JP2003088127A - Power converter - Google Patents

Abstract

(57) [Problem] To provide a power conversion device capable of suppressing the magnetic polarization of a transformer and balancing the magnetic flux of each transformer. SOLUTION: A primary side is connected in series to an AC power supply 201, and an AC side is connected to each of transformers 101a and 101b in which a phase of a secondary side voltage is shifted by 60 ° / n, and a secondary side of each of the transformers. Self-excited voltage type converters 103a, 10a
3b, a smoothing capacitor 105 connected to each DC side of the self-excited voltage type converter, and a pulse for supplying a switching signal of a pulse pattern with a phase shift of 60 ° / n to each of the self-excited voltage type converters. In the power converter having the pattern generator 17, the pulse pattern generator 17 controls the pulse width in a direction to reduce the magnetic flux generated in each transformer detected by the magnetic flux detectors 11a and 11b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter for converting AC power into DC power.

[0002]

2. Description of the Related Art Some power converters convert AC power into DC power.

FIG. 9 is a circuit diagram showing the structure of a conventional power converter for converting AC power into DC power.
[FIG. 3] is a diagram showing operation waveforms of this power converter.

As shown in FIG. 9, a conventional power conversion device includes transformers 101a and 101b, a self-excited voltage type converter 1
03a and 103b, a smoothing capacitor 105, and a pulse pattern generator 107, a three-phase AC power supply 201 of U, V, and W is connected as an input AC power supply, and supplies DC power to a load 203. Here, the number of multiplexes of this power converter is n = 2.

The transformers 101a and 101b are AC power sources 2
The voltage of 01 is set to a desired voltage, the primary side is connected in series to the AC power supply 201, and the phase of the secondary side voltage of the transformer 101a is advanced by 30 ° with respect to the transformer 101b.

Self-excited voltage type converters 103a and 103b
Are switching elements 113a to 113 made of semiconductor elements such as power transistors, IGBTs and GTOs.
f and 133a to 123f and rectifying elements 143a to 143f and 153a to 1 connected in antiparallel to the switching elements 113a to 113f and 133a to 123f.
It consists of 53f.

The self-excited voltage type converters 103a, 1
03b is composed of two sets, U side and X side, respectively. In self-excited voltage converter 103a, switching element 113a is used.
~ 113c is on the U side, and 113d to 113f is on the X side. Similarly, the self-excited voltage converter 103b
Then, the side with the switching elements 133a to 123c is the U side, and the side with the switching elements 123d to 123f is the X side.

These self-excited voltage type converters 103a and 103
The AC side of b is connected to the secondary sides of the transformers 101a and 101b, respectively.

The pulse pattern generator 107 generates a pulse pattern of a switching signal given to the self-excited voltage type converters 103a and 103b. The pulse pattern given to the self-excited voltage type converters 103a and 103b is
Although the pulse patterns are the same, the self-excited voltage converter 103a is provided with a phase that is advanced by 30 ° with respect to the pulse pattern given to the self-excited voltage converter 103b. The phase of the pulse pattern is 60 ° / n, where n is the number of multiplexes.

The basic power conversion operation is the transformer 103.
The three-phase alternating currents respectively output from a and 103b are supplied to the two sets of switching elements and rectifying elements for each phase, and the pulse patterns from the pulse pattern generator 107 cause the switching elements 113a to 113f and 133a.
By switching ~ 123f, a DC component is extracted for each phase, AC is converted to DC, and smoothing is performed by the smoothing capacitor 105, and then supplied to the load 203 as DC power.

The operation waveforms shown in FIG. 10 are switching signal pulse patterns Gu1, Gv1, G provided to the U-phase and V-phase switching elements Su1, Sv1, Su2, Sv2 of the self-excited voltage type converters 103a, 103b.
7 shows an example of u2, Gv2, secondary-side line voltage waveforms Vuv1, Vuv2 of each transformer 101a, 101b, and transformer primary-side line voltage waveform Vsuv at the AC power supply connection point. The voltage across the smoothing capacitor 105 is Vd.

