JP2012110099A - Main circuit structure for power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To laterally lengthen a stack constituting a power converter, to increase the capacity of electrolytic capacitors, to unbalance a generation loss between parallel-connected power semiconductor modules, and to reduce a surge voltage at the time of turning off.SOLUTION: By devising an arrangement of electrolytic capacitors 1-6 constituting a DC circuit part and power semiconductor modules 11-16 constituting a power conversion part as shown in a figure, the wiring inductance between the electrolytic capacitors 1, 2, and 3 and the power semiconductor modules 11, 13, and 15 and the wiring inductance between the electrolytic capacitors 4, 5, and 6 and the power semiconductor modules 12, 14, and 16, for example, are controlled to be substantially the same as each other.

Description

  The present invention relates to a power converter that converts direct current to alternating current or from alternating current to direct current, and more particularly to an arrangement structure of a large-capacity capacitor in a direct current section and a power semiconductor module in the power conversion section.

FIG. 5 shows a circuit example of an inverter as a general example of this type.
Reference numerals 1 to 6 denote capacitors provided in the DC circuit unit, where the positive side potential is Pc and the negative side potential is Nc, which is a smoothed voltage without DC fluctuation during normal operation. In general, when the direct current circuit unit is composed of an alternating current power source, it can be formed via a diode rectifier circuit (not shown). Here, an example of six parallel connections is shown for increasing the capacity, and electrolytic capacitors are often used for the capacitors 1 to 6.

  Reference numerals 7 and 8 denote IGBTs and diodes connected to the positive potential Pc, and reference numerals 9 and 10 denote IGBTs and diodes connected to the negative potential Nc. By using the stand, a DC-AC conversion circuit for three phases can be configured. In FIG. 5, since one phase has two parallel configurations for increasing the capacity, the power semiconductor modules are composed of six units 11, 12, 13, 14, 15 and 16. Reference numeral 17 denotes a three-phase AC load, typically a motor (AC motor).

FIG. 6 shows a circuit (only one phase is shown) in which power semiconductor modules are configured in parallel for one phase in order to further increase the capacity compared to FIG.
In FIG. 7, the external appearance example of a power semiconductor module is shown. A C1 terminal 18 connected to the Pc potential, an E2 terminal 19 connected to the Nc potential, a U terminal (AC output terminal) 20 connected to the AC output, and the like are illustrated.

Examples of installation of six electrolytic capacitors and six power semiconductor modules are shown as top views in FIGS.
FIG. 8 shows an example in which six electrolytic capacitors and power semiconductor modules are arranged in a horizontal row, and FIG. 9 shows six electrolytic capacitors and power semiconductor modules in a 2 × 3 arrangement in the vertical and horizontal directions. An example of arrangement in the direction is shown.

Moreover, the side view corresponding to FIG. 8, FIG. 9 is shown to FIG. 10, FIG.
Reference numerals 21 and 22 denote power semiconductor module cooling radiators, reference numerals 23 and 24 denote negative-side potential Nc wiring conductors, and reference numerals 25 and 26 denote positive-side potential Pc wiring conductors, respectively.
The installation or arrangement of such an electrolytic capacitor and a power semiconductor module is disclosed in, for example, Patent Document 1 and the like.

JP 2006-042406 A

  FIG. 12 (a) shows an example in which the configuration of FIG. 8 is connected in parallel for 6 phases per phase of the power semiconductor module and configured for 3 phases. As shown in the figure, 18 power semiconductor modules are arranged in a horizontal row, so that they become extremely long in the horizontal direction, and there is a problem that if the stack is accommodated in the board, the board itself becomes very large. In the configuration of FIG. 8, if the three phases are not installed in a row but are installed in the board separately for each phase, the board itself can be accommodated without increasing the size. Since an alternating current for each phase flows, there arises a problem that the capacity of the electrolytic capacitor is increased as compared with the three-phase batch method as shown in FIG.

