JP2000232786A - Twelve-pulse power-converting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply balance the output current of two three-phase full-wave rectifying circuits for composing a 12-pulse power converting device, without using a 12-pulse connection transformer which is specially manufactured and a two-coil winding reactor for balancing. SOLUTION: The DC output side of a first three-phase full-wave rectifying circuit 2 connected to star connection secondary coil winding 1B of a 12-pulse connection transformer 1 is connected to that of a second three-phase full-wave rectifying circuit 3 which is connected to dalta connection secondary coil winding 1C in parallel by two parallel connection lines 32, and a DC reactor for balancing and a parallel connection line are inserted between the parallel connection point and a load. Also, the DC output side of the first three-phase full-wave rectifying circuit 2 is connected to a first DC reactor 4 and a first smoothing capacitor 6, the second three-phase full-wave rectifying circuit 3 is connected to a second DC reactor 5 and a second smoothing capacitor 7, the power supply side of both the DC reactors 4 and 5 are connected each other by the connection line of a power supply side, and both the ends of the smoothing capacitors 6 and 7 are connected by the connection lines 16 and 17 of positive and negative electrode sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 12-pulse power converter for balancing the outputs of two sets of power converters for separately performing full-wave rectification of two sets of three-phase AC power supplies having a phase difference of 30 degrees.

[0002]

2. Description of the Related Art FIG. 3 is a main circuit connection diagram showing a first conventional example of a 12-pulse power converter. In the first conventional circuit shown in FIG. 3, a 12-pulse connection transformer 1 is connected to a three-phase AC power supply 15. This 12-pulse connection transformer 1
Is composed of a primary winding 1A and two sets of secondary windings, that is, a star connection secondary winding 1B and a delta connection secondary winding 1C. One of the two sets of secondary windings is a star connection. If it is a connection, the other is a delta connection.

[0003] The first inverter device 12 is inserted into a first three-phase full-wave rectifier circuit 2 and a first inverter circuit 8 as a first power converter, and a DC intermediate circuit connecting the DC sides of these two. The first DC reactor 4 and the first
The first inverter device 12 is connected to the star-connected secondary winding 1B of the 12-pulse connection transformer 1, and the first inverter device 12 has a desired voltage and frequency. AC power to the first AC load 1
0. Similarly, the second inverter device 13 also
A second three-phase full-wave rectifier circuit 3 and a second inverter circuit 9 as power converters, a second DC reactor 5 inserted in a DC intermediate circuit connecting the DC sides of both, and a second smoothing circuit The second inverter device 13 is connected to the delta connection secondary winding 1C of the 12-pulse connection transformer 1 to supply AC power of a desired voltage and frequency to the second AC load 11. Supply.

[0004] Between the three-phase AC output of the star-connected secondary winding 1B and the three-phase AC output of the delta-connected secondary winding 1C is 30.
Each secondary winding 1B and 1C
By connecting the separate three-phase full-wave rectifier circuits 2 and 3 to each other, a so-called 12-pulse power converter is formed, and the effect of reducing the harmonic current flowing to the three-phase AC power supply 15 can be obtained. However, when the first three-phase full-wave rectifier circuit 2 and the second three-phase full-wave rectifier circuit 3 separately supply DC power to respective loads, the outputs of the two three-phase full-wave rectifier circuits 2 and 3 are usually Since they are not the same, the above-described effect of reducing the harmonic current cannot be expected.

[0005] A first DC reactor 4 and a first smoothing capacitor 6 are connected to the DC output side of the first three-phase full-wave rectifier circuit 2 to smooth this DC output. The second DC reactor 5 and the second smoothing capacitor 7 are also connected to the DC output side of the DC power supply 3 to smooth its DC output.
And the negative electrode side connection line 17 are connected in parallel. This allows
The output current of the first three-phase full-wave rectifier circuit 2 and the output current of the second three-phase full-wave rectifier circuit 3 are in a balanced state even when power is supplied to the first AC load 10 and the second AC load 11. .

