JP2008061466A - Power conversion system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion system which downsizes the whole apparatus and provides cost reduction by eliminating use of an auxiliary appliance such as an interphase reactor while using a non-insulation type phase-shifting transformer. <P>SOLUTION: The power conversion system includes: a three-phase AC power supply 3; the non-insulation type phase-shifting transformers which are connected to the power supply 3 and outputs two sets of three-phase AC voltages; first and second rectifiers 1A, 1B into which the two sets of three-phase AC voltages are inputted respectively; and a load 6 which is connected to each of the output sides of the rectifiers 1A, 1B and has two load elements (wirings 6a, 6b) insulated from each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion system that performs AC / DC conversion by a rectifier and supplies DC power to a load, or DC / AC converts an output of the rectifier by an inverter and supplies AC power to a load. .

  As a power converter that converts three-phase AC power into DC power, a 6-pulse rectifier that frequently performs six commutations in one cycle of the power supply voltage is often used. If a plurality of these 6-pulse rectifiers are combined, a multi-pulse rectifier such as a 12-pulse rectifier or an 18-pulse rectifier can be configured. According to these multipulse rectifiers, it is known that the harmonic current flowing in the power source can be reduced by increasing the number of commutations.

Here, in FIG. 8, 6-pulse rectifiers 1A and 1B composed of diodes are connected in series to form a 12-pulse rectifier, and these rectifiers 1A and 1B are connected to the three-phase AC power source 3 via the isolation transformers 20A and 20B. The power converter connected to is shown. Reference numeral 4 denotes a load connected between the positive output terminal of the rectifier 1A and the negative output terminal of the rectifier 1B.
In the present specification, a circuit including peripheral circuits such as a power supply and a transformer in a rectifier is referred to as a rectifier or a power converter, and an entire circuit including a load is referred to as a power conversion system.

  In the configuration of FIG. 8, since it is necessary to insulate the AC input sides of the two 6-pulse rectifiers 1A and 1B in principle, the isolation transformers 20A and 20B are used. Further, in order to operate as a 12-pulse rectifier, the phase difference between the secondary voltages of the isolation transformers 20A and 20B, that is, the phase difference between the input voltages of the rectifiers 1A and 1B needs to be 30 degrees. The primary windings of the transformers 20A and 20B are delta connection, the secondary winding of the transformer 20A is delta connection, and the secondary winding of the transformer 20B is star connection.

On the other hand, Non-Patent Document 1 and Patent Document 1 disclose a conventional technique using a non-insulated phase shift transformer in place of the insulating transformer shown in FIG.
FIG. 9 is an equivalent circuit diagram of the rectifier described in Non-Patent Document 1. In FIG. 9, reference numeral 2 denotes a non-insulated phase shift transformer, the primary winding of which is delta-connected and connected to the three-phase AC power source 3, and the secondary winding is an open winding. Each of the three secondary windings has an intermediate tap, and these intermediate taps are connected to each phase terminal of the three-phase AC power source 3, and both ends of the three secondary windings are 6-pulse rectifiers 1A and 1B. Are connected to each input terminal.

That is, since the intermediate tap of the secondary winding of the phase-shifting transformer 2 is connected to the power source 3, the primary winding and the secondary winding of the transformer 2 are not insulated and are not insulated. It has become.
In FIG. 9, 5A and 5B are interphase reactors connected between the positive output terminals and the negative output terminals of the rectifiers 1A and 1B, respectively, and 4 is a load connected between these interphase reactors 5A and 5B. It is.

In the above configuration, the phase difference between the input voltages of the rectifiers 1A and 1B can be set to 30 degrees by appropriately selecting the turns ratio of the primary winding and the secondary winding of the phase shift transformer 2. Specifically, if the number of turns of the primary winding of the phase shift transformer 2 is N2 and the number of turns from the intermediate tap of the secondary winding to both ends is N2, N2 / N1 is designed to be about 0.15. The
Here, since two sets of three-phase AC voltages are input to the rectifiers 1A and 1B without being isolated, and these rectifiers 1A and 1B are connected in parallel, the rectifiers 1A and 1B are connected via the load 4. Ancillary equipment for suppressing the circulating current flowing between them is required. In FIG. 8, interphase reactors 5A and 5B are used as the ancillary equipment.

