JP4664104B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device using a high-speed switching semiconductor element, and more particularly to improvement of an internal wiring structure of a snubber circuit capacitor (snubber capacitor) that includes a snubber circuit necessary for suppressing a surge voltage.

  In recent years, power semiconductor elements used for converters and inverters have been remarkably developed for high-speed switching. As the high-speed switching element, there are, for example, GCT and the like in the current drive type, and IGBTs and IEGTs (Injection Enhanced Gate Transistors) that are the insulated gate type in the voltage drive type. These high-speed switching elements are currently being developed and put into practical use with a voltage of 3 k to 6 kV and a cutoff current of 5 k to 6 kA. Also, since the voltage change rate dV / dt withstand during turn-off has been improved, a reduction in size and loss of the snubber circuit compared to conventional devices is being studied.

  FIG. 9 shows an example of a conventional NPC main circuit and uses a GTO as a switching element. The snubber circuits 2a to 5a configured by capacitors and resistors for suppressing switching surges of the GTO elements 2 to 5 are provided for each GTO element. Provided.

  Recently, with the commercialization of high-performance GCT, IGBT, and IEGT, a collective snubber circuit and a capacitor are provided in the DC power supply unit. The high-speed switching element can reduce a current of several kA to zero in 1 μ to 2 μs in operation. At this time, a surge voltage of L * dl / dt is generated by the wiring inductance L and the current change rate di / dt. If the surge voltage peak or dV / dt is larger than the voltage tolerance of the high-speed switching element, the element may be permanently destroyed. It is important to suppress this surge voltage below the withstand capability of the switching element.

  In large-capacity conversion devices using large-capacity high-speed switching elements in recent years, charge / discharge snubbers and clamp snubbers are provided in each element. There is a demand for a device that suppresses a surge voltage only by a collective snubber circuit of a power source without providing a snubber circuit for each element as in the case of an element.

  For this reason, Patent Document 1 proposes a power conversion device that can suppress a surge voltage only by a power supply collective snubber circuit and protect a semiconductor element from a surge overvoltage.

In Patent Document 1, the wiring inductance other than the capacitor can be reduced. However, the influence of the internal inductance of the capacitor itself is large, and this reduction becomes important.
JP 2001-78467 A

  An object of the present invention is to provide a power conversion device that can protect a semiconductor element from a surge voltage by minimizing the internal inductance of the capacitor itself.

In order to achieve the above object, an invention corresponding to claim 1 includes a DC power source, a semiconductor stack connected to the DC power source and press-contacting a semiconductor element group composed of a plurality of types of semiconductor elements and a cooling fin, A snubber circuit connected in parallel to a DC power source, a capacitor and a diode connected in series, and a resistor connected in parallel to the diode, and one terminal connected to the case of the capacitor of the snubber circuit connected to the cooling fin In the power converter device, the other terminal insulated and connected to the other end of the capacitor is connected to one end of the diode, and the other terminal of the diode is connected to the cooling fin. Case, external terminal, capacitor element, first internal wiring and second internal wiring, insulator, and capacitor The capacitor element is housed in the conductive case, the capacitor element is fixed to the inner wall surface of the conductive case via the insulator, and the capacitor element includes the first terminal. one end of the internal wiring and the second internal wiring are electrically connected, respectively, wherein the outside of the conductive case and the external terminal and the capacitor case terminals spaced apart from each other are those set fixed, the external terminal and the first The other end of the internal wiring is electrically connected, the other end of the capacitor case terminal and the second internal wiring are electrically connected via the conductive case, and the second internal wiring the current direction flowing to the conductive case be reversed, said second internal wiring and in close proximity to said conductive case said second internal wiring and the conductive case and By increasing the each other inductance, a power conversion apparatus being characterized in that so as to reduce the internal inductance.

