JP2014128154A - Serial multiple power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a serial multiple power conversion device capable of enhancing a utilization factor of a device to eliminate waste cost.SOLUTION: Power supply voltages insulated from each other are inputted to N (N is a positive integer) single-phase inverter cells 31 and one single-phase piece arm inverter cell 32A, and the inverter cells 31 and 32A are connected in series to configure a power converter for one phase so that output voltages of the inverter cells 31 and 32A are added. One AC output terminal of this power converter is set to be a neutral point O, and the other AC output terminal is set to be an AC output terminal for one phase. By star-connecting M (M is an integer of 2 or more) power converters, an M-phase AC voltage can be output. As opposed to the case that only the plurality of single-phase inverter cells are connected in series, a desired output voltage can be obtained by an optimum number of series connections of the inverter cells. A utilization factor of the device can be improved without wasting capacity of each inverter cell, and the number of components and cost can be reduced.

Description

  The present invention relates to a serial multiple power conversion device configured by connecting a single-phase inverter cell and a single-phase single-arm inverter cell in series.

FIG. 5 shows a conventional series multiple power converter configured by connecting a plurality of single-phase inverter cells in series, where 1 is a three-phase AC power source and 2 is a plurality of secondary windings insulated from each other. Transformers having (three phases), 31 to 39 are single phase three level inverter cells. Here, in the single-phase three-level inverter cells 31 to 39, two AC input terminals are connected to the secondary winding of the transformer 2, respectively. Further, the AC output terminals of the inverter cells 31, 32, 33 are connected in series to constitute a U-phase power converter, and the AC output terminals of the inverter cells 34, 35, 36 are connected in series to form a V-phase power converter. And the AC output terminals of the inverter cells 37, 38, 39 are connected in series to form a W-phase power converter.
These U-phase power converter, V-phase power converter, and W-phase power converter are star-connected by a neutral point O, and one AC output terminal of each of inverter cells 33, 36, and 39 is connected to each of U, V, and W. It is a phase output terminal.

The serial multiplex power conversion device having the above configuration is known as a power conversion device capable of outputting a three-phase high voltage. For example, Patent Literature 1 and Patent Literature 2 include serial multiplex power devices configured in substantially the same manner as FIG. A power converter is described.
That is, FIG. 6 schematically shows the serial multiple power conversion device described in Patent Documents 1 and 2, 30 is a single-phase three-level inverter cell that converts DC voltage to AC voltage, 40 is a battery or A DC voltage source such as a capacitor, and M is a load such as a three-phase AC motor. This series multiple power conversion device has the same basic operation as that of FIG. 5 except that the input of the single-phase three-level inverter cell 30 is a DC voltage.

Here, the configuration of the single-phase three-level inverter cell (for example, 31) shown in FIG. 5 is as shown in FIG. 7, and the main part of this inverter cell is shown in FIG. This is also described in FIG. 6 of Patent Document 2.
In FIG. 7, 101 is a first AC input terminal connected to the secondary winding of the transformer 2, 102 is a first forward converter (rectifier), 103 is a first smoothing capacitor, and 104 is the second input terminal. A second AC input terminal connected to a secondary winding of a different system insulated from the secondary winding, 105 is a second forward converter, 106 is a second smoothing capacitor, 107 to 114 are IGBTs, etc. Semiconductor switching elements, 115 to 122 are freewheeling diodes, 123 to 126 are clamp diodes, 127 is a first AC output terminal, and 128 is a second AC output terminal.
Here, the upper and lower arm portions having the switching elements 107 to 110 are referred to as first upper and lower arm portions, and the upper and lower arm portions having the switching elements 111 to 114 are referred to as second upper and lower arm portions. Further, the upper arm composed of the switching elements 107 and 108 is the first upper arm, the lower arm composed of 109 and 110 is the first lower arm, the upper arm composed of 111 and 112 is the second upper arm, This lower arm is called a second lower arm.