  The rectifier described in Patent Document 1 aims to further reduce the harmonic current by adding two interphase transformers and another rectifier to the output side of the two six-pulse rectifiers. However, in terms of providing a phase difference in the input voltage of the 6-pulse rectifier using a non-insulated phase-shifting transformer and providing an auxiliary device for suppressing circulating current on the output side of the 6-pulse rectifier, It is equivalent.

Hisao Matsumoto, “12-pulse converter with a single transformer connection”, IEEJ Transaction B, Vol.96, No.8, 406-412, August 1976 Japanese Patent Laying-Open No. 2004-215401 ([0022] to [0049], FIG. 1 etc.)

The non-insulated phase shift transformer described in Non-Patent Document 1 and Patent Document 1 has a very small number of secondary windings compared to the primary winding, and as described above, N2 / N1 is about Designed to be 0.15. With such a turns ratio, the ratio of the output voltage to the input voltage is about 1.035, which is almost 1.
When this is compared with an insulation transformer having a transformation ratio of 1, the phase shift transformer reduces the secondary capacity by the amount of secondary turns, and the primary capacity also decreases correspondingly. For this reason, if a non-insulated phase shift transformer is used, it is possible to reduce the size and price as compared with an insulated transformer.

However, when using a non-insulated phase shift transformer, two 6-pulse rectifiers cannot be connected in series as shown in FIG. 8, and these rectifiers are connected in parallel as shown in FIG. The structure to do is taken. When two 6-pulse rectifiers are connected in parallel, an auxiliary device such as an interphase reactor is required to suppress the circulating current flowing between the two rectifiers, as described above. Because it is connected to, it is a cause of large size and high price.
In other words, if a non-insulated phase-shifting transformer is used on the input side of the rectifier, the transformer itself can be miniaturized. However, if incidental equipment such as an interphase reactor is included, the overall device can be made smaller and less expensive. There was a problem that was damaged.

  Therefore, the problem to be solved by the present invention is to provide a power conversion system that uses a non-insulated phase shift transformer and eliminates the need for ancillary equipment such as an interphase reactor, thereby enabling downsizing and cost reduction of the entire apparatus. It is in.

  In order to solve the above-mentioned problems, the invention described in claim 1 is a non-insulated type that outputs a three-phase AC power source and two sets of three-phase AC voltages connected to the three-phase AC power source and having a predetermined phase difference. Are connected to the output sides of the first and second rectifiers, and are insulated from each other. And a load composed of two load elements.

  The invention described in claim 2 is a three-phase AC power source, and a non-insulated phase shift transformer that is connected to the three-phase AC power source and outputs two sets of three-phase AC voltages having a predetermined phase difference; The first and second rectifiers to which the two sets of three-phase AC voltages are respectively input; the first and second inverters connected to the output sides of the first and second rectifiers; And a load composed of two load elements that are respectively connected to the output sides of the two inverters and insulated from each other.

  According to a third aspect of the present invention, there is provided a three-phase AC power source and a non-insulated power source connected to the three-phase AC power source and outputting n (n is a natural number of 3 or more) sets of three-phase AC voltages having a predetermined phase difference. Type transformer, n rectifiers to which the n sets of three-phase AC voltages are respectively input, and n load elements connected to the output sides of the n rectifiers and insulated from each other Load.

  The invention described in claim 4 outputs a three-phase AC power source and n-1 (n is a natural number of 3 or more) sets having a predetermined phase difference connected to the three-phase AC power source. A non-insulated phase shift transformer, n-1 rectifiers to which the n-1 sets of three-phase AC voltages are respectively input, and the n-1 sets of three phases connected to the three-phase AC power supply A rectifier to which a three-phase AC voltage having a predetermined phase difference with respect to the AC voltage is input, and a load composed of n load elements connected to the output sides of all the rectifiers and insulated from each other. It is provided.

