JP2011188584A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a transformer by simplifying an insulation structure by inhibiting a high voltage from being impressed between adjacent secondary windings of the transformer to which a plurality of single-phase three-level inverter cells are connected. <P>SOLUTION: When first AC input terminals 11-14 of at least first and second single-phase three-level inverter cells S1, S2 are connected to secondary windings Ls1-Ls4 of the transformer 2, the first and second AC input terminals are connected to the secondary windings facing each other for either one of the single-phase three-level inverter cells and the first and second AC input terminals are connected to the secondary windings crossing each other for the other single-phase three-level inverter cells to inhibit a high voltage from being impressed between the adjacent secondary windings. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power converter having a configuration in which single-phase three-level inverters are connected in series.

  As this type of power conversion device, for example, a plurality of single-phase inverter cells U1 to U6, V1 to V6, and W1 to W6 having a forward conversion unit and an inverse conversion unit are connected in series, and forward conversion of each single-phase inverter cell is performed. AC power is input to the unit via two input transformers, and each single-phase inverter cell can be pulled out by an insulating support frame provided in the panel, with a high voltage inverter device housed in the panel. A controller that supports and fixes the wiring from the two input transformers to each single-phase inverter cell and the wiring between each single-phase inverter cell by the front face in the panel, and controls the semiconductor switching elements constituting each single-phase inverter cell There is known a high-voltage inverter device in which an optical cable as a signal line is supported and fixed by an insulating support frame (see, for example, Patent Document 1).

  As a single-phase inverter cell used in such a high-voltage inverter device, a single-phase three-level inverter cell is applied as shown in FIG. The single-phase three-level inverter cell includes a first forward converter 102 connected to the first AC input terminal 101, a first smoothing capacitor 103 connected to the output side of the first forward converter 102, A DC converter 107 having a second forward converter 105 connected to the two AC input terminals 104 and a second smoothing capacitor 106 connected to the output side of the second forward converter 105 is provided. In the DC converter 107, the first forward converter 102 and the second forward converter 105 are connected in series, and the smoothing capacitors 103 and 106 are connected in series, whereby the series circuit of the smoothing capacitors 103 and 106 is obtained. A high potential output line Lp, a neutral point line Lm, and a low potential output line Ln are derived from.

  An upper switching arm 109 in which two switching elements are connected in series is connected between the high potential output line Lp and the first AC output terminal 108. In addition, a lower switching arm 110 in which two switching elements are connected in series is connected between the first AC output terminal 108 and the low potential output line Ln. Furthermore, diodes 111 and 112 are connected between the connection midpoint of the upper switching arm 109 and the lower switching arm 110 and the neutral point line Lm.

  Similarly, an upper switching arm 115 having the same configuration as that of the upper switching arm 109 is connected between the high potential output line Lp and the second AC output terminal 114. Further, a lower switching arm 116 having the same configuration as the lower switching arm 110 is connected between the second AC output terminal 114 and the low potential output line Ln. Furthermore, diodes 117 and 118 are connected between the connection middle point of the upper switching arm 115 and the lower switching arm 116 and the neutral point line Lm.

  As shown in FIG. 12, the single-phase three-level inverter cells S1 and S2 having the above-described configuration have secondary windings 121, 122, and 123 of the transformer 120 in which the primary winding is connected to the AC power source 119. The first AC input terminal 101 and the second AC input terminal 104 are connected to each other. The second AC output terminal 114 of the single-phase three-level inverter cell S1 is connected to the first AC output terminal 108 of the single-phase three-level inverter cell S2.

JP 2006-254673 A

However, in the conventional example shown in FIGS. 11 and 12, the single-phase three-level inverter cell is connected to the secondary side windings 121, 122 and 123, 124 of the transformer 120 in which the primary winding is connected to the AC power source 119. Since the first input terminal 101 and the second input terminal 104 of S1 and S2 are connected, depending on the operation mode of the single-phase three-level inverter cells S1 and S2, it is applied between adjacent secondary windings. When the voltage between the terminals of the smoothing capacitors 103 and 106 described above is Edc, the voltage may be as high as 4Edc, and it is necessary to ensure insulation according to the maximum voltage between the secondary windings. There is an unsolved problem that the size of the transformer is increased.
Therefore, the present invention has been made paying attention to the unsolved problems of the above conventional example, and a high voltage is applied between adjacent secondary windings of a transformer connecting a plurality of single-phase three-level inverter cells. An object of the present invention is to provide a power converter capable of reducing the size of a transformer by suppressing the generation of the transformer and simplifying the insulating structure.