According to the invention corresponding to claim 1, the capacitor element is housed in the conductive case, the capacitor element is fixed to the inner wall surface of the case via the insulator, and the capacitor element is fixed to the capacitor element. One end of each of the first and second internal wirings is electrically connected,
The external terminal and the capacitor case terminal are spaced apart and fixed to the outside of the case, the external terminal and the other end of the first internal wiring are electrically connected, and the capacitor case terminal and the first The other end of the second internal wiring is electrically connected, and the direction of the current flowing through the second internal wiring and the capacitor case terminal is opposite, and the second internal wiring and the capacitor case terminal are close to each other. Since the magnetic coupling is strengthened, the wiring loop inductance of the collective snubber circuit can be reduced, and in order to further reduce the wiring loop inductance, the internal wiring with the capacitor case potential whose current direction is the opposite direction And the capacitor case can be closely spaced to increase the mutual inductance. It is possible to reduce the parts inductance.

In order to achieve the above object, the invention corresponding to claim 2 is directed to a DC power supply, a semiconductor stack connected to the DC power supply and press-contacting a semiconductor element group composed of a plurality of types of semiconductor elements and a cooling fin, and the DC A snubber circuit connected in parallel to the power supply, and connecting a capacitor and a diode in series and a resistor connected in parallel to the diode, and one terminal connected to the capacitor case of the snubber circuit is close to the cooling fin In the power conversion apparatus, the other terminal insulated from the capacitor case is connected to one end of the diode, and the other terminal of the diode is connected to the cooling fin.
The capacitor of the snubber circuit includes a conductive case, first and second external terminals, a capacitor element, first and second internal wirings, an insulator, and a capacitor case terminal conductor.
The capacitor element is housed in the conductive case, the capacitor element is housed in the case, and is fixed in the case so as to be electrically insulated from the case. And the second internal wiring are respectively electrically connected,
The first and second external terminals are spaced apart and fixed to the outside of the case, the first external terminal and the first internal wiring are electrically connected, and the capacitor case terminal conductor is The second external terminal and the capacitor case terminal conductor are electrically connected to the outside of the case via the insulator, and flow to the second internal wiring and the capacitor case terminal conductor. The power conversion device is characterized in that the current direction is reversed and magnetic coupling is strengthened by bringing the second internal wiring and the capacitor case terminal conductor close to each other.

According to the invention corresponding to claim 2, the capacitor element is housed in the conductive case, the capacitor element is housed in the case, and is electrically insulated from the case. The first and second internal wirings are electrically connected to the capacitor element,
The first and second external terminals are spaced apart and fixed to the outside of the case, the first external terminal and the first internal wiring are electrically connected, and the capacitor case terminal conductor is The second external terminal and the capacitor case terminal conductor are electrically connected to the outside of the case via the insulator, and flow to the second internal wiring and the capacitor case terminal conductor. Since the current direction is reversed and the magnetic coupling is strengthened by bringing the second internal wiring and the capacitor case terminal conductor close to each other, the wiring loop inductance of the collective snubber circuit can be reduced, and further the wiring In order to reduce the loop inductance, the distance between the capacitor case and the internal wiring having the capacitor case potential with the opposite current direction is closely To be able to increase the mutual inductance, as a result, it is possible to reduce the capacitor internal inductance.

The invention corresponding to claim 3 is as follows. That is, the power converter according to claim 1 or claim 2, characterized in that constitutes the internal wiring of a plurality of lead wires.

  According to the invention corresponding to claim 3, the internal wiring having the capacitor case potential with the current direction opposite to each other is constituted by a plurality of lead wires, and the mutual inductance is increased by increasing the distance from the case. The internal inductance is reduced.

The invention corresponding to claim 4 is as follows. That is, the power converter according to claim 1 or claim 2, characterized in that said internal wiring constituted by flat conductor.

  According to the invention corresponding to claim 4, the mutual inductance is increased by reducing the distance between the case and the internal wiring, and the internal inductance of the capacitor is reduced.

The invention corresponding to claim 5 is as follows. That is, the internal wiring is insulated from the case, and is electrically connected to the terminal and the external wiring outside the case, and the external wiring is disposed so that the current direction of the internal wiring is opposite. The power conversion device according to claim 1 , wherein the power conversion device is a power conversion device.

  According to the invention corresponding to claim 5, when insulated from the case potential, external wiring is performed so that the current direction of the internal wiring is opposite, and the distance between the external wiring and the capacitor case is made close. Thus, the mutual inductance is increased to reduce the wiring loop inductance. In this case, since the case potential is a floating potential, it is necessary to insulate the external wiring and the capacitor case with an insulator or the like.

