JP6807632B2 - Power converter - Google Patents

Description

Embodiments of the present invention relate to a power converter.

There is a power conversion device that performs AC / DC conversion using a plurality of semiconductor elements. In such a power conversion device, a plurality of semiconductor elements may be connected in parallel for the purpose of increasing the capacity or the like. When a plurality of semiconductor elements are connected in parallel, the wiring length of each wiring is substantially made uniform in order to make the wiring inductance of the wiring connected to each semiconductor element uniform (for example, Patent Document). 1).

However, when a plurality of phases are arranged side by side, even if the wiring inductance is made uniform, the influence of the mutual inductance becomes non-uniform, and as a result, the current flowing through each semiconductor element may be unbalanced. was there. Therefore, in the power conversion device, it is desired to be able to further reduce the imbalance of the current flowing through each semiconductor element.

Japanese Unexamined Patent Publication No. 2006-203974

An embodiment of the present invention provides a power conversion device capable of further reducing the imbalance of currents flowing through a plurality of semiconductor elements.

According to an embodiment of the present invention, a power conversion device including a conversion unit and a wiring unit is provided. The conversion unit has a plurality of semiconductor elements, and the plurality of semiconductor elements perform AC / DC conversion. The wiring unit connects the AC sides of the plurality of semiconductor elements in parallel. The plurality of semiconductor elements are arranged side by side in a predetermined direction. The wiring portion includes a first conductor portion that connects a part of the plurality of semiconductor elements in parallel, and the first conductor portion and the wiring portion arranged side by side in the predetermined direction, and another part of the plurality of semiconductor elements. It has a second conductor portion connected in parallel. The direction of the current flowing through the second conductor portion is opposite to the direction of the current flowing through the first conductor portion. As the first conductor portion is separated from the second conductor portion, the wiring length of the plurality of semiconductor elements with respect to the part thereof is shortened. As the second conductor portion is separated from the first conductor portion, the wiring length of the plurality of semiconductor elements with respect to the other part is shortened.

A power conversion device capable of further reducing the imbalance of currents flowing through a plurality of semiconductor elements is provided.

It is a block diagram which shows typically the power conversion apparatus which concerns on embodiment. It is a top view which shows an example of the wiring part which concerns on embodiment. It is a top view which shows typically the reference conductive part. It is a graph which shows an example of the characteristic of a reference conductive part. It is a graph which shows an example of the characteristic of the conductive part which concerns on embodiment. It is a graph which shows an example of the characteristic of a conductive part. It is a graph which shows an example of the characteristic of a conductive part. It is a top view which shows the modification of the wiring part which concerns on embodiment schematically. It is a top view which shows typically the modification of the 1st conductive part which concerns on embodiment.

Hereinafter, each embodiment will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between the parts, and the like are not necessarily the same as the actual ones. Further, even when the same parts are represented, the dimensions and ratios may be different from each other depending on the drawings.
In addition, in the present specification and each figure, the same elements as those described above with respect to the above-mentioned figures are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

FIG. 1 is a block diagram schematically showing a power conversion device according to an embodiment.
As shown in FIG. 1, the power conversion device 10 includes a conversion unit 12 and a wiring unit 14. The conversion unit 12 includes a first circuit unit 21 and a second circuit unit 22. The first circuit unit 21 has a plurality of semiconductor modules 21a to 21d. The second circuit unit 22 has a plurality of semiconductor modules 22a to 22d.

The semiconductor module 21a includes switching elements 31 and 32 (semiconductor elements) and rectifying elements 33 and 34 (semiconductor elements). The switching element 32 is connected in series with the switching element 31. For the switching elements 31 and 32, for example, a power semiconductor such as an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET is used. The rectifying element 33 is connected in antiparallel to the switching element 31. The rectifying element 34 is connected in antiparallel to the switching element 32. The rectifying elements 33 and 34 are so-called freewheeling diodes.