In this power converter, the AC side line voltage waveform Vsuv becomes sinusoidal even when the switching frequency is the same as the frequency of the AC power supply 201. The harmonic component included in the AC input current waveform is the converter AC voltage Vs.
Since the converter AC voltage Vsuv has a sinusoidal shape, the AC input current waveform also has a sinusoidal shape, so that the contained harmonics can be reduced. Therefore, the harmonic component contained in the AC input current waveform can be reduced without increasing the switching frequency.

[0013]

However, in the conventional power converter, as a result of lowering the switching frequency and the harmonic components contained in the AC input current waveform, the influence of the magnetic flux generated in the transformer becomes large. all right.

For example, in a transformer, a DC magnetic flux is generated by a DC component contained in an AC power source or a DC component generated by a self-exciting voltage type converter, and the DC magnetic flux causes the transformer to be demagnetized. There is a possibility that, when the demagnetization proceeds, the transformer is saturated, and the operation of the power conversion device may be difficult due to overcurrent or the like.

Further, since the primary side windings of the transformers are connected in series, the difference between the impedances of the transformers and the voltage difference of the AC voltage output by each self-excited voltage type converter causes a difference between the transformers. There is also a risk that magnetic flux imbalance will occur.

The present invention has been made in view of the above,
An object of the present invention is to provide a power conversion device capable of suppressing the magnetic bias of the transformers and balancing the magnetic fluxes of the transformers without increasing the harmonic components included in the switching frequency and the AC input current waveform. It is to be.

[0017]

The invention according to claim 1 is
In order to solve the above problems, the primary side is connected in series with an AC power source, and the phase of the secondary side voltage is shifted by 60 ° / n.
Transformers, n self-exciting voltage type converters whose AC side is connected to each secondary side of the transformers, magnetic flux detecting means for detecting magnetic flux generated in the transformers, and the magnetic flux detecting means. And a pulse pattern generation means for supplying a pulse pattern whose pulse width is controlled according to the magnetic flux detected by the above-mentioned to each of the self-excited voltage type converters by shifting the phase by 60 ° / n. .

According to the present invention, the magnetic flux generated in the transformer is detected by the magnetic flux detecting means, and the pulse width of the pulse pattern supplied to each of the self-excited voltage type converters is determined by the pulse pattern generating means according to the detected magnetic flux. By controlling, changing the interval that each self-excited voltage type converter is on,
Thereby, the amount of current flowing through each transformer is controlled to control the magnetic flux generated in each transformer.

According to a second aspect of the present invention, in the power converter according to the first aspect, the pulse pattern generating means is
The gist is to change the pulse width in the same direction among the n self-exciting voltage type converters in a direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detecting means decreases.

According to the present invention, by changing the pulse width of the pulse pattern between the self-excited voltage type converters in the direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detecting means is decreased, It is intended to reduce the deviation of the generated magnetic flux.

According to a third aspect of the present invention, in the power converter according to the first aspect, the pulse pattern generating means is
The gist is to change the pulse width among the n self-excited voltage type converters in a direction to reduce the difference in magnetic flux between the transformers detected by the magnetic flux detecting means.

According to the present invention, by changing the pulse width of the pulse pattern between the self-exciting voltage type converters in the direction of reducing the magnetic flux difference between the transformers detected by the magnetic flux detecting means, the voltage between the transformers is changed. It is intended to reduce the imbalance of the magnetic flux in.

According to a fourth aspect of the present invention, in the power converter according to the first aspect, the pulse pattern generating means is
The pulse widths of the n units are set in a direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detection unit is reduced and a difference in magnetic flux between the transformers detected by the magnetic flux detection unit is reduced. The gist is to change between the self-excited voltage type converters.

According to the present invention, the pulse width of the pulse pattern is changed in the direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detecting means is reduced, and the difference in magnetic flux between the transformers detected by the magnetic flux detecting means is reduced. By changing the pulse width of the pulse pattern in the direction in which the voltage is changed, the magnetic bias between the transformers is suppressed and the magnetic flux between the transformers is balanced.

