JP2002095260A - Harmonics current suppressing power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a harmonics current suppressing power converter capable of suppressing a harmonics component very well and easily with a simple structure without using any capacitor. SOLUTION: Three-phase power from a distributing path is provided for each phase of an arm reactor section having a commutation overlapping angle of 30 degrees between a three-phase transformer 1 and a rectifying circuit 2. The output (b) of each primary winding of arm reactors 4, 5, 6 is connected to a rectifying circuit 2 formed out of diodes. Both ends of respective secondary windings of the arm reactors 4, 5, 6 are connected to a commutation overlapping angle regulator 7. The commutation overlapping angle regulator 7 always sets the commutation overlapping angle of the arm reactor at 30 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter that can easily suppress harmonic components with a simple configuration without using a capacitor.

[0002]

2. Description of the Related Art In recent years, devices having a high-frequency generation load, such as inverters, have been used for industrial equipment, office automation, and home electric appliances. A relatively large-capacity power converter uses, for example, a rectifier circuit as shown in FIGS.

FIG. 12A shows a parallel 12-pulse connection power converter that combines a three-phase bridge connection with a △-△ connection and a three-phase bridge connection with a △ -Y connection.
FIG. 11B shows a power conversion device connected in series 12 pulses.

In these power converters, as shown in FIG. 13, the AC current on the △-△ connection side becomes a 6-pulse AC current I11 shown in FIG. 13A, and the AC current on the △ -Y connection side becomes A six-pulse alternating current I12 shown in FIG. Therefore, the three-phase bridge connection of the △-△ connection and the △ -Y
When combined with a three-phase bridge connection, the alternating current I10 becomes 12 pulses shown in FIG.

[0005] That is, since the conventional power converter as described above uses a semiconductor, a harmonic current is generated.

For example, if the number of converted pulses is p and the harmonic order is n, the amount of generation of harmonic current in an AC to DC power converter is n = kp ± 1 (where k = 1,
2, 3,...), And the effective value I _pn of the n-th harmonic current is I _pn = (1 / n) I _p1 .

That is, the line current on the alternating current side when the commutation overlap angle u = 0 is expressed by the following equation.

I = I1 ＝ sinwt + 1 / 11sin11ωt
+1/13 sin13ωt + 1/23 sin23ωt + 1/2
5 sin25ωt +...｝ Table 1 shows an example (p = 6, 12) of the harmonic current I _pn when the commutation overlap angle u is set to 0. To explain using Table 1 as an example, when n = 12, the content of the harmonic current is n
At = 11 and 13, they are 9.1 and 7.7%.

[Table 1]

[0009] Such a harmonic current is the alternating current I10
, And flowed into the distribution line, causing an increase in voltage distortion. Under the influence, devices (including other companies) connected to the distribution line were subjected to harmonic interference.

[0010] Most of the harmonic interference occurs in the power capacitor equipment, and in some cases, may cause damage. Therefore, measures against harmonics in the capacitor equipment have become important.

[0011] In view of the above, in recent years, technical guidelines for harmonic suppression have been established, and in this technical guideline, consumers to whom the guidelines apply are those who meet any of the following requirements. Have a house.

(1) A power receiver that receives power from a 6.6 kv system has a total equivalent capacity of more than 50 kVA, and (2) A power receiver that receives power from a 22 kv or 33 kv system has a total equivalent capacity of 300 kVA. (3) For power receivers receiving power from a system of 66 kV or more, power receivers whose total equivalent capacity exceeds 2000 kVA, and the allowable upper limit value of the harmonic outflow current flowing out of the specific customer to the system is: Table 2 shows the contract power per 1 kW.

[0013]

[Table 2] As a measure for preventing the harmonic current from flowing into the power supply system in order to maintain the regulation of such a guideline, generally, as shown in FIG.
A resonance filter is connected so that the harmonic current of each harmonic flows into the filter, or an active filter (not shown) is used to prevent the harmonic current from flowing out to the power supply system.

[0014]

However, since such a filter uses a capacitor, it is possible to suppress harmonic components on its own device side. There has been a problem that the capacitor may be damaged as a result of being affected by the harmonic components.

In addition, such a filter has a problem that the cost is high because a number of capacitors are used for each harmonic.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a harmonic current suppressing type power converter which can easily suppress a harmonic component easily with a simple configuration without using a harmonic filter. The purpose is to gain.