Next, the operation of the circuit of FIG. 7 will be briefly described.
When the switching elements 107 and 108 are turned on and the switching elements 109 and 110 are turned off while a three-phase AC voltage is applied to the AC input terminals 101 and 104 from the secondary winding of the transformer 2 or the like, respectively, A voltage on the high potential side of the DC circuit (positive output voltage of the capacitor 103) is output from the AC output terminal 127. Further, when the switching elements 107 and 110 are made non-conductive and the switching elements 108 and 109 are made conductive, the clamp diodes 123 and 124 cause the neutral point potential (the connection point between the capacitors 103 and 106) from the AC output terminal 127. Is output). Further, when the switching elements 107 and 108 are turned off and the switching elements 109 and 110 are turned on, a low potential side voltage (negative output voltage of the capacitor 106) is output from the AC output terminal 127.

By repeating the above operation, a three-level AC voltage can be output from the AC output terminal 127. Similarly, the AC output terminal 128 can output a three-level AC voltage by controlling the conduction / non-conduction of the switching elements 111 to 114. For this reason, the voltage between the AC output terminals 127 and 128 changes at five levels. Generally, when n (n is an integer of 2 or more) single-phase three-level inverter cells are connected in series, the level of the output voltage The maximum number is 4n + 1.
Thus, the method of connecting a plurality of single-phase three-level inverter cells in series increases the output voltage per cell and the number of cells is smaller than the method of connecting a plurality of single-phase two-level inverter cells in series. There is an advantage that a high voltage can be output.

Japanese Unexamined Patent Publication No. 2006-320103 (FIGS. 1, 11, 19, etc.) JP 2012-147559 A (FIG. 1 etc.)

  Now, as shown in FIG. 5, when an output voltage that is 1/2 of the output voltage when three single-phase three-level inverter cells are connected in series for each phase is required, theoretically, Although 1.5 phase 3-level inverter cells may be connected in series, such a circuit configuration is physically impossible. In particular, when single-phase three-level inverter cells are connected to system voltages of various sizes, there arises a situation where the optimum number of inverter cells connected in series cannot be selected.

For this reason, for example, when the theoretical number of inverter cells connected in series is 1.5, as shown in FIG. It is necessary to obtain a desired output voltage (output voltage corresponding to 1.5 inverter cells connected in series).
However, in the serial multiple power conversion device of FIG. 8, the voltage that can be output in each phase is 2/3 of the serial multiple power conversion device of FIG. 5, whereas the voltage actually used is the serial multiple power conversion of FIG. 1/2 of the power converter. That is, the voltage that can be output by the serial multiple power conversion device of FIG. 8 must be intentionally reduced and used, so the utilization rate of the device is low, and the cost is wasted by the amount that the output voltage is reduced. become.
SUMMARY OF THE INVENTION Accordingly, the problem to be solved by the present invention is to provide a serial multiple power conversion device that increases the utilization factor of the device and eliminates waste in cost.

In order to solve the above-described problem, the invention according to claim 1 is configured such that power supply voltages insulated from each other are input to N (N is a positive integer) single-phase inverter cells and a single single-phase single-arm inverter cell. Then, all inverter cells are connected in series so that the output voltage of the single-phase inverter cell and the output voltage of the single-phase single-arm inverter cell are added to form a power converter for one phase. One AC output terminal of the power converter is a neutral point and the other AC output terminal is an AC output terminal for one phase, and M (M is an integer of 2 or more) power conversions. By connecting the devices at a neutral point and star-connecting, an M-phase AC voltage can be output.
Here, the single-phase inverter cell has two upper and lower arm portions formed by connecting a plurality of semiconductor switching elements in series, connected in parallel, and an AC voltage from a connection point between the upper and lower arms of the upper and lower arm portions. Is output.
The single-phase single-arm inverter cell has a single upper and lower arm portion connected in parallel with a single upper and lower arm portion formed by connecting a plurality of semiconductor switching elements in series and a series circuit of two smoothing capacitors. AC voltage is output from the connection point between the arms and the connection point between the two smoothing capacitors.

