JPH08251940A - Series multiplex power converter - Google Patents

Abstract

PURPOSE: To eliminate breakdown when switching elements are connected in parallel by arranging switching elements connected in series and arranging clamp diodes on the opposite sides thereof. CONSTITUTION: Switching element modules 11a-14a, 11b-14b are arranged in the center and clamp diodes 15a, 15b, 16a, 16b, connected in parallel, are arranged symmetrically on the opposite sides of the switching element modules 11a-14a, 11b-14b. Consequently, the switching element modules 11a-14a, 11b-14b can be arranged proximately and the wiring connecting the switching element and a gate drive therefor can be shortened. Since the inductance of wiring connecting the switching element and the gate drive, as well as the inductance among the switching element modules 11a-14a, 11b-14b is reduced, oscillatory current is reduced between the switching elements which are thereby protected against breakdown.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting arrangement of elements constituting a power converter when a plurality of switching elements of a series multiple power converter are connected in parallel and used.

[0002]

2. Description of the Related Art In recent years, as an inverter for driving an electric vehicle, the output voltage for an induction motor is changed to a conventional binary level to be ternary to increase the apparent switching frequency and thereby reduce the ripple of the fundamental wave voltage. A so-called serial multiple inverter (three-level inverter) is being put to practical use. On the other hand, a module type large capacity IGBT (Insulated Gate Bipolar Transistor) is also being developed as a switching element constituting a power converter.

However, even though the capacity has been increased, the capacity is still insufficient for electric vehicles.
IGBT module as described in Japanese Patent Publication,
Two parallel connections are used for each arm. As a mounting arrangement in this case, this publication describes that a clamp diode of a series multiple inverter is linearly arranged in the center and four IGBTs connected in series are arranged on both sides thereof.

[0004]

In the prior art, however, there is a problem that the IGBT breaks down when two parallel connections are used.

An object of the present invention is to prevent breakdown even when switching elements are connected in parallel.

[0006]

In order to achieve the above object, according to the present invention, switching element modules connected in parallel are arranged in the center, and clamp diodes connected in parallel are arranged symmetrically on both sides of the switching element module. It is a thing.

[0007]

By arranging the switching element modules connected in parallel in the center, the switching element modules can be arranged close to each other, and the wiring between the gate drive for driving the switching element and the switching element can be shortened. Therefore, the inductance of the wiring between the switching element modules connected in parallel and between the gate drive and the switching element is reduced, and as a result, the oscillating current between the switching elements, which is the main cause of the breakdown, is reduced and the break Not down.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows one phase of a serial multiple inverter that supplies a three-phase alternating current with a variable voltage and variable frequency to an induction motor 3 that is a load. The mechanism of supplying three-level voltage to the induction motor that is the load 3 is that when the IGBTs 11a to 12a are turned on, the total voltage of the DC power supplies 1 and 2 is applied to the induction motor, and when the IGBTs 12a to 13b are turned on, the voltage of the DC power supply 2 is changed. Clamp diode 15
Output to the induction motor via a to 16b, and also IGBT
This is because the negative side of the DC power supply 2 is connected to the induction motor when 13a to 14b are turned on. Also, this DC power supply 1,
In the case of a DC electric vehicle, 2 is a voltage dividing capacitor that receives DC from a DC overhead wire (not shown) by a pantograph and divides it. In the case of an AC electric vehicle, a DC voltage output of a converter that converts AC into DC is divided. It is a piezoelectric capacitor. Further, the diodes connected in parallel to the IGBTs in the IGBT modules 11a-14b are freewheel diodes.

Four IGBT modules 11 connected in series
IGBT modules 11b, 12b, 13b, 14b adjacent to a, 12a, 13a, 14a and connected in parallel, respectively.
Are arranged on both sides of each of the clamp diodes 15a.
16b are mounted and arranged.