  On the other hand, in the configuration of FIG. 9, it is possible to avoid the stack from spreading laterally even in the case of a three-phase package as shown in FIG. 12B, but an equivalent circuit taking into account the wiring inductance as shown in FIG. As shown in the figure, the power semiconductor modules 11, 13, and 15 on the side closer to the electrolytic capacitor and the terminals 12, 14, and 16 on the far side have a difference in physical distance from the electrolytic capacitor. A difference (L1 and L1 + L2) occurs in the wiring inductance value. In the configuration of FIG. 8, the wiring inductance value is almost equal L1 among all power semiconductor modules. An equivalent circuit diagram in this case is shown in FIG.

FIG. 16 shows a waveform example when the IGBT is turned on for each of the power semiconductor modules connected in parallel when there is a difference in the wiring inductance value. It is assumed that the power semiconductor module in this case has a two-parallel configuration as shown in FIG.
In general, the change rate di / dt of the collector current when the IGBT is turned on depends on the wiring inductance value between the power semiconductor module and the electrolytic capacitor. That is, the power semiconductor module having the larger wiring inductance value (L1 + L2) has a smaller di / dt (Ic2 side in FIG. 17), and the power semiconductor module having the smaller wiring inductance value (L1) has a larger di / dt. (Ic1 side in FIG. 17).

As a result, the current waveforms are particularly different as shown in FIG. 16, and there is a large difference in turn-on loss (Eon = ∫Vce · Ictt). Further, since there is a distance between the power semiconductor module far from the electrolytic capacitor and the electrolytic capacitor, the absolute value (L1 + L2) of the wiring inductance value also increases, and the surge voltage at turn-off also increases.
On the other hand, in the configuration of FIG. 8, the wiring inductance values are almost equal between the power semiconductor modules connected in parallel, and the value is small (L1), so the waveform at turn-on is as shown in FIG. The turn-on loss is substantially equal, and the surge voltage at turn-off is prevented from being increased.

From the above, when implementing the radiator design and IGBT junction temperature design with the configuration of FIG. 9, it is necessary to implement on the basis of the power semiconductor module on the side where the generated loss and surge voltage increase, so as a whole When viewed, a high heat dissipation capability and a low thermal resistance are required, which contributes to an increase in size and cost of the device.
Accordingly, an object of the present invention is to devise the arrangement of the electrolytic capacitor and the power semiconductor module, thereby making the stack longer, increasing the capacity of the electrolytic capacitor, and imbalance of the generated loss between the power semiconductor modules connected in parallel. The aim is to reduce the surge voltage during turn-off and turn-off.

In order to solve such a problem, according to the first aspect of the present invention, a plurality of capacitors are connected in parallel to the DC circuit section for increasing the capacity, and a power semiconductor element is connected to the power conversion section for increasing the capacity. In a power converter that connects multiple modules in parallel and converts DC to AC or AC to DC,
A plurality of capacitors connected in parallel are divided and arranged opposite to each other, and at least two of the power semiconductor element modules are arranged opposite to each other between the opposed capacitors, and wiring between the capacitors and the power semiconductor modules is performed. It is characterized by that.

  In the first aspect of the invention, the capacitor and the power semiconductor module can be arranged so as to be line symmetric with respect to the power semiconductor modules connected in parallel as the axis of symmetry (invention of claim 2). In the invention of claim 2, the power semiconductor module can be arranged so that the AC output terminal side is closest to the line symmetry axis (invention of claim 3).

  According to the present invention, in a power conversion system for increasing the capacity by connecting a plurality of capacitors and power semiconductor modules in a direct current section in parallel, the power semiconductor module is configured to have a longer stack, a larger electrolytic capacitor, and a parallel connection. It is possible to prevent unbalance of generated loss and increase of turn-off surge voltage. As a result, a small and inexpensive power conversion system can be constructed. In addition, although the case where the power semiconductor module is 2 parallel and 6 parallel was demonstrated, of course, the same effect is acquired even if it is 4 parallel and 8 parallel.