[0006]

However, in practice, 12
There is a slight unbalance between the no-load voltage of the star connection secondary winding 1B of the pulse connection transformer 1 and the no-load voltage of the delta connection secondary winding 1C, and there is a slight unbalance between the two secondary windings 1B and 1C. Since the winding inductances do not have the same value, even if the smoothed DC outputs of the three-phase full-wave rectifier circuits 2 and 3 are connected in parallel by the positive connection line 16 and the negative connection line 17, the DC output of both Imbalance may occur in the current. Here, the first DC reactor 4 and the second DC reactor 5 inserted in the DC intermediate circuit of both inverter devices 12 and 13 are configured such that both inverter devices 12 and 13 function as a single 6-pulse power converter (that is, the positive electrode side). This is to improve the respective input power factors when operating (with the connection line 16 and the negative connection line 17 removed). Therefore, the first DC reactor 4 operates so as to keep only the output DC current of the first three-phase full-wave rectifier circuit 2 constant, and the second DC reactor 5 operates the output DC current of the second three-phase full-wave rectifier circuit 3. It operates so as to keep only the current constant, and cannot be expected to operate as a balancer for balancing the output DC currents of the three-phase full-wave rectifier circuits 2 and 3.

In order to reduce the unbalance of the no-load voltage and the unbalance of the winding inductance of the star-connected secondary winding 1B and the delta-connected secondary winding 1C, a special-purpose dedicated transformer is manufactured. However, there is a drawback that this production takes a long time and the price rises. Further, it is theoretically difficult to completely eliminate the above-mentioned imbalance.

FIG. 4 is a main circuit connection diagram showing a second conventional example of a 12-pulse power converter, showing a case where AC power is supplied to a single load. In the second prior art circuit shown in FIG. 4, a 12-pulse power converter 20 is a first three-phase full-power converter as a first power converter connected to a star-connected secondary winding 1B of a 12-pulse connection transformer 1. Wave rectifier circuit 2,
A second three-phase full-wave rectifier circuit 3 as a second power converter connected to the delta connection secondary winding 1C of the 12-pulse connection transformer 1, a balance two-winding reactor 21, a smoothing capacitor 22, and an inverter circuit The AC load 24 is operated with AC power of a desired voltage and frequency output from the inverter circuit 23. The balancing two-winding reactor 21 includes one coil through which the output DC current of the first three-phase full-wave rectifier circuit 2 flows and the other coil through which the output DC current of the second three-phase full-wave rectifier circuit 3 flows. Since these two coils are wound around a common iron core, the unbalance of the output currents of the three-phase full-wave rectifier circuits 2 and 3 can be suppressed. However, in the conventional circuit shown in FIG. 4, since the two-winding reactor 21 for balancing must be specially manufactured, there are disadvantages that the apparatus is expensive and the delivery time of the apparatus is long.

Accordingly, an object of the present invention is to use a specially manufactured 12-pulse connecting transformer, a balancing 2-winding reactor, and the like to convert the output currents of the two three-phase full-wave rectifier circuits constituting the 12-pulse power converter. To balance easily without using.

[0010]

In order to achieve the above object, a 12-pulse power converter according to the present invention is connected to a three-phase AC power supply and obtains DC by full-wave rectification. An output side and a DC output side of a second power converter that obtains DC by full-wave rectification by connecting to another three-phase AC power supply having a phase difference of 30 degrees with this three-phase AC power supply, are connected in parallel, It is assumed that a DC reactor and a smoothing capacitor are inserted between the parallel connection point and the load.

Alternatively, a first DC reactor and a first smoothing capacitor are connected to a DC output side of the first power converter, and a second DC reactor and a second smoothing capacitor are connected to a DC output side of the second power converter. The power supply side of the first DC reactor and the power supply side of the second DC reactor are connected in common, and the first smoothing capacitor and the second smoothing capacitor are connected in parallel, and then the load is connected. .

[0012]

FIG. 1 is a main circuit connection diagram showing a first embodiment of the present invention. The transformer for 12-pulse connection 1 (primary winding 1A and 1A) described in the circuit of the first embodiment is shown in FIG. Star connection secondary winding 1B and delta connection secondary winding 1C), the first
A first three-phase full-wave rectifier circuit 2 as a power converter, a second three-phase full-wave rectifier circuit 3 as a second power converter, a three-phase AC power supply 15, a smoothing capacitor 22, an inverter circuit 23,
The names, applications, and functions of the AC load 24 are the same as those in the case of the second conventional circuit described above with reference to FIG.

