JP2010283989A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion apparatus capable of keeping current equilibrium between three phases. <P>SOLUTION: According to the power conversion apparatus, out of a pair of input terminals of a second rectifying circuit 201 in a single-phase power conversion unit 12, one input terminal is connected to a neutral point of a power supply 10, while the other input terminal is connected to a negative output end of a first rectifying circuit 101 in a three-phase power conversion unit 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion device, and more particularly to a power conversion device applicable to a power utilization system in which a three-phase load and a single-phase load are mixed.

When driving a composite device in which a three-phase load and a single-phase load are mixed using a three-phase four-wire power source with a neutral wire in addition to a three-phase power wire, either one of the three phases It has been proposed to generate single-phase AC power using phases and supply this single-phase AC power to a single-phase load.
For example, in Patent Document 1, as shown in FIG. 11, single-phase AC power is generated from a phase voltage between any one of three phases and a neutral point, and a single-phase AC power is supplied to a single-phase load. A power conversion device that supplies power is disclosed.

No. 2005/006531 (FIG. 1)

However, as disclosed in Patent Document 1, when single-phase AC power is generated using one of the three phases, there are the following problems.
That is, in FIG. 11, when the phase current of the phase connected to the single-phase power converter is I _L1 ′ and the other two-phase currents are I _L2 ′ and I _L3 ′, respectively, as shown in FIG. There is a problem that the single-phase load current I _L4 ′ supplied to the single-phase load is superimposed on the phase current I _L1 ′, and current balance among the three phases cannot be maintained.
Furthermore, since the single-phase load current I _L4 ′ has many third-order harmonic components, harmonics are included in the phase current I _L1 ′, and depending on the magnitude of the harmonics, predetermined harmonics There was a problem that standards (for example, IEC / EN61000-3-2 etc.) could not be satisfied.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the power converter device which can maintain the current balance between three phases.

In order to solve the above problems, the present invention employs the following means.
The present invention is a power conversion device applicable to a three-phase four-wire power source, and includes a three-phase power conversion unit that supplies power to a three-phase load, and a single-phase power conversion unit that supplies power to a single-phase load The three-phase power converter includes a first rectifier circuit that converts three-phase AC power output from the power source into DC power, and three-phase AC power that is rectified by the first rectifier circuit. A first inverter that converts the first-phase power converter, wherein one input terminal is connected to a neutral point of the power source, and the other input terminal is connected to a negative output side of the first rectifier circuit. And a second inverter that converts DC power output from the second rectifier circuit into single-phase AC power.

  According to the present invention, in the single-phase power converter, one input terminal of the second rectifier circuit is connected to the neutral point of the power supply, and the other input terminal is connected to the negative output side of the first rectifier circuit. Therefore, the rectified current in the three-phase power converter can be input to the single-phase power converter. As a result, the current supplied to the single-phase power conversion unit can be balanced between the three phases of the power supply, and as a result, the current between the three phases can be balanced.

  The power converter includes a reactor connected in series between a positive output terminal of the second rectifier circuit and a positive input terminal of the second inverter, and a resonance capacitor connected in parallel with the reactor. And may be further provided.

  In this way, the energization time in the single-phase power converter can be extended by connecting the reactor and the resonance capacitor in parallel. Thereby, the frequency component of the current in the single-phase power converter can be changed as compared with the case where no resonance capacitor is provided. As a result, it is possible to reduce the third-order harmonic component generated when the resonance capacitor is not provided, and to suppress the third-order harmonic component of each phase current input to the three-phase power converter. It becomes possible to do.

  The power conversion device may further include a resistor connected in series with the resonance capacitor.

  Thus, by connecting the resistor in series with the resonance capacitor, it is possible to reduce the steep rise (peak value) of the current generated by connecting the resonance capacitor. Thereby, the harmonic component of the single phase load current supplied to the single phase load can be further suppressed, and as a result, the harmonic component of each phase current input to the three-phase power converter is further suppressed. Is possible.

