JP7175649B2 - Three-phase power converter and uninterruptible power supply - Google Patents

Description

The present invention relates to a three-phase power converter and an uninterruptible power supply (UPS) that inputs three-phase alternating current and outputs three-phase alternating current.

A constant inverter type UPS requires an isolation transformer to reduce noise on the output side. However, the isolation transformer causes an increase in size and a high cost. Therefore, a transformerless UPS has been proposed in which the isolation transformer is eliminated by sharing the V phase (see, for example, Patent Document 1).

Further, in Prior Document 2, an uninterruptible power supply system is proposed in which 2n single-phase AC power supplies are operated in parallel as n power supply units to obtain a three-phase AC output as a transformerless UPS with a common V-phase. .

JP 2010-172141 A JP 2003-018866 A

However, when a transformerless UPS is connected in parallel with a plurality of power supply units, the current cannot be controlled because the V phase is shared, and current concentration may occur in the V phase of one of the power supply units.

The transformerless UPS 10 shown in FIG. 4 has two power supply units 20a and 20b connected in parallel, and a three-phase alternating current consisting of U-phase, V-phase, and W-phase is input as a U-phase input, a V-phase input, and a W-phase input, respectively. input terminals 11u, 11v and 11w, and output terminals 12u, 12v and 12w for outputting three-phase alternating current consisting of U-phase, V-phase and W-phase as U-phase output, V-phase output and W-phase output, respectively. I have it.

The power supply units 20a and 20b have the same configuration, input terminals 21u, 21v and 21w respectively connected to the input terminals 11u, 11v and 11w, and output terminals 22u and 22u respectively connected to the output terminals 12u, 12v and 12w. 22v, 22w, a converter circuit 23 that converts a three-phase AC input consisting of a U-phase input, a V-phase input, and a W-phase input into DC power, and an inverter circuit 24 that converts the DC power into a U-phase output and a W-phase output. are provided respectively.

The converter circuit 23 includes a first capacitor C1 connected between the positive bus 25 and the neutral terminal 26 connected to the input terminal 21v and the output terminal 12v, and connected between the neutral terminal 26 and the negative bus 27. a first arm 28 connected between the positive bus 25 and the negative bus 27 to convert the power between the U-phase input and the V-phase input into DC power; A second arm 29 is connected between the negative bus 27 and converts the power between the V-phase input and the W-phase input into DC power.

The inverter circuit 24 is connected between the positive bus 25 and the negative bus 27, is connected between a third arm 30 that converts the DC power into a U-phase output, and is connected between the positive bus 25 and the negative bus 27 to generate the DC power. to a W-phase output.

In FIG. 4, the wiring impedance Za between the input terminal 11v and the neutral terminal 26 of the power supply unit 20a and the wiring impedance Zb between the input terminal 11v and the neutral terminal 26 of the power supply unit 20b are different from each other. If there is an imbalance due to variations in length or between units, the V-phase current will be unbalanced between units as shown in FIG. 5(c). Therefore, there is a problem that current concentration occurs in one of the power supply units 20 with the smallest wiring impedance Z, which causes problems such as shortening of life and breakage. In FIG. 5, (a) is a voltage waveform diagram of U-phase input and W-phase input of three-phase AC input, and (b) is a current waveform diagram of each phase output of three-phase AC output.

SUMMARY OF THE INVENTION An object of the present invention is to provide a three-phase power conversion device and an uninterruptible power supply that can solve the above problems of the prior art and prevent excessive current concentration in any one of the power supply units connected in parallel. It is in.

The three-phase power converter of the present invention converts a three-phase AC input consisting of a U-phase input, a V-phase input, and a W-phase input into DC power , and converts the DC power into a U-phase output, a V A three-phase power converter that converts a three-phase AC output consisting of a phase output and a W-phase output , comprising: a converter circuit that converts the three-phase AC input into the DC power; A plurality of power supply units each having an inverter circuit for converting the three-phase AC output into the U-phase output and the W-phase output are connected in parallel, and the V-phase input is input to the V-phase input. A V-phase exclusive line is provided for directly connecting the terminal and the V-phase output terminal from which the V-phase output is output.

According to the present invention, the V-phase input terminal and the V-phase output terminal are directly connected by the V-phase dedicated line without passing through the power supply unit, thereby preventing excessive current concentration in any one of the power supply units connected in parallel. There is an effect that it can be prevented.