By arranging in this way, the parallel IGBT
The reason why the oscillating current between T decreases will be described with reference to FIG. In FIG. 2, when the clamp diode module is arranged between 11a and 11b of the parallel IGBTs shown in FIG. 1 as shown in the prior art, the wiring length between the parallel IGBTs is correspondingly increased. . It is desirable that the wiring inductance LG1 between the gate drive circuit 21 and the gate of the IGBT 11a and the wiring inductance LG2 between the gate drive circuit 21 and the gate of the IGBT 11a be equal, but if the wiring length is long, they are equal in mounting. Is difficult. At this time, the wiring inductance L
Assuming that G2 is large, the gate current from the gate drive circuit 21 flows to the IGBT 11a, and the IGBT 11b precedes the IGBT 11b.
a is turned on, and the load current flows from the power source through the IGBT 11a and the wiring inductance LE1. At this time, the electromagnetic energy stored in the wiring inductance LE1 makes a round through the junction capacitance C1 existing between the gate and emitter of the IGBT 11a and the junction capacitance C2 of the IGBT 11b. Due to this current, a potential is generated in the junction capacitance C1 and the IGBT 11a is turned off. When the IGBT11b is turned on at this timing, the wiring inductance LE
Electromagnetic energy is stored in 2 and the IGBT 11b is turned off and the IGBT 11a is turned on. When the oscillating current resulting from the energy transfer between the wiring inductance and the junction capacitance flows in this way, the IGBTs connected in parallel are alternately turned on and off, and may be broken down depending on the on / off timing. is there.

In this embodiment, the IGs connected in parallel are connected.
Since the BTs are arranged close to each other, when the gate drive circuit 21 and the IGBTs are wired, even if the centers of the IGBTs are slightly deviated from each other, the wiring inductance LG1
And LG2 are not increased, and the wiring inductance itself can be reduced. Further, since the wiring inductances LE1 and LE2 are reduced due to the close arrangement, the voltage of the junction capacitance does not increase so much even if the stored electromagnetic energy decreases and an oscillating current flows. Therefore, the IGBT does not turn off against the gate signal. .

Further, in this embodiment, the IGs connected in parallel are connected.
The flow of current into and out of BT is symmetrical (Fig. 1, A,
B, C, D). Therefore, there is no difference in the current paths of the left and right IGBTs connected in parallel, and the current imbalance can be avoided. If current imbalance occurs, IG
Immediately after the BT is turned on or off, the current is concentrated in one of the IGBTs, and there is a risk of causing element breakdown.

When driving a load having a larger capacity while maintaining the current capacity of one element, the number of parallel connections must be further increased. This will be described with reference to FIG. FIG. 3 is a perspective view in which four IGBTs are connected in parallel to one phase of the serial multiple inverter. As for the arrangement of the elements, four IGBTs are connected in parallel (11a to 1).
4d) is arranged in the center, and two clamp diodes (15a to 16d), which are also connected in parallel in four, are arranged symmetrically on each side of two pieces. As for the connection of these elements, two of the four parallel-connected elements were connected, and the midpoints of their mutual connection points were connected. By doing so, not only the wiring inductance between the elements can be minimized, but also the current paths of the four elements connected in parallel can be equalized. Three connection lines to the DC power source should be taken out from the center in the downward or upward direction as shown in the figure, and one connection line to the load should be taken out in the downward or upward direction as well. To This is because the interaction between the current to the DC power supply or load and the current flowing through the element is minimized to reduce the inductance of the wiring.

Further, in the case of an inverter for driving an electric vehicle, for example, a cooling device such as a heat pipe is attached to the rear surface of these element modules to be exposed to the outside, and the surface shown in the figure is hermetically housed in a housing. Therefore, the surface facing the surface shown in the figure is inside the housing, and various devices, gate drive circuits, snubber circuits, etc. are mounted and arranged on the surface.

The arrangement of the gate drive circuit 21 will be described with reference to FIG. In FIG. 4, only the gate drive circuit for the IGBT 14 is shown and other gate drive circuits are omitted. IG with four gate drive circuits 21 connected in parallel
The gate line and the emitter line are arranged above the central portion of the BT module 14, and the four IGBTs are wired so as to have the same wiring length. The four parallel-connected elements are divided into two groups from the center to the left and right, the respective gates and emitters are connected to each other, the centers of the connection lines are connected to each other, and the central portion and the gate drive circuit 21 are connected. By doing so, the oscillating current generated due to the imbalance of the wiring inductance of the gate circuit described above can be reduced, and four parallel-connected IGBT modules are arranged closer to each other as compared with the prior art in which a clamp diode is arranged in the central portion. Since the wiring from the gate drive circuit 21 is shortened, the wiring inductance, which is a main member for generating the oscillating current, can be reduced, and the element breakdown can be reduced.