The configurations of the semiconductor modules 21b to 21d and 22a to 22d are substantially the same as the configurations of the semiconductor modules 21a. Therefore, detailed description of these will be omitted.

The conversion unit 12 has a plurality of semiconductor elements such as switching elements 31, 32, rectifying elements 33, and 34, and performs AC / DC conversion by these plurality of semiconductor elements. In this example, the conversion unit 12 is a single-phase full bridge circuit that converts DC power into AC power.

The power conversion device 10 further includes, for example, a pair of DC side wirings 16a and 16b that are electrically connected to the DC power supply 2. The DC side wiring 16a is electrically connected to the high potential terminal of the DC power supply 2. The DC side wiring 16b is electrically connected to the low potential terminal of the DC power supply 2. The DC side wirings 16a and 16b are, for example, parallel flat plate-shaped laminated bus bars.

The conversion unit 12 is electrically connected to the DC power supply 2 via the DC side wirings 16a and 16b, and is also electrically connected to the AC load 4 via the wiring unit 14. The conversion unit 12 converts the DC power supplied from the DC power supply 2 into AC power, and supplies the converted AC power to the AC load 4.

The AC / DC conversion by the conversion unit 12 is not limited to the conversion from DC power to AC power, but may be conversion from AC power to DC power or conversion from AC power to AC power. The conversion unit 12 may be, for example, a diode bridge circuit that converts AC power into DC power. The plurality of semiconductor elements provided in the conversion unit 12 are not limited to switching elements, but may be rectifying elements. The conversion unit 12 may be a circuit capable of bidirectional conversion between conversion from DC power to AC power and conversion from AC power to DC power. The circuit configuration of the conversion unit 12 may be any circuit configuration capable of converting DC power to AC power and converting AC power to DC power. The AC power may be single-phase AC or three-phase AC. The conversion unit 12 may be a three-phase full bridge circuit or the like. Hereinafter, in the present specification, a single-phase full bridge circuit will be described as an example.

In each of the semiconductor modules 21a to 21d and 22a to 22d, one main terminal (for example, a collector) of the switching element 31 is electrically connected to the DC side wiring 16a on the high potential side. The other main terminal (for example, an emitter) of the switching element 31 is electrically connected to one main terminal of the switching element 32. The other main terminal of the switching element 32 is electrically connected to the DC side wiring 16b on the low potential side.

In this example, the switching element 31 and the rectifying element 33 are semiconductor elements of the upper arm, and the switching element 32 and the rectifying element 34 are semiconductor elements of the lower arm. Then, in this example, the connection point between the switching element 31 and the switching element 32 is the AC output point of the conversion unit 12.

Each semiconductor module 21a to 21d and 22a to 22d has, for example, a pair of DC terminals 35a and 35b and an AC terminal 36. The DC terminal 35a is connected to one main terminal of the switching element 31. The switching element 31 is connected to the DC side wiring 16a via the DC terminal 35a. The DC terminal 35b is connected to the other main terminal of the switching element 32. The switching element 32 is connected to the DC side wiring 16a via the DC terminal 35b. The AC terminal 36 is connected to a connection point between the switching element 31 and the switching element 32.

The wiring portion 14 has a first conductive portion 41 and a second conductive portion 42. The first conductive portion 41 is connected to the connection points (AC terminals 36) of the switching elements 31 and 32 of the first circuit portion 21. The first conductive section 41 connects the switching elements 31 and 32 of the first circuit section 21 in parallel. The second conductive portion 42 is connected to the connection points (AC terminals 36) of the switching elements 31 and 32 of the second circuit portion 22. The second conductive section 42 connects the switching elements 31 and 32 of the second circuit section 22 in parallel.

In this way, the first conductive portion 41 connects a part of the plurality of semiconductor elements in parallel, and the second conductive portion 42 connects another part of the plurality of semiconductor elements in parallel. The wiring unit 14 connects the AC sides of the switching elements 31 and 32, which are a plurality of semiconductor elements, in parallel.