  According to the present invention, it is possible to maintain a current balance between the three phases.

It is the figure which showed schematic structure of the power converter device which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the effect of the power converter device which concerns on the 1st Embodiment of this invention. It is the figure which showed an example of the electric current which flows into the smoothing capacitor of the power converter device which concerns on the 1st Embodiment of this invention, and the voltage between terminals. It is the figure which showed the comparative example of FIG. It is the figure which showed schematic structure of the power converter device which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the effect of the power converter device which concerns on the 2nd Embodiment of this invention. It is the figure which showed schematic structure of the power converter device which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the effect of the power converter device which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the effect of the power converter device which concerns on the 3rd Embodiment of this invention. It is a figure for demonstrating the effect of the power converter device which concerns on the 3rd Embodiment of this invention. It is the figure which showed schematic structure of the conventional power converter device. It is the figure which showed each phase current and single phase load current in the power converter device shown in FIG.

Below, each embodiment of the power converter device concerning the present invention is described with reference to drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of the power conversion device according to the first embodiment of the present invention. The power conversion device according to the present embodiment is a power conversion device applicable to a three-phase four-wire power source, and includes a three-phase power conversion unit 11 that supplies power to a three-phase load, and power to a single-phase load. And a single-phase power converter 12 to be supplied.

  The three-phase power conversion unit 11 converts the three-phase AC power output from the three-phase four-wire power source 10 into DC power, and three DC power rectified by the first rectifier circuit 101. And a first inverter 102 for converting into phase AC power. A smoothing capacitor 103 is connected between the positive output terminal P1 and the negative output terminal N1 of the first rectifier circuit 101. In other words, the smoothing capacitor 103 is connected in parallel between the first rectifier circuit 101 and the first inverter 102. Further, the positive output terminal P 1 of the first rectifier circuit 101 and the connection point P 2 on the positive side of the smoothing capacitor 103 are connected via a reactor 104.

The single-phase power converter 12 includes a second rectifier circuit 201 having one input terminal connected to the neutral point N of the power supply 10 and the other input terminal connected to the negative output side of the first rectifier circuit 101; And a second inverter 202 that converts DC power output from the rectifier circuit 201 into single-phase AC power. Specifically, the other input terminal of the second rectifier circuit 201 is directly connected to the wiring connecting the negative output terminal N1 of the first rectifier circuit 101 and the negative input terminal of the first inverter 102, or directly to the terminal itself. It is connected.
A smoothing capacitor 203 is connected between the positive output terminal P3 and the negative output terminal N3 of the second rectifier circuit 201. Further, the positive output terminal P 3 of the second rectifier circuit 201 and the connection point P 4 on the positive side of the smoothing capacitor 203 are connected via a reactor 204.

  In such a circuit configuration, the three-phase AC power output from the power supply 10 is converted into DC power by the first rectifier circuit 101 and output. The DC power output from the first rectifier circuit 101 is input to the first inverter 102. In the first inverter 102, the input DC power is converted into three-phase AC power and output to the three-phase AC motor 300 that is a three-phase load. For example, when the power conversion device according to the present embodiment is applied to a power supply device that supplies power to an air conditioner, an example of a three-phase AC motor 300 is a motor that drives a compressor of the air conditioner.

  In the single-phase power converter 12, one input terminal of the second rectifier circuit 201 is connected to the neutral point N of the power supply 10, and the other input terminal is connected to the negative output side of the first rectifier circuit 101. Thus, power between the neutral point N of the power supply 10 and the negative output side of the first rectifier circuit 101 is supplied to the second rectifier circuit 201 as input power (three-phase full-wave rectified non-smooth DC voltage). The DC power output from the second rectifier circuit 201 is smoothed and suppressed by harmonic components (ripple) by the action of the reactor 204 and the smoothing capacitor 203, and is input to the second inverter 202. At this time, the rectifier circuit 201 has a role to prevent the single-phase load current from flowing back to the first rectifier circuit. In the second inverter 202, the input DC power is converted into single-phase AC power and output to the single-phase AC motor 400 that is a single-phase load. For example, when the power conversion device according to the present embodiment is applied to a power supply device that supplies power to an air conditioner, an example of a single-phase AC motor 400 is a motor that drives a fan of an outdoor unit of the air conditioner. Can be mentioned.