According to a fifth aspect of the present invention, in the power converter according to the first to fourth aspects, the voltage detecting means for detecting the voltage applied to the transformer and the voltage detecting means are used in place of the magnetic flux detecting means. Integrating the detected voltage value, the pulse pattern generating means controls the pulse width by using the voltage value integrated by the integrating means as a magnetic flux equivalent value output from the magnetic flux detecting means. The point is to use it for.

The present invention intends to reduce the number of parts and the cost by using the integrated value of the voltage applied to the transformer as the magnetic flux equivalent value for control instead of directly detecting the magnetic flux of the transformer. is there.

According to a sixth aspect of the present invention, in the power conversion device according to the first to fourth aspects, instead of the magnetic flux detecting means, there is provided current detecting means for detecting the current of the transformer.
The gist of the pulse pattern generation means is to use the current value detected by the current detection means as the magnetic flux equivalent value output from the magnetic flux detection means for controlling the pulse width.

The present invention intends to reduce the number of parts and the cost by using the current value of the transformer as a magnetic flux equivalent value for control instead of directly detecting the magnetic flux of the transformer.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a configuration of a power conversion device according to a first embodiment of the present invention, and FIG. 2 operates this power conversion device. It is drawing which shows the pulse pattern used for it. In the drawings, the same members as those in the related art are designated by the same reference numerals, and the description of those members is partially omitted. The basic power conversion operation is also the same as the conventional one, and thus the description thereof is omitted.

This power conversion device includes transformers 101a, 1
01b, self-excited voltage converters 103a and 103b, smoothing capacitor 105, magnetic flux detectors 11a and 11b, adder 13, calculator 15, and pulse pattern generator 17.

The input AC power source is the same as the conventional one.
It is a three-phase AC power supply 201 of U, V, W and supplies DC power to the load 203. The number of multiplexes determined by the number n of transformers or self-excited voltage type converters connected in parallel is two.

The primary sides of the transformers 101a and 101b are connected in series to the AC power source 201, and the phase of the secondary side voltage of the transformer 101a leads the transformer 101b by 30 °.

The magnetic flux detectors 11a and 11b are each transformer 1
The magnetic fluxes Φu1 and Φu2 of the respective phases 01a and 101b are detected.

As the magnetic flux detector, for example, a Hall element or a magnetoresistive effect element is used, and the magnetic flux detectors 11a and 11b directly detect the magnetic flux with respect to the transformers 101a and 101b. To be installed.

The adder 13 includes magnetic flux detectors 11a and 11b.
Therefore, the detected in-phase magnetic fluxes between the transformers 101a and 101b are averaged.

The computing unit 15 averages the in-phase average magnetic flux between the transformers 101a and 101b output from the adder 13 for one cycle of the AC power source, and calculates the transformers 101a and 101b.
Of the DC magnetic flux Φdc of the pulse pattern generator 1
Input to 7.

The pulse pattern generator 17 is, for example, a pulse width modulation (PWM) control circuit and generates a pulse pattern for switching the switching elements of the self-excited voltage type converters 103a and 103b, and will be described later. Thus, the magnetic flux DC component Φd from the calculator 15
The pulse width of the generated pulse pattern is controlled according to c.

The operation of the first embodiment will be described below with reference to FIG.

FIG. 2 shows each self-excited voltage type converter 103a,
Switching elements Su1, Sx1, Su2, Sx of U-phase arm (connected to U-phase of converter) 103b
Switching signal pulse pattern Gu given to 2
1, Gx1, Gu2 and Gx2 are shown.

Each self-excited voltage type converter 103a, 103b
The U-side and X-side switching elements are normally alternately switched with the same pulse width.

Here, at the time of U side switching, the transformer 10
A control method in the case where the magnetic flux detectors 11a and 11b detect that a magnetic flux DC component is generated in the positive direction of the U phase will be described, assuming that the positive magnetic flux is generated in the U phase of 1a and 101b.

In this case, the pulse width of the pulse widths of the pulse patterns Gu1 and Gu2 supplied to the U side of the self-excited voltage converters 103a and 103b (on The pulse patterns Gx1 and Gx supplied to the X side are shortened in proportion to the magnetic flux DC component Φdc.
The pulse width of x2 is lengthened in proportion to the magnetic flux DC component Φdc.