In this example, the first conductive portion 41 connects four switching elements 31 and 32 (four semiconductor modules 21a to 21d) in parallel. The second conductive portion 42 connects four switching elements 31 and 32 (four semiconductor modules 22a to 22d) in parallel. The number of semiconductor elements connected in parallel between the first conductive portion 41 and the second conductive portion 42 is not limited to four, and may be two, three, or five or more.

The first conductive portion 41 is electrically connected to one end of the AC load 4. The second conductive portion 42 is electrically connected to the other end of the AC load 4. The first conductive portion 41 is electrically connected to one end of the AC load 4 via, for example, the external wiring 6a. The second conductive portion 42 is electrically connected to the other end of the AC load 4 via, for example, the external wiring 6b. The external wirings 6a and 6b are, for example, parallel flat plate-shaped laminated bus bars. When the conversion unit 12 converts AC to DC, the first conductive unit 41 and the second conductive unit 42 are electrically connected to the AC power supply via the external wirings 6a and 6b.

The first circuit unit 21 corresponds to one leg (phase) of the full bridge circuit. The second circuit unit 22 corresponds to another leg of the full bridge circuit. The conversion unit 12 connects a plurality of switching elements 31 and 32 in parallel in each leg. Thereby, for example, it is possible to cope with the increase in the capacity of the conversion unit 12 while suppressing the withstand voltage of one switching element 31 and 32. For example, it is possible to increase the capacity of the conversion unit 12 while suppressing the increase in size of the conversion unit 12. The circuit configuration of the conversion unit 12 may be any circuit configuration capable of performing AC / DC conversion in a state where the AC sides of a plurality of semiconductor elements are connected in parallel.

FIG. 2 is a plan view schematically showing an example of the wiring portion according to the embodiment.
As shown in FIG. 2, the semiconductor modules 21a to 21d and 22a to 22d are arranged side by side in a predetermined direction. That is, the switching elements 31, 32 and the rectifying elements 33, 34 are arranged side by side in a predetermined direction. The semiconductor modules 21a to 21d and 22a to 22d are arranged side by side on the heat sink, for example, at predetermined intervals.

The second conductive portion 42 is arranged side by side with the first conductive portion 41 in a predetermined direction in which the semiconductor modules 21a to 21d and 22a to 22d are lined up. In this case, the direction of the current flowing through the second conductive portion 42 is opposite to the direction of the current flowing through the first conductive portion 41.

The first conductive portion 41 has a plate shape that continuously connects the AC terminals 36 of the semiconductor modules 21a to 21d. The second conductive portion 42 has a plate shape that continuously connects the AC terminals 36 of the semiconductor modules 22a to 22d. The first conductive portion 41 and the second conductive portion 42 are so-called bus bars.

The wiring length of the first conductive portion 41 with respect to the switching elements 31 and 32 becomes shorter as the distance from the second conductive portion 42 increases. Here, the wiring length is, for example, the length from the AC terminal 36 to the connection end with the external wiring 6a. In this example, the wiring length IL14 for the semiconductor module 21d closest to the second conductive portion 42 is the longest, the wiring length IL13 for the semiconductor module 21c, the wiring length IL12 for the semiconductor module 21b, and the wiring length IL11 for the semiconductor module 21a gradually. The first conductive portion 41 is formed so as to be shortened.

The wiring length of the second conductive portion 42 with respect to the switching elements 31 and 32 becomes shorter as the distance from the first conductive portion 41 increases. In this example, the wiring length IL21 for the semiconductor module 22a closest to the first conductive portion 41 is the longest, the wiring length IL22 for the semiconductor module 22b, the wiring length IL23 for the semiconductor module 22c, and the wiring length IL24 for the semiconductor module 22d gradually. The second conductive portion 42 is formed so as to be shortened.