  The invention described in claim 5 is a non-insulated device that outputs a three-phase AC power source and n (n is a natural number of 3 or more) sets of three-phase AC voltages connected to the three-phase AC power source and having a predetermined phase difference. Of n-type transformers, n rectifiers to which each of the n sets of three-phase AC voltages is input, n inverters connected to the output sides of the n rectifiers, and n inverters And a load composed of n load elements connected to the output side and insulated from each other.

  According to a sixth aspect of the present invention, in the power conversion system according to the second or fifth aspect, the inverter is a three-phase inverter, and the load includes a plurality of three-phase windings as load elements. It is a phase AC motor.

  The invention described in claim 7 is a three-phase AC power source and a first non-insulated phase shift transformer connected to the three-phase AC power source and outputting two sets of three-phase AC voltages having a predetermined phase difference. And non-insulated second and third phase shift transformers that are connected to the secondary side of the first phase shift transformer and output four sets of three-phase AC voltages having a predetermined phase difference from each other; A load comprising four load elements connected to the output sides of the first to fourth rectifiers to which the four sets of AC voltages are respectively input and the first to fourth rectifiers being insulated from each other. And.

  According to an eighth aspect of the present invention, in the power conversion system according to any one of the first to seventh aspects of the present invention, the power conversion system includes a control unit that operates so that input currents or output currents of a plurality of rectifiers are substantially equal to each other. It is a thing.

  According to a ninth aspect of the present invention, in the power conversion system according to any one of the second, fifth, and sixth aspects, a control unit that operates so that output currents of a plurality of inverters are substantially equal to each other is provided. Is.

  According to the invention described in claims 1 to 9, the load of the rectifier is constituted by load elements insulated from each other, so that even when a non-insulated phase shift transformer is used, an interphase reactor or the like is provided on the output side of the rectifier. Since the circulating current can be suppressed without connecting any additional equipment, it is possible to reduce the size and cost of the entire apparatus.

  In particular, according to the invention described in claim 2 or 5, a plurality of general-purpose inverters that are relatively inexpensive and easily available are used to increase the capacity, and the load elements and non-insulated phase shifts that are insulated from each other are provided. By combining transformers, it is possible to realize a power conversion system that can reduce power supply harmonics and does not require ancillary equipment for suppressing circulating current.

A three-phase AC motor has a relatively large capacity limit that can be manufactured compared to an inverter, and is designed to increase the capacity by supplying power from a plurality of inverters to a plurality of three-phase windings that are insulated and multiplexed. Is usually done.
That is, the invention described in claim 6 is suitable as a power conversion system for driving a three-phase AC motor as described above, and insulates a DC intermediate circuit of a plurality of inverters to provide a non-insulated phase shift transformer. By combining these, it is possible to realize a power conversion system that can reduce power harmonics and does not require an auxiliary device for suppressing circulating current.

  According to the invention described in claim 8 or 9, a plurality of rectifiers are controlled by controlling a plurality of input currents or output currents of a plurality of rectifiers or a plurality of output currents of a plurality of inverters substantially the same. It is possible to realize a power conversion system that does not require an auxiliary device for suppressing circulating current without impairing the effect of reducing harmonics by pulsing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, 2 is a non-insulated phase shift transformer as described above, and the primary winding 2a is delta-connected and connected to the three-phase AC power source 3, and the secondary winding 2b is an open winding. ing. Further, the three secondary windings 2b have intermediate taps, and these three intermediate taps are connected to the respective phase terminals of the three-phase AC power source 3, and each end of each of the three secondary windings 2b is made of a diode. Are connected to the input terminals of the 6-pulse rectifiers 1A and 1B. If the number of turns of the primary winding 2a of the phase shift transformer 2 is N2 and the number of turns from the intermediate tap to both ends of the secondary winding 2b is N2, N2 / N1 is about 0.15. Therefore, the phase difference between the input voltages of the rectifiers 1A and 1B is designed to be 30 degrees.