[0017]

SUMMARY OF THE INVENTION A harmonic current suppressing type power converter of the present invention transforms three-phase power from a distribution line into a delta connection on the primary side and a delta connection and a star connection on the secondary side. A power transformer composed of one unit or a power transformer composed of two units, a three-phase bridge rectifier circuit connected to the secondary delta connection, and a three-phase bridge rectifier circuit connected to the secondary star connection In a power converter that supplies DC power to a load by connecting both three-phase bridge rectifier circuits in parallel, between the power transformer and the rectifier circuit, each of the three-phase bridge rectifier circuits is associated with each phase. And a commutation overlap angle adjustment unit that maintains a constant product of the impedance on the power supply side including the reactor and the load current flowing to the load so that the commutation overlap angle is close to 30 degrees. Have The the gist.

As a result, a triangular wave having a commutation overlap angle of 30 degrees of the current flowing through the reactor of each phase is obtained.
Unlike the conventional case, the three phases obtained by combining the triangular waves, instead of the rectangular waves, become the three phases of the distribution circuit. As a result, the harmonics are reduced to 1 / n ² of the harmonic order.

Further, the harmonic current suppressing type power converter of the present invention includes a first power transformer for transforming three-phase power from a power distribution line by a predetermined connection, and a first power transformer via the first power transformer. A first rectifier circuit for rectifying all three phases to supply the first load to the first load, a primary winding and a secondary winding, and the first power transformer and the first rectifier circuit are connected to each other. And a main circuit including an arm reactor connected to one end of each primary winding for each phase and the other end connected to a corresponding diode of the first rectifier circuit.

The three-phase power from the power distribution circuit is transformed by a connection having characteristics similar to those of the first power supply transformer, and each phase is subjected to a secondary winding of the arm reactor of a corresponding phase of the main circuit. A second power transformer connected to one end of the wire;
The other end of the secondary winding of the reactor of each phase of the main circuit is connected to a predetermined diode in a diode configuration connected in the same manner as the rectifier circuit, and the current of the secondary winding is connected to each phase of the main circuit. A second rectifier circuit that rectifies the current in synchronization with the current.

A current adjusting circuit provided between the three-phase line of the power distribution circuit and the second transformer for adjusting a current to the second transformer; By controlling the current flowing to the second power transformer based on the load current and the detected value of the three-phase voltage of the distribution circuit to control the current flowing through the secondary winding of the arm reactor of each phase. And a commutation overlap angle controller for maintaining the commutation overlap angle at 30 degrees.

Further, the harmonic current suppressing type power converter of the present invention includes a first power transformer for transforming three-phase power from a power distribution line by a predetermined connection, and a first power transformer via the first power transformer. A first rectifier circuit for rectifying all three phases and supplying the rectified load to a load, a primary winding and a secondary winding, and provided between the first power transformer and the first rectifier circuit. And a main circuit having one end of each primary winding connected to each phase and an arm reactor having the other end connected to a corresponding diode of the first rectifier circuit, and a secondary circuit of the arm reactor. An inverter circuit having the main circuit output DC voltage as a power source, to which both ends of each of the windings are connected, and a three-phase power from the power distribution line having the same characteristics as the first power transformer. A second power transformer that transforms at Consists of a diode connected, by connecting to said second power transformer, a second rectifying circuit for rectifying in synchronism with each phase of current in the main circuit,
And a sub-circuit comprising:

A three-phase power supply voltage detector, a synchronous signal detector for extracting a synchronous signal of a secondary current of the second power transformer, and a direct current detector for detecting a load current of the main circuit. Is provided.

The commutation overlap angle is maintained at 30 degrees by controlling the inverter based on the output value from each of these detectors and controlling the current flowing through the secondary winding of the arm reactor of each phase. The point is to have a commutation overlap angle controller.

As a result, a current commensurate with the load current from the main circuit is obtained from the sub-circuit and flows through the secondary winding of the arm reactor of the main circuit, so that the impedance of the arm reactor is adjusted. The timing with the current of the secondary winding is synchronized with the current flowing through the primary winding of the arm reactor of the main circuit.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a conceptual diagram of a harmonic current suppressing type power converter of the present invention. The power converter of the harmonic current suppression type shown in FIG. 1A has two three-phase power transformers 1 (△-△ connected Trs) for transforming three-phase power from a distribution line.
1, △ -Y connection Tr2) and rectifier circuit 2 (2a, 2a,
The harmonics are suppressed by providing the arm reactors 3 (3a, 3b) for maintaining the commutation overlap angle at 30 degrees between them and b).