  According to the present invention, since the internal inductance of the snubber capacitor is reduced, it is possible to minimize the wiring loop inductance of the collective snubber circuit, and it is possible to use the power supply without providing a snubber circuit for each of the semiconductor elements constituting the power converter. Surge voltage can be suppressed simply by providing a collective snubber.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A three-level NPC power converter using, for example, an IEGT (Injection Enhanced Gate Transistor) according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the main circuit in the present embodiment includes a smoothing capacitor 1 that is a DC power supply, first to fourth switching elements 6 to 9 each including an IEGT and a diode connected in reverse parallel to the IEGT. The first and second coupling diodes 10 and 11 and a snubber circuit 12 including a capacitor 12a (hereinafter referred to as a snubber capacitor), a diode 12b (hereinafter referred to as a snubber diode), and a discharge resistor 12c. This group unit has one phase and constitutes a U-phase, V-phase, and W-phase three-level NPC main circuit.

  Next, the semiconductor stack 18 on which the main circuit is mounted will be described. Generally, the main circuit is cooled by air cooling or water cooling. FIG. 2 shows a water-cooled semiconductor stack 18 configured by cascading and fastening one phase of the main circuit semiconductor element shown in FIG. However, the description about water cooling piping is abbreviate | omitted.

  As shown in FIG. 2, in the semiconductor stack 18, the first and second coupling diodes 10 and 11 are arranged in the center of the semiconductor stack 18 in series via a neutral point bus bar 14C. The first coupling diode 10, the insulating spacer 16, and the first and second IEGTs 6, 7 are on the positive electrode side on the right side of the figure, with the bus bar 14 C serving as the neutral point electrode of the coupling diodes 10, 11 as a boundary. , IEGTs 6 and 7 are arranged via cooling fins 13 for cooling. Further, the second coupling diode 11, the insulating spacer 16, the third and fourth IEGTs 8 and 9, and the IEGTs 8 and 9 are arranged on the negative electrode side on the left side in the figure via cooling fins 13 for cooling.

  The IEGTs 8 and 9, the coupling diodes 10 and 11, the cooling fins 13, and the insulating spacers 16 are fastened together at a predetermined pressure. For example, the skewered stacks fastened together in this way are provided in the direct current power supply Ed and the collective snubber circuit 12 is attached as described below.

  The material of the case 12a1 itself of the snubber capacitor 12a is an electrode formed of a conductive material such as brass, and the case 12a1 is directly attached to the cooling fin 13 for cooling the IEGTs 6 and 9. The other terminal includes a plurality of terminals, has an insulator 12a2, is electrically insulated from the case 12a1, and is directly attached to one end (an anode electrode or a cathode electrode of the snubber diode 12b. The snubber diode 12b). The other terminal has a neutral point potential and is directly attached to the cooling fin 17 of the snubber diode 12b.

  Further, the cooling fins 17 that serve as both the terminal connection and the cooling of the snubber diode 12b are attached to the neutral point bus bar 14c, which is the neutral point of the NPC circuit. The neutral point bus bar 14c is located between the cathode electrode and the anode electrode of the coupling diodes 10 and 11 disposed in the central portion of the semiconductor stack 18, and has a T shape. The bus bar of the T-shaped horizontal portion is a wide conductor that is larger than the area of the plane of the cooling fin 17 that cools the snubber diode 12b.

  An NPC energization mode that outputs three levels of positive (positive electrode), zero (neutral point), and negative (negative electrode) in the semiconductor stack 18 according to the embodiment will be described with reference to FIGS.

  The minus level output mode is not described because the current direction of the plus output mode is just reversed and the relationship of the energization direction with respect to the elements, the cooling pieces, and the bus bars in the semiconductor stack is the same.

  The energization mode in the plus output circuit diagram is indicated by arrows A and B in FIG. A current flows in the order of IEGT6 → IEGT7 → output bus 14U from the positive bus bar 14P which is a DC power source. The current flow in the semiconductor stack 18 on which the IEGTs 6 and 7 are mounted flows in the direction of the arrow A shown in FIG. 2 in the positive bus bar 14P → the cooling fin 13 → IEGT 6 → the cooling fin 13 → IEGT 7 → the cooling fin 13 → the output cubbar 14U. It flows in the route.

