposed on the left side of the N potential pole at the center of the third skewer stack 8RU3, and a snubber diode 4U2 is disposed on the right side. In either case, the cathode is the central N electrode, and the anode electrodes are floated by the insulators 93 and 94, respectively, for the reasons described above.

  As the second and third semiconductor elements from the left end of the skew stack 8RU3, clamp diodes 3R1 and 3R2 are arranged, respectively. The cathode electrode of the clamp diode 3R1 is connected to the cathode electrode of the switching element 1R1 at the left end of the first skew stack 8RU1. The anode electrode of the clamp diode 3R1 is shared with the cathode electrode of the clamp diode 3R2, and this electrode serves as a C potential terminal. The anode electrode of the clamp diode 3R2 is connected to the cathode electrode of the third switching element 1R3 from the left end of the first skewer stack 8RU1. Similarly, clamp diodes 3U1 and 3U2 are arranged as the second and third semiconductor elements from the right end, respectively. The cathode electrode of the clamp diode 3U1 is connected to the cathode electrode of the switching element 1U1 at the right end of the first skewer stack 8RU1. The anode electrode of the clamp diode 3U1 is shared with the cathode electrode of the clamp diode 3U2, and this electrode serves as a C potential terminal. The anode electrode of the clamp diode 3U2 is connected to the cathode electrode of the third switching element 1U3 from the right end of the first skewer stack 8RU1.

  With the above configuration, the power conversion unit 8PU shortens the wiring distance of the connection conductor between the semiconductor elements, and realizes the arrangement of the semiconductor elements with the number of insulators minimized. Then, pressure is applied collectively to each skewer stack in the longitudinal direction.

  FIG. 3 is a schematic structural diagram of the three-level power converter according to the present invention. The three-level power converter is basically composed of three power conversion units 8PU, 8SV, and 8TW, and the AC terminal on the converter 12 side of the power conversion units 8PU, 8SV, and 8TW becomes an AC input, and the power conversion units 8PU, 8SV And the AC terminal on the inverter 13 side of 8 TW becomes the AC output. The mutual wiring of the power conversion units 8PU8, SV and 8TW and wiring including other parts are performed according to the circuit configuration diagram shown in FIG. 1, but these are not shown in FIG.

  Note that FIG. 3 illustrates an example in which the three-level power conversion device includes three power conversion units 8PU, 8SV, and 8TW. However, the number of power conversion units is set to four, for example, two power conversion units are connected in parallel. You may make it comprise more than a stand.

  FIG. 4 is a configuration diagram of a power conversion unit used in the three-level power conversion device according to the second embodiment of the present invention. About each part of this Example 2, the same part as each part of the block diagram of the power conversion unit used for the 3 level power converter device which concerns on Example 1 of this invention of FIG. 2 is shown with the same code | symbol, and the description is abbreviate | omitted. The second embodiment is different from the first embodiment in that the arrangement of the P potential electrode and the N potential electrode is changed in all skewer stacks.

  The arrangement in which the arrangement of the P potential electrode and the N potential electrode is switched is, for example, in the case of the skewer stack 8RU1, the left end of the skewer is the N electrode, and the switching elements 1R4, 1R3, 1R2, The electrodes are arranged in the order of 1R1, the right end is also an N electrode, and the switching elements 1U4, 1U3, 1U2, and 1U1 are arranged in this order from the right end toward the center. At this time, the central electrode is a common P electrode. Also in the skewer stack 8RU2 and the skewer stack 8RU3, the arrangement order of the semiconductor elements from the left end to the center and from the right end to the center is reversed from that in the first embodiment.

  Even with the configuration of the second embodiment described above, the power conversion unit 8PU can shorten the wiring distance of the connection conductor between the semiconductor elements and can realize the arrangement of the semiconductor elements with the number of insulators I minimized. .

  As mentioned above, although the Example of this invention was described, these Examples are shown as an example and are not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, the snubber circuit of the three-level power converter is not limited to the circuit shown in FIG. 1, and various circuits that use more snubber diodes have been proposed. In this case, a compact power conversion unit can be realized by appropriately changing the third skewer stack according to the configuration of the snubber diode of the snubber circuit.

  The power conversion unit in FIGS. 2 and 4 is composed only of a semiconductor element, but may be configured to include the wiring of the C potential terminal, or may be configured to integrally mount components such as a snubber capacitor.