In the above-described power transformer Tr1, the primary winding side has a △ connection, and the secondary winding side has a △ connection. Further, the power transformer Tr2 has a primary winding side with a △ connection,
The secondary winding side is Y-connected. -The power converter of the harmonic suppression type shown in FIG. 1B is a single power transformer 8 of {-Y-} connection. This power transformer 8 shares the primary winding side with the △ connection and the secondary winding side with the △ connection and the Y connection.

The arm reactor 3 of the power converter shown in FIG. 1 includes a U-phase arm reactor 4 corresponding to the U-phase (R) and a V-phase arm corresponding to the V-phase (S). Reactor 5 and W corresponding to W phase (T)
, And each of the arm reactors includes a primary winding 6a, a secondary winding 6b, and an iron core 6.
c. In the present embodiment, only W-phase arm reactor 6 will be described as an example.

The output b of each of the primary windings of the arm reactors 4, 5, and 6 is connected to a rectifier circuit 2 composed of a diode, and both ends of each of the secondary windings of the arm reactors 4, 5, and 6 are connected to both ends. , Are connected to a commutation overlap angle controller 7. By this commutation overlap angle controller 7,
The commutation overlap angle of the arm reactor is always maintained at 30 degrees.

That is, the inter-phase voltage in the rectifier circuit is E,
Assuming that the commutation reactance per phase including the impedance of the three-phase power transformer Tr is X, the commutation overlap angle is u, the DC current is _ID , and the constant is K, 1−cosu = K · ｛(Id · X) / E｝ (1) In the equation, the product of Id and X is made constant. That is, by keeping the product of Id · X constant, the commutation overlap angle can be maintained at 30 ° el even when the load _ID changes.

The above-described arm reactor is constructed by winding a primary winding 6a and a secondary winding 6b around an iron core 6c as shown in FIG.

However, it is difficult to manufacture an arm reactor composed of only the primary winding in which the product of the impedance X of the arm reactor and the load current _ID is constant.

The arm reactor is composed of a laminated core and a coil. The characteristics of the laminated core are indicated by a magnetizing force H (A / m) and a magnetic flux density B (T). (A / m) changes, and the magnetic flux density B of the laminated core
(T) also changes. For this reason, the desired product of X and _ID is generally not constant.

For example, as shown in FIG. 3, when a manufacturable arm reactor satisfies the target value of the solid line over the entire range, the characteristic becomes as shown by the broken line. In order to make the characteristic of the broken line the characteristic of the solid line: (A) Since the predetermined characteristic cannot be obtained only by the primary winding of the arm reactor, a secondary winding is provided and the ampere-turn AT of the secondary winding is controlled. As a result, the predetermined characteristic of the above equation (1) is obtained.

The method (A) is referred to as the first embodiment, and a description will be given as a parallel 12-pulse connection having two transformers. <First Embodiment> FIG. 4 is a schematic configuration diagram of a power converter of a harmonic current control type according to the first embodiment. Δ- △ connection power transformer Tr1 and △ -Y connection power transformer Tr
2 and an arm reactor 3 is provided between the power transformer Tr and the rectifier circuit 2.

The power transformer Tr2 and the rectifier circuit 14
The arm reactor 10 (similar to the arm reactor 3) is provided between the two.

VR6 connected to both ends of each secondary winding of the arm reactors 4, 5, 6 of the arm reactor 3 and the arm reactors 11, 12, 13 of the arm reactor 10. And a commutation overlap angle adjustment unit 15 having the following.

The operation of the power converter of the first embodiment configured as described above will be described with reference to the waveform diagram of FIG. 5 and the equivalent circuit of FIG.

In this description, the load current Id is detected or
While detecting the terminal voltage or the load current Id of the arm reactors 4, 5, 6, 11, 12, and 13 of the arm reactor 3 and the arm reactor 10 and the voltage between the terminals, as shown in the above equation (1), Each of the variable resistors VR1, VR2,... VR6 is adjusted so that the product of Id and X is constant, and the commutation overlap angle is maintained at 30 °.