In order to achieve the above object, a power converter according to an embodiment of the present invention includes a first AC input terminal and a second AC input terminal to which AC is input, and a first AC output terminal that outputs a single-phase AC. And a plurality of N single-phase three-level inverter cells having a second AC output terminal,
A secondary winding of a transformer having one primary winding and a plurality of 2N secondary windings is connected to the first and second AC input terminals of the N single-phase three-level inverters. The AC output terminals of the single-phase three-level inverter cell are connected in series.

Furthermore, the N single-phase three-level inverter cells connected in series with the AC output terminals are defined as a first cell, a second cell, a third cell,. The first secondary winding, the second secondary winding, the third secondary winding, ... the 2N-1 secondary winding, the 2N secondary, in the order of the structural positions of the windings Winding.
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
A second M-1 and a second M secondary winding are connected to two AC input terminals of the Mth (M is an integer of 1 to N) cell. As the connection method, there are a first connection method and a second connection method, and one of these is selected.

The first connection method is to connect the 2nd M-1 secondary winding to the first AC input terminal of the cell and the 2nd M secondary winding to the second AC input terminal of the cell for a cell having an odd M. Connect to. On the other hand, for the cells with an even number M, the 2nd M-1 secondary winding is connected to the second AC input terminal of the cell, and the 2M secondary winding is connected to the first AC input terminal of the cell.
The second connection method is to connect the 2nd M-1 secondary winding to the second AC input terminal of the cell and the 2nd M secondary winding to the first AC input terminal of the cell for a cell having an odd M. Connect to. On the other hand, for cells with an even number M, the second M-1 secondary winding is connected to the first AC input terminal of the cell, and the second M secondary winding is connected to the second AC input terminal of the cell.

  In addition, the first and second AC input terminals of the single-phase three-level inverter cell for a plurality of N × K phases having the above-described configuration are connected to one primary winding and a plurality of 2N × K-phase secondary windings. Are connected to the secondary winding of a transformer having N, and each K output terminal of the K sets in which the AC output terminals of the N single-phase three-level inverter cells for the K phase are connected in series is commonly connected. The power converter which outputs the K-phase high voltage by using the other output terminal as each output is configured.

Further, the N single-phase three-level inverter cells commonly connected to the AC output terminals are defined as a first cell, a second cell, a third cell,. The structural positions of the windings are the first secondary winding, the second secondary winding, the third secondary winding,... 2N secondary winding.
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
A second M-1 and a second M secondary winding are connected to two AC input terminals of the Mth (M is an integer of 1 to N) cell. As the connection method, there are a third connection method and a fourth connection method, and one of these is selected.

The third connection method is to connect the second M-1 secondary winding to the first AC input terminal of the cell and the second M secondary winding to the second AC input terminal of the cell for a cell having an odd M. Connect to. On the other hand, for the cells with an even number M, the 2nd M-1 secondary winding is connected to the second AC input terminal of the cell, and the 2M secondary winding is connected to the first AC input terminal of the cell.
In the fourth connection method, for a cell having an odd number M, the 2nd M-1 secondary winding is connected to the second AC input terminal of the cell, and the second M secondary winding is connected to the first AC input terminal of the cell. Connect to. On the other hand, for cells with an even number M, the second M-1 secondary winding is connected to the first AC input terminal of the cell, and the second M secondary winding is connected to the second AC input terminal of the cell.

  The single-phase three-level inverter cell described above is configured as follows. That is, a first forward converter that converts an AC voltage input from the first AC input terminal to DC, a first smoothing capacitor that smoothes an output voltage of the forward converter, and the second AC input terminal A second forward converter that converts the AC voltage input from the converter into a direct current, and a second smoothing capacitor that smoothes the output voltage of the forward converter, the low potential side of the first smoothing capacitor; A high-voltage side of the second smoothing capacitor is connected to form a DC series circuit having a high-potential side, a neutral point, and a low-potential side. An upper arm in which two parallel circuits of semiconductor switching elements and antiparallel diodes are connected in series is connected between the high potential side of the DC series circuit and the first AC output terminal. A lower arm in which two parallel circuits of a semiconductor switching element and an antiparallel diode are connected in series is connected between the first AC output terminal and the low potential side. Further, a diode is connected between each intermediate connection point of the two series circuits of each arm and the neutral point. These upper arm and lower arm and the diode constitute a first output circuit.

On the other hand, between the high potential side and the second AC output terminal, an upper arm in which two parallel circuits of semiconductor switching elements and antiparallel diodes are connected in series is connected. A lower arm in which two parallel circuits of a semiconductor switching element and an antiparallel diode are connected in series is connected between the second AC output terminal and the low potential side. Further, a diode is connected between each intermediate connection point of the two series circuits of each arm and the neutral point. The upper and lower arms and the diode form a second output circuit.
The first and second forward converters, the first and second smoothing capacitors, and the first and second output circuits constitute a single-phase three-level inverter cell.

