JPS5840429B2 - Multiplex current source inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multiplex current source inverter that uses a plurality of current source inverters to improve the output current waveform.

The main circuit configuration of a general current source inverter is as shown in FIG.

It is comprised of a converter 2 that converts AC power from an AC power source 1 into DC power, a DC reactor 3 that smoothes the flowing current, and an inverter 4 that converts the DC power of the converter 2 into AC power of an arbitrary frequency.

The output end of the inverter 4 is connected to an AC motor 5 which is a load.

The converter 1 is typically composed of six cyrisks 201-206.

The inverter 4 includes six cyrisks 401 to 406, diodes 407 to 412, and commutation capacitors 413 to 4.
It consists of 18.

The output current waveform of this current source inverter is a square wave with 120 degree conduction, as shown in the figure.

Therefore, the content of harmonic components is high, the torque generated by the AC motor 5 pulsates, and the loss also increases.

In order to reduce this harmonic component, multiplexing is performed to obtain a stepped current by using a plurality of current source inverters and operating them with their output current phases shifted.

FIG. 2 shows the main circuit configuration of a conventional multiplex current source inverter.

In the case of this figure, multiplexing is performed using a transformer at the output end.

1 to 5 are the same components as in FIG. 6 to 8 are DC reactors like 3 in Fig. 1, 9 is a second inverter with exactly the same configuration as 4 in Fig. 1, 10 is a star shape on the primary side (first inverter side), and a star shape on the secondary side (motor side). ) A transformer 11 has a triangular connection, and 11 is a second transformer with a star connection on both the primary side (second inverter side) and the secondary side (motor side).

In the case of Fig. 2, the DC reactors 3, 6, 7, and 8 are connected to current pulsations caused by the difference in DC voltage between converter 2 and inverter 4 or inverter 9, and current fluctuations caused by the DC voltage difference between inverter 4 and inverter 8. It functions to suppress

FIG. 3 shows current waveforms at various parts in FIG. 2.

The output current waveform of the first inverter 4, that is, the input current of the first transformer 10 is a1, the output current is a/, and the output current waveform of the second inverter 9, that is, the input terminal waveform of the second transformer 11. The b1 output current waveform is changed to b' (b and b' have different amplitudes depending on the turns ratio of the transformer 11, but the waveform shapes are the same.

), a' and b', that is, the input terminal to the AC motor 5 which is the load is shown as C.

In this case, it is assumed that the magnitude of the DC current flowing through the inverters 4 and 9 is Id, and that the turns ratio (between the lines) of the transformers 10 and 11 is 1.

As shown in ab, the current phase of inverter 4 is controlled to advance by 30 degrees with respect to inverter 8.

As a result, a current as shown in C flows through the AC motor 5.

In the waveform shown in C, the fifth and seventh harmonic components become zero, and the torque pulsation of the AC motor 5 becomes small.

In the case of FIG. 2, in order to suppress current pulsations due to the DC voltage difference between converter 2 and inverter 4 or 9 and current fluctuations due to DC voltage difference between inverter 4 and inverter 9, , 7.8 is used.

Although the inductance value of the DC reactor for suppressing current pulsations due to the DC voltage difference between the converter 2 and the inverter 4 or 9 may be small, the DC voltage difference between the inverter 4 and the inverter 9 is a load on the AC motor 5. Therefore, in order to suppress current fluctuations due to this voltage difference, it is necessary to select a large inductance value of the DC reactor.

Therefore, in the case of Fig. 2, the DC reactors 3, 6, 7, 8
As the size of the device becomes larger and the entire device becomes larger,
It also has the disadvantage of being expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multiple current source inverter that has a simple circuit configuration, is small in size, and is inexpensive.

The present invention is characterized in that an interphase reactor as an AC reactor is used between the M-flow input terminals of each inverter in order to suppress fluctuations in current due to a DC voltage difference between each inverter.

FIG. 4 shows a specific embodiment of the present invention.

In the figure, 1 to 6 and 9 to 11 are the same as the components in FIG.

12 and 13 are interphase reactors for suppressing current fluctuations due to the DC voltage difference between the inverters 4 and 9.

The interphase reactors 12 and 13 connect to the DC reactor 3 at the midpoint.
and 6.

Similarly to FIG. 2, inverter 4 is 30°
Control it so that it moves forward.

At this time, what kind of voltage is applied to the interphase reactors 12 and 13 will be considered.

Figure 5 shows the results.