1 is a configuration diagram showing a configuration example of an embodiment of a three-phase power converter according to the present invention; FIG. FIG. 2 is a waveform diagram showing voltages and currents of respective parts shown in FIG. 1; 1. It is a figure which shows an example of an uninterruptible power supply provided with the three-phase power converter shown in FIG. 1 is a configuration diagram showing a configuration example of a conventional three-phase power converter; FIG. FIG. 5 is a waveform diagram showing voltages and currents of respective parts shown in FIG. 4;

Embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that, in the following embodiments, the same reference numerals are given to the structures showing the same functions, and the description thereof will be omitted as appropriate.

Referring to FIG. 1, the three-phase power converter 40 of the present embodiment has two power supply units 50a and 50b connected in parallel. Input terminals 11u, 11v, and 11w are input as V-phase input and W-phase input, respectively, and a three-phase alternating current consisting of U-phase, V-phase, and W-phase is output as U-phase output, V-phase output, and W-phase output, respectively. and a V-phase dedicated line 60 that directly connects the input terminal 11v and the output terminal 12v without going through the power supply units 50a and 50b.

The power supply units 50a and 50b have the same configuration, with input terminals 21u, 21v and 21w respectively connected to the input terminals 11u, 11v and 11w, and output terminals 22u and 22w respectively connected to the output terminals 12u and 12w. , input terminals 11u, 11v, and 11w. An inverter circuit 24 that outputs from the output terminal 12u and converts DC power into a W-phase output and outputs from the output terminal 12w is provided.

The converter circuit 51 includes a first capacitor C1 connected between the positive bus 25 and the neutral terminal 26 connected to the input terminal 21v, and a second capacitor C1 connected between the neutral terminal 26 and the negative bus 27. a capacitor C2; and a second arm 29 connected between the V-phase input and the W-phase input for converting the power between the V-phase input and the W-phase input into DC power.

An uninterruptible power supply (UPS) is configured by connecting storage batteries (not shown) in parallel to the first capacitor C1 and the second capacitor C2.

In the converter circuit 51 shown in FIG. 1, the first arm and the second arm 29 are configured by two switch elements Q connected in series to form a two-level converter. A three-level converter may be formed by four switching elements Q connected in series.

The inverter circuit 24 is connected between the positive bus 25 and the negative bus 27, is connected between a third arm 30 that converts the DC power into a U-phase output, and is connected between the positive bus 25 and the negative bus 27 to generate the DC power. to a W-phase output.

In the inverter circuit 24 shown in FIG. 1, the third arm 30 and the fourth arm 31 are configured by two switch elements Q connected in series to form a two-level converter. 31 may be composed of four switch elements Q connected in series to form a three-level inverter.

In this embodiment, the input terminal 11v and the output terminal 12v are directly connected by the V-phase dedicated line 60 without passing through the power supply units 50a and 50b. Therefore, the wiring impedance Za between the input terminal 11v and the neutral terminal 26 of the power supply unit 50a and the wiring impedance Zb between the input terminal 11v and the neutral terminal 26 of the power supply unit 50b are unbalanced. However, as shown in FIG. 5(c), the imbalance of the wiring impedance Z appears only as the magnitude of the ripple of the V-phase current. Therefore, it is possible to prevent excessive power concentration on the power supply units 50a and 50b connected in parallel. In FIG. 2, (a) is a voltage waveform diagram of U-phase input and W-phase input of three-phase AC input, and (b) is a current waveform diagram of each phase output of three-phase AC output.

In principle, the current from the neutral terminal 26, which is the connection point between the first capacitor C1 and the second capacitor C2, to the V-phase is V-phase current=U-phase current+W-phase current. Therefore, if the U-phase and W-phase can be controlled, they can be arbitrarily controlled.

FIG. 3 shows a three-phase power converter 40, a U-phase bypass line 80 connecting a U-phase input and a U-phase output via a bypass switch 70, and a W-phase input and a W-phase output via a bypass switch 70. A constant inverter power feeding system uninterruptible power supply 100 is shown, which is provided with a W-phase bypass line 90 connecting the .

In the uninterruptible power supply 100 of the constant inverter power supply system, when the three-phase power conversion device 40 is stopped or malfunctions, the bypass switch 70 is turned on and the inverter circuit 24 of each power supply unit is gate-blocked. It is possible to switch to a direct feed operation via the phase dedicated line 60 , the U-phase bypass line 80 and the W-phase bypass line 90 . In other words, the V-phase dedicated line 60 can be used also as a V-phase bypass line during direct feed operation.

In this embodiment, an example in which the two power supply units 50a and 50b are connected in parallel has been described, but the number of units connected in parallel may be three or more.