  According to the present invention, as described above, the power conversion for generating a high voltage by connecting the AC input terminals of a plurality of single-phase three-level inverter cells to the secondary side of the transformer and connecting the AC output terminals in series. In the device, by selecting either the first connection method or the second connection method, it is possible to suppress the application of high voltage between adjacent secondary windings of the transformer, and to simplify the insulation structure. Thus, the transformer can be miniaturized.

It is a block diagram which shows the power converter device which shows the 1st Embodiment of this invention. It is a circuit diagram which shows the specific structure of the single phase 3 level inverter cell of FIG. It is a block diagram which shows the power converter device when the same connection as a prior art example is performed. It is explanatory drawing which shows the combination of the output potential of one 2nd output terminal of the single phase 3 level inverter cell of a prior art example, and the other 1st output terminal. It is explanatory drawing which shows the voltage model between cell input terminals corresponding to the combination of the 1st-3rd output potential in FIG. 3, and each input terminal voltage. It is explanatory drawing which shows the voltage model between cell input terminals corresponding to the combination of the 4th-6th output potential in FIG. 3, and each input terminal voltage. It is explanatory drawing which shows the voltage model between cell input terminals corresponding to the combination of the 7th-9th output potential in FIG. 3, and each input terminal voltage. It is a block diagram which shows the 2nd Embodiment of this invention. It is a block diagram which shows the 3rd Embodiment of this invention. It is a block diagram which shows the 4th Embodiment of this invention. It is a circuit diagram which shows the specific structure of the conventional single row 3 level inverter cell. It is a block diagram which shows the power converter device of a prior art example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Here, a single-phase output circuit will be described as an example.
FIG. 1 is a block diagram of a power conversion device showing a first embodiment of the present invention. In the figure, 1 is an AC power source, and AC power output from the AC power source 1 is input to the primary winding Lf of the transformer 2. On the secondary side of the transformer 2, four secondary windings Ls1 to Ls4 are provided. The first single-phase three-level inverter cell S1 is connected to the secondary windings Ls1 and Ls2, and the second single-phase three-level inverter cell S2 is connected to the secondary windings Ls3 and Ls4.

The single-phase three-level inverter cell S <b> 1 has a first AC input terminal 11 and a second AC input terminal 12, a first AC output terminal 15, and a second AC output terminal 16. The single-phase three-level inverter cell S2 includes a first AC input terminal 13, a second AC input terminal 14, a first AC output terminal 17, and a second AC output terminal 18.
The first input terminal 11 and the second input terminal 12 of the first single-phase three-level inverter cell S1 are connected to the secondary windings Ls1 and Ls2 of the transformer 2. Further, the first AC input terminal 13 of the second single-phase three-level inverter cell S2 is connected to the secondary winding Ls4 of the transformer, and the second AC input terminal 14 is connected to the secondary winding Ls3 of the transformer. ing.

Furthermore, the second AC output terminal 16 of the first single-phase three-level inverter cell S1 is connected in series to the first AC output terminal 17 of the second single-phase three-level inverter cell S2.
The first AC output terminal 15 of the first single-phase three-level inverter cell S1 and the second AC output terminal 18 of the second single-phase three-level inverter cell S2 are connected to a single-phase load such as an electric motor (not shown). .
Each single-phase three-level inverter cell S1 is configured as shown in FIG. That is, the first AC input terminal 11 is connected to the first forward converter 21 that converts AC to DC, and the second AC input terminal 12 is connected to the second forward converter 22 that converts AC to DC. Yes. A first smoothing capacitor 23 is connected to the output side of the first forward converter 21, and a second smoothing capacitor 24 is connected to the output side of the second forward converter 22.

  The first forward converter 21 and the second forward converter 22 are connected in series, the first smoothing capacitor 23 and the second smoothing capacitor 24 are connected in series, and the DC converter 25 is It is configured. From this DC converter 25, a high potential side line Lp is derived from the connection point between the positive output side of the first forward converter 21 and the smoothing capacitor 23, and the first and second smoothing capacitors 23 and 24 are connected. A neutral point line Lm is derived from the point, and a low potential side line Ln is derived from a connection point between the negative electrode side of the second forward converter 22 and the second smoothing capacitor 24.

The upper switching arm 30 is connected between the high potential side line Lp and the first AC output terminal 15. In the upper switching arm 30, a parallel circuit of a semiconductor switching element 31 and an antiparallel diode 32 connected to the high potential side line Lp and a parallel circuit of a semiconductor switching element 33 and an antiparallel diode 34 are connected in series. Have a configuration.
Further, the lower switching arm 36 is connected between the first AC output terminal 15 and the low potential side line Ln. The lower switching arm 36 includes a parallel circuit of a semiconductor switching element 37 and an antiparallel diode 38 connected to the first AC output terminal 15 and a parallel circuit of a semiconductor switching element 39 and an antiparallel diode 40 in series. It has a connected configuration.