As a result, the self-excited voltage type converter 103a
And 103b, the U side and the X side change with the same pulse width. Therefore, a difference occurs between the voltages applied to the transformers 103a and 103b on the U side and the X side, and the generated magnetic flux also differs.

In this example, the self-excited voltage type converter 103
Since the period in which the voltage is applied to the U side of a and 103b becomes shorter and the X side becomes longer, the bias of the magnetic flux of the transformers 103a and 103b is in the negative direction of the U phase, and the magnetic flux DC component in the positive direction decreases.

As described above, in the first embodiment, in the direction in which the magnetic flux DC component of the transformers 101a and 101b decreases,
Since the pulse width of the pulse pattern is changed in the same direction between the self-exciting voltage type converters, the switching frequency and the harmonic components included in the AC input current waveform are not increased, and the transformers 101a and 101b are not affected. Demagnetization can be suppressed.

(Second Embodiment) FIG. 3 is a circuit diagram showing a configuration of a power converter in a second embodiment to which the present invention is applied, and FIG. 4 operates this power converter. It is drawing which shows the pulse pattern used for it. In the drawings, the same members as those in the conventional art are designated by the same reference numerals, and the description of those members is omitted.

In the power converter of the second embodiment, the subtractor 2 is used instead of the adder 13 and the calculator 15 in the power converter of the first embodiment described above.
1 is provided. Other configurations are similar to those of the first embodiment.

This subtracter 21 is composed of a magnetic flux detector 11a,
The magnetic flux difference ΔΦ between the transformers is calculated by subtracting the magnetic fluxes Φu1 and Φu2 of the respective phases of the transformers 101a and 101b detected by 11b.

Further, in the second embodiment, the pulse pattern generator 17 generates the pulse pattern to be supplied to the self-excited voltage type converters 103a and 103b, as in the first embodiment described above. However, here, as will be described later, the pulse width of the generated pulse pattern is controlled according to the magnetic flux difference ΔΦ output from the subtractor 21.

The operation of the second embodiment will be described below with reference to FIG.

FIG. 4 shows each self-excited voltage type converter 103a,
Switching elements Su1 and Sx of the U-phase arm 103b
1 shows switching signal pulse patterns Gu1, Gx1, Gu2, Gx2 given to 1, Su2, Sx2.

Each self-excited voltage type converter 103a, 103b
The U-side and X-side switching elements are normally alternately switched with the same pulse width.

Here, the transformer 1 is used during U-side switching.
A method of controlling when the magnetic fluxes of the transformers 101a and 101b detected by the magnetic flux detectors 11a and 11b are different from each other will be described, assuming that a positive magnetic flux is generated in the U phase of 01a and 101b.

In this case, the magnetic flux difference ΔΦ output from the subtractor 21 is unbalanced in the positive direction.

In the pulse pattern generator 17 to which this magnetic flux difference ΔΦ is input, the pulse width of the pulse pattern Gu1 supplied to the U side of the self-excited voltage converter 103a is set to the pulse width of the original pulse pattern P0. The pulse width of the pulse pattern Gx1 supplied to the X side is shortened in proportion to the magnetic flux difference ΔΦ, and lengthened in proportion to the magnetic flux difference ΔΦ. On the contrary, the pulse width of the pulse pattern Gu2 supplied to the U side of the self-excited voltage converter 103b is lengthened in proportion to the magnetic flux difference ΔΦ, and the pulse width of the pulse pattern Gx2 supplied to the X side is magnetic flux difference ΔΦ.
Shorten in proportion to Φ.

As a result, the pulse widths on the U side and the X side between the self-excited voltage type converters 103a and 103b change in opposite directions.

In this way, the self-excited voltage type converter 103a,
By providing a difference in the voltage applied to the U side and the X side so that the voltage difference between the U side and the X side is opposite between 103b, a difference also occurs in the magnetic flux between the self-excited voltage type converters 103a and 103b. In this example, the period in which the voltage is applied to the U side of the self-excited voltage converter 103a becomes shorter and the U side of the self-excited voltage converter 103b becomes longer. Therefore, the magnetic flux difference between the transformers 101a and 101b is negative. , The magnetic flux difference in the positive direction decreases.