Further, FIG. 4 shows a mounting arrangement of the snubber circuit. 22a to 25b are snubber diodes, 26a
˜27b are snubber capacitors connected in a Δ type (or star type). The snubber diodes 22a to 25b and the snubber capacitors 26a to 27b are symmetrical with respect to the center line.
To place. Then, the above-mentioned gate drive circuit is arranged in the central portion to reduce the oscillating current. Such an arrangement is possible because the snubber capacitor is adopted by adopting the Δ type (or star type) snubber circuit instead of the individual snubber method in which the snubber circuit is attached to each switch element as described in the related art. Another factor is the ability to concentrate.

As described above, according to the present embodiment, since the wiring length between the gate drive circuit and the IGBT module can be shortened, the error at the time of mounting can be reduced and the imbalance of the wiring inductance can be reduced.
Since the wiring inductance itself becomes small, the absolute value of the oscillating current between the IGBTs connected in parallel can be reduced. Furthermore, the current imbalance can be reduced by equalizing the current paths from any of the elements connected in parallel (detailed wiring is omitted in FIGS. 4 and 5 and only the circuit is shown).

Although the switching element has been described as an IGBT in the above embodiments, it is a voltage driven type element having a junction capacitance and is a module type element, for example,
It is also applicable to power transistors and the like.

In the above embodiment, the inverter has been described as an example, but the same applies not only to the inverter but also to the PWM converter. Further, it goes without saying that the present invention is not limited to the electric power converter for driving an electric vehicle.

[0020]

As described above, according to the present invention, it is possible to eliminate the breakdown when the switching elements forming the serial multiple inverter are connected in parallel.

[Brief description of drawings]

FIG. 1 is a mounting layout diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view of the principle of oscillating current generation.

FIG. 3 is a diagram showing an embodiment of the present invention in which the number of parallel connection elements is increased.

FIG. 4 is a diagram showing an arrangement of gate drive circuits in addition to the arrangement shown in FIG.

FIG. 5 is a diagram in which snubber circuits are arranged in addition to the arrangement shown in FIG.

[Explanation of symbols]

1, 2 ... DC power supply, 3 ... Load, 11-14 ... IGBT module, 15, 16 ... Clamp diode, 21 ... Gate drive circuit, 22-25 ... Snubber diode, 2
6, 27 ... Snubber capacitors.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Saito 1070 Ichimo, Hitachinaka City, Ibaraki Prefecture Mito Plant, Hitachi, Ltd. (72) Toshio Takasaki 1070 Ichige, Hitachinaka City, Ibaraki Hitachi Ltd. Mito Factory (72) Inventor Takashi Tsuboi 1070 Imo, Hitachinaka City, Ibaraki Prefecture Hitachi Ltd. Mito Factory (72) Inventor ▲ Takahiko Hisa 2 days System Plaza Katsuta, 832 Horiguchi, Hitachinaka City, Ibaraki Prefecture Within Hitachi Mito Engineering Co., Ltd.

Claims (4)

[Claims] 1. Each switching element is connected in parallel,
These switching elements connected in parallel are connected in series,
In a series multiple power conversion device having a configuration in which respective clamp diodes are connected in parallel to obtain a voltage of three levels or more on the AC side, the switching elements connected in series are arranged in the center, and the clamp diodes are connected in series. Series multiple power converters arranged on both sides of the switching element. 2. The serial multiple power converter according to claim 1, wherein a gate drive circuit for driving the switching elements is arranged at a position facing the switching elements. 3. The serial multiple power converter according to claim 1, wherein the switching element and the clamp diode are parallel in four. 4. The serial multiple power converter according to claim 3, wherein two of the elements connected in parallel are connected in parallel and the midpoints of these elements are connected.