  Further, reference numeral 6 denotes an inductive load, which includes two windings 6a and 6b as load elements insulated from each other. Both ends of one winding 6a are connected to positive and negative output terminals of the rectifier 1A, and both ends of the other winding 6b are connected to positive and negative output terminals of the rectifier 1B.

In the present embodiment, the output current of the rectifiers 1A and 1B flows through the windings 6a and 6b of the load 6 to generate magnetic fluxes, so that the rectifiers 1A and 1B are equivalently connected in parallel or in series. It is possible to suppress the circulating current from flowing between the rectifiers 1A and 1B.
Accordingly, it is not necessary to separately provide ancillary equipment such as an interphase reactor, and it is possible to reduce the size and cost of the entire apparatus by using the non-insulated phase shift transformer 2.

Next, FIG. 2 is a circuit diagram showing a second embodiment of the present invention.
In this embodiment, in order to supply a three-phase AC voltage to a load (three-phase AC load) 8 composed of two three-phase windings 8a and 8b as load elements insulated from each other, the six-pulse rectifiers 1A and 1B Three-phase inverters 7A and 7B are connected to the DC output side, respectively, and these AC output terminals are connected to one ends of the three-phase windings 8a and 8b, respectively.

The three-phase inverters 7A and 7B are composed of a semiconductor switching element 71 and a DC intermediate capacitor 72 connected in a three-phase bridge. Other configurations are the same as those in FIG.
In this embodiment, as the load 8, a three-phase AC motor including two three-phase windings 8a and 8b insulated from each other, that is, a two-multiplex winding three-phase AC motor can be used.

  The operation principle of this embodiment is basically the same as that of FIG. 1, and the circulating current between the rectifiers 1A and 1B is suppressed by the three-phase windings 8a and 8b insulated from each other. It is possible to reduce the size and cost of the entire apparatus by eliminating the need for incidental equipment.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.
In FIG. 3, the first phase-shifting transformer 2A has the same connection as the phase-shifting transformer 2 in FIGS. 1 and 2, but the turn ratio (N2 / N1) is designed to be about 0.21. As a result, the voltage across the secondary winding 2b has a phase difference of ± 20 degrees with respect to the power supply voltage, and the ratio of the output voltage to the input voltage is about 1.064.
Further, the intermediate taps of the three secondary windings 2b of the phase shift transformer 2A are connected to the respective phase terminals of the three-phase AC power supply 3, and both ends of the three secondary windings 2b are connected to the 6-pulse rectifiers 1A and 1B. Each is connected to a three-phase input terminal.

  On the other hand, for the second non-insulated transformer 2B, the primary winding 2c is star-connected and the secondary winding 2d is an open winding having no intermediate tap. Each one end of the secondary winding 2d is connected to each phase terminal of the three-phase AC power supply 3 together with each one end of the primary winding 2c, and each other end of the secondary winding 2d is the three-phase of the 6-pulse rectifier 1C. Each is connected to an input terminal.

  By configuring the second transformer 2B as described above, the transformer 2B does not have a phase shift characteristic and has only a transforming function. Further, when the number of turns of the primary winding 2c is N1 and the number of turns of the secondary winding 2d is N2, the turn ratio (N2 / N1) is set to about 0.064, so that the three secondary windings 2d The output voltage has the same voltage value, and the phase difference with respect to the power supply voltage is −20 degrees, +20 degrees, and 0 degrees, respectively.

The positive and negative output terminals of the three six-pulse rectifiers 1A, 1B, and 1C are connected to an inductive load 9 including windings 9a, 9b, and 9c as load elements that are insulated from each other.
With the above configuration, the rectifier according to this embodiment is an 18-pulse rectifier.
Also in this embodiment, the circulating currents between the rectifiers 1A, 1B, and 1C can be suppressed by the windings 9a, 9b, and 9c insulated from each other, and an auxiliary device such as an interphase reactor can be made unnecessary.