The block diagram which shows embodiment of this invention. FIG. 2 is an equivalent circuit diagram corresponding to FIG. 1. The top view which shows another embodiment of this invention. The top view which shows another embodiment of this invention. The circuit diagram which shows an example of a general inverter main circuit. The circuit diagram which shows another example of a general inverter main circuit. The external view which shows an example of a general power semiconductor module. The top view which shows the example of arrangement | positioning of a power semiconductor module and an electrolytic capacitor. The top view which shows another example of arrangement | positioning of a power semiconductor module and an electrolytic capacitor. The side view of FIG. The side view of FIG. FIG. 10 is a top view showing the difference between FIG. 8 and FIG. 9 and FIG. The main circuit equivalent diagram in the case of FIG. FIG. 10 is a main circuit equivalent diagram in the case of FIG. 9. FIG. 9 is a turn-on waveform diagram in the case of FIG. 8. FIG. 10 is a turn-on waveform diagram in the case of FIG. 9. The equivalent circuit diagram in the case of FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.
As shown in the figure, the electrolytic capacitors 1, 2, 3 and the electrolytic capacitors 4, 5, 6 are arranged to face each other, and the power semiconductor modules 11 to 16 are arranged to face each electrolytic capacitor. When six power semiconductor modules are arranged in parallel, the power semiconductor modules 11 to 16 are all connected in parallel as shown in FIG. When two parallel circuits are used, the power semiconductor modules 11 and 12, 13 and 14, 15 and 16 are connected in parallel as shown in FIG. Configure. In either case, they are symmetrically arranged with the symmetry axis indicated by X in FIG.

  In the configuration of FIG. 1, the wiring inductances 27 and 28 between the electrolytic capacitors 1, 2, 3 and the power semiconductor modules 11, 13, 15 and between the electrolytic capacitors 4, 5, 6 and the power semiconductor modules 12, 14, 16 are substantially equal. Since (L1), the turn-on waveform of each IGBT is substantially equal in all power semiconductor modules as shown in FIG. Further, the distance between the electrolytic capacitor and the power semiconductor module is almost the same for all the power semiconductor modules, and a low wiring inductance can also be realized for the power semiconductor modules 12, 14, and 16 in the case of FIG. Further, in FIG. 12 showing the case of the configuration as shown in FIG. 1 in contrast with the cases of FIG. 8 and FIG. 9, the volume is almost equal to the case of FIG. 12B as in FIG. It becomes a realistic configuration.

3 and 4 show another embodiment.
FIG. 3 shows the case of the power semiconductor module 2 parallel configuration, and FIG. 4 shows the case of the 6 parallel configuration. In these, the power semiconductor modules are arranged so that the AC output terminals (U terminals; 29 to 31 (FIG. 3), 32 (FIG. 4)) are in the center. Thereby, since the AC output terminals of the power semiconductor modules connected in parallel approach each other, wiring becomes easy.

  In the above, the arrangement of the electrolytic capacitor and the power semiconductor module is line-symmetric with respect to the central axis, but it is not necessary to be strictly line-symmetric (for example, the electrode position of the electrolytic capacitor is opposite (reverse) to FIG. 1). If the structure is such that two or more power semiconductor modules are installed between the electrolytic capacitors disposed opposite to each other, substantially the same effect can be obtained.

  DESCRIPTION OF SYMBOLS 1-6 ... Electrolytic capacitor, 7, 9 ... IGBT, 8, 10 ... Diode, 11-16 ... Power semiconductor module, 17 ... Three-phase load (motor), 18 ... C1 terminal, 19 ... E2 terminal, 20 ... U terminal 21, 22 ... radiator, 23 to 26 ... wiring conductor, 27 and 28 (L1) ... wiring inductance, 29 to 32 ... AC output terminal.

Claims (3)

A plurality of capacitors are connected in parallel to the DC circuit section to increase the capacity, and a plurality of power semiconductor element modules are connected in parallel to the power converter section to increase the capacity, from DC to AC or from AC to DC. In the power converter to convert,
A plurality of capacitors connected in parallel are divided and arranged opposite to each other, and at least two of the power semiconductor element modules are arranged opposite to each other between the opposed capacitors, and wiring between the capacitors and the power semiconductor modules is performed. The main circuit structure of the power converter characterized by the above.   2. The main circuit structure of the power converter according to claim 1, wherein the capacitors and the power semiconductor modules are arranged so as to be line symmetric with respect to a power semiconductor module connected in parallel as an axis of symmetry.   The main circuit structure of the power converter according to claim 2, wherein the power semiconductor module is arranged so that the AC output terminal side is closest to the line symmetry axis.

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