  The energization mode in the circuit diagram of zero output is indicated by arrows B and C in FIG. From the neutral point bus bar 14C of the DC power source, current flows in the order of the first coupling diode 10 → IEGT7 → output cub bar 14U and output cub bar 14U → IEGT8 → second coupling diode 11 → neutral point bus bar 14C. The current flow in the semiconductor stack 18 in which the coupling diode 10 and the IEGT 7 are mounted is as follows. In the direction of arrow B in FIG. 6, the neutral bus bar 14C → the coupling diode 10 → the cooling fin 13 → the bus bar 15P → the cooling fin 13 → It flows through the route of IEGT7 → cooling fin 13 → output cubs bar 14U and output cubbar 14U → cooling fin 13 → IEGT8 → cooling fin 13 → bus bar 15N → cooling fin 13 → coupling diode 11 → neutral point bus bar 14C.

  The generation principle of the surge voltage in this energization mode will be described with reference to FIG. Now, as shown in FIG. 3, when IEGT6 and IEGT7 are on and the load current 1L flows, when the gate voltage Vge of IEGT6 is negatively biased at time t1 in FIG. 8, IEGT6 is turned off and the voltage rises. The current Ic flowing through the current decreases. A surge voltage is generated in the semiconductor element IEGT6 due to the current reduction rate (−dl / dt) and the wiring inductance at this time. The surge voltage Vs1 generated at time t2 in FIG. 4 is expressed by the following equation (1). In order to suppress the surge voltage, a diode having a low wiring inductance (L), a snubber capacitor internal inductance (Ls), and a low transient on-voltage (Vfr) is required.

Vs1 = Vo + (L + Ls) · dl / dt + Vfr (1)
The voltage Vs2 generated at time t3 is expressed by the following equation (2).

Vs2 = Vo + {√ (Lo / C)} * Ic (2)
Here, Vo: DC voltage, Lo: inductance L from the power supply capacitor of FIG. 3 to the collective snubber circuit 12, L: L1 + L2 + L3 + L4 + L5, C: snubber capacitor capacity, Vfr: snubber D transient on-voltage.

  In the embodiment configured as described above, a configuration for reducing the internal inductance (Ls) of the snubber capacitor will be described with reference to FIG. FIG. 5 shows a capacitor 12a of the snubber circuit 12 in the above-described power converter, which includes a conductive case 12a1, an external terminal such as an insulator 12a2, a capacitor element 12a4, first and second internal wirings 12a6 and 12a6, An insulator 12a5 for preventing contact of the case 12a1 made of a conductive material such as brass and a capacitor case terminal 12a3 are provided and configured as follows.

  That is, the capacitor element 12a4 is accommodated in the conductive case 12a1, and the capacitor element 12a4 is fixed to the inner wall surface of the case 12a1 via the insulator 12a5, and the first and second internal wirings 12a6, One end of 12a6 is electrically connected to each other.

In addition, the insulator 12a2 and the capacitor case terminal 12a3 are spaced apart and fixed to the outside of the case 12a1, and the insulator 12a2 and the other end of the first internal wiring 12a6 are electrically connected, and the case 12a1 and the second The other end of the internal wiring 12a6 is electrically connected, and the direction of the current flowing through the second internal wiring 12a6 and the case 12a1 is opposite, and is generated by the current flowing through the second internal wiring 12a6 and the case 12a1 , respectively. The magnetic coupling is strengthened by canceling out the magnetic flux, that is, by bringing the second internal wiring 12a6 and the case 12a1 close to each other.

By increasing the mutual inductance Thus current direction D is in the close distance between the internal wiring 12a6 and to case 12a1 with capacitor case potential is opposite, is intended to reduce the internal inductance.

  By using such a snubber capacitor, it is possible to minimize the inductance of the circuit wiring, suppress the surge voltage applied to the switching element in the energization mode of the three-level operation, and enable the IEGT to be individually snubberless. It becomes.