Next, FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.
In this embodiment, the phase-shifting transformer 10 includes three transformers each including a primary winding 10a, a secondary winding 10b, and two tertiary windings 10c and 10d. In this configuration, two tertiary windings are added to the phase shift transformer 2A including the primary winding 2a and the secondary winding 2b in FIG.
Also, both ends of the three secondary windings 10b in the phase shift transformer 10 are connected to the three-phase input terminals of the 6-pulse rectifiers 1A and 1B via the tertiary windings 10c and 10d of the other transformers, respectively. ing.
With the above configuration, the phase shift transformer 10 has a transformation ratio of 1, and the phase difference between the input voltages of the rectifiers 1A and 1B with respect to the power supply voltage is set to −20 degrees and +20 degrees.

On the other hand, a transformer is not connected to the input side of the 6-pulse rectifier 1C, and is directly connected to each phase terminal of the three-phase AC power supply 3.
In the present embodiment, the input voltages of the rectifiers 1A, 1B, and 1C are all equal, and the phase difference with respect to the power supply voltage is −20 degrees, +20 degrees, and 0 degrees.

Similarly to FIG. 3, the positive and negative output terminals of the rectifiers 1A, 1B, and 1C are connected to an inductive load 9 including windings 9a, 9b, and 9c as load elements insulated from each other.
With the above configuration, the rectifier according to this embodiment is an 18-pulse rectifier.
Also in this embodiment, the circulating currents between the rectifiers 1A, 1B, and 1C are suppressed by the windings 9a, 9b, and 9c that are insulated from each other as in FIG. 3, and an auxiliary device such as an interphase reactor can be made unnecessary. .

FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention.
In this embodiment, the circuit configuration on the output side of the 6-pulse rectifiers 1A, 1B, and 1C in the embodiment of FIG. 3 is changed, and 7A, 7B, and 7C are connected to the output sides of the rectifiers 1A, 1B, and 1C, respectively. The three-phase inverter 11 is connected to the AC output side of the inverters 7A, 7B, and 7C, and has a load (three-phase AC load) having three-phase windings 11a, 11b, and 11c as load elements insulated from each other. ). The load 11 may be a three-phase AC motor including three three-phase windings 11a, 11b, and 11c insulated from each other, that is, a three-multiplex winding three-phase AC motor.

  In this embodiment, the DC output voltages of the rectifiers 1A, 1B, and 1C are converted into three-phase AC voltages by inverters 7A, 7B, and 7C, respectively, and applied to the three-phase windings 11a, 11b, and 11c of the load 11. The three-phase windings 11a, 11b, and 11c that are insulated from each other basically have the same effects as the embodiment of FIG. 3 in that the circulating current is suppressed.

FIG. 6 is a circuit diagram and a control block diagram showing a sixth embodiment of the present invention.
In this embodiment, the non-insulated transformer 2B in the embodiment of FIG. 5 is removed and the input side of the rectifier 1C is directly connected to the three-phase AC power source 3, and the current detectors 12A, 12B, 12C, Current control means comprising units 13A, 13B, 13C and PWM circuits 14A, 14B, 14C is added. These current control means are representatively shown only for the one-phase portion on the output side of each inverter 7A, 7B, 7C.

In the configuration of FIG. 6, by directly connecting the input side of the rectifier 1C to the three-phase AC power supply 3, the DC intermediate voltage of the inverter 7C is lower than the DC intermediate voltages of the other inverters 7A and 7B.
The current adjusters 13A, 13B, and 13C are the current command value i ^* sent from a control circuit (not shown ⁾ and the detected current values i _A , i _B , and i _C obtained from the current detectors 12A, 12B, and 12C. Each deviation is amplified, and the output current is controlled by turning on and off the switching elements of the inverters 7A, 7B, and 7C by pulses generated via the PWM circuits 14A, 14B, and 14C.

