JP3019655B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device using a large-capacity semiconductor power converter for general industry, electric power, vehicles and the like, and particularly to a power converter using a large capacity using multiple transformers. It can be used in the field where

[0002]

2. Description of the Related Art As a method of increasing the capacity of a semiconductor power converter, for example, IEE, Transaction on Magnetics, Vol. 26, No. 5, 1990
Years 2247 to 2249 (IEEE Trans Magnetics Vo
l.26, No.5 (1990), pp2247-224
As discussed in 9), there is a method of multiplexing two converters using two transformers. 2
One of the converters is operated at a phase difference of 30 degrees to achieve a large capacity and low harmonics.

[0003] The Institute of Electrical Engineers of Japan, "Semiconductor Power Conversion Circuit" 1
As discussed on pages 00-101, there are also methods of reducing harmonics using a staggered winding transformer.

[0004]

However, a method for further reducing harmonics according to the above method has not been studied.
Further, it does not describe an effective method for increasing the number of converters to be multiplexed, or how to reduce the harmonics by changing the operation phase of each converter. Also, when using a staggered winding transformer, the structure of the transformer becomes complicated.

An object of the present invention is to multiplex converters of the order of 2 to the power of n (n ≧ 2, an integer) using a transformer that does not use a special winding, thereby reducing harmonics. It is to obtain a large capacity power converter.

[0006]

In order to achieve the above-mentioned object, the output of a n-th power of 2 (n ≧ 2, an integer) of a three-phase power converter using a self-extinguishing element is converted to a three-phase transformer. In the multiplexed power converter, the power converter group A of the (2−1) -th power stage is connected to the delta connection side of the delta open-star connection three-phase transformer, respectively, and the other two (n) are connected. -1) The power converter group B of the platform is connected to the delta connection side of the delta / open delta connection three-phase transformer, respectively, and the open delta windings of the three-phase transformers of the group B are connected in series in the same phase. The open star windings of the three-phase transformers of the group A are connected in series in the same phase, and one end of each of the series-connected windings of the star windings is connected to the delta connection of the group B. Each connected to a connection point, and outputs power from the other end of the series connection winding of the star winding. The power converters of the groups A and B connected to the input side of the three-phase transformer of the group B are provided with a power converter having voltage phase control means for driving the output voltage of the fundamental wave with a phase difference of 30 degrees. I do. Further, the voltage phase is changed in each group of power converters.

For example, when the number of converters is eight (n = 3), the operation is performed by changing the phases of four units in each group. In this case, the four units in each group are A ₁ , A ₂ , A ₃ , A ₄ and B ₁ , B ₂ ,
Assuming that B ₃ and B ₄ , the operation phase differences between A ₁ and A _{2 and} between A ₃ and A _{4 for the} group A are both φ ₁ . Further A
The operation phase difference between ₁ (A ₂ ) and A ₃ (A ₄ ) is set to φ ₂ . That is, when A ₁ is a reference (0 °), A ₂ is φ ₁ and A ₃ is φ
The _2, A ₄ is operated at φ ₁ + φ _2. The same relation is applied to the group B. In this case, the values of φ ₁ and φ ₂ are converted to the (12 × i ± 1) -order harmonics (i = 12) included in the output voltages of the two converters.
180 ° / (12) so that 1, 2, 3,.
× i ± 1) (i = 1, 2, 3,...).

[0008]

The phase difference between the output voltages of the power converters of groups A and B is 3
By setting it to 0 degree, the fifth, seventh, 17, 19, 29, 31 ...
Can be set to zero. Furthermore, φ ₁ , φ
By selecting the values of ₂ ,..., Φ _n-1 as described above, harmonics are added in opposite phases between the two converters, so that these components can be made theoretically zero by multiplexing. . As described above, the capacity of the device can be increased and harmonics can be reduced by the 2n power converters.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration in the case of multiplexing using eight converters. DC power supply 4 is shared by eight converters 10 to 17
Are connected in parallel. The converters 10 to 13 are connected in series on the open winding side by three-phase transformers 20 to 23 of delta open star connection. The converters 14 to 17 are connected in series on the open winding side by three-phase transformers 24 to 27 having a delta / open delta connection. The former converter group 100 and the latter converter group 200 are further connected in series, and further connected to the load or the power system 3. Hereinafter, the transformer winding on the converter side is referred to as a primary winding, and the winding on the load side or the power system side is referred to as a secondary winding. Outputs of the pulse generation circuits 710 to 717 are input as gate pulses to the converters 10 to 17 via the operation phase difference adding circuits 700 to 707. Operation phase difference adding circuit 70
The phase setting values of 0 to 707 are set to 0 °, φ ₁ , φ ₂ , φ ₁ + φ ₂ ,
_{30 °, 30 ° + φ 1} , 30 ° + φ 2, 30 ° + φ 1 + φ
_{Assume 2} . The operation phase difference adding circuits 700 to 707 can be easily realized using a timer, and may generate a time delay corresponding to each operation phase. Normally, software processing is performed using a microcomputer, so that it can be easily realized without adding a special circuit. FIG. 2 shows a winding configuration of the transformers 20 to 27. All the primary windings are delta-connected to make the third harmonic component zero. Secondary windings are connected in series as shown to obtain three-phase output terminals U, V, and W. Winding group a1-a8, b1-b8, c1-c8 and winding group A1
To A4, B1 to B4, C1 to C4 and winding groups A5 to A
8, the turns ratio of B5 to B8 and C5 to C8 is 1: a: √3a
And converters 10 and 14, 11 and 15, 12 and 16,
13 and 17 are each operated at a phase difference of 30 degrees. In this case, the fifth, seventh, seventeenth, and seventeenth voltages of the transformer secondary side line voltage v _UV are obtained.
9, 29, 31 ... The next component can be made theoretically zero. As described above, the harmonic component included in the transformer secondary-side line voltage v _UV can be made only the (12 × i ± 1) -order component.