The 12-pulse power converter 30 in the circuit of the first embodiment shown in FIG. 1 includes a DC output side of a first three-phase full-wave rectifier circuit 2 connected to a star connection secondary winding 1B and a delta connection secondary winding. 1C, the DC output side of the second three-phase full-wave rectifier circuit 3 is connected in parallel with two parallel connection lines 32, and a smoothing capacitor is connected between this parallel connection point and the DC side of the inverter circuit 23. 22 and a DC reactor 31 for balance are inserted. By connecting the DC output sides of the two three-phase full-wave rectifier circuits 2 and 3 in parallel with the two parallel connection lines 32, the DC reactor 31 for balancing is connected to the output DC current of the first three-phase full-wave rectifier circuit 2 and 2 Three-phase full-wave rectifier circuit 3
It operates to keep the output DC current constant. That is, in the conventional circuit of FIG. 4, the same current balance action as that of the two-winding reactor 21 for balance described above can be obtained.

FIG. 2 is a main circuit connection diagram showing a second embodiment of the present invention. In the circuit of the second embodiment, a power supply side connection line 41 is added to the first conventional circuit shown in FIG. Only the components are added, and the names, applications, and functions of the other devices are all the same as those of the first conventional example circuit shown in FIG. 3, so that the description thereof will be omitted.

In the circuit of the second embodiment, in order to make the DC output side of the first three-phase full-wave rectifier circuit 2 and the DC output side of the second three-phase full-wave rectifier circuit 3 common, they are connected to the power supply side. Connection line 41
Connect with. As a result, the first DC reactor 4 and the second DC reactor 5 operate so as to keep the DC current output from the three-phase full-wave rectifier circuits 2 and 3 constant. The same effect as the reactor 21 is exerted.

With the circuit configuration shown in the circuit of the second embodiment shown in FIG. 2, the first three-phase full-wave rectifier circuit 2 and the second three-phase full-wave rectifier circuit 3 are operated in parallel to provide an unbalanced circuit. DC power can be supplied to a load common to both without the occurrence of the above-mentioned problem, and the first three-phase full-wave rectifier circuit can be provided by removing the positive connection line 16, the negative connection line 17 and the power supply connection line 41. It is also possible to separately operate the second and second three-phase full-wave rectifier circuits 3 to supply power to different loads.

FIG. 5 is a circuit diagram of the first prior art circuit shown in FIG.
FIG. 4 is a current waveform diagram in which the output current of the pulse connection transformer is drawn by a simulation calculation. The no-load voltage appearing in the star connection secondary winding 1B of the 12-pulse connection transformer 1 in the first conventional circuit of FIG. And delta connection secondary winding 1C
Are calculated under the condition that there is a difference of 3 volts from the no-load voltage appearing in the above and a difference of 10% in the inductance of both secondary windings. The vertical axis of this current waveform diagram represents the current, and the horizontal axis represents the time. The broken line represents the output current I _B of the star-connected secondary winding 1B, and the solid line represents the output current I _C of the delta-connected secondary winding 1C. , Each shows.

FIG. 6 is a circuit diagram of the second embodiment shown in FIG.
FIG. 6 is a current waveform diagram in which the output current of the pulse connection transformer is drawn by a simulation calculation. The conditions of the simulation calculation at this time are the same as those in the case of the above-described current waveform diagram of FIG. In the current waveform diagram of FIG. 6, the output current I _{B of} the star-connected secondary winding 1B shown by the broken line and the output current I _{C of} the delta-connected secondary winding 1C shown by the solid line are almost the same (both currents). (The degree of balance is 90% in effective value), and it can be seen that the current imbalance in the conventional circuit shown in FIG. 5 is greatly improved.