Further, the upper switching arm 50 is connected between the high potential side line Lp and the second AC output terminal 16. In the upper switching arm 50, a parallel circuit of the semiconductor switching element 51 and the antiparallel diode 52 connected to the high potential side line Lp and a parallel circuit of the semiconductor switching element 53 and the antiparallel diode 54 are connected in series. Have a configuration.
The lower switching arm 56 is connected between the second AC output terminal 16 and the low potential side line Ln. The lower switching arm 56 includes a parallel circuit of a semiconductor switching element 57 and an antiparallel diode 58 connected to the second AC output terminal 16 and a parallel circuit of a semiconductor switching element 59 and an antiparallel diode 60 in series. It has a connected configuration.

Furthermore, a diode 61 is connected between the neutral point line Lm and the connection point of the parallel circuit of the upper switching arm 30, and a diode 62 is connected between the neutral point line Lm and the connection point of the parallel circuit of the lower switching arm 36. Is connected.
Furthermore, a diode 63 is connected between the neutral point line Lm and the connection point of the parallel circuit of the upper switching arm 50, and a diode is connected between the neutral point line Lm and the connection point of the parallel circuit of the lower switching arm 56. 64 is connected. A switching element such as an IGBT or a power MOSFET can be applied as the semiconductor switching element.

The second single-phase three-level inverter cell S2 also has the same configuration as that in FIG.
The first AC input terminal 11 of the first single-phase three-level inverter cell S1 is connected to the first secondary winding Ls1 of the transformer 2, and the second AC input terminal 12 is connected to the second of the transformer. Is connected to the second secondary winding Ls2, the first AC input terminal 13 of the second single-phase three-level inverter cell S2 is connected to the fourth secondary winding Ls4 of the transformer 2, and the second AC input terminal 14 is connected to the third secondary winding Ls3 of the transformer 2 to suppress application of a high voltage between adjacent secondary windings of the transformer 2.

  That is, similarly to FIG. 8 of the conventional example described above, the first and second AC input terminals 11 and 12 of the first single-phase three-level inverter cell S1 are connected to the first and second second terminals of the transformer 2. The first and second AC input terminals 13 and 14 of the second single-phase three-level inverter cell S2 are connected to the secondary windings Ls1 and Ls2, and the third and fourth secondary windings of the transformer 2 are connected. When connected to Ls3 and Ls4, there are nine combinations of output potentials depending on the operation mode of the first single-phase three-level inverter cell S1 and the second single-phase three-level inverter cell S2. That is, when the output potential of the output terminal 16 of the first single-phase three-level inverter cell S1 is P, which is a high potential, the output potential of the output terminal 17 of the second single-phase three-level inverter cell S2 is a high potential. P, which is N, M which is a neutral potential, and N which is a low potential. Similarly, when the output potential of the output terminal 16 of the first single-phase three-level inverter cell S1 is a neutral potential M and when the output potential is a low potential N, the second single-phase three-level inverter cell S2 There are three output potentials of the output terminal 17: P, which is a high potential, M, which is a neutral potential, and N, which is a low potential.

The voltage model between the input terminals and the voltage between the input terminals of the single-phase three-level inverter cell for each combination of these output potentials is the first voltage when the voltage between the terminals of the first and second smoothing capacitors 23 and 24 is Edc. When the output potential of the second AC output terminal 16 of the single-phase three-level inverter cell S1 is the high potential P, the combinations shown in FIGS.
At this time, when the output potential of the first output terminal 17 of the second single-phase three-level inverter cell S2 is the high potential P, the connection relationship shown in FIG. The inter-terminal voltage between the terminals 11 to 13 is Edc, the inter-terminal voltage between the input terminals 11 to 14 is 2Edc, the inter-terminal voltage between the input terminals 12 to 13 is 2Edc, and the inter-terminal voltage between the input terminals 12 to 14 The voltage is Edc.

When the output potential of the output terminal 17 of the second single-phase three-level inverter cell S2 is the neutral potential M, the connection relationship shown in FIG. 5B is established, and the input terminal voltage is between the input terminals 11 to 13. 2Edc, Edc between the input terminals 11-14, 2Edc between the input terminals 12-13, and 2Edc between the input terminals 12-14.
Further, when the output potential of the output terminal 17 of the second single-phase three-level inverter cell S2 is a low potential N, the connection relationship shown in FIG. 5C is established, and the input terminal voltage is 3Edc between the input terminals 11-13. 2Edc between the input terminals 11-14, 4Edc between the input terminals 12-13, and 3Edc between the input terminals 12-14.