As a result, as shown in FIG. 5, the arm current in the △ connection becomes as shown in FIG. 5D, the arm current in the Y connection becomes as shown in FIG. The line current I11 is as shown in FIG. 5A, the AC line current I12 is as shown in FIG. 5B, and as a result, the AC line current I10 is as shown in FIG. 5C.

In other words, only between the RSs will be described. By providing the arm reactor section 10, as shown in FIG. 6, commutation (diode system with black marks) occurs in both the three-phase systems of △ -Y. When the commutation overlap angle is set to 30 degrees by the variable resistance of the commutation overlap angle adjusting unit 15, the arm current becomes a triangular wave as shown in FIGS.

Therefore, when u = 30 ° el,
Unlike the conventional case where u = 0 °, the AC line current I10 ignoring the excitation current of the power transformer is expressed by the following equation when expanded into a Fourier series.

I = I _A ｛sinωt + 8.23 × 10 ⁻³ sin9ωt−8.26 × 10 ⁻³ sin11ωt−1.89 × 10 ⁻³ sin23ωt (2) That is, in comparison with the conventional art, Although the method generates 12n ± 1st harmonic currents and the magnitude is 1 / n, this method generates 9, 11, and 23rd harmonics as shown in equation (2). However, it is reduced to 1 / n ² of the harmonic order, the magnitude is 1% or less, and the total fluctuation value up to the 23rd order is extremely small at 1.2%.

<Second Embodiment> In the second embodiment, the commutation overlap angle adjusting section detects the load current and changes the current flowing through the secondary winding in a stepwise manner. Also in the present embodiment, there are two power transformers, rectifier circuits, and arm reactors, but in this description, only one side will be described as an example.

FIG. 8 is a schematic configuration diagram of the second embodiment.
The three-phase power transformer 20 in FIG.
-Y connection or △ -Y- △ connection is used. An arm reactor 21 is provided between the transformer 20 and the rectifier circuit 2 to maintain the commutation overlap angle at 30 degrees.

The above-described arm reactor 21 includes an R-phase arm reactor 22 corresponding to the R-phase, an S-phase arm reactor 23 corresponding to the S-phase, and a T-phase arm reactor corresponding to the T-phase. 24, each arm reactor includes a primary winding 6a, a secondary winding 6b, and an iron core 6c. In the present embodiment, only the T phase will be described as an example.

The arm reactor 24 includes the primary winding 6a
Is connected to the output terminal of the secondary winding 6b, and the output terminal of the primary winding 6a is connected to the cathode of the diode of the rectifier circuit 2.

The output end of the primary winding 6a and the input end (black circle) of the secondary winding 6b are connected to a commutation overlap angle adjusting element circuit 27 to be described later.

In the commutation overlap angle adjusting element circuit 27, a plurality of series circuits each having resistors R1, R2, R3 and switches S1, S2, S3 connected in series are connected in parallel with each other. These resistors have different resistance values.

The opening and closing of each switch is controlled by the controller 29. The controller 29
It is connected to a detector 29 for detecting the load current Id, and closes a switch corresponding to the value of the load current Id.

That is, the controller 29 has a control table shown in FIG. This control table associates the load current Id with the switch name Si. For example, when the load current Id is in the range of Ida to Idb, the switch S1 is closed, and when the load current Id is in the range of Idb to Idc, the switch S1 is closed.
By closing the switch 2 and closing the switch S3 when the load current Id is in the range of Idc to Idd, the product of Id and X is always kept constant. That is, by keeping the product of Id · X constant, the commutation overlap angle is set to 30 ° even when the load _ID changes.
so that you can keep it to el.

In this embodiment, the commutation overlap angle is maintained at 30 degrees by using a switch, but a power transistor may be used instead of the switch.

<Third Embodiment> FIG. 10 is a schematic configuration diagram of a third embodiment. The third embodiment is a method of synchronizing the timing of a secondary current flowing to adjust the impedance X of the arm reactor with the arm reactor of the main circuit, and supplies the energy source from another power source.

The synchronous power converter of the arm reactor shown in FIG. 10 includes a main circuit and a sub-circuit, and the main circuit is a power transformer Tr1 (△ −) for inputting three phases from a power distribution line.
Arm reactors 32 and 33 are provided between the rectifier circuits 30 and 31 (Y- △ connection).

The arm reactor 32 includes a power transformer T
Arm reactors 35, 36, and 37 are provided for each of the U, V, and W phases in the △ -Y connection of r1.