  According to this embodiment, even when the DC intermediate voltage values of the inverters 7A, 7B, and 7C are slightly different, it is possible to perform control so that the input current values of the rectifiers 1A, 1B, and 1C are equal, and a normal 18-pulse rectifier Equivalent effect is obtained. That is, the fifth-order, seventh-order, eleventh-order, and thirteenth-order harmonic currents flowing through the three-phase AC power supply 3 can be ideally zero.

Next, FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention.
This embodiment relates to a 24-pulse rectifier, and the connection of the non-insulated phase shift transformers 2A and 2C is the same as that of the phase shift transformer 2 of FIG. 1 and the phase shift transformer 2A of FIG. It is. The connection of the non-insulated phase shift transformer 2 'connected between the primary side of these phase shift transformers 2A and 2C and the three-phase AC power supply 3 is the same as that of the phase shift transformers 2A and 2C. However, if the number of turns of the primary winding 2e of the phase shift transformer 2 'is N3 and the number of turns from the intermediate taps of the secondary winding 2f to both ends is N3, the turns ratio (N3 / N1) is about Designed to 0.076.

In the overall connection configuration of this embodiment, both ends of the secondary winding 2f of the phase shift transformer 2 ′ are connected to the intermediate tap of the secondary winding 2b of the phase shift transformers 2A and 2C and the two primary windings. It is connected to a connection point between the windings 2a. Then, both ends of the three secondary windings 2b of the phase shift transformer 2A are connected to respective input terminals of the 6-pulse rectifiers 1A and 1B, respectively, and both ends of the three secondary windings 2b of the phase shift transformer 2C are 6 The pulse rectifiers 1C and 1D are connected to the respective input terminals.
Reference numeral 15 denotes an inductive load including four windings 15a, 15b, 15c, and 15d as load elements insulated from each other. These windings 15a, 15b, 15c, and 15d include rectifiers 1A and 1B. , 1C, 1D are connected to positive and negative output terminals, respectively.

In the above configuration, the phase difference between the input voltages of the rectifiers 1A and 1B is 30 degrees, and similarly, the phase difference between the input voltages of the rectifiers 1C and 1D is also 30 degrees. In addition, as described above, the phase difference between the input voltages of the phase shift transformers 2A and 2C is 15 degrees by setting the turn ratio (N3 / N1) of the phase shift transformer 2 ′ to about 0.076.
As described above, the input voltage phase difference between the rectifiers 1A and 1C, the input voltage phase difference between 1C and 1B, and the input voltage phase difference between 1B and 1D are all 15 degrees, and this apparatus operates as a 24-pulse rectifier.

  In the embodiment shown in FIGS. 2 and 5 described above, if the current control means as shown in FIG. 6 is added to control the output current of the inverter, the input current values of a plurality of rectifiers can be made equal. And the effect of increasing the number of pulses is increased. In the embodiments of FIGS. 1, 3, 4, and 7 that do not use an inverter, the same effect can be obtained by using, for example, a thyristor rectifier instead of a diode rectifier and controlling its input current and output current. be able to.

1 is a circuit diagram showing a first embodiment of the present invention. It is a circuit diagram which shows 2nd Embodiment of this invention. It is a circuit diagram which shows 3rd Embodiment of this invention. It is a circuit diagram which shows 4th Embodiment of this invention. It is a circuit diagram which shows 5th Embodiment of this invention. It is the circuit diagram and control block diagram which show 6th Embodiment of this invention. It is a circuit diagram which shows 7th Embodiment of this invention. It is a circuit diagram which shows the conventional 12 pulse rectifier using an insulation transformer. 2 is an equivalent circuit diagram of a rectifier described in Non-Patent Document 1. FIG.