  Here, as described in claim 2, the single-phase inverter cell is a single-phase three-level inverter cell configured as in claim 3 in which the potential of each AC output terminal has three levels, The single-phase single-arm inverter cell may be a single-phase single-arm three-level inverter cell configured as in claim 4 in which the output AC voltage is ½ of the output voltage of the single-phase three-level inverter cell. it can.

Further, as described in claim 5, in the power converter for one phase, the phase difference is sequentially increased by 60 ° / (from the secondary windings respectively connected to the N single-phase three-level inverter cells. 2N + 1) shifted AC voltages are input to each single-phase three-level inverter cell, and the single-phase single-arm three-level inverter cell is supplied with an input voltage from another secondary winding to the adjacent single-phase three-level inverter cell. It is desirable to input AC voltages having a phase difference of 60 ° / (2N + 1) and having the same phase.
In this case, as described in claim 6, the secondary winding capacity connected to each of the N single-phase three-level inverter cells is different from that of the other two connected to the single-phase single-arm three-level inverter cell. The capacity of the next winding can be 50 to 60%.

  Furthermore, as described in claim 7, the single-phase inverter cell is a single-phase two-level inverter cell configured as in claim 8, wherein each AC output terminal has two levels of potential. The single-phase single-arm two-level inverter cell configured as in claim 9 may be used as the single-phase single-arm inverter cell, in which the AC voltage that can be output is ½ of the output voltage of the single-phase two-level inverter cell.

  According to the present invention, N single-phase inverter cells and one single-phase single-arm inverter cell are connected in series to form a power converter for one phase, whereby only a plurality of single-phase inverter cells are connected in series. Compared to the case of connection, the required output voltage can be obtained by the optimum number of series connections. For this reason, the utilization factor of the apparatus can be improved without wasting the capacity of each inverter cell, and the number of parts and the cost can be reduced.

It is a block diagram of the serial multiple power converter device which concerns on embodiment of this invention. It is a block diagram of the single phase single arm 3 level inverter cell in FIG. It is a block diagram of a single phase 2 level inverter cell. It is a block diagram of a single phase single arm 2 level inverter cell. It is a block diagram which shows the prior art of a serial multiple power converter device. It is a schematic block diagram of the serial multiple power converter device described in patent document 1,2. It is a block diagram of a single phase 3 level inverter cell. It is a block diagram of the serial multiple power converter device which has the power converter for 1 phase which connected two single phase 3 level inverter cells in series.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a serial multiple power conversion device according to an embodiment of the present invention. In FIG. 1, 1 is a three-phase AC power source, 2 is a primary winding 21 connected to the three-phase AC power source 1, and a plurality of secondary windings (three-phase) 231a, 231b, 234a, 234b, 237a, 237b, 232a, 232b, 235a, 235b, 238a, 238b. 31, 34, and 37 are single-phase three-level inverter cells in which two sets of AC input terminals are connected to the two secondary windings 231 a, 231 b, 234 a, 234 b, 237 a, and 237 b, respectively. The circuit configuration is as shown in FIG.
Further, 32A, 35A, and 38A are single-phase single-arm three-level inverter cells in which two sets of AC input terminals are respectively connected to the two secondary windings 232a, 232b, 235a, 235b, 238a, and 238b. The circuit configuration of these inverter cells 32A, 35A, and 38A will be described later.

The AC output terminals of the single-phase three-level inverter cell 31 and the single-phase single-arm three-level inverter cell 32A are connected in series to form a U-phase power converter, and the single-phase three-level inverter cell 34 and the single-phase single-arm three-level inverter cell The AC output terminal of 35A is connected in series to form a V-phase power converter, and the AC output terminals of the single-phase three-level inverter cell 37 and the single-phase single-arm three-level inverter cell 38A are connected in series to be W-phase power conversion. Make up the vessel.
The AC output terminals of the single-phase three-level inverter cells 31, 34, and 37 are commonly connected at a neutral point O, and the AC output terminals of the single-phase single-arm three-level inverter cells 32A, 35A, and 38A. (AC output terminal on the side opposite to the inverter cells 31, 34, 37) is an output terminal for each of the U, V, and W phases.
Note that the number of single-phase three-level inverter cells in each phase is not limited to one, and a plurality of single-phase three-level inverter cells may be connected in series, and generally N (N is a positive integer).