When the direction of the current flowing through the second conductive portion 42 is opposite to the direction of the current flowing through the first conductive portion 41, the mutual inductances act so as to cancel each other out. The effect of mutual inductance increases as the distance increases. Therefore, the first conductive portion 41 is made to have a shorter wiring length with respect to the switching elements 31 and 32 as it is separated from the second conductive portion 42, and the second conductive portion 42 is separated from the first conductive portion 41. The wiring length for the switching elements 31 and 32 is shortened. That is, in the portion where the influence of the mutual inductance is large, the wiring length is lengthened to increase the wiring inductance, and in the portion where the influence of the mutual inductance is small, the wiring length is shortened to reduce the wiring inductance. Thereby, the imbalance of the inductance with respect to each of the switching elements 31 and 32 can be suppressed.

As described above, in the power conversion device 10 according to the present embodiment, the wiring unit 14 responds to the influence of the mutual inductance caused by the currents flowing through the switching elements 31 and 32, respectively. The wiring length with respect to 32 is different. As a result, the imbalance of inductance with respect to the switching elements 31 and 32 can be further suppressed as compared with the case where the wiring length is made uniform. The imbalance of the current flowing through the switching elements 31 and 32 can be further reduced, and the specifications of the switching elements 31 and 32 can be fully utilized. As described above, according to the present embodiment, the power conversion device 10 capable of further reducing the imbalance of the currents flowing through the plurality of semiconductor elements is provided.

By appropriately setting the spacing PT in which the semiconductor modules 21a to 21d and 22a to 22d (plurality of semiconductor elements) are lined up, when the semiconductor modules 21a to 21d and 22a to 22d are connected in parallel and a current is passed, The influence of the mutual inductance caused by the current flowing through each of the semiconductor modules 21a to 21d and 22a to 22d becomes large. In such a case, as described above, the wiring portions 14 having different wiring lengths are adopted. As a result, the imbalance of the current flowing through each element can be reduced while the semiconductor modules 21a to 21d and 22a to 22d are arranged at high density. The specifications of each element can be fully utilized while suppressing the increase in size of the power conversion device 10. The spacing PT in which the semiconductor modules 21a to 21d and 22a to 22d (plurality of semiconductor elements) are lined up may be constant or different.

The influence of the mutual inductance caused by the current flowing through the switching elements 31 and 32 can be analyzed by, for example, an analysis system using the finite element method. The shapes of the first conductive portion 41 and the second conductive portion 42 may be determined based on these analysis results. In other words, each wiring length IL11 to IL14 and IL21 to IL24 may be determined based on the analysis result of the analysis using the finite element method or the like.

FIG. 3 is a plan view schematically showing a reference conductive portion.
As shown in FIG. 3, in the reference conductive portions BS1 and BS2, the wiring lengths IL31 to IL34 and IL41 to IL44 are made substantially uniform. The inventors of the present application examined the characteristics of the conductive portions 41 and 42 and the reference conductive portions BS1 and BS2 according to the present embodiment, respectively.

FIG. 4 is a graph showing an example of the characteristics of the reference conductive portion.
FIG. 5 is a graph showing an example of the characteristics of the conductive portion according to the embodiment.
FIG. 4 shows an example of the analysis result of the current imbalance when a current is passed through the reference conductive portion BS1. FIG. 5 shows an example of the analysis result of the current imbalance when a current is passed through the first conductive portion 41 according to the embodiment. The current imbalance is evaluated as a relative value to the average value. The horizontal axes of FIGS. 4 and 5 represent the semiconductor modules 21a to 21d, and the vertical axis represents the imbalance of the current flowing through the semiconductor modules 21a to 21d. The analysis was performed using the finite element method analysis system "Femtet (registered trademark)".

As shown in FIG. 4, in the reference conductive portion BS1, as the frequency of the flowing current increases, the ratio of the current flowing through the semiconductor module 21d close to the conductive portion BS2 tends to increase.

On the other hand, as shown in FIG. 5, it can be seen that in the first conductive portion 41, the ratio of the current flowing through the semiconductor module 21d is suppressed as compared with the conductive portion BS1 even when the frequency of the current becomes high. ..