Generally, a transformer primary voltage v can be expressed as the following equation as a sum of harmonic components.

[0011]

(Equation 1)

[0012] In this case, the transformer secondary side inter-line voltage v _UV first (12 × i ± 1) because contains only the following harmonic component can be expressed by the following equation.

[0013]

(Equation 2)

In the equation (2), k ₁ and k _{12i ± 1} are voltage reduction coefficients of the respective components, and are shown in the equation (3).

[0015]

(Equation 3)

As shown in FIG. 3, the operation phase difference adding circuit 7
The set values of 00 to 707 are all 0 degrees in the converter group 100,
If the converter group 200 is set at 30 degrees (φ ₁ = φ ₂ = 0 °), an output voltage four times that in the case of one converter in each group can be obtained, and the capacity of the converter can be increased. be able to. In this case, all of the voltage reduction coefficients in equation (3) are “1”. Next, consider the case where the four converters in each group are operated at different phases. As shown in FIG. 1, the converter 10 is referenced (0
°), converter 11 is φ ₁ , converter 12 is φ ₂ , converter 1
3 is operated at φ ₁ + φ ₂ . The same applies to the converter group 200. In this case, the converter 10 and the converter 11
The operating phase difference between converters 12 and 13 is φ ₁ , and the operating phase difference between converters 10 and 11 and converters 12 and 13 is φ
It becomes ₂ . If φ ₁ and φ ₂ are set to 180 ° / (12 × i ± 1), the (12 × i ± 1) generated by two inverters
1) Since the next higher harmonic voltage becomes out of phase and can be canceled by multiplexing, this component can be reduced to zero theoretically. By setting φ ₁ and φ ₂ to different values, the harmonic components of the two orders can be made zero. Usually, in order to reduce the size of the harmonic filter equipment, components are removed from low-order components. Therefore, φ _{2 is set} so that the eleventh and thirteenth components are zero.
= 180 ° / 11 and φ ₁ = 180 ° / 13. In this case, k ₁₁ = k ₁₃ = 0, and the 11th and 13th order components can be made zero. FIG. 4 shows the relationship between the selection of φ ₁ and φ ₂ and the voltage reduction coefficient k _{12i ± 1} .

In the above embodiment, φ ₁ = 180 ° / 13,
Although φ ₂ = 180 ° / 11 (case 1 in FIG. 4), φ ₁ and φ ₂ are selected from FIG. 4 so that i is different. For example, as shown in FIG. 5, φ ₁ = 180 ° / 25, φ ₂ = 1
If 80 ° / 13 (case 5), k ₂₅ and k from FIG.
₁₃ can be made zero, and the voltage reduction coefficients k of other orders
₁₁ and k ₂₃ can also be reduced. Therefore, there is an effect that harmonic components can be reduced as a whole. This is because when i of 12 × i ± 1 is the same and the decryption is different, 180 ° / (12 × i +
1) and the difference between the values of 180 ° / (12 × i−1) is small.
This is because if the (2 × i + 1) -order harmonics are reversed in phase and canceled, the other (12 × i−1) -order harmonics also have a substantially reversed-phase relationship.