[0019]

The 12-pulse power converter has a configuration in which a separate three-phase full-wave rectifier is connected to two sets of three-phase alternating currents having a phase difference of 30 degrees. In order to obtain two sets of three-phase alternating currents, a 12-pulse connection transformer with a star connection secondary winding and a delta connection secondary winding is used. However, it is in principle difficult to equalize the no-load voltages of the two secondary windings and the impedance values of the two secondary windings of the 12-pulse connection transformer. Therefore, conventionally, a 12-pulse connection transformer specially designed and manufactured so as to reduce the unbalance of the no-load voltage and the unbalance of the winding impedance can be used, or a specially designed and manufactured balance 2 transformer can be used. Since it is necessary to suppress the unbalance between the two currents by using the winding reactor, the cost of the entire device increases, and there is a problem that it takes a long time to manufacture the device.

On the other hand, in the present invention, after the DC output sides of the three-phase full-wave rectifiers separately connected to the two secondary windings are connected in parallel, the common balance for both three-phase full-wave rectifiers is set. Connect a DC reactor and a smoothing capacitor. Alternatively, in the case of two three-phase full-wave rectifiers having separate balancing DC reactors and smoothing capacitors, a connection in which the output side of each three-phase full-wave rectifier is common and a connection in which two smoothing capacitors are connected in parallel Is applied. By doing this,
The current balance between the two is almost completely obtained. In other words, only the work of connecting several connection lines is added,
Since a transformer for two-pulse connection and a two-winding reactor for balance are not required, the effect of suppressing an increase in the cost of the device and avoiding an increase in the manufacturing period can be obtained, and the overall size of the device can be reduced. The effect that can be suppressed is also obtained.

[Brief description of the drawings]

FIG. 1 is a main circuit connection diagram showing a first embodiment of the present invention.

FIG. 2 is a main circuit connection diagram showing a second embodiment of the present invention.

FIG. 3 is a main circuit connection diagram showing a first conventional example of a 12-pulse power converter.

FIG. 4 is a main circuit connection diagram showing a second conventional example of a 12-pulse power converter.

FIG. 5 is a current waveform diagram in which the output current of the 12-pulse connection transformer shown in the first conventional circuit of FIG. 3 is drawn by simulation calculation.

FIG. 6 is a current waveform diagram in which the output current of the 12-pulse connection transformer shown in the circuit of the second embodiment in FIG. 2 is drawn by simulation calculation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 12 pulse connection transformer 1A primary winding 1B star connection secondary winding 1C delta connection secondary winding 2 first three-phase full-wave rectifier circuit 3 second three-phase full-wave rectifier circuit 4 first DC reactor 5th 2 DC reactor 6 First smoothing capacitor 7 Second smoothing capacitor 8 First inverter circuit 9 Second inverter circuit 12 First inverter device 13 Second inverter device 15 Three-phase AC power supply 16 Positive side connection line 17 Negative side connection line 20, Description of Reference Numerals 30 12 pulse power conversion device 21 balance 2-winding reactor 22 smoothing capacitor 23 inverter circuit 31 balance DC reactor 32 parallel connection line 41 power supply side connection line

Claims (2)

[Claims] 1. A DC output side of a first power converter which is connected to a first three-phase AC power supply and obtains DC by full-wave rectification, and a second power converter having a phase difference of 30 degrees with the first three-phase AC power supply. Connect the DC output side of the second power converter, which is connected to a three-phase AC power supply to obtain DC by full-wave rectification, in parallel with the DC output side, and insert a DC reactor and a smoothing capacitor between this parallel connection point and the load 12. A 12-pulse power converter. 2. A first direct current reactor and a first smoothing capacitor are connected to a direct current output side of a first power converter for obtaining direct current by full-wave rectification by connecting to a first three-phase alternating current power supply. A second DC reactor and a second smoothing capacitor are connected to a DC output side of a second power converter that obtains DC by full-wave rectification by connecting to an AC power supply and a second three-phase AC power supply having a phase difference of 30 degrees, A 12-pulse power converter, wherein a power supply side of the first DC reactor and a power supply side of the second DC reactor are commonly connected, and the first smoothing capacitor and the second smoothing capacitor are connected in parallel.