As described above, according to the present embodiment, the power source (three-phase full-wave rectification non-smoothing) of the single-phase power conversion unit 12 from the neutral point N of the power source 10 and the negative output side of the first rectifier circuit 101. Therefore, the current supplied to the load (hereinafter referred to as “single-phase load current”) can be balanced between the three phases of the power supply 10 in a balanced manner.
As a result, as shown in FIG. 2, the current between the three phases can be balanced. In FIG. 2, I _L1 , I _L2 , and I _L3 indicate currents flowing through the three phases as shown in FIG. 1, and I _L4 is a single-phase load current. FIG. 2 shows that the single-phase load current I _L4 is distributed in a balanced manner to the phase currents I _L1 , I _L2 , and I _L3 .

  Further, since the input power of the single-phase power converter 12 is supplied from the neutral point N of the power supply 10 and the negative output side of the first rectifier circuit 101, the capacity of the smoothing capacitor 203 can be reduced. FIG. 3 shows the current Ic and the terminal voltage Vc flowing through the smoothing capacitor 203 of the power converter according to this embodiment. Also, in FIG. 4, as a comparative example, input power is supplied from the neutral point N of the AC power source and one of the three phases to the single-phase power conversion unit, for example, as in the configuration shown in FIG. The current Ic flowing through the smoothing capacitor 203 and the terminal voltage Vc are shown.

  According to the power conversion device according to the present embodiment, as shown in FIG. 1, a part of the current after being three-phase full-wave rectified by the first rectifier circuit 101 is supplied to the single-phase power conversion unit 12. The charging / discharging cycle of the smoothing capacitor 203 can be made shorter than in the circuit configuration shown in FIG. As a result, as shown in FIG. 3, the current Ic flowing through the smoothing capacitor 203 and the terminal voltage Vc can be reduced as compared with FIG. 4, and the smoothing capacitor 203 can be reduced in capacity.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a diagram illustrating a schematic configuration of the power conversion device according to the present embodiment. As shown in FIG. 5, the power conversion device according to the present embodiment is the same as the first embodiment described above in that the resonance capacitor 205 is connected in parallel with the reactor 204 in the single-phase power conversion unit 12. It differs from the power converter which concerns.

By connecting the resonance capacitor 205 in parallel with the reactor 204, the frequency component of the single-phase load current can be changed.
FIG. 6 shows the case where the resonance capacitor 205 is not connected to the single-phase load current I _L4-1 and the phase current I _L-1 when the resonance capacitor 205 is connected, that is, the first embodiment described above. It illustrates by comparing the input current I _L4 and the phase current I _L of the electric power converter according to. Here, the phase current I _L-1 indicates _one of the phase currents I _L1-1 , I _L2-1 , I _L3-1 . That is, in this embodiment, since the phase currents I _L1-1 , I _L2-1 , and I _L3-1 are all different in phase and have the same waveform, these phase currents I _L1-1 , I _{L2 -1} or _IL3-1 is shown as a representative example. The same applies to the phase current I _L.

As shown in FIG. 6, by connecting a resonance capacitor 205, it is possible to increase the energization time of the single-phase load current I _L4-1 (see, for example, the area A in FIG. 6). That is, the single-phase load current I _L4 when the resonance capacitor 205 is not connected periodically shows a time during which no current flows. In this way, the third harmonic component can be reduced by lengthening the time during which the single-phase load current I _L4-1 is flowing. Specifically, in the case of the conventional circuit shown in FIG. 11, the load current varies depending on the load, but generally, about one third of the period for one cycle of the power supply voltage (20 ms at 50 Hz). Minutes will flow. For this reason, the single-phase load current of the conventional circuit shown in FIG. On the other hand, according to the power converter device which _concerns on this embodiment, the energization time of single phase load current _IL4-1 can be lengthened, and a tertiary component can be reduced. Furthermore, the peak value of the phase current I _L-1 can be reduced by changing the frequency component of the single-phase load current I _L4-1 (see region B in FIG. 6).