Next, the circuit configuration of the single-phase single-arm three-level inverter cells 32A, 35A, and 38A will be described with reference to FIG. In addition, since all the configurations of these inverter cells 32A, 35A, and 38A are the same, the inverter cell 32A will be described as an example here.
In FIG. 2, 201 is a third AC input terminal connected to the secondary winding 232a of the transformer 2, 202 is a third forward converter (rectifier), 203 is a third smoothing capacitor, and 204 is a transformer. A fourth AC input terminal connected to the second secondary winding 232b, 205 a fourth forward converter, 206 a fourth smoothing capacitor, and 207-210 semiconductor switching elements such as IGBTs connected in series with each other , 215 to 218 are free-wheeling diodes connected in reverse parallel to the switching elements 207 to 210, 223 and 224 are clamp diodes, 227 is a third AC output terminal, and 228 is a fourth AC output terminal. The AC output terminal 227 is a U-phase output terminal in FIG. 1, and the AC output terminal 228 is connected to one AC output terminal of the single-phase three-level inverter cell 31.
Here, the upper and lower arm portions having the switching elements 207 to 210 are referred to as third upper and lower arm portions, the upper arm including the switching elements 207 and 208 is the third upper arm, and the lower arm including the 209 and 210 is the third lower arm. This is called an arm.
As apparent from FIG. 2, the single-phase single-arm three-level inverter cell 32A has a configuration in which one of the first and second upper and lower arm portions of the single-phase three-level inverter cell 31 shown in FIG. It corresponds to.

  In the above configuration, the series circuit of the clamp diodes 223 and 224 is connected between the connection point between the switching elements 207 and 208 and the connection point between the switching elements 209 and 210. The connection point between the switching elements 208 and 209 is connected to the third AC output terminal 227, the connection point between the forward converters 202 and 205, the connection point between the smoothing capacitors 203 and 206, and a clamp diode. All the connection points between 223 and 224 are connected to the fourth AC output terminal 228.

Next, the operation of this embodiment will be described.
The operations of the single-phase three-level inverter cells 31, 34, 37 in FIG. 1 are the same as the operations of the single-phase three-level inverter cell 31 shown in FIG. 7, and from the AC output terminals of the inverter cells 31, 34, 37. A three-level AC voltage is output.

The operation of the single-phase single-arm three-level inverter cell 32A shown in FIG. 2 (as well as 35A and 38A) is as follows.
When the switching elements 207 and 208 are turned on and the switching elements 209 and 210 are turned off while a three-phase AC voltage is applied from the secondary windings 232a and 232b to the AC input terminals 201 and 204, respectively, the AC output terminal 227 is turned off. Outputs a high potential side voltage (positive output voltage of the capacitor 203). Further, when the switching elements 207 and 210 are made non-conductive and the switching elements 208 and 209 are made conductive, the action of the clamp diodes 223 and 224 causes a neutral point potential (a connection point between the capacitors 203 and 206) from the AC output terminal 227. Is output). Further, when the switching elements 207 and 208 are turned off and the switching elements 209 and 210 are turned on, a low potential side voltage (negative output voltage of the capacitor 206) is output from the AC output terminal 227.

By repeating the above operation, a three-level AC voltage is output from the AC output terminal 227. Compared with the single-phase three-level inverter cell 31 of FIG. Since it is fixed, the magnitude of the voltage that can be output between the AC output terminals 227 and 228 is ½ that of the single-phase three-level inverter cell 31 of FIG. The same applies to the other single-phase single-arm three-level inverter cells 35A and 38A.
Therefore, according to the embodiment of FIG. 1, the voltage that can be output by each of the U, V, and W phases is 1.5 times that of the single-phase three-level inverter cells 31, 34, and 37, respectively.