The arm reactors 38, 39, 4 for each of the U-phase, V-phase, and W-phase in the 変-変 connection of the transformer Tr1.
0 is provided. As shown in FIG. 2, these arm reactors are configured by winding primary windings 6a and 6b around an iron core 6c, and the input terminals of the secondary windings of each arm reactor are connected to the U-phase and V-phase Phase, W phase, and the output terminal is connected to the diode of the rectifier circuit of the sub-circuit.

On the other hand, the sub-circuit includes a transformer Tr2 (２-Y- △ connection) having the same winding ratio as the main circuit, and a rectifier circuit 4
Arm reactor portions 32, 3 of the main circuit
3 is connected to the secondary winding of each arm reactor.

For example, US of the △ -Y connection of the transformer Tr1
1 and the secondary winding 35b of the arm reactor 35 of the main circuit
The output terminal of the secondary winding 35b of the arm reactor 35 is connected to the diode 4 of the rectifier circuit 43.
3a and 43b.

This power converter includes a power supply voltage detector 46 and a current regulator 47 in three phases from the distribution line, and adjusts between the transformer Tr2 and the current regulator 47 of the sub-circuit. And a DC current detector 50 for detecting a load current from the main circuit.

Then, the current regulator 47 is controlled based on the output values from these detectors to control the current of each arm reactor.
By controlling the current flowing to the next winding, the commutation overlap angle is always 3
It has a commutation overlap angle controller 49 that maintains it at 0 degrees.

That is, the power transformers TR1 and TR2 have the same phase in the main circuit and the sub-circuit, and the rectifier circuits 30, 31, 43 and 44 have the same characteristics. So that the commutation overlap angle is 3
It is maintained at 0 degrees.

More specifically, in the equation 1-cosu = K ｛{(Id ・ X) / E}, the product of Id and reactance X is always kept constant. That is, the current regulator 4 is controlled so that the product of Id and X is constant from the detection value of the power supply voltage detector 46, the detection value of the adjustment current detector 48, and the detection value of the DC current detector 50.
At 7, the current to the transformer Tr2 of the sub-circuit is adjusted. It is preferable that this adjustment value is provided by providing a table in which the range of each detection value and the actual adjustment value correspond to each other as described above.

It should be noted that whether the secondary winding of the arm reactor is connected to the additional polarity or the negative polarity is preferably determined initially based on the difference between the theoretically required impedance and the impedance of the manufactured arm reactor.

<Fourth Embodiment> FIG. 11 is a schematic configuration diagram of a fourth embodiment. Embodiment 4 is a method of synchronizing the timing of the secondary current flowing in order to adjust the impedance X of the arm reactor with the arm reactor of the main circuit, and supplying the energy source from the DC voltage circuit of the main circuit. It is.

The synchronous power converter of the arm reactor shown in FIG. 11 includes a main circuit and a sub-circuit, and the main circuit is a power transformer Tr1 (△ −) for inputting three phases from a power distribution line.
Arm reactors 32 and 33 are provided between the rectifier circuits 30 and 31 (Y- △ connection).

The arm reactor section 32 includes a power transformer T
Arm reactors 35, 36, and 37 are provided for each of the U, V, and W phases in the △ -Y connection of r1.

The arm reactors 38, 39, 4 for each of the U-phase, V-phase, and W-phase in the 変-△ connection of the transformer Tr1.
0 is provided. As shown in FIG. 2, these arm reactors are configured by winding primary windings 6a and 6b around an iron core 6c, and the input terminals and the output terminals of the secondary windings of each arm reactor use a main circuit DC voltage as a power supply. Each is connected to an inverter circuit 51 composed of a power transistor or the like.

The timing for controlling the inverter is determined by the transformer Tr2 of the sub-circuit having the same phase as the main circuit.
(△ -Y- △ connection) and the rectifier circuits 43 and 44 are detected by a synchronization signal detector 48 (current transformer).

For example, the secondary terminals US1 and US2 of the arm reactor inserted into one phase of the △ -Y connection of the transformer Tr1 are connected to US1 and US of the inverter circuit 51.

This power converter includes a power supply voltage detector 46 on the sub-circuit side in three phases from the power distribution line, and a synchronous signal detector 48 for extracting a synchronous signal with the transformer Tr2 of the sub-circuit. And a DC current detector 50 for detecting a load current from the DC main circuit.