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
FIG. 7 is a diagram illustrating a schematic configuration of the power conversion device according to the present embodiment. As shown in FIG. 7, in the power conversion device according to this embodiment, in the single-phase power conversion unit 12, a series connection circuit 210 in which a resonance capacitor 205 and a resistor 206 are connected in series is connected in parallel with the reactor 204. This is different from the power converter according to the first embodiment described above. That is, the power converter according to the present embodiment has a resistor 206 connected in series with the resonance capacitor 205 in the power converter according to the second embodiment.

For example, when the resonance capacitor 205 is connected in parallel with the reactor 204 as in the power conversion device according to the second embodiment, as described above, the energization time of the single-phase load current I _L4-1 can be increased. However, a phenomenon occurs in which the current value increases momentarily periodically (see region A in FIG. 6). Therefore, a resistor 206 is connected in series with the resonance capacitor 205 in order to suppress an instantaneous increase in the single-phase load current I _L4-1 that occurs periodically. FIG. 8 shows changes in the single-phase load current I _L4-2 when the value of the resistor 206 is changed to three patterns of 1Ω, 5Ω, and _10Ω . Here, when the 5Ω resistor 206 was employed, the peak value of the single-phase load current I _L4-2 was the smallest. FIG. 9 shows the phase current _IL-2 when the value of the resistor 206 is changed to three patterns of 1Ω, 5Ω, and 10Ω. As shown in FIG. 9, it can be seen that the harmonic component of the phase current I _L-2 is suppressed as the single-phase load current I _L4-2 decreases. The definition of the phase current I _L-2 is the same as in the second embodiment described above.

Thus, according to the power conversion device according to the present embodiment, since the connecting a series connection circuit 210 connected to the resonance capacitor 205 and a resistor 206 in series with a reactor 204 in parallel, each phase current I _L1-2 , I _L2-2 , I _L3-2 can further suppress harmonic components. Thereby, for example, as shown in FIG. 10, a result satisfying IEC / EN61000-3-2 that is a harmonic standard can be obtained. FIG. 10 shows a test result when 5Ω is adopted as the resistor 206 in the circuit configuration shown in FIG. In FIG. 10, PWHD (Partial weighted harmonic distortion) is partially weighted harmonic distortion, and THD (Total harmonic distortion) is total harmonic distortion.

DESCRIPTION OF SYMBOLS 10 Power supply 11 Three-phase power converter 12 Single-phase power converter 101 1st rectifier circuit 102 1st inverter 103,203 Smoothing capacitor 104,204 Reactor 201 2nd rectifier circuit 202 2nd inverter 205 Resonance capacitor 206 Resistance 300 Three-phase AC motor 400 Single-phase AC motor

Claims (3)

A power conversion device applicable to a three-phase four-wire power source,
A three-phase power converter for supplying power to a three-phase load;
A single-phase power converter for supplying power to a single-phase load,
The three-phase power converter is
A first rectifier circuit that converts three-phase AC power output from the power source into DC power;
A first inverter that converts DC power rectified by the first rectifier circuit into three-phase AC power;
The single-phase power converter is
A second rectifier circuit having one input terminal connected to a neutral point of the power supply and the other input terminal connected to the negative output side of the first rectifier circuit;
A power conversion device comprising: a second inverter that converts DC power output from the second rectifier circuit into single-phase AC power. A reactor connected in series between a positive output terminal of the second rectifier circuit and a positive input terminal of the second inverter;
A resonance capacitor connected in parallel with the reactor;
The power converter device according to claim 1 comprising:   The power conversion device according to claim 2, further comprising a resistor connected in series with the resonance capacitor.

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