JP2006246576A - Multi-level inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-level inverter capable of attaining size and cost reductions by reducing the number of wires and large components as many as possible, and capable of facilitating cooling. <P>SOLUTION: Fig. 1 (a) shows a basic circuit of a 5-level inverter. Qu1 and Du1, Qu2 and Dc1, Qu3 and Dx1, Du4 and Qx2, Dc4 and Qx3, and Dx4 and Qx4, each of which comprises a serial circuit of IGBT and a clamp diode, are constituted as single modules M1, M2, M3, M5, M6 and M7 respectively. Moreover, Du2 and Du3, Dc2 and Dc3, Dx2 and Dx3, each of which comprises a serial circuit of clamp diodes, are constituted as single modules M8, M9 and M10 respectively. Furthermore, Qu4 and Qx1, which comprises a serial circuit of IGBTs as a single module M4, is constituted as a single module M4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power conversion device, and more particularly to a multi-level inverter that can output a plurality of voltages of different levels.

FIG. 6 shows one phase of a power conversion device (inverter) using an IGBT (insulated gate bipolar transistor) as a switching element.
6A1 shows a two-level inverter, FIG. 6B1 shows a three-level inverter, and FIG. 6C1 shows a five-level inverter. By arbitrarily turning on and off each IGBT, in FIG. 6 (a1 to a3), the output voltage Vo is two potentials P and N, and in the same (b1 to b3), three potentials P, C, and N (c1 ~ C3) can output five potentials P, P ', C, N', and N. Inverters that can output three or more potentials are collectively referred to as multi-level inverters.

  The on / off signal given to the IGBT is generally determined by comparing the voltage waveform Vs to be output with the triangular wave Vc. The frequency of the triangular wave Vc is called a switching frequency or a carrier frequency, and the ripple output from the inverter can be suppressed by increasing this frequency, but there is a trade-off that the loss generated at the time of switching of the IGBT increases. In addition, by using a multi-level inverter rather than a two-level inverter, output current ripple can be suppressed without increasing the switching frequency, but there is a trade-off that the number of elements used increases and wiring becomes complicated.

On the other hand, the IGBT module used for the inverter is a module (2) connected in series as shown in FIG. 7A in addition to the one (1 in (1)) contained in the package. In 1), the C1 and E2 terminals shown in the figure are connected with a conductor such as copper, and the C2 and E1 terminals of each module are connected to a load such as a motor to construct a motor drive system using a two-level inverter. Can do. FIG. 7B shows an example of a three-phase inverter in which three 2-in-1 modules are arranged.
An example of modularization or packaging as described above is disclosed in Patent Document 1, for example.

Furthermore, there is a package structure with an external appearance as shown in FIG. 8, and there is also a module in which a three-phase inverter is connected as shown in FIG. 9 inside the package. Some require only connection and gate line connection.
Further, in a multi-level inverter such as a three-level inverter, the number of elements used is increased as compared with a two-level inverter, and an inductance component parasitic on the wiring increases as the wiring becomes longer. In order to eliminate these inconveniences, for example, as shown in FIG. 10, an example in which capacitors Cdu, Cdx, Cdv, Cdy, Cdw, and Cdz that smooth DC voltage are provided for each phase is disclosed in Patent Document 2, for example. .

Japanese Patent Laid-Open No. 05-0083947 (5th page, FIG. 1) Japanese Patent No. 2664275 (page 3-4, FIG. 1)

  In a multilevel inverter, a plurality of capacitors for smoothing a DC voltage are connected in series. Therefore, when a capacitor is connected for each phase, the number of large components increases, resulting in an increase in cost and an apparatus. In addition, as in Patent Document 1, when the IGBTs connected in series are configured in one package, heat generation inside the package is increased, and not only the cooling efficiency for each package has to be increased, but also the temperature of the entire package. Problems such as a large cycle due to change occur.