The base current of the inverter 51 is controlled based on the output values from these detectors to control the current flowing in the secondary winding of each arm reactor, so that the commutation overlap angle is always maintained at 30 degrees. A commutation overlap angle controller 49 is provided.

That is, the power transformers TR1 and TR2 have the same phase in both the main circuit and the sub-circuit, and the rectifier circuits 30, 31, 43 and 44 have the same characteristics. So that the commutation overlap angle is 3
It is maintained at 0 degrees.

More specifically, in the equation 1-cosu = K リ ア {(Id ・ X) / E} as described above, the product of Id and reactance X is always kept constant. That is, based on the detection value of the power supply voltage detector 46, the detection value of the synchronization signal detector 48, and the detection value of the DC current detector 50, the inverter 5 is controlled so that the product of Id · X is constant.
Step 1 adjusts the current of the arm reactor.

It is preferable that the adjustment values are prepared by providing a table in which the ranges of the respective detection values correspond to the actual adjustment values as described above.

It should be noted that whether the secondary winding of the arm reactor is connected to an additional polarity or a negative polarity is initially determined by the theoretically required impedance and the impedance characteristics of the manufactured arm reactor.

[0076]

As described above, according to the present invention, a reactor provided for each phase is provided between a power transformer and a rectifier circuit of a power converter, and the impedance of the reactor is reduced. By maintaining the product of the load current constant to make the commutation overlap angle 30 degrees,
A triangular wave having a commutation overlap angle of 30 degrees of the current flowing through the reactor of each phase is obtained. As a result, the harmonics are reduced to 1 / n ² of the harmonic order.

Therefore, the harmonics can be reduced without using a harmonic filter or an active filter, so that the cost can be reduced and the external devices connected to the power distribution line are not damaged by the harmonics. Have been obtained.

Further, according to the harmonic current suppressing type power converter of the present invention, the main circuit and the sub-circuit having the same characteristics as the main circuit are provided, and the current from the sub-circuit is used for each phase of the main circuit. By adjusting the current flowing through the secondary winding of the reactor, a current corresponding to the load current from the main circuit is obtained from the sub-circuit, which flows through the secondary winding of the reactor of the main circuit. Therefore, the timing with the current of the secondary winding for adjusting the impedance of the arm reactor is synchronized with the current flowing through the primary winding of the reactor of the main circuit. That is, the effect is obtained that the commutation overlap angle of each phase can be maintained at 30 degrees with good timing without affecting the main circuit.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a harmonic current suppression type power converter of the present invention.

FIG. 2 is an external view of an arm reactor used in the power converter of the present invention.

FIG. 3 is an explanatory diagram illustrating characteristics of an arm reactor.

FIG. 4 is a schematic configuration diagram of a harmonic current suppression type power converter of the first embodiment.

FIG. 5 is a waveform chart for explaining the operation of the first embodiment.

FIG. 6 is an equivalent circuit diagram showing a current flow according to the first embodiment.

FIG. 7 is an explanatory diagram for explaining the reason why the commutation angle is 30 degrees.

FIG. 8 is a schematic configuration diagram of a harmonic current suppression type power conversion device according to a second embodiment.

FIG. 9 is an explanatory diagram illustrating a table used in the second embodiment.

FIG. 10 is a schematic configuration diagram of a harmonic current suppression type power conversion device according to a third embodiment.

FIG. 11 is a schematic configuration diagram of a harmonic current suppression type power conversion device according to a fourth embodiment.

FIG. 12 is a schematic configuration diagram of a conventional power converter.

FIG. 13 is an alternating current waveform diagram of a conventional power converter.