The maximum value of the current imbalance in the conductive portion BS1 is about + 46% of that of the semiconductor module 21d at 50,000 Hz. On the other hand, the maximum value of the current imbalance in the first conductive portion 41 is about + 23% of that of the semiconductor module 21a at 5000 Hz. As described above, in the first conductive portion 41, the maximum value of the current imbalance is reduced as compared with the conductive portion BS1.

FIG. 6 is a graph showing an example of the characteristics of the conductive portion.
FIG. 6 shows an example of the frequency characteristics of the impedance of the first conductive portion 41 and the conductive portion BS1. The horizontal axis of FIG. 6 is frequency, and the vertical axis is impedance. The frequency characteristics were obtained by analysis by the above finite element method analysis system. At this time, since it is only necessary to confirm which of the real part and the imaginary part of the impedance of each path is dominant, the impedance of the total of 4 parallels was analyzed.

In FIG. 6, the characteristic CTR1 represents the frequency characteristic of the actual portion of the impedance of the first conductive portion 41. The characteristic CTI1 represents the frequency characteristic of the imaginary portion of the impedance of the first conductive portion 41. The characteristic CTR2 represents the frequency characteristic of the actual portion of the impedance of the conductive portion BS1. The characteristic CTI2 represents the frequency characteristic of the imaginary portion of the impedance of the conductive portion BS2.

As shown in FIG. 6, in the low frequency region, the real part (resistance component) of the impedance is larger than the imaginary part, or the real part and the imaginary part are about the same. Therefore, the difference in impedance can be reduced by making the lengths of the paths equal. On the other hand, in the high frequency region, the imaginary part of impedance (inductance component) becomes dominant. Therefore, like the first conductive portion 41, the conductor shape is made in consideration of mutual inductance rather than the path length of the current. This makes it possible to suppress the imbalance of the currents flowing through the plurality of semiconductor elements.

FIG. 7 is a graph showing an example of the characteristics of the conductive portion.
FIG. 7 shows the results of testing by connecting in parallel using copper conductors having the same shape as each of the first conductive portion 41 and the conductive portion BS1. The horizontal axis of FIG. 7 represents the semiconductor modules 21a to 21d, and the vertical axis represents the imbalance of the current flowing through the semiconductor modules 21a to 21d.

Further, in FIG. 7, the characteristic DC1 is a result when a direct current is passed through the first conductive portion 41. The characteristic AC1 is a result when a step-like voltage is applied to the first conductive portion 41 and an alternating current is passed through the first conductive portion 41. The characteristic DC2 is the result when a direct current is passed through the conductive portion BS1. The characteristic AC2 is the result when a step-like voltage is applied to the conductive portion BS1 and a transient current is applied.

As shown in FIG. 7, when a direct current is applied, the current flows substantially evenly in the semiconductor modules 21a to 21d regardless of which of the first conductive portion 41 and the conductive portion BS1 is used.

On the other hand, it was confirmed that when an alternating current was applied, the current flowing on the semiconductor module 21d side increased. At this time, the current imbalance of the first conductive portion 41 is approximately −8.2% to + 17%. The current imbalance of the conductive portion BS1 is approximately -16% to + 26%. As described above, it was also confirmed that the balance of the current changes due to the influence of the inductance component, and the imbalance of the first conductive portion 41 becomes smaller than that of the conductive portion BS1. From these results, it can be seen that the current imbalance can be reduced by designing the wiring portion 14 of the parallel connection into an appropriate shape.

FIG. 8 is a plan view schematically showing a modified example of the wiring portion according to the embodiment.
As shown in FIG. 8, in this example, the first conductive portion 41 has a plurality of wirings 41a to 41d corresponding to each of the plurality of semiconductor modules 21a to 21d, and the second conductive portion 42 has a plurality of wires. It has a plurality of wirings 42a to 42d corresponding to each of the semiconductor modules 22a to 22d.