  In addition, if two IGBTs connected in series are made into a single package as in Patent Document 2, a period in which heat is generated simultaneously due to loss occurring in both IGBTs connected in series as shown in FIG. And the temperature of the module package itself rises. Furthermore, if the DC voltage is high, the insulation breakdown voltage (ISOL) between the main terminals and the base plate shown in FIG. 12 must be taken into consideration, and it becomes difficult to arrange all the packages in the same cooling body. As a result, if the cooling body is divided and arranged for each package or each base plate is provided with a dielectric strength, there is a possibility that the thermal resistance increases and cooling cannot be sufficiently performed.

  Accordingly, an object of the present invention is to reduce the size and cost of the apparatus and facilitate cooling by reducing wiring as much as possible and reducing the number of large parts.

In order to solve such a problem, in the invention of claim 1, a multi-level inverter in which an arm is constituted by a plurality of DC power sources having different potentials and a semiconductor element including a plurality of switching elements and a clamp diode between the positive and negative electrodes. In
The series circuit of the switching element and the clamp diode is constituted by a single module, and the series circuit other than the series circuit of the switching element and the clamp diode is constituted by a single module.

  In the first aspect of the invention, the circuit in which the switching element is connected in antiparallel with the clamp diode can be constituted by a single module (invention of the second aspect). In the invention of claim 1, the module directly connected to the DC power supply is a single module for all phases (invention of claim 3), or the module directly connected to the DC power supply. Can be arranged in a common cooling body (invention of claim 4).

  According to the present invention, in consideration of the operation of the multi-inverter, elements that do not turn on at the same time are configured in the same package, and wiring between the packages is reduced. In addition, elements with small potential differences are packaged together for each phase, thereby minimizing wiring and reducing the number of large parts, thereby reducing the size and cost of the device. As a result, it is possible to reduce the duty of heat and pressure resistance of the package.

FIG. 1 shows an embodiment of the present invention. This shows the circuit shown in FIG. 6C1 in module units.
That is, as shown in FIG. 1 (a), Qu1 and Du1, Qu2 and Dc1, Qu3 and Dx1, Du4 and Qx2, Dc4 and Qx3, and Dx4 and Qx4 constituting a series circuit of an IGBT and a clamp diode are respectively combined into a single module M1. , M2, M3, M5, M6 and M7. In addition, Du2 and Du3, Dc2 and Dc3, and Dx2 and Dx3 that form a series circuit with clamp diodes other than the above are configured as a single module M8, M9, and M10, respectively, and further, a series circuit of IGBTs is configured. Qu4 and Qx1 are configured as a single module M4. Thus, it is clear that wiring is facilitated by using a 2-in-1 module in which two elements are connected in series. For example, since the connection between Qu1 and Du1, the connection between Qu2 and Dc1, the connection between Qu3 and Qx1, and so on are connected inside the module, wiring in this portion is not necessary.

  The operation of Qu1 and Du1 in the 5-level inverter will be described with reference to FIG. Qu1 and Du1 are alternately turned on, and no current flows at the same time. That is, when Qu1 is on as shown in FIGS. 3A and 3C, Du1 is off, and when Du1 is on as shown in FIGS. 3B and 3D, Qu1 is off. . Similarly, when the current direction is reversed, Du1 is off when the FWD of Qu1 is on, and the FWD of Qu1 is off when Du1 is on. Similarly, since there is no period to turn on at the same time for the modules that are single modules such as Qu2 and Dc1, Qu3 and Qx1,..., The period that is turned on at the same time like Qu1 and Qu2 shown in FIG. The temperature difference ΔT inside the package is smaller than in the case where the elements that are included are configured in the same package.

These are also apparent from the operation path of FIG. 2 for the single module M9 of Du2 and Du3 constituting the series circuit of the diodes and the single module M4 of Qu4 and Qx1 constituting the series circuit of the IGBT.
Next, while Du2 and Du3 and Dx2 and Dx3 are turned on at the same time, they are diodes and are smaller than the conduction loss of the IGBT. Further, at the time of reverse recovery, voltage is divided by three elements with respect to the DC voltage of Ed / 4, so that the reverse recovery loss is small and therefore heat generation is small. In addition, since the elements of Qu1 to Qu4 and Qx1 to Qx4 have different responsibilities, it is possible to sort the modules alone without sorting the IGBTs contained in the same package.