As described above, in the second embodiment, when the magnetic flux difference is generated between the transformers, the pulse pattern of the pulse pattern to be supplied to the self-excited voltage type converters 103a and 103b is reduced. Since the pulse width is controlled, the transformer 101a, the switching frequency and the harmonic components included in the AC input current waveform are not increased.
The magnetic flux between 101b can be balanced.

(Third Embodiment) FIG. 5 is a circuit diagram showing a configuration of a power conversion device according to a third embodiment of the present invention, and FIG. 6 operates this power conversion device. It is drawing which shows the pulse pattern used for it. In the drawings, the same members as those in the conventional art are designated by the same reference numerals, and the description of those members is omitted.

In the power conversion device according to the third embodiment, the adder 13 and the calculator 15 in the power conversion device according to the first embodiment described above and the subtracter 21 according to the second embodiment described above. Are provided together.

Therefore, the pulse pattern generator 17
Is the transformer 101a in which the in-phase magnetic fluxes between the transformers 101a and 101b detected by the magnetic flux detectors 11a and 11b are averaged by the adder 13 and one AC power supply cycle is averaged by the calculator 15. , 101b of the magnetic flux DC component of the magnetic flux detector 11
Each transformer 101a, 101 detected by a, 11b
The magnetic flux difference ΔΦ between the transformers, which is obtained by subtracting the magnetic fluxes Φu1 and Φu2 of each phase of b, is input.

In the third embodiment, the pulse pattern generator 17 includes the self-excited voltage type converter 103.
a, the pulse width of the pulse pattern supplied to 103b,
As will be described later, control is performed according to the magnetic flux DC component Φdc and the magnetic flux difference ΔΦ.

The operation of the third embodiment will be described below with reference to FIG.

FIG. 6 shows each self-excited voltage type converter 103a,
Switching elements Su1 and Sx of the U-phase arm 103b
1 shows switching signal pulse patterns Gu1, Gx1, Gu2, Gx2 given to 1, Su2, Sx2.

Self-excited voltage type converters 103a and 103b
The U-side and X-side switching elements are normally alternately switched with the same pulse width.

Here, at the time of U side switching, each transformer 1
It is assumed that the positive magnetic flux is generated in the U phase in 01a and 101b, and the magnetic flux DC component is generated in the positive direction of the U phase, and the magnetic flux difference ΔΦ between the self-excited voltage type converters 103a and 103b is positive. The control method when the balance is achieved is shown below.

In this case, the variation of the pulse width by the pulse pattern generator 17 is such that the pulse width on the U side is shortened and the pulse width on the X side is shortened between the self-excited voltage converters 103a and 103b in proportion to the magnetic flux DC component Φdc. Increase the width. Further, in proportion to the magnetic flux difference ΔΦ, the self-exciting voltage type converter 103a shortens the pulse width on the U side and lengthens the pulse width on the X side. on the other hand,
The self-excited voltage type converter 103b is the opposite.

Therefore, the pulse pattern generator 17
Means that the pulse width of the pulse pattern Gu1 supplied to the U side of the self-excited voltage converter 103a is shortened in proportion to (Φdc + ΔΦ), and the pulse width of the pulse pattern Gx1 supplied to the X side is proportional to (Φdc + ΔΦ). And make it longer. on the other hand,
In the self-excited voltage converter 103b, the pulse width of the pulse pattern Gu2 supplied to the U side is shortened in proportion to (Φdc−ΔΦ), and the pulse width of the pulse pattern Gx2 supplied to the X side is (Φdc−ΔΦ). Lengthen in proportion to.

In this way, each self-excited voltage type converter 103 is
By providing a difference in the voltage applied to the transformers 101a and 101b between the U side and the X side of a and 103b and between the self-exciting voltage type converters 103a and 103b, a difference occurs in the magnetic flux.