If the voltage on the primary side of the first transformer 10 (output side of the inverter 4) is uj 9vw as shown in FIG. )
The voltages are Vu and Vv.

■The voltage will be 30 degrees behind the cc.

If the power factor angle of the electric motor 5 is ψ (delay), then the inverter 4
The DC voltage vde of is as shown in FIG. 5B.

On the other hand, in the case of inverter 9, the AC voltage is V shown in A.
u)■ Since it is a voltage that is 30 degrees behind vtvw and is controlled with a 30 degree delay from the inverter 4, this DC voltage vf2 has exactly the same waveform as shown in B and is 30 degrees behind "de."

Voltage waveform vdf applied to interphase reactors 12 and 13
, Ve2 is the voltage waveform of the difference between vde and Vf, so
The waveform becomes as shown in FIG. 5C.

The voltage waveform shown in C is an AC voltage with a frequency six times the inverter operating frequency.

Therefore, this interphase reactor. 12.13 can be manufactured as an AC reactor and is much smaller than a DC reactor.

The voltage shown in FIG. 5C is absorbed by the inductance values of the interphase reactors 12 and 13, and fluctuations in current due to this voltage are suppressed.

Although interphase reactors 12 and 13 can suppress current fluctuations due to the DC voltage difference between inverter 4 and inverter 9, they do not have the effect of suppressing current pulsations due to DC voltage between converter 2 and inverter 4 or inverter 9.

DC reactors 3 and 6 are used to suppress this current pulsation.
are connected.

However, the inductance values of the DC reactors 3 and 6 may be much smaller than the inductance values of the DC reactors 3, 6, 7, and 8 shown in FIG. 2, and the DC reactors can also be made small.

According to one embodiment of the present invention, an interphase reactor that can be manufactured as an AC reactor is used instead of a DC reactor in order to suppress fluctuations in current due to differences in DC voltage between each inverter. This has the effect of making it more compact, and also contributes to a reduction in price.

FIG. 6 shows another specific embodiment of the present invention.

The difference from FIG. 4 is that the DC reactors 3 and 6 are combined into one DC reactor 3.

The inductance value of DC reactor 3 in Figure 6 needs to be equal to the sum of the inductance values of DC reactors 3 and 6 in Figure 4, but since the two are combined into one,
It can be made smaller than the one shown in FIG.

FIG. 7 shows still another embodiment of the present invention.

In the case of FIG. 7, the DC reactors 3.6 in FIG. 4 are combined into one DC reactor 3, and the interphase reactors 12.13 are combined into one interphase reactor 12.

In this case, the inductance value of the DC reactor 3 is the fourth
The sum of the inductance values of DC reactors 3 and 6 in the figure is
The inductance value of the interphase reactor 12 needs to be equal to the sum of the inductance values of the interphase reactors 12 and 13 in FIG. 4, but since there is one DC reactor and one interphase reactor, the inductance value is even more It has the effect of being smaller and lower in price.

Additionally, reliability is improved because the number of parts is reduced.

According to the present invention, since an interphase reactor that can be manufactured as an AC reactor is used instead of a DC reactor,
This has the advantage that the entire device can be downsized and an inexpensive multiplex current source inverter can be provided.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of a general current source inverter, Figure 2
The figure is a block diagram of a conventional multiplex current source inverter, Figure 3 is a current waveform of each part to explain the operation of Figure 2, Figure 4 is a block diagram showing an embodiment of the present invention, and Figure 5 is a block diagram of a conventional multiplex current source inverter. FIG. 4 shows voltage waveforms for explaining the operation, FIG. 6 is a block diagram showing another embodiment of the present invention, and FIG. 7 is a block diagram showing still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Converter, 3... DC reactor, 4... Inverter, 5... AC motor, 6-8... DC reactor, 12-13... Interphase reactor .

Claims (1)

[Claims] 1 first and second current source inverters that convert direct current to alternating current, a first transformer connected to the alternating current output terminal of the first current source inverter, and a first transformer connected to the alternating current output terminal of the second current source inverter. a second transformer connected to the first and second transformers;
A multiple current source inverter that supplies alternating current power to a load by commonly connecting windings of the transformer that are different from the windings connected to the first and second current source inverters. D, at least one interphase reactor is connected between the DC input terminals of the first and second current source inverters, at least one DC reactor is connected to a midpoint between the phase reactors, and the A multiple current inverter device characterized in that a terminal other than the terminal connected to the intermediate point of the phase reactor is connected to a common DC power source.