Other potential combinations are as shown in FIGS. 6A to 6C and FIGS. 7A to 7C, and the maximum voltage between the input terminals is 4Edc in the end as shown in FIG. 5C. There are only two combinations, the combination and the combination of FIG.
That is, in FIG.5 (c), the 2nd alternating current output terminal 16 of 1st single phase 3 level inverter cell S1 is the high electric potential P, and the 1st alternating current output terminal 17 of 2nd single phase 3 level inverter cell S2 is. Is a combination with a low potential N, and the voltage between the input terminals 12 to 13 at this time is 4 Edc. In FIG. 7A, the second output terminal 16 of the first single-phase three-level inverter cell S1 is at a low potential N, and the first output terminal 17 of the second single-phase three-level inverter cell S2 is high. The combination is the potential P, and the voltage between the input terminals 11 to 14 at this time is the maximum voltage 4Edc.

  Here, in the case of Fig.7 (a), it is between input terminals 11-14, and if it sees with the secondary winding of the transformer 2, it is between 1st Ls1 and 4th Ls4. There is no problem because a high voltage is not applied to the adjacent secondary winding. However, in the case of FIG. 5C, the input terminals 12 to 13 are adjacent to each other, and the secondary winding of the transformer 2 is also adjacent to the second Ls2 and the third Ls3. A high voltage is applied between them. For this reason, it is necessary to ensure a high insulating property by requiring a withstand voltage value corresponding to the inter-terminal voltage 4Edc, and the height of the transformer 2 is increased and the size is increased as it is.

For this reason, in this embodiment, there are two input terminals that generate the maximum inter-terminal voltage 4Edc, and the actual input terminals are the input terminals 12 to 13, so that the input terminal 13 is replaced with a transformer. By connecting the input terminal 14 to the third secondary winding Ls3, as shown in FIG. 5C, the input terminals 12 and 13 are connected to the second secondary winding Ls4. Even if the inter-terminal voltage becomes 4Edc, the transformer 2 side prevents a high voltage from being applied between the adjacent secondary windings, and the inter-terminal voltage between the adjacent secondary windings Ls2 and Ls3. Can be suppressed from 4 Edc to 3 Edc.
For this reason, the withstand voltage value required between the adjacent secondary windings of the transformer 2 can be reduced, the height of the transformer 2 is prevented from being increased, and the configuration of the entire power converter is reduced. Can be

  In the first embodiment, the case where there are two single-phase three-level inverter cells connected in series has been described. However, the present invention is not limited to this, and the number of single-phase three-level inverter cells connected in series is N. When N is a positive integer and the number of secondary windings of the transformer 2 is 2N, it is as follows. That is, for a cell in which M of the Mth single-phase three-level inverter cell is an odd number, the second M−1th secondary winding is connected to the first AC input terminal of the single-phase three-level inverter cell. Further, the second Mth secondary winding is connected to the second AC input terminal of the single-phase three-level inverter cell. On the other hand, for the single-phase three-level inverter cell in which M is an even number, the 2M-1th secondary winding is connected to the second AC input terminal of the single-phase three-level inverter cell. Further, the first connection method can be implemented by connecting the Mth secondary winding to the first AC input terminal of the single-phase three-level inverter cell.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, contrary to the first embodiment described above, the first AC input terminal 11 is connected to the second secondary of the transformer 2 for the first single-phase three-level inverter cell S1. The second AC input terminal 12 is connected to the winding Ls2 and the first secondary winding Ls1 of the transformer 2 is connected. On the other hand, for the second single-phase three-level inverter cell S2, the first AC input terminal 13 is connected to the third secondary winding Ls3 of the transformer 2, and the second AC input terminal 14 is connected to the transformer first. The second connection method is to connect to the fourth secondary winding Ls4.

  According to the second embodiment, the secondary winding of the transformer 2 to which the first AC input terminal 11 and the second AC input terminal 12 are connected is replaced on the first single-phase three-level inverter cell S1 side. Therefore, as in the first embodiment described above, the secondary windings to which the input terminals 12 and 13 having the maximum input terminal voltage of 4Edc in FIG. 5C are connected are Ls1 and Ls3. Thus, no high voltage is applied between adjacent secondary windings, and the withstand voltage value can be suppressed to prevent the transformer from becoming high.

  In the second embodiment, the case where there are two single-phase three-level inverter cells connected in series has been described. However, the present invention is not limited to this, and the number of single-phase three-level inverter cells connected in series is N. When N is a positive integer and the number of secondary windings of the transformer 2 is 2N, it is as follows. That is, for the M-th single-phase three-level inverter cell in which M is an odd number, the second M-1th secondary winding is connected to the second AC input terminal of the single-phase three-level inverter cell. Further, the second M-th secondary winding is connected to the first AC input terminal of the single-phase three-level inverter cell. On the other hand, for the single-phase three-level inverter cell in which M is an even number, the 2M-1th secondary winding is connected to the first AC input terminal of the single-phase three-level inverter cell. Further, the second connection method can be implemented by connecting the Mth secondary winding to the second AC input terminal of the single-phase three-level inverter cell.