In this example, since the period in which the voltage is applied to the U side is short and the X side is long, the bias of the magnetic flux of the transformer is in the negative direction of the U phase and the direct current magnetic flux is reduced. Furthermore, the period in which the voltage is applied to the U side of the self-excited voltage type converter 103a becomes shorter, and the U side of the self-excited voltage type converter 103b becomes longer, so that the magnetic flux difference of the transformer is in the negative direction and the positive direction magnetic flux. The difference decreases.

As described above, in the third embodiment, the pulse width of the pulse pattern is changed in the direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detectors 11a and 11b is decreased, and the magnetic flux detector 11a is changed. , 11b, the pulse width of the pulse pattern is changed between the self-excited voltage-type converters in the direction of decreasing the magnetic flux difference between the transformers. Without increasing the wave component,
Suppressing the magnetic bias of the transformers and the transformers 101a, 101
The magnetic flux between b can be balanced.

(Fourth Embodiment) FIG. 7 is a circuit diagram showing a configuration of a power conversion device according to a fourth embodiment of the present invention. In the drawings, the same members as those in the conventional art are designated by the same reference numerals, and the description of those members is omitted.

In the power converter according to the fourth embodiment, the U-phase voltage Vu1 of each transformer 101a, 101b.
And voltmeters 31a and 31b for measuring Vu2,
Integrators 33a and 33b are provided for integrating the detected voltages, respectively.

The integrators 33a and 33b are the transformers 101, respectively.
The phase voltages applied to a and 101b are respectively integrated, and this is input to the pulse pattern generator 17 as a magnetic flux equivalent value of each phase of each transformer 101a and 101b.

The control in the pulse pattern generator 17 may be the same as that in any of the above-described first to third embodiments. For example, if the same control as in the above-described first embodiment is performed, the outputs from the integrators 33a and 33b are averaged for one cycle of the AC power supply using an adder and an arithmetic unit (not shown), and then the pulse is output. Input to the pattern generator 17. Similarly, in order to perform control similar to that of the second embodiment described above, an integrator 33a,
The output from 33b is subtracted and the difference signal is input to the pulse pattern generator 17. Further, in order to perform control similar to that of the above-described third embodiment, integrators 33a and 33b are required.
A signal obtained by averaging the output from the AC power supply for one cycle and a difference signal obtained by subtracting the outputs from the integrators 33a and 33b by the subtracter are input to the pulse pattern generator 17.

As a result, in the fourth embodiment, it is not necessary to equip the transformers 101a and 101b with the magnetic flux detector, so that the number of parts and the cost can be reduced.

Although the U-phase output voltage of the transformer is measured in the fourth embodiment, instead of this,
It suffices to measure the voltage of either the V phase or the W phase, and is not limited to the measurement of the U phase voltage.

(Fifth Embodiment) FIG. 8 is a circuit diagram showing a configuration of a power conversion device according to a fifth embodiment of the present invention. In the drawings, the same members as those in the conventional art are designated by the same reference numerals, and the description of those members is omitted.

In the power converter according to the fifth embodiment, the U-phase current Iu1 of each transformer 101a, 101b.
And ammeters 41a and 41b for measuring Iu2 are provided.

The ammeters 41a and 41b correspond to the transformers 101
The phase currents Iu1 and Iu2 of a and 101b are detected and used as magnetic flux equivalent values of the respective phases of the transformers 101a and 101b.

The control in the pulse pattern generator 17 may be the same as that in any of the above-described first to third embodiments. For example, if the same control as in the above-described first embodiment is performed, the outputs from the ammeters 41a and 41b are output to the AC power supply 1 using an adder and an arithmetic unit (not shown).
After averaging for a period, it is input to the pulse pattern generator 17. Similarly, in order to perform control similar to that of the second embodiment described above, the ammeters 41a, 41
The output from b is subtracted and the difference signal is input to the pulse pattern generator 17. Further, in order to perform control similar to the third embodiment described above, a signal obtained by averaging the outputs from the ammeters 41a and 41b for one cycle of the AC power supply and the output from the ammeters 41a and 41b by the subtractor are used. The subtracted difference signal is input to the pulse pattern generator 17.

As a result, in the fifth embodiment, it is not necessary to equip the transformers 101a and 101b with the magnetic flux detector, so that the number of parts and the cost can be reduced.