Therefore, in the conventional case, as shown in FIG. 8, the output voltage for 1.5 pieces, which is realized within the voltage range obtained by connecting two single-phase three-level inverter cells in series, is obtained. It can be realized by a series connection circuit of a single-phase three-level inverter cell and a single-phase single-arm three-level inverter cell.
In other words, it is possible to obtain a desired output voltage by using 100% of the output capability of each of the two inverter cells, improving the utilization factor of the apparatus, and using fewer parts than the prior art of FIG. Thus, the circuit configuration can be simplified and the cost can be reduced.

In addition, there exists a request | requirement which reduces an input harmonic in a power converter device. For example, in the circuit configuration of FIG. 5, the phase of the AC voltage (output voltage of 6 secondary windings) of 2 systems, 6 systems in total, each input to the U-phase single-phase 3-level inverter cells 31 to 33 is set. Shifting by 60 ° / 6 = 10 ° is effective in reducing input harmonics. The same applies to the V-phase and W-phase single-phase three-level inverter cells 34 to 36 and 35 to 38.
From the same viewpoint as described above, in the circuit configuration of FIG. 8, the AC voltage of all four systems input to the single-phase three-level inverter cells 31 and 32 (the phase of the output voltage of the four secondary windings is 60 ° / 4 It is effective to shift by = 15 °, which is the same for the V-phase and W-phase single-phase three-level inverter cells 34 and 36, and 37 and 38.
When the output power of the secondary winding of the transformer 2 is the same, it is possible to reduce the input harmonics by sequentially shifting the phase angle of the output voltage of the secondary winding as described above. In the case of FIG. 1, single-phase three-level inverter cells 31, 34, and 37 and single-phase single-arm three-level inverter cells 32 </ b> A, 35 </ b> A, and 38 </ b> A are mixed on the secondary side of the transformer 2. Since the output power is not the same, the method of shifting the phase angle of the output voltage of the secondary winding of the transformer 2 as described above cannot be adopted.

First, the voltage that can be output from the single-phase single-arm three-level inverter cell shown in FIG. 2 is ½ that of the single-phase three-level inverter cell shown in FIG. When the inverter cell and the single-phase single-arm three-level inverter cell are connected in series, the output voltage of the single-phase single-arm three-level inverter cell is controlled to be ½ of the output voltage of the single-phase three-level inverter cell. In this case, in the connection state shown in FIG. 1, since the output current of the single-phase single-arm three-level inverter cell and the single-phase three-level inverter cell is common, the output power of each inverter cell is proportional to the above-described ratio of the output voltage. Therefore, the output power of the single-phase single-arm three-level inverter cell is ½ that of the single-phase three-level inverter cell.
Accordingly, the capacity of the secondary windings 232a, 232b, 235a, 235b, 238a, 238b of the transformer 2 connected to the single-phase single-arm three-level inverter cells 32A, 35A, 38A in FIG. The capacity of the secondary windings 231a, 231b, 234a, 234b, 237a, and 237b connected to 31, 34, and 37 can be about ½ (about 50% to 60%).

  As a result, the total output power of the secondary windings 232a and 232b connected to the single-phase single-arm three-level inverter cell 32A and the secondary windings 231a and 231b connected to the single-phase three-level inverter cell 31 The output power is almost equal. Similarly, the total output power value of the secondary windings 235a and 235b connected to the single-phase single-arm three-level inverter cell 35A and the respective outputs of the secondary windings 234a and 234b connected to the single-phase three-level inverter cell 34 Power, total output power of secondary windings 238a and 238b connected to single-phase single-arm three-level inverter cell 38A, and output power of secondary windings 237a and 237b connected to single-phase three-level inverter cell 37 Are almost equal to each other.