FIG. 14 is a configuration diagram of a conventional filter for removing harmonics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Three-phase transformer 2 Rectifier circuit 3 Arm reactor part 6a Primary winding 6b Secondary winding 7 Commutation overlap angle adjustment part

Claims (7)

[Claims] 1. A power transformer comprising one unit or a power transformer comprising two units for transforming three-phase power from a distribution line into a delta connection on a primary side and a delta connection and a star connection on a secondary side. A three-phase bridge rectifier circuit connected to the secondary delta connection and a three-phase bridge rectifier circuit connected to the secondary star connection, and these two three-phase bridge rectifier circuits are connected in parallel. And a reactor provided between the power transformer and the rectifier circuit so as to correspond to each phase, such that a commutation overlap angle is close to 30 degrees. And a commutation overlap angle adjustment unit for maintaining a constant product of the impedance on the power supply side including the reactor and the load current flowing through the load. 2. The reactor as an arm reactor, wherein one end of a primary winding is connected to one of phases of the power transformer, and the other end is connected to a corresponding diode of the rectifier circuit; The harmonic current suppression type power converter according to claim 1, wherein both ends of the line are connected to the commutation overlap angle adjustment unit, and the current is adjusted by the adjustment unit. 3. The power supply transformer and the rectifier circuit include: a first power converter circuit including a first power supply transformer and a first rectifier circuit; a second power supply transformer and a second rectifier circuit. And a second power conversion circuit comprising: a first power transformer and a first rectifier circuit provided between the first power transformer and the first rectifier circuit so as to correspond to each phase of the first power transformer. A first arm reactor group, a second arm transformer group provided between the second power transformer and the second rectifier circuit, the second arm transformer being provided for each phase of the second power transformer. The harmonic current suppression according to claim 1 or 2, further comprising a reactor group, wherein a secondary winding of each arm reactor of the arm reactor group is connected to the commutation overlap angle adjustment unit. Type power converter. 4. The commutation overlap angle adjustment unit includes a variable resistor corresponding to the arm reactor for each phase, and maintains the commutation overlap angle of 30 degrees by adjusting the variable resistance. The harmonic current suppression type power converter according to claim 1, 2 or 3. 5. The commutation overlap angle adjustment section includes: a plurality of series circuits each including a switching element connected in series to a resistance element having a different value from each other; and the switching element in a plurality of types of current ranges flowing through the arm reactor. And a means for closing a switching element in a current range of the table corresponding to the load current when the load current is detected. 5. The harmonic current suppression type power converter according to 3 or 4. 6. A first power transformer for transforming three-phase power from a power distribution line by a predetermined connection, and rectifying the three phases via the first power transformer to supply the rectified three-phase power to a first load. A first rectifier circuit, and a primary winding and a secondary winding. The first rectifier circuit is provided between the first power transformer and the first rectifier circuit. A main circuit consisting of an arm reactor having one end connected to the corresponding diode of the first rectifier circuit and the other end connected to a corresponding diode of the first rectifier circuit; A second power transformer in which each phase is connected to one end of a secondary winding of the arm reactor of the corresponding phase of the main circuit, and the same as the first rectifier circuit. The secondary winding of the arm reactor of each phase of the main circuit in the diode configuration connected to And a second rectifier circuit that connects the end to a predetermined diode and rectifies the current of the secondary winding in synchronization with the current of each phase of the main circuit. A current adjusting circuit that is provided between the three-phase line and the second power transformer and adjusts a current to the second power transformer; and a load current to the first load and The current to the second power transformer is adjusted based on the detected values of the three-phase voltages to control the current flowing through the secondary windings of the arm reactors of the respective phases, so that the commutation overlap angle is 30 degrees. And a commutation overlap angle controller for maintaining the power supply at a higher harmonic current. 7. A first power supply transformer for transforming three-phase power from a distribution line by a predetermined connection, and a first power supply for rectifying the three-phase power via the first power supply transformer and supplying the rectified three-phase power to a load. And a primary winding and a secondary winding, provided between the first power transformer and the first rectifier circuit, and one end of each primary winding for each phase. And a main circuit consisting of an arm reactor having the other end connected to a corresponding diode of the first rectifier circuit, and both ends of each of the secondary windings of the arm reactor connected to each phase. An inverter circuit that uses a main circuit output DC voltage as a power supply; a second power transformer that transforms three-phase power from the power distribution line with a connection having characteristics similar to those of the first power transformer; And a diode connected in the same manner as the rectifier circuit of And a sub-circuit comprising: a second rectifier circuit that rectifies the current in each phase of the main circuit in synchronization with the main circuit by connecting to the power transformer. A synchronous signal detector for extracting a synchronous signal of the secondary current of the power transformer; and a DC current detector for detecting a load current of the main circuit. The inverter is controlled based on an output value from each of these detectors. A commutation overlap angle controller for controlling the current flowing through the secondary winding of the arm reactor of each phase to maintain the commutation overlap angle at 30 degrees. Power converter.