In the fifth embodiment, the U-phase output current of the transformer is measured, but instead of this,
It suffices to measure the current of one of the V phase and the W phase, and is not limited to the measurement of the U phase current.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in the above-described embodiments, the number of multiplexes is 2, but the present invention is also applicable to a power conversion device having a larger number of multiplexes.

[0086]

As described above, according to the present invention,
It is possible to reduce the magnetic bias of the transformer and reduce the imbalance of the magnetic flux between the transformers without increasing the harmonic components included in the switching frequency and the AC input current waveform.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a drawing showing a pulse pattern for explaining the operation of the power conversion device according to the first embodiment.

FIG. 3 is a circuit diagram showing a configuration of a power conversion device according to a second embodiment of the present invention.

FIG. 4 is a drawing showing a pulse pattern for explaining the operation of the power conversion device according to the second embodiment.

FIG. 5 is a circuit diagram showing a configuration of a power conversion device according to a third embodiment of the present invention.

FIG. 6 is a drawing showing a pulse pattern for explaining the operation of the power conversion device according to the third embodiment.

FIG. 7 is a circuit diagram showing a configuration of a power conversion device according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a configuration of a power conversion device according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a conventional power conversion device.

FIG. 10 is an operation waveform diagram for explaining the operation of the conventional power conversion device.

[Explanation of symbols]

103a, 103b transformer 11a, 11b Magnetic flux detector 13 adder 15 arithmetic unit 17 pulse pattern generator 21 subtractor 31a, 31b Voltmeter 33a, 33b integrator 41a, 41b ammeter 101a, 101b Transformer 103a, 103b Self-excited voltage type converter 105 Smoothing capacitor 107 pulse pattern generator 113a-f, 133a-f switching elements 143a-f, 153a-f Rectifying element 201 AC power supply 203 load

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hironobu Kim             No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation             Fuchu Office (72) Inventor Takehiro Tanaka             1-1 Shibaura, Minato-ku, Tokyo Co., Ltd.             Toshiba headquarters office F-term (reference) 5H006 CA01 CA07 CB01 CC01 CC04                       DA02 DB01 DC02 DC05 FA02                       FA03

Claims (6)

[Claims] 1. The n transformers whose primary side is connected in series with an AC power source and whose secondary voltage phase is shifted by 60 ° / n, and the AC side is connected to each secondary side of said transformer. N
Self-exciting voltage type converter, a magnetic flux detecting means for detecting the magnetic flux generated in the transformer, and a pulse pattern in which the pulse width is controlled according to the magnetic flux detected by the magnetic flux detecting means, And a pulse pattern generating means for supplying a phase-shifted 60 ° / n to each of the converters. 2. The pulse pattern generation means sets the pulse width in the same direction between the n self-exciting voltage type converters in a direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detection means decreases. The power conversion device according to claim 1, wherein the power conversion device is changed to. 3. The pulse pattern generating means reduces the pulse width between the n self-exciting voltage type converters in a direction to reduce the difference in magnetic flux between the transformers detected by the magnetic flux detecting means. The power conversion device according to claim 1, wherein the power conversion device is changed. 4. The pulse pattern generating means reduces the magnetic flux difference between the transformers detected by the magnetic flux detecting means in a direction in which the magnetic flux DC component of the transformer detected by the magnetic flux detecting means decreases. The power converter according to claim 1, wherein the pulse width is changed between the n self-excited voltage type converters in a decreasing direction. 5. The pulse pattern comprises: instead of the magnetic flux detecting means, voltage detecting means for detecting a voltage applied to the transformer, and integrating means for integrating a voltage value detected by the voltage detecting means. The generating means uses the voltage value integrated by the integrating means as the magnetic flux equivalent value output from the magnetic flux detecting means for controlling the pulse width. The power converter described. 6. Instead of the magnetic flux detecting means, a current detecting means for detecting a current of the transformer is provided, and the pulse pattern generating means uses the current value detected by the current detecting means as the magnetic flux detecting means. The power conversion device according to any one of claims 1 to 4, wherein the power conversion device is used for controlling the pulse width as a magnetic flux equivalent value output from the power conversion device.