As described above, the present embodiment converts a three-phase AC input consisting of a U-phase input, a V-phase input, and a W-phase input into DC power, and converts the DC power to a U-phase output, a V-phase output, and a W-phase output. A three-phase power conversion device 40 that converts to a three-phase AC output consisting of a converter circuit 51 that converts the three-phase AC input to DC power, and a DC power to the U-phase output and W-phase output of the three-phase AC output. Power supply units 50a and 50b, each having an inverter circuit 24 for conversion, are connected in parallel and provided with a dedicated V-phase line 60 for directly connecting a V-phase input and a V-phase output.
With this configuration, the input terminal 11v and the output terminal 12v are directly connected by the V-phase dedicated line 60 without passing through the power supply units 50a and 50b, thereby preventing excessive current concentration in any one of the power supply units connected in parallel. can be prevented.

Furthermore, according to the present embodiment, the converter circuit 51 includes the first capacitor C1 connected between the positive bus 25 and the neutral terminal 26 connected to the V-phase input, the neutral terminal 26 and the negative bus 27, and a first arm 28 connected between the positive bus 25 and the negative bus 27 for converting power between the U-phase input and the V-phase input into DC power. and a second arm 29 connected between the positive bus 25 and the negative bus 27 for converting the power between the V-phase input and the W-phase input into DC power. A third arm 30 connected between the bus 25 and the negative bus 27 to convert DC power into a U-phase output, and a third arm 30 connected between the positive bus 25 and the negative bus 27 to convert DC power into a W-phase output. and a fourth arm 31 that

Furthermore, uninterruptible power supply 100 of the present embodiment includes three-phase power converter 40, U-phase bypass line 80 connecting U-phase input and U-phase output via bypass switch 70, and bypass switch 70. A W-phase bypass line 90 connects the W-phase input and the W-phase output via the W-phase bypass line 90 .
With this configuration, by turning on the bypass switch 70 and gate-blocking the inverter circuit 24 of each power supply unit, switching to direct operation via the V-phase dedicated line 60, the U-phase bypass line 80 and the W-phase bypass line 90 is possible. can be done.

As described above, the present invention has been described in terms of specific embodiments, but the above-described embodiments are merely examples, and needless to say, modifications can be made without departing from the scope of the present invention.

10, 40 Three-phase power converters 11u, 11v, 11w Input terminals 12u, 12v, 12w Output terminals 20, 20a, 20b, 50, 50a, 50b Power supply units 21u, 21v, 21w Input terminals 22u, 22v, 22w Output terminals 23 , 51 converter circuit 24 inverter circuit 25 positive bus 26 neutral terminal 27 negative bus 28 first arm 29 second arm 30 third arm 31 fourth arm 60 V-phase dedicated line 70 bypass switch 80 U-phase bypass line 90 W-phase bypass Line 100 Uninterruptible power supply C1 First capacitor C2 Second capacitor Q Switch elements Z, Za, Zb Wiring impedance

Claims (3)

A three-phase AC input consisting of a U-phase input, a V-phase input, and a W-phase input is converted into DC power, and the DC power is converted from a U-phase output, a V-phase output, and a W-phase output. A three-phase power conversion device that converts to a three-phase AC output consisting of
A power supply comprising: a converter circuit that converts the three-phase AC input into the DC power; and an inverter circuit that converts the DC power into the U-phase output and the W-phase output of the three-phase AC output. Multiple units are connected in parallel,
A three-phase power converter comprising a V-phase dedicated line that directly connects a V-phase input terminal to which the V-phase input is input and a V-phase output terminal to which the V-phase output is output. The converter circuit is
a first capacitor connected between a positive bus and a neutral terminal connected to a V-phase input terminal to which the V-phase input is input ;
a second capacitor connected between the neutral terminal and the negative bus;
a first arm connected between the positive bus and the negative bus for converting power between the U-phase input and the V-phase input into the DC power;
a second arm connected between the positive bus and the negative bus for converting power between the V-phase input and the W-phase input into the DC power;
The inverter circuit is
a third arm connected between the positive bus and the negative bus for converting the DC power into the U-phase output ;
2. The three-phase power converter according to claim 1, further comprising a fourth arm connected between said positive bus and said negative bus for converting said DC power into said W-phase output . A three-phase power converter according to claim 1 or 2,
Via a U-phase bypass line connecting a U-phase input terminal to which the U-phase input is input via the U-phase bypass switch and a U-phase output terminal to which the U-phase output is output, and a W-phase bypass switch and a W-phase bypass line connecting a W-phase input terminal to which the W-phase input is input and a W-phase output terminal to which the W-phase output is output. .

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