11 Transformer 12 3-level converter 12R, semiconductor element portion 1R1, 1R2, 1R3, 1R4, 1S1, 1S2, 1S3, 1S4, 1T1, 1T2, 1T3, 1T4 switching elements 2R1, 2R2, 2R3, 2R4, 2S1, switching leg 2S2, 2S3, 2S4, 2T1, 2T2, 2T3, 2T4 Flywheel diodes 3R1, 3R2, 3S1, 3S2, 3T1, 3T2 Clamp diodes 4R1, 4R2, 4S1, 4S2, 4T1, 4T2 Snubber diodes 5R1, 5R2, 5S1, 5S2, 5T1, 5T2 Snubber capacitors 6R1, 6R2, 6S1, 6S2, 6T1, 6T2 Fuses 7R1, 7R2, 7S1, 7S2, 7T1, 7T2 DC capacitor 13 Three-level inverter 13U Semiconductor element of switching leg 1U1, 1U2, 1U3, 1U4, 1V1, 1V2, 1V3, 1V4, 1W1, 1W2, 1W3, 1W4 Switching elements 2U1, 2U2, 2U3, 2U4, 2V1, 2V2, 2V3, 2V4, 2W1, 2W2, 2W3, 2W4 Fly Wheel diode 3U1, 3U2, 3V1, 3V2, 3W1, 3W2 Clamp diode 4U1, 4U2, 4V1, 4V2, 4W1, 4W2 Snubber diode 5U1, 5U2, 5V1, 5V2, 5W1, 5W2 Snubber capacitor 6U1, 6U2, 6V1, 6V2, 6W1 , 6W2 fuse 7U1, 7U2, 7V1, 7V2, 7W1, 7W2 DC capacitor 14 AC motor 8RU, 8SV, 8TW Power conversion unit 8RU1, 8RU2, 8RU3 Skewer stack 91, 92, 93, 94 Insulator

Claims (4)

A three-level converter that converts alternating current into direct current of a three-level potential of P, C, and N; a three-level inverter that converts the direct current into alternating current; and a pressure-contact type semiconductor element for one phase of the three-level converter; A three-level power conversion device comprising three power conversion units having a pressure contact type semiconductor element for one phase of the three-level inverter,
The power conversion unit is
A first skewer stack composed of main circuit switching elements;
A second skewer stack composed of flywheel diodes;
A third skewer stack composed of a clamp diode and a snubber diode;
The first skewer stack and the second skewer stack are:
A common N-potential electrode at the center and P-potential electrodes at both ends, respectively, one of the electrodes between the center and both ends is an AC input for one phase of the 3-level converter, and the other is the 3-level inverter A three-level power converter characterized by having an AC output for one phase. A three-level converter that converts alternating current into direct current of a three-level potential of P, C, and N; a three-level inverter that converts the direct current into alternating current; and a pressure-contact type semiconductor element for one phase of the three-level converter; A three-level power conversion device comprising three power conversion units having a pressure contact type semiconductor element for one phase of the three-level inverter,
The power conversion unit is
A first skewer stack composed of main circuit switching elements;
A second skewer stack composed of flywheel diodes;
A third skewer stack composed of a clamp diode and a snubber diode;
The first skewer stack and the second skewer stack are:
A common P potential electrode is arranged at the center and N potential electrodes are arranged at both ends. One of the middle electrodes between the center and both ends is an AC input for one phase of the three-level converter, and the other is the three-level inverter. A three-level power converter characterized by having an AC output for one phase. The third skewer stack is
A common N potential electrode is arranged at the center and P potential electrodes are arranged at both ends.
The first and second snubber diodes for the three-level converter are respectively disposed at one portion adjacent to the central electrode and one end on the same side, and the other portion adjacent to the central electrode and The third and fourth snubber diodes for the three-level inverter are arranged on the other end on the same side,
The first and second clamp diodes for the three-level converter are insulated from the middle portions of the first and second snubber diodes via insulators, respectively, and the middle portions of the third and fourth snubber diodes are insulated from each other. Arranging the third and fourth clamp diodes for the three-level inverter through the object,
2. The three-level power conversion according to claim 1, wherein the electrode to which the first and second clamp diodes are connected and the electrode to which the third and fourth clamp diodes are connected are C potential electrodes. apparatus. The third skewer stack is
A common P potential electrode is arranged at the center and N potential electrodes are arranged at both ends.
The first and second snubber diodes for the three-level converter are respectively disposed at one portion adjacent to the central electrode and one end on the same side, and the other portion adjacent to the central electrode and The third and fourth snubber diodes for the three-level inverter are arranged on the other end on the same side,
The first and second clamp diodes for the three-level converter are insulated from the middle portions of the first and second snubber diodes via insulators, respectively, and the middle portions of the third and fourth snubber diodes are insulated from each other. Arranging the third and fourth clamp diodes for the three-level inverter through the object,
3. The three-level power conversion according to claim 2, wherein the electrode connected to the first and second clamp diodes and the electrode connected to the third and fourth clamp diodes are C potential electrodes. apparatus.

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