In the above embodiment, the operation phase difference is set so as to make the harmonic component of a specific order zero. An embodiment in which the specific order is not made zero will be described below. Harmonic reduction factor is a function of phi ₁ and phi _2, COS as shown in equation (3)
Can be expressed by the product of (nφ _1/2) and COS (nφ _2/2). FIG. 6 shows the relationship between COS (nφ / 2) and φ. (A) n = 11, (b) n = 13, (c) n = 23,
(D) shows the case where n = 25. The horizontal axis is the operation phase difference φ
Thus, two values can be selected. This value is φ ₁ ,
and φ _2. It can be seen that one φ should be set near the region 2 to reduce the 11th and 13th order components, and the other φ should be set near the region 1 to reduce the 23rd and 25th order components. FIG. 7 shows an enlargement in the vicinity of the regions 1 and 2. (A) shows the values of | COS (23φ / 2) | and | COS (25φ / 2) |, and (b) shows the values of | COS (11φ / 2) | and | COS (13φ /
2) Indicates the value of |. To make it zero by focusing only on the eleventh harmonic, _one of φ ₁ and φ ₂ is set to 180 ° / 1
1 (the right end of area 2) and the other 0 °, | COS (11
φ / 2) | = 0, and | COS (13φ / 2) | = 0.28. Therefore, | k ₁₁ | = 0, | k ₁₃ | = 0.28, and the effect of reducing the 13th harmonic component is 28%. Conversely, if one of the values of φ ₁ and φ ₂ is set to 180 ° / 13 (the left end of the area 2) and the other is set to 0 ° in order to make it zero by focusing only on the 13th harmonic, | COS (11φ / 2) | = 0.24, | COS
(13φ / 2) | = 0. Therefore, | k ₁₁ | = 0.24, |
k ₁₃ | = 0, and the effect of reducing the eleventh harmonic component is 24
%. The same can be said for region 1.
φ ₁ . Assuming that one of the values of φ ₂ is 180 ° / 23 (the right end of region 1) and the other is 0 °, | COS (23φ / 2) | = 0, and that the 23rd harmonic can be made zero, but | k ₂₅ | = 0.1
4 and the effect of reducing the 25th harmonic is 14%.
Conversely, if one value is 180 ° / 25 (the left end of region 1) and the other is 0 °, | COS (23φ / 2) | = 0.13, and although the 25th harmonic can be made zero, | k ₂₃ | = 0.13, and the effect of reducing the 23rd harmonic is 13%. In the above-described embodiment, the method of selecting the left and right end values in each region has been described. However, it is better to select a value between the respective regions, but the values of the two functions can be set to zero, although neither can be set to zero. Can be reduced at the same time. For example, assuming that an intermediate value is 180 ° / 24 in region 1, | COS (23φ / 2) | = | COS
(25φ / 2) | = 0.065, which is about の of the value when both ends are selected. Assuming 180 ° / 12 in region 2, | COS (11φ / 2) | = | COS (13φ / 2) |
= 0.13, which is about 1/2 of the value when both ends are selected
Becomes Eventually, the product of the values selected from the two regions will be the harmonic reduction coefficient k _{12i ± 1} , so if the operation phase difference is set to 180 ° / 24 in region ₁ and 180 ° / 12 in region 2 , 11th, 13th, 23rd, and 25th-order components can be reduced as a whole. In this case, the harmonic reduction coefficient of each order is | k ₁₁ | ≒ 0.10, |
k ₁₃ | ≒ 0.09, | k ₂₃ | ≒ 0.07, | k ₂₅ | ≒ 0.07
And the components of any order can be reduced on average.

In the above embodiment, the value of each area is 180
Although a value of ° / (12 × i) is selected, almost the same effect can be obtained by selecting a value exactly in the middle of each region. φ
₁ between 180 ° / 25 and 180 ° / 23, φ ₂
The value may be selected between 80 ° / 13 and 180 ° / 11.

In the above embodiment, n = 3, that is, the case where the number of converters is 8, 16 units (n = 4), 3
When the number increases to two (n = 5), selectable angle φ
Increases to 3 or 4, and the effect of harmonic reduction is further increased accordingly. In the case of 16 units, there are _three selectable angles, φ ₁ , φ ₂ , φ ₃ ,
The operation phase of each converter is as shown in FIG.

Further, if the pulse width (PWM) control is used together, the harmonic voltage V _{12i ± 1} itself generated by one converter in the equation (2) can be reduced, so that the harmonics can be further reduced. it can.

In the above embodiment, the configuration on the inverter side is multiplexed to reduce the harmonic voltage on the load side or the power system side, but the forward converter side has the same configuration as in FIG. It can be applied to a circuit configuration. The forward converter is connected to the power system 6 and connected to the inverter via the capacitors 4 and 5 in the DC section. In the present embodiment, the harmonics on the power system 6 side can also be reduced, so that there is an effect that harmonic interference with respect to devices connected to the same power system can be reduced.