The wirings 41a to 41d connect the semiconductor modules 21a to 21d (a part of a plurality of semiconductor elements) in parallel by connecting the AC terminals 36 of the semiconductor modules 21a to 21d to the external wiring 6a. The wirings 42a to 42d connect the semiconductor modules 22a to 22d (another part of the plurality of semiconductor elements) in parallel by connecting the AC terminals 36 of the semiconductor modules 22a to 22d to the external wiring 6b.

As described above, the first conductive portion 41 and the second conductive portion 42 may be composed of one plate-shaped member, or may be composed of a plurality of wirings 41a to 41d and 42a to 42d. Thereby, the imbalance of the current flowing through each semiconductor element can be reduced as in the above embodiment.

FIG. 9 is a plan view schematically showing a modified example of the first conductive portion according to the embodiment.
As shown in FIG. 9, in this example, in the first conductive portion 41 of the wiring portion 14, the wiring lengths IL12 and IL13 with respect to the semiconductor modules 22b and 22c arranged in the central portion in the predetermined direction are in the predetermined direction. The wiring lengths for the semiconductor modules 22a and 22d arranged at both ends are made shorter than the wiring lengths IL11 and IL14.

For example, when the distance between the first conductive portion 41 and the second conductive portion 42 is sufficiently large and the influence of the mutual inductance between the first conductive portion 41 and the second conductive portion 42 is small, the influence of the mutual inductance is small. The influence of the mutual inductance between the semiconductor modules 21a to 21d connected to the first conductive portion 41 becomes large. In this case, since the currents flow in the same direction, the mutual inductances act to strengthen the inductances. Since the central portion is affected by the semiconductor elements on both sides, the influence of the mutual inductance is greater than that of both ends affected by only one side. Therefore, as described above, the wiring lengths IL12 and IL13 in the central portion are made shorter than the wiring lengths IL11 and IL14 in both ends. Thereby, as in the above embodiment, the imbalance of the current flowing through the plurality of semiconductor elements can be suppressed.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

2 ... DC power supply, 4 ... AC load, 6a, 6b ... External wiring, 10 ... Power converter, 12 ... Conversion unit, 14 ... Wiring unit, 16a, 16b ... DC side wiring, 21 ... 1st circuit unit, 21a ~ 21d, 22a to 22d ... semiconductor module, 22 ... second circuit unit, 31, 32 ... switching element (semiconductor element), 33, 34 ... rectifying element (semiconductor element), 35a, 35b ... DC terminal, 36 ... AC terminal, 41 ... 1st conductive part, 42 ... 2nd conductive part, BS1, BS2 ... Conductive part

Claims (2)

A conversion unit having a plurality of semiconductor elements and performing AC / DC conversion by the plurality of semiconductor elements,
A wiring unit that connects the AC sides of the plurality of semiconductor elements in parallel,
With
The plurality of semiconductor elements are arranged side by side in a predetermined direction, and the plurality of semiconductor elements are arranged side by side.
The wiring part is
A first conductor portion that connects a part of the plurality of semiconductor elements in parallel, and
A second conductor portion that is arranged side by side in the predetermined direction with the first conductor portion and connects another part of the plurality of semiconductor elements in parallel.
Have,
The direction of the current flowing through the second conductor portion is opposite to the direction of the current flowing through the first conductor portion.
As the first conductor portion is separated from the second conductor portion, the wiring length of the plurality of semiconductor elements with respect to the part thereof is shortened.
The second conductor portion is a power conversion device that shortens the wiring length of the plurality of semiconductor elements with respect to the other portion as the distance from the first conductor portion increases. The conversion unit is a bridge circuit.
The plurality of semiconductor elements include a semiconductor element for the upper arm and a semiconductor element for the lower arm.
The power conversion device according to claim 1 , wherein the wiring portion is connected to a connection point between the semiconductor element for the upper arm and the semiconductor element for the lower arm.

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