Therefore, the phase of the output voltage of the secondary windings of the two systems of the single-phase single-arm three-level inverter cell is made the same, and the phase of the output voltage of each secondary winding input to the single-phase three-level inverter cell is sequentially shifted. As a result, input harmonics can be reduced. For example, the phases of the output voltages of the two secondary windings 232a and 232b connected to the single-phase single-arm three-level inverter cell 32A are the same, and the single-phase three-level inverter cell 31 is connected to this phase. The phase of the output voltage of the secondary windings 231a and 231b may be sequentially shifted by 20 °.
In general, when there are N single-phase three-arm inverter cells connected in series to one single-phase single-arm three-level inverter cell (N is a positive integer), the single-phase single-arm three-level inverter cell is connected. The phase of the output voltage of the two secondary windings is the same, and this one phase and 2N output voltages that are the total number of secondary windings connected to the N single-phase three-level inverter cells. The input harmonics are reduced by shifting the phase of the output voltage of the secondary winding so that the phase difference is 60 ° / (2N + 1) for (2N + 1) phases, which is the total value with the phase. Can do.

In the embodiment shown in FIG. 1, the U, V, and W power converters connect the single-phase three-level inverter cell of FIG. 7 and the single-phase single-arm three-level inverter cell of FIG. 2 in series. However, instead of these, a single-phase two-level inverter cell and a single-phase single-arm two-level inverter cell may be connected in series.
FIG. 3 shows a configuration diagram of the single-phase two-level inverter cell 51, in which 301 is a fifth AC input terminal, 303 is a fifth forward converter, 304 is a fifth smoothing capacitor, and 305 to 308 are semiconductor switching circuits. Elements 309 to 312 are free-wheeling diodes, and 313 and 314 are fifth and sixth AC output terminals. The upper and lower arm portions having the semiconductor switching elements 307 and 308 are referred to as fourth upper and lower arm portions, and the upper and lower arm portions having the semiconductor switching elements 305 and 306 are referred to as fifth upper and lower arm portions.
4 shows a configuration diagram of the single-phase single-arm two-level inverter cell 52A. 331 is a sixth AC input terminal, 333 is a sixth forward converter, 315 and 316 are sixth and seventh smoothing. Capacitors 317 and 318 are semiconductor switching elements, 319 and 320 are free-wheeling diodes, and 321 and 322 are seventh and eighth AC output terminals. Here, the upper and lower arm portions having the semiconductor switching elements 317 and 318 are referred to as sixth upper and lower arm portions.

As is well known, these inverter cells 51 and 52A are ones in which the potentials of the respective AC output terminals 313, 314, 321, and 322 change to two levels, positive or negative, and single-phase single-arm two-level inverters. The magnitude of the voltage that can be output between the AC output terminals 321 and 322 of the cell 52A is ½ of the voltage that can be output between the AC output terminals 313 and 314 of the single-phase two-level inverter cell 51.
Accordingly, the two secondary windings of the transformer whose primary winding is connected to the AC power source are insulated from each other, and the AC input terminal 301 of the single-phase two-level inverter cell 51 and the single-phase single arm 2 are connected to these secondary windings. The AC input terminal 331 of the level inverter cell 52A is connected to each other, one AC output terminal 314 of the single-phase two-level inverter cell 51 is connected to the neutral point O, and the other AC output terminal 313 is connected to the single-phase single arm 2 What is necessary is just to obtain the output for one phase from the other AC output terminal 321 by connecting to one AC output terminal 322 of the level inverter cell 52A. Similarly, a single-phase two-level inverter cell and a single-phase single-arm two-level inverter cell are connected in series to form another phase power converter. For example, a three-phase power converter is star-connected to form a three-phase power converter. A serial multiple power converter can be configured.

  Thus, even when a single-phase two-level inverter cell and a single-phase single-arm two-level inverter cell are connected in series, a desired output voltage can be obtained by using 100% of the output capability of each of the inverter cells. In addition to improving the utilization factor of the apparatus, the number of components can be reduced compared to the case where only a plurality of single-phase two-level inverter cells are connected in series, and the circuit configuration can be simplified and the cost can be reduced.