As described above, in addition to facilitating wiring, the effect of improving heat dispersion in a package unit can be obtained. In addition, when the IGBT chip and the diode chip have the same rating, the diode chip has a smaller chip size. Therefore, if the IGBT, the FWD chip, and the diode chip are accommodated, the other module sizes are reduced, and the size is reduced. be able to.
Of course, the circuit of FIG. 1A may be configured as shown in FIG. 1B by using a general IGBT 2-in-1 module shown in FIG. 7A.

FIG. 4 shows another embodiment of the present invention. This is an example of a three-phase inverter.
As shown, 6-in-1 modules are used for the modules M111, M888, M100, M999, and M777 that are directly connected to the smoothing capacitors CP2, CP1, CN1, and CN2.
The terminals of the modules M111, M888, M100, M999, and M777 on the opposite side to the capacitors CP1, CP2, CN1, and CN2 are connected to STu, STv, and STw that constitute the respective phases, and the AC output terminals U, V, By adopting a configuration in which the load is connected from W to the load, a large capacitor disposed in each phase becomes unnecessary.

  Even if an arbitrary voltage is output from U, V, and W, only the potential of 2 × Ed / 4 + ΔVsp is applied to modules M111, M888, M100, M999, and M777 with reference to the potential directly connected to the capacitor. Therefore, it can be used without increasing the dielectric strength of the package.

  When the current rating is large as shown in FIG. 4 and a single package configuration cannot be formed in a three-phase package, each arm may be arranged in the immediate vicinity of the capacitor as shown in FIG. At this time, the insulation withstand voltage V (ISOL) of each IGBT package only needs to have an insulation withstand voltage of Ed / 4 + ΔV as in FIG. 4, and one potential is fixed, so as shown in FIG. It can be installed in the same cooling body F1, F7, F8, F9, F10. What is necessary is just to connect the electric potential of a cooling body with the electric potential in which the electric potential of a capacitor | condenser is being fixed.

In FIG. 5, only the series circuit of the IGBT and the clamp diode directly connected to the capacitor is packaged separately. However, the modules M888, M999, and M100 constituting the diode series circuit can be similarly applied. is there.
Also, one set (1 in 1) is used for the modules M1r, M1s, M1t, MD1r, MD1s, MD1t, MD7r, MD7s, MD7t, M7r, M7s, and M7t that are directly connected to the capacitor. Needless to say, an in-1 module may be used.

Circuit configuration diagram for explaining an embodiment of the present invention Current path diagram for explaining the operation of FIG. FIG. 1 is an explanatory diagram of the operation. The circuit block diagram which shows another embodiment of this invention The circuit block diagram which shows another embodiment of this invention Circuit diagram and output voltage waveform diagram explaining conventional inverter General IGBT module and its connection example External view of a typical IGBT module 6-in-1 module internal wiring diagram Circuit diagram showing a typical three-level three-phase inverter example Operation explanatory diagram of two IGBTs connected in series Illustration of dielectric strength between main terminals and base plate

Explanation of symbols

  CP1, CP2, CN1, CN2 ... smoothing capacitors, P, P ', C, N', N ... potential, Qu1-Qu4, Qx1-Qx4 ... IGBT (insulated gate bipolar transistor), Du1-Du4, Dc1-Dc4, Dx1 ~ Dx4 ... diode, M1 to M11, M22, M33, M55, M66, M77, M100, M111, M777, M888, M999 ... module, F1 to F10 ... cooling body.

Claims (4)

In a multi-level inverter that constitutes an arm with a plurality of DC power supplies having different potentials and a semiconductor element including a plurality of switching elements and a clamp diode between the positive and negative electrodes,
The multi-level inverter, wherein the series circuit of the switching element and the clamp diode is constituted by a single module, and the series circuit other than the series circuit of the switching element and the clamp diode is constituted by a single module.   The multilevel inverter according to claim 1, wherein a circuit in which a switching element is connected in antiparallel with the clamp diode is configured by a single module.   The multi-level inverter according to claim 1 or 2, wherein the module directly connected to the DC power supply is a single module for each phase.   The multilevel inverter according to claim 1 or 2, wherein the module directly connected to the DC power supply is disposed in a common cooling body.

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