Explanation of symbols

1A to 1D: 6-pulse rectifiers 2, 2 ', 2A, 2C, 10: phase-shifting transformer 2B: non-insulated transformers 2a, 2c, 2e: primary windings 2b, 2d, 2f: secondary windings
3: Three-phase AC power supply 6, 8, 9, 11, 15: Loads 6a, 6b, 9a, 9b, 9c, 15a, 15b, 15c, 15d: Windings 7A to 7C: Three-phase inverter 71: Switching element 72: DC intermediate capacitors 8a, 8b, 11a, 11b, 11c: three-phase winding 10a: primary winding 10b: secondary winding 10c, 10d: tertiary windings 12A, 12B, 12C: current detectors 13A, 13B, 13C: Current regulators 14A, 14B, 14C: PWM circuit

Claims (9)

A three-phase AC power supply,
A non-insulated phase shift transformer connected to the three-phase AC power source and outputting two sets of three-phase AC voltages having a predetermined phase difference;
First and second rectifiers to which the two sets of three-phase AC voltages are respectively input;
A load comprising two load elements connected to the output sides of the first and second rectifiers and insulated from each other;
A power conversion system comprising: A three-phase AC power supply,
A non-insulated phase shift transformer connected to the three-phase AC power source and outputting two sets of three-phase AC voltages having a predetermined phase difference;
First and second rectifiers to which the two sets of three-phase AC voltages are respectively input;
First and second inverters respectively connected to the output sides of the first and second rectifiers;
A load comprising two load elements connected to the output sides of the first and second inverters and insulated from each other;
A power conversion system comprising: A three-phase AC power supply,
A non-insulated transformer that is connected to the three-phase AC power source and outputs a three-phase AC voltage having a predetermined phase difference (n is a natural number of 3 or more);
N rectifiers to which the n sets of three-phase AC voltages are respectively input;
A load comprising n load elements respectively connected to the output sides of the n rectifiers and insulated from each other;
A power conversion system comprising: A three-phase AC power supply,
A non-insulated phase shift transformer that is connected to the three-phase AC power source and outputs a three-phase AC voltage of n-1 (n is a natural number of 3 or more) sets having a predetermined phase difference;
N-1 rectifiers to which the n-1 sets of three-phase AC voltages are respectively input;
A rectifier connected to the three-phase AC power source and receiving a three-phase AC voltage having a predetermined phase difference with respect to the n-1 sets of three-phase AC voltages;
A load consisting of n load elements connected to the output sides of all the rectifiers and insulated from each other;
A power conversion system comprising: A three-phase AC power supply,
A non-insulated transformer that is connected to the three-phase AC power source and outputs a three-phase AC voltage having a predetermined phase difference (n is a natural number of 3 or more);
N rectifiers to which the n sets of three-phase AC voltages are respectively input;
N inverters respectively connected to the output side of the n rectifiers;
A load comprising n load elements respectively connected to the output sides of the n inverters and insulated from each other;
A power conversion system comprising: In the power conversion system according to claim 2 or 5,
The inverter is a three-phase inverter, and the load is a three-phase AC motor having a plurality of three-phase windings as load elements. A three-phase AC power supply,
A non-insulated first phase-shifting transformer connected to the three-phase AC power source and outputting two sets of three-phase AC voltages having a predetermined phase difference;
Non-insulated second and third phase-shifting transformers connected to the secondary side of the first phase-shifting transformer and outputting four sets of three-phase AC voltages having a predetermined phase difference from each other;
First to fourth rectifiers to which the four sets of alternating voltages are respectively input;
A load comprising four load elements respectively connected to the output sides of the first to fourth rectifiers and insulated from each other;
A power conversion system comprising: In the power conversion system according to any one of claims 1 to 7,
A power conversion system comprising control means that operates so that input currents or output currents of a plurality of rectifiers are substantially equal to each other. The power conversion system according to any one of claims 2, 5, and 6,
A power conversion system comprising control means that operates so that output currents of a plurality of inverters are substantially equal to each other.

Images