In the above embodiment, a single-phase (3-level or 2-level) inverter cell and a single-phase single-arm (3-level or 2-level) inverter cell are connected in series to constitute a power converter for one phase, and this power conversion An example in which a three-phase (U, V, W phase) output series multiple power converter is configured by star connection of three units has been described.
However, the present invention is not limited to a three-phase output. Generally, a plurality of single-phase (three-level or two-level) inverter cells and a single-phase single-arm (three-level or two-level) inverter cell are connected in series. By connecting M power converters (M is an integer of 3 or more) and star connection, an M-phase output series multiple power converter can be configured.

1: three-phase AC power supply 2: transformer 21: primary windings 231a, 231b, 234a, 234b, 237a, 237b, 232a, 232b, 235a, 235b, 238a, 238b: secondary windings 31, 34, 37: single Phase 3 level inverter cells 32A, 35A, 38A: Single phase single arm 3 level inverter cell 51: Single phase 2 level inverter cell 52A: Single phase single arm 2 level inverter cell 101, 104: AC input terminals 102, 105: Forward converter 103 106: smoothing capacitors 107-114: semiconductor switching elements 115-122: freewheeling diodes 123, 126: clamp diodes 127, 128: AC output terminals 201, 204: AC input terminals 202, 205: forward converters 203, 206: smoothing Capacitors 207 to 210: Semiconductor switches Elements 215 to 218: freewheeling diodes 223, 224: clamp diodes 227, 228: AC output terminals 301, 331: AC input terminals 303, 333: forward converters 304, 315, 316: smoothing capacitors 305-308, 317, 318 : Semiconductor switching elements 309 to 312, 319, 320: Free-wheeling diodes 313, 314, 321, 322: AC output terminals

Claims (9)