  Further, as a specific example of the internal wiring 12a6 of the snubber capacitor 12a shown in the embodiment, the self-inductance can be reduced by wiring with a plurality of lead wires as shown in FIG. 6, and the internal inductance can be further reduced.

  Furthermore, as a specific example of the internal wiring of the snubber capacitor 12a6 shown in the embodiment, a thin and wide flat conductor 12a6 as shown in FIG. 7 can reduce the self-inductance and further reduce the internal inductance.

  FIG. 8 shows a configuration for reducing the internal inductance (Ls) of the snubber capacitor, which is an embodiment different from FIG. 5, and this will be described below. FIG. 8 shows the power converter described above. The capacitor 12a of the snubber circuit 12 includes a conductive case 12a1, first and second external terminals such as insulators 12a2 and 12a2, a capacitor element 12a4, and first and second terminals. The internal wiring 12a6, 12a6, the insulator 12a5, and the capacitor case terminal conductor 12a3 are provided as follows.

  That is, the capacitor element 12a4 is accommodated in the conductive case 12a1, the capacitor element 12a4 is accommodated in the case 12a1, and is fixed in the case 12a1 so as to be electrically insulated from the case 12a1, and the capacitor element 12a4 The first and second internal wirings 12a6 and 12a6 are electrically connected to each other.

  Also, the first and second insulators 12a2, 12a2 are fixedly spaced apart from each other outside the case 12a1, the first insulator 12a2 and the first internal wiring 12a6 are electrically connected, and the capacitor case terminal conductor Is fixed to the outside of the case 12a1 via an insulator 12a5, the second insulator 12a2 and the capacitor case terminal conductor 12a3 are electrically connected, and the second internal wiring 12a6 and the capacitor case terminal conductor 12a3 flow. The current direction is reversed, and the magnetic coupling is strengthened by bringing the second internal wiring 12a6 and the capacitor case terminal conductor 12a3 close to each other.

  In addition, when the terminal of the snubber capacitor shown in the embodiment is a capacitor terminal insulated from the case potential as shown in FIG. 8, the external wiring 12a3 is opposite to the current direction D flowing through the internal wiring 12a6. In order to increase the mutual inductance by reducing the distance between the external wiring and the capacitor case 12a1, the wiring loop inductance is reduced. In this case, since the case potential is a floating potential, it is necessary to insulate the external wiring 12a3 and the capacitor case 12a1 with an insulator 12a5 or the like.

  According to each embodiment described above, since the internal inductance of the snubber capacitor is reduced, the wiring loop inductance of the collective snubber circuit can be minimized, and the snubber circuit is individually provided for each semiconductor element constituting the power converter. Surge voltage can be suppressed only by providing a collective snubber in the power supply without providing it.

The schematic block diagram which shows the main circuit of the 3 level power converter device in embodiment of this invention. The schematic block diagram which shows the semiconductor stack in embodiment of this invention. The figure explaining the generation | occurrence | production principle of the surge voltage in the main circuit for 1 phase of a 3 level power converter device. The time chart which shows the surge voltage waveform added to the switching element of a 3 level power converter device. The snubber capacitor wiring diagram in embodiment of this invention. The internal view of the snubber capacitor in embodiment of this invention. The internal view of the snubber capacitor in embodiment of this invention. The snubber capacitor wiring diagram in embodiment of this invention. The schematic block diagram which shows the main circuit of the 3 level power converter device using the conventional GTO.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Main circuit semiconductor element, 2 ... GTO element, 2a-5a ... Snubber circuit, 6-9 ... 1st-4th switching element, 6.7 ... 2nd IEGT, 6.7 ... IEGT, 6.9 ... IEGT, 6 ... IEGT, 6 ... semiconductor element IEGT, 7 ... IEGT, 8.9 ... fourth IEGT, 8.9 ... IEGT, 8.9 ... IEGT, 8 ... IEGT, 10.11 ... second coupling diode 10.11 ... coupling diode, 10 ... first coupling diode, 10 ... coupling diode, 11 ... second coupling diode, 11 ... coupling diode, 12a ... capacitor, 12b ... diode, 12c ... discharge resistor, 12 ... Snubber circuit, 12 ... Batch snubber circuit, 12a ... Snubber capacitor, 12a1 ... Case, 12a2 ... Insulator, 12b ... Snubber diode, 12a1 ... Conductive case, 12a4 ... Co Capacitor element, 12a6.12a6 ... second internal wiring, 12a5 ... insulator, 12a3 ... capacitor case terminal, 12a6 ... first internal wiring, 12a6 ... second internal wiring, 12a6 ... internal wiring, 12a1 ... capacitor case, 12a6 ... snubber capacitor, 12a6 ... flat plate conductor, 12a2.12a2 ... insulator, 12a3 ... capacitor case terminal conductor, 12a2.12a2 ... second insulator, 12a2 ... first insulator, 12a2 ... second insulator, 12a3 ... external wiring , 13 ... Cooling fin, 14C ... Neutral point bus bar, 14C ... Bus bar, 14P ... Positive electrode bus bar, 14U ... Output bus, 14U ... Out bus bar, 15P ... Bus bar, 15N ... Bus bar, 16 ... Insulating spacer, 18 ... Semiconductor stack.