Next, a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, a plurality of N × K-phase single-phase three-level inverter cells are provided, and a circuit with N = 2 and K = 3 is shown.
That is, in the third embodiment, as shown in FIG. 9, the power conversion device includes three first-phase power conversion units PT <b> 1, three single-phase three-level inverter cells S <b> 1 and S <b> 2 in the first embodiment, A two-phase power converter PT2 and a third-phase power converter PT3 are provided.

  And about 1st phase electric power conversion part PT1, the 1st alternating current input terminal 11 and the 2nd alternating current input terminal 12 of 1st single phase 3 level inverter cell S1 are the transformer 2 similarly to 1st Embodiment mentioned above. Secondary windings Ls11 and Ls12. The first AC input terminal 13 of the second single-phase three-level inverter cell S2 is connected to the transformer secondary winding Ls14, and the second AC input terminal 14 is connected to the transformer secondary winding Ls13. ing.

Similarly, for the second phase power converter PT2, the first AC input terminal 11 and the second AC input terminal 12 of the first single-phase three-level inverter cell S1 are connected to the secondary windings Ls21 and Ls22 of the transformer 2, respectively. It is connected. Further, the first AC input terminal 13 of the second single-phase three-level inverter cell S2 is connected to the secondary winding Ls24 of the transformer, and the second AC input terminal 14 is connected to the secondary winding Ls23 of the transformer. ing.
Further, for the third phase power converter PT3, the first AC input terminal 11 and the second AC input terminal 12 of the first single-phase AC three-level inverter cell S1 are connected to the secondary windings Ls31 and Ls32 of the transformer 2, respectively. It is connected. The first AC input terminal 13 of the second single-phase three-level inverter cell S2 is connected to the transformer secondary winding Ls34, and the second AC input terminal 14 is connected to the transformer secondary winding Ls33. ing.

Further, the second output terminal 16 of the first single-phase three-level inverter cell S1 and the first output terminal 17 of the second single-phase three-bell inverter cell S2 of each power conversion unit PT1 to PT3 are connected, and each power The second output terminals 18 of the second single-phase three-level inverter cells S2 of the converters PT1 to PT3 are commonly connected to each other.
Further, the first output terminal 15 of the first single-phase three-level inverter cell S1 of each power conversion unit PT1 to PT3 is connected to a three-phase load such as a three-phase electric motor (not shown).

According to the third embodiment, since each of the phase power converters PT1 to PT3 has the same configuration as that of the first embodiment described above, the same effect as that of the first embodiment described above can be obtained. Can do.
In the third embodiment, the single-phase three-level inverter cells connected in series are N (N is a positive integer) as in the first embodiment described above for each of the power converters PT1 to PT3. ) And the number of secondary windings of the transformer 2 is 2N, and the first connection method can be implemented.
Moreover, in the said 3rd Embodiment, although the case where the number of phases was made into three phases was demonstrated, it is not restricted to this, It can be set as the arbitrary number of phases more than four phases.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
As in the third embodiment described above, the fourth embodiment includes a plurality of N × K-phase single-phase three-level inverter cells, and N = 2 and K = 3 circuits. It is shown.
That is, in the fourth embodiment, the power conversion device includes single-phase three-level inverter cells S1 and S2 in the first embodiment, respectively, as in the third embodiment described above, as shown in FIG. Three first-phase power converters PT1, second-phase power converters PT2, and third-phase power converters PT3 are provided.

  And about 1st phase electric power conversion part PT1, the 1st alternating current input terminal 11 of 1st single phase 3 level inverter cell S1 is the 2nd secondary of the transformer 2 similarly to 2nd Embodiment mentioned above. The second AC input terminal 12 is connected to the winding Ls12, and is connected to the first secondary winding Ls11 of the transformer. The first AC input terminals 13 and 14 of the second single-phase three-level inverter cell S2 are connected to the third and fourth secondary windings Ls13 and Ls14 of the transformer, respectively.

  Similarly, for the second phase power converter PT2, the first AC input terminal 11 of the first single-phase three-level inverter cell S1 is connected to the sixth secondary winding Ls22 of the transformer 2, and the second The AC input terminal 12 is connected to the fifth secondary winding Ls21 of the transformer. The first AC input terminals 13 and 14 of the second single-phase three-level inverter cell S2 are connected to the seventh and eighth secondary windings Ls23 and Ls24 of the transformer, respectively.

  Further, also for the third phase power converter PT3, the first AC input terminal 11 of the first single-phase three-level inverter cell S1 is connected to the tenth secondary winding Ls32 of the transformer 2, and the second AC The input terminal 12 is connected to the ninth secondary winding Ls31 of the transformer. The first AC input terminals 13 and 14 of the second single-phase three-level inverter cell S2 are connected to the eleventh and twelfth secondary windings Ls33 and Ls34 of the transformer, respectively.