N (N is a positive integer) that connects two upper and lower arm parts connected in series with a plurality of semiconductor switching elements in parallel and outputs an AC voltage from the connection point between the upper arm and lower arm of the upper and lower arm parts ) Pieces of single-phase inverter cells,
A single upper and lower arm part in which a plurality of semiconductor switching elements are connected in series and a series circuit of two smoothing capacitors are connected in parallel, and a connection point between the upper arm and lower arm of the single upper and lower arm part And a single-phase single-arm inverter cell that outputs an alternating voltage from a connection point between the smoothing capacitors,
To the single-phase inverter cell and the single-phase single-arm inverter cell, input power supply voltages insulated from each other,
The AC output side of all inverter cells is connected in series so that the output voltage of the single-phase inverter cell and the output voltage of the single-phase single-arm inverter cell are added together to form a power converter for one phase. ,
One AC output terminal of the power converter is a neutral point, and the other AC output terminal of the power converter is an AC output terminal for one phase,
A serial multiple power conversion apparatus characterized in that M (M is an integer of 2 or more) power converters can be star-connected by the neutral point to output an M-phase AC voltage. The serial multiple power converter according to claim 1,
The single-phase inverter cell is a single-phase three-level inverter cell in which the potential of each AC output terminal has three levels,
The single-phase single-arm inverter cell is a single-phase single-arm three-level inverter cell whose outputable AC voltage is 1/2 of the output voltage of the single-phase three-level inverter cell. In the serial multiple power converter according to claim 2,
The single-phase three-level inverter cell is
A first forward converter that converts an AC voltage input from a first AC input terminal into a DC voltage;
A first smoothing capacitor for smoothing the output voltage of the first forward converter;
A second forward converter for converting an AC voltage input from the second AC input terminal into a DC voltage;
A second smoothing capacitor for smoothing the output voltage of the second forward converter and connected in series with the first smoothing capacitor;
A first upper arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the high potential side of the first smoothing capacitor and the first AC output terminal;
A first lower arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the low potential side of the second smoothing capacitor and the first AC output terminal;
Diodes respectively connected between a connection point between the semiconductor switching elements constituting the first upper arm and the first lower arm and a neutral point which is a connection point between the first and second smoothing capacitors;
A second upper arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the high potential side of the first smoothing capacitor and the second AC output terminal;
A second lower arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the low potential side of the second smoothing capacitor and the second AC output terminal;
A diode connected between a connection point between the semiconductor switching elements constituting the second upper arm and the second lower arm and the neutral point;
A serial multiple power conversion device comprising: In the serial multiple power converter device according to claim 2 or 3,
The single-phase single-arm three-level inverter cell is
A third forward converter for converting an AC voltage input from the third AC input terminal into a DC voltage;
A third smoothing capacitor for smoothing the output voltage of the third forward converter;
A fourth forward converter for converting an AC voltage input from the fourth AC input terminal into a DC voltage;
A fourth smoothing capacitor for smoothing the output voltage of the fourth forward converter and connected in series with the third smoothing capacitor;
A third upper arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the high potential side of the third smoothing capacitor and the third AC output terminal;
A third lower arm formed by connecting two anti-parallel circuits of a semiconductor switching element and a free-wheeling diode in series between the low potential side of the fourth smoothing capacitor and the third AC output terminal;
Diodes respectively connected between a connection point between the semiconductor switching elements constituting the third upper arm and the third lower arm and a neutral point which is a connection point between the third and fourth smoothing capacitors;
With
A serial multiple power conversion device, wherein the neutral point is connected to a fourth AC output terminal. The series multiple power converter according to any one of claims 2 to 4, further comprising a transformer having a plurality of secondary windings in which the primary winding is connected to an AC power source and insulated from each other.
In the power converter for one phase,
AC voltages whose phase differences are sequentially shifted by 60 ° / (2N + 1) from the secondary windings respectively connected to the N single-phase three-level inverter cells are respectively input to the single-phase three-level inverter cells,
The single-phase single-arm three-level inverter cell has a phase difference of 60 ° / (2N + 1) from another secondary winding to the input voltage to the adjacent single-phase three-level inverter cell and is in phase with each other. A serial multiple power conversion device characterized by inputting a voltage. In the serial multiple power converter device according to claim 5,
The capacity of secondary windings connected to the single-phase single-arm three-level inverter cell is 50-60 with respect to the capacity of secondary windings connected to the N single-phase three-level inverter cells. A serial multiple power conversion device characterized by the following: The serial multiple power converter according to claim 1,
The single-phase inverter cell is a single-phase two-level inverter cell in which the potential of each AC output terminal has two levels,
The single-phase single-arm inverter cell is a single-phase single-arm two-level inverter cell whose AC voltage that can be output is 1/2 of the output voltage of the single-phase two-level inverter cell. In the serial multiple power converter device according to claim 7,
The single-phase two-level inverter cell is
A fifth forward converter for converting an AC voltage input from the fifth AC input terminal into a DC voltage;
A fifth smoothing capacitor for smoothing the output voltage of the fifth forward converter;
A fourth upper and lower arm portion in which a pair of DC input terminals are connected to both ends of the fifth smoothing capacitor, and two anti-parallel circuits of a semiconductor switching element and a free wheel diode are connected in series between the pair of DC input terminals. When,
A fifth upper and lower arm part in which two anti-parallel circuits of a semiconductor switching element and a reflux diode are connected in series between the pair of DC input terminals;
With
The connection point between the semiconductor switching elements constituting the fourth upper and lower arm portion is connected to a fifth AC output terminal, and the connection point between the semiconductor switching elements constituting the fifth upper and lower arm portion is connected to a sixth AC output. A serial multiplex power converter characterized by being connected to a terminal. The serial multiple power converter according to claim 7 or 8,
The single-phase single-arm two-level inverter cell is
A sixth forward converter for converting an AC voltage input from a sixth AC input terminal into a DC voltage;
A series circuit of seventh and eighth smoothing capacitors for smoothing the output voltage of the sixth forward converter;
A sixth upper and lower arm unit connected in parallel to a series circuit of seventh and eighth smoothing capacitors, and connected in series with two anti-parallel circuits of a semiconductor switching element and a free wheeling diode;
With
The connection point between the semiconductor switching elements constituting the sixth upper and lower arm part is connected to the seventh AC output terminal, and the connection point between the seventh and eighth smoothing capacitors is connected to the eighth AC output terminal. A serial multiple power converter characterized by the above.

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