[0023]

According to the present invention, by multiplexing using a transformer, the capacity of the power converter can be increased to 2 @ n times the capacity of a single unit, and the harmonic component contained in the output voltage can be increased. Therefore, there is an effect that harmonic interference given to other devices can be reduced accordingly. Also,
This also has the effect of reducing the installed capacity of a filter for removing generated harmonics.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a transformer winding according to an embodiment of the present invention.

FIG. 3 is a diagram showing voltage waveforms for explaining the operation of the present invention.

FIG. 4 is a diagram showing a relationship between an operation phase difference and a voltage reduction coefficient.

FIG. 5 is a diagram showing voltage waveforms for explaining the operation of the present invention.

FIG. 6 is a diagram illustrating a relationship between an operation phase difference and a voltage reduction coefficient for each order.

FIG. 7 is an enlarged view showing a relationship between an operation phase difference and a voltage reduction coefficient for each order.

FIG. 8 is a main circuit configuration diagram showing another embodiment of the present invention.

FIG. 9 is a main circuit configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

3 ... load or power _{system, φ 1, φ 2, φ} 3, ..., φ n-1
... Phase difference, k ₁ ... Basic wave reduction coefficient, k _{12i ± 1} ...
× i ± 1) Reduction coefficient of higher harmonic component, 700 to 707: operation phase difference adding circuit, a: transformer turns ratio, 710 to 717
... Pulse generation circuit.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akiteru Ueda 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-63-7167 (JP, A) JP-A-3-3 215171 (JP, A) JP-A-2-101968 (JP, A) JP-A-6-276747 (JP, A) Japanese Utility Model Laid-Open No. 49-125226 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M ⁷ /42-7/98

Claims (7)

(57) [Claims] 1. A three-phase power converter using a self-turn-off device, multiplexes the outputs of the power of 2.sup.n (n.gtoreq.2, an integer) using a three-phase transformer, and multiplexes the outputs of two (n-1). The power converter group A of the platform is connected to the delta connection side of the delta-open star connection three-phase transformer, respectively, and the power converter group B of the other 2 (n-1) platform is delta-open delta connection. The three-phase transformers are respectively connected to the delta connection side, and the open delta windings of the three-phase transformers of the B group are connected in series in the same phase to form a delta connection, and the three-phase transformers of the A group are opened. The star windings are connected in series in the same phase, one end of each of the series connected windings of the star winding is connected to each of the delta-connected connection points of the group B, and In a power converter that outputs power from the other end, an output voltage phase control unit of a fundamental wave of each power converter is connected to each converter. A power converter, comprising: 2. The voltage phase control means for a power converter according to claim 1, wherein an output of any one of the power converters of the group A is output.
The power voltage phase as a reference, the reference and each of the remaining power converters
And the mutually different shall the phase difference between the output voltage, the output voltage phase of each power converter of the B group, each of said group A
A power converter, wherein a phase difference of 30 degrees is provided for each output voltage phase of the power converter. 3. The voltage phase of any one of the power converters of each group is based on the voltage phase of any one of the power converters, and the voltage phase of the remaining power converters is 180 ° / (12 × i ± 1). ) (I
= 1, 2,..., N−1). 4. The method according to claim 3, wherein the voltage phase of the remaining power converter is 180 ° / (12 × i ± 1) (i = 1, 2, 2).
.., N−1), wherein only one of the ± signs in each of i is selected over i. 5. The method according to claim 1, wherein the voltage phase of any one of the power converters in each group is set as a reference, and the voltage phases of the remaining power converters are i (= 1, 2, 2, 3). .., N−1) from 180 ° / (12 × i + 1) to 180 ° / (12
Xi-1), and n-1 types of angles having values selected from the middle of xi-1) and their sums are obtained (2
(N-1) -th power converter, wherein voltage phase control means for setting based on (n) kinds of angles are provided for each of the 2n-th three-phase power converters. 6. The method according to claim 1, wherein the voltage phase of any one of the power converters of each group is set as a reference, and the voltage phases of the remaining power converters are each i (= 1, 2, 2). ..., n-1)
180 ° × ｛1 / (12 × i + 1) + 1 / (1
The phase of the voltage phase control means is set based on (n-1) kinds of angles of 2 × i-1)｝ / 2 and (2 (n-1) th power-n) kinds of angles formed by combining these angles. A power conversion device characterized in that: 7. The method according to claim 1, wherein the voltage phase of any one of the power converters in each group is set as a reference, and the voltage phases of the remaining power converters are i (= 1, 2, 2, 3). ..., n-1)
(N-1) types of angles of 180 ° / (12 × i) and combinations of these (2 (n−
1) The power conversion apparatus, wherein the phase of the voltage phase control means is set based on the power-n) types of angles.