Further, the second output terminal 16 of the first single-phase three-level inverter cell S1 and the first output terminal 17 of the second single-phase three-bell inverter cell S2 of each power conversion unit PT1 to PT3 are connected, and each power The second output terminals 18 of the second single-phase three-level inverter cells S2 of the converters PT1 to PT3 are commonly connected to each other.
Further, the first output terminal 15 of the first single-phase three-level inverter cell S1 of each power conversion unit PT1 to PT3 is connected to a three-phase load such as a three-phase electric motor (not shown).

According to the fourth embodiment, since each of the phase power converters PT1 to PT3 has the same configuration as that of the second embodiment described above, the same effects as those of the second embodiment described above can be obtained. Can do.
In the fourth embodiment, as in the first embodiment described above for each of the power converters PT1 to PT3, single-phase three-level inverter cells connected in series are N (N is a positive integer). ) And the number of secondary windings of the transformer 2 is 2N, and the second connection method can be implemented.

Moreover, in the said 4th Embodiment, although the case where the number of phases was made into three phases was demonstrated, it is not restricted to this, It can be set as the arbitrary number of phases more than four phases.
In addition, the configuration of the single-phase three-level inverter cell is not limited to the above configuration, and the number of semiconductor switching elements in each of the upper switching arm and the lower switching arm can be set to any even number. Instead of 64, a switch circuit whose conduction is controlled when desired can be applied.

  DESCRIPTION OF SYMBOLS 1 ... AC power source, 2 ... Transformer, Lf ... Primary winding, Ls1-Ls4 ... Secondary winding, S1, S2 ... Single phase 3 level inverter cell, 11 ... First AC input terminal, 12 ... Second AC input Terminals 13 ... 1st AC input terminal 14 ... 2nd AC input terminal 15 ... 1st AC output terminal 16 ... 2nd AC output terminal 17 ... 1st AC output terminal 18 ... 2nd AC output terminal DESCRIPTION OF SYMBOLS 21 ... 1st forward converter, 22 ... 2nd forward converter, 23 ... 1st smoothing capacitor, 24 ... 2nd smoothing capacitor, 25 ... DC conversion part, Lp ... High potential side line, Lm ... Medium Sex point line, Ln: Low potential side line, 30: Upper switching arm, 31, 33 ... Semiconductor switching element, 32, 34 ... Anti-parallel diode, 36 ... Lower switching arm, 37, 39 ... Semiconductor switching element, 38, 40 ... reverse parallel diode 50, upper switching arm, 51, 53 ... semiconductor switching element, 52, 54 ... reverse connection diode, 56 ... lower switching arm, 57, 59 ... semiconductor switching element, 58, 60 ... reverse connection diode, 61-64 ... diode , PT1 ... first phase power converter, PT2 ... second phase power converter, PT3 ... third phase power converter, Ls11 to Ls14, Ls21 to Ls24, Ls31 to Ls34 ... secondary winding

Claims (5)

