JP2019054665A - Power conversion device - Google Patents

Abstract

To provide a power conversion device for railroad capable of suppressing a short-circuit current at the time of short-circuit and protecting an arm short-circuit of an inverter employing a wide bandgap semiconductor and the like.SOLUTION: A power conversion device comprises: a pair of DC terminals connected to a DC power supply; an AC terminal connected to a load; an inverter power unit including an inverse conversion circuit composed of a plurality of semiconductor elements and converting DC power to AC power and a switching capacitor connected to an input side of the inverse conversion circuit to supply electric charge when the semiconductor element is switched; and a smoothing capacitor provided between the pair of DC terminals and an input side of the inverter power unit. The smoothing capacitor is connected to the inverter power unit via wiring including an inductance of a prescribed value or higher.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device.

  An example of the configuration of a railway vehicle power converter is shown in FIG. In FIG. 2, 21 is a current collector (pantograph), 24 is a high-speed circuit breaker, 25 is a current breaker, 26 is a charging resistor, 11 is a reactor, 28 is a smoothing capacitor, 22 is a motor, 13 'is an inverter power unit, 23 Is a wheel and 27 is a rail.

  The operation of the circuit of FIG. 2 will be described. The DC power obtained from the overhead wire is collected by a current collector (pantograph) 21 and supplied to the inverter power unit 13 ′ via the high-speed circuit breaker 24, the current breaker 25, and the reactor 11.

  A charge resistor 26 is connected in parallel to the circuit breaker 25 in order to suppress an inrush current when the power is turned on. The reactor 11 is disconnected to limit the current increase rate di / dt so that an overcurrent does not flow from the substation when a so-called ground fault occurs in which a part of the main circuit is short-circuited to the ground potential. It is connected in series with the flow device 25.

  The inverter power unit 13 ′ stabilizes the DC voltage by a plurality of power semiconductor modules 2 ′ (PU, NU, PV, NV, PW, NW), a gate drive circuit 15 that controls the gate of the power semiconductor module 2 ′, and the like. For smoothing capacitor 28. The inverter power unit 13 ′ converts the input DC power into a three-phase AC having an arbitrary frequency and an arbitrary voltage, and drives the motor 22. Further, the inverter power unit 13 'has a cooler (not shown) for cooling the power semiconductor module 2'.

  In the inverter power unit 13 ', an IGBT (Insulated Gate Bipolar Transistor) using Si (silicon) as a material is generally widely used as a power semiconductor. When an IGBT is applied to an inverter power unit, a design that takes into account an arm short circuit due to a malfunction of the gate drive circuit or the IGBT itself is required. The arm short circuit means that a plurality of IGBTs connected in series between power supply lines, for example, the power semiconductor module 2 ′ (PU) and the power semiconductor module 2 ′ (NU) in FIG. This is a phenomenon in which the minus is short-circuited. When the power supply is short-circuited, an excessive current is supplied from the smoothing capacitor 28 to the semiconductor element (IGBT), leading to destruction.

  The time it takes for the power semiconductor to break down when a short circuit occurs is called the short circuit tolerance. If the short circuit is detected in a shorter time than the short circuit tolerance, the power semiconductor is turned off and the current is stopped to protect the power semiconductor. In the case of an IGBT having a withstand voltage of 1.7 kV to 6.5 kV used for a power conversion device for a railway vehicle, there is generally a short circuit withstand capability of about 10 μs or more, and protection is possible with a short circuit protection circuit.

JP 2006-103897 A

  In recent years, power semiconductors using wide band gap semiconductors such as SiC (silicon carbide) and GaN (gallium nitride) instead of IGBTs are becoming widespread. Wide bandgap semiconductors have the advantage of low loss, but short-circuit withstand capability is short (generally 1/2 or less of Si-IGBT), and the above-mentioned short-circuit protection circuit cannot keep up with the short-circuit protection circuit before operation. There is a problem that the semiconductor element is destroyed.

  In order to solve this problem, the time until the breakdown, that is, the short-circuit withstand capability is increased by more than twice by suppressing the increase rate di / dt of the current at the time of short-circuit to