Claims (5)

A DC power source, a semiconductor stack connected to the DC power source and press-contacting a semiconductor element group consisting of a plurality of types of semiconductor elements and a cooling fin, and a parallel connection to the DC power source, and a capacitor and a diode connected in series to provide resistance A snubber circuit connected in parallel to the diode, one terminal connected to the capacitor case of the snubber circuit is disposed close to the cooling fin, and the other terminal insulated from the capacitor case is In the power converter connected to one end of the diode and the other terminal of the diode connected to the cooling fin,
The snubber circuit capacitor includes a conductive case, an external terminal, a capacitor element, a first internal wiring and a second internal wiring, an insulator, and a capacitor case terminal.
The capacitor element is housed in the conductive case, the capacitor element is fixed to the inner wall surface of the conductive case via the insulator, and the first internal wiring and the second wiring are connected to the capacitor element. One end of each internal wiring is electrically connected, and the external terminal and the capacitor case terminal are spaced apart and fixed to the outside of the conductive case. The external terminal and the other end of the first internal wiring And the capacitor case terminal and the other end of the second internal wiring are electrically connected via the conductive case, and the second internal wiring and the conductive case are connected to each other. current flow direction be reversed, the mutual inductance of said second internal wiring and is close to said conductive casing in said second internal wiring and the conductive case By increasing the power conversion device is characterized in that so as to reduce the internal inductance. A DC power source, a semiconductor stack connected to the DC power source and press-contacting a semiconductor element group consisting of a plurality of types of semiconductor elements and a cooling fin, and a parallel connection to the DC power source, and a capacitor and a diode connected in series to provide resistance A snubber circuit connected in parallel to the diode, one terminal connected to the capacitor case of the snubber circuit is disposed close to the cooling fin, and the other terminal insulated from the capacitor case is In the power converter connected to one end of the diode and the other terminal of the diode connected to the cooling fin,
The capacitor of the snubber circuit includes a conductive case, first and second external terminals, a capacitor element, first and second internal wirings, an insulator, and a capacitor case terminal conductor.
The capacitor element is housed in the conductive case, the capacitor element is housed in the case, and is fixed in the case so as to be electrically insulated from the case. And the second internal wiring are respectively electrically connected,
The first and second external terminals are spaced apart and fixed to the outside of the case, the first external terminal and the first internal wiring are electrically connected, and the capacitor case terminal conductor is The second external terminal and the capacitor case terminal conductor are electrically connected to the outside of the case via the insulator, and flow to the second internal wiring and the capacitor case terminal conductor. A power conversion device characterized in that the current direction is reversed, and magnetic coupling is strengthened by bringing the second internal wiring and the capacitor case terminal conductor close to each other.   The power converter according to claim 1, wherein the internal wiring is configured by a plurality of lead wires.   The power converter according to claim 1, wherein the internal wiring is configured by a flat conductor.   The internal wiring is insulated from the case, is electrically connected to the terminal and the external wiring outside the case, and the external wiring is disposed so that the current direction of the internal wiring is opposite. The power converter according to claim 1 or 2, characterized by these.

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