A plurality of N single-phase three-level inverter cells having a first AC input terminal and a second AC input terminal to which AC is input, and a first AC output terminal and a second AC output terminal that output single-phase AC are provided. ,
A secondary winding of a transformer having one primary winding and a plurality of 2N secondary windings is connected to the first and second AC input terminals of the N single-phase three-level inverters. The AC output terminals of the single-phase three-level inverter cell are connected in series,
The N single-phase three-level inverter cells connected in series with the AC output terminals are defined as a first cell, a second cell, a third cell,..., An Nth cell in the order of connection, and the secondary winding of the transformer. The first secondary winding, the second secondary winding, the third secondary winding, ... the 2N-1 secondary winding, the 2N secondary winding in the order of the structural positions of If
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
The 2M-1 and 2M secondary windings are connected to the two AC input terminals of the Mth cell (M is an integer from 1 to N). -1 secondary winding is connected to the first AC input terminal of the cell, the second M secondary winding is connected to the second AC input terminal of the cell, and for cells with an even M, the second M-1 The secondary winding is connected to the second AC input terminal of the cell, and the second M secondary winding is connected to the first AC input terminal of the cell. A plurality of N single-phase three-level inverter cells having a first AC input terminal and a second AC input terminal to which AC is input, and a first AC output terminal and a second AC output terminal that output single-phase AC are provided. ,
A secondary winding of a transformer having one primary winding and a plurality of 2N secondary windings is connected to the first and second AC input terminals of the N single-phase three-level inverters. The AC output terminals of the single-phase three-level inverter cell are connected in series,
The N single-phase three-level inverter cells connected in series with the AC output terminals are defined as a first cell, a second cell, a third cell,..., An Nth cell in the order of connection, and the secondary winding of the transformer. The first secondary winding, the second secondary winding, the third secondary winding, ... the 2N-1 secondary winding, the 2N secondary winding in the order of the structural positions of If
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
The 2M-1 and 2M secondary windings are connected to the two AC input terminals of the Mth cell (M is an integer from 1 to N). -1 secondary winding is connected to the second AC input terminal of the cell, the second M secondary winding is connected to the first AC input terminal of the cell, and for cells with an even M, the second M-1 The secondary winding is connected to the first AC input terminal of the cell, and the second M secondary winding is connected to the second AC input terminal of the cell. Single phase 3 level for multiple N × K phases having first AC input terminal and second AC input terminal for AC input, and first AC output terminal and second AC output terminal for outputting single phase AC Equipped with an inverter cell,
A secondary winding of a transformer having one primary winding and a plurality of 2N × K secondary windings is provided for the first and second AC input terminals of the N single-phase three-level inverters for each of K phases. Connecting the AC output terminals of the N single-phase three-level inverter cells in series, and connecting one output terminal of each of the K sets of circuits in common and outputting the other output terminal as a K-phase output,
The N single-phase three-level inverter cells commonly connected to the AC output terminals are defined as a first cell, a second cell, a third cell,..., An Nth cell in the order of connection, and the secondary winding of the transformer. The first secondary winding, second secondary winding, third secondary winding,... 2N-1 secondary winding, 2N If it is a secondary winding,
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
The 2M-1 and 2M secondary windings are connected to the two AC input terminals of the Mth cell (M is an integer from 1 to N). -1 secondary winding is connected to the first AC input terminal of the cell, the second M secondary winding is connected to the second AC input terminal of the cell, and for cells with an even M, the second M-1 The secondary winding is connected to the second AC input terminal of the cell, and the second M secondary winding is connected to the first AC input terminal of the cell. Single phase 3 level for multiple N × K phases having first AC input terminal and second AC input terminal for AC input, and first AC output terminal and second AC output terminal for outputting single phase AC Equipped with an inverter cell,
A secondary winding of a transformer having one primary winding and a plurality of 2N × K secondary windings is provided for the first and second AC input terminals of the N single-phase three-level inverters for each of K phases. Connecting the AC output terminals of the N single-phase three-level inverter cells in series, and connecting one output terminal of each of the K sets of circuits in common and outputting the other output terminal as a K-phase output,
The N single-phase three-level inverter cells commonly connected to the AC output terminals are defined as a first cell, a second cell, a third cell,..., An Nth cell in the order of connection, and the secondary winding of the transformer. The first secondary winding, second secondary winding, third secondary winding,... 2N-1 secondary winding, 2N If it is a secondary winding,
The connection relationship between the secondary winding of the transformer and the single-phase three-level inverter cell is as follows:
The 2M-1 and 2M secondary windings are connected to the two AC input terminals of the Mth cell (M is an integer from 1 to N). -1 secondary winding is connected to the second AC input terminal of the cell, the second M secondary winding is connected to the first AC input terminal of the cell, and for cells with an even M, the second M-1 The secondary winding is connected to the first AC input terminal of the cell, and the second M secondary winding is connected to the second AC input terminal of the cell. The single-phase three-level inverter cell includes a first forward converter that converts an AC voltage input from the first AC input terminal into a direct current, and a first smoothing capacitor that smoothes the output voltage of the forward converter. A second forward converter for converting an alternating voltage input from the second alternating current input terminal into a direct current; and a second smoothing capacitor for smoothing the output voltage of the forward converter; Connecting the low potential side of the smoothing capacitor and the high potential side of the second smoothing capacitor to form a DC series circuit having a high potential side, a neutral point and a low potential side, and a high potential side of the DC series circuit Between the first AC output terminal and the upper arm in which two parallel circuits of semiconductor switching elements and antiparallel diodes are connected in series, between the first AC output terminal and the low potential side, Between semiconductor switching element and anti-parallel diode A lower arm column circuit connected two series, a first output circuit comprising a respective connecting the diode between the neutral point each of the intermediate connection points of the two series circuits of the respective arms,
An upper arm in which two parallel circuits of semiconductor switching elements and antiparallel diodes are connected in series between the high potential side and the second AC output terminal, the second AC output terminal and the low potential side Between the upper arm in which two parallel circuits of a semiconductor switching element and an antiparallel diode are connected in series, and between the second AC output terminal and the low potential side, the semiconductor switching element and the antiparallel diode A second output circuit comprising: a lower arm in which two parallel circuits are connected in series; an intermediate connection point of each of the two series circuits of each arm; and a diode connected between each of the neutral points; The power converter according to any one of claims 1 to 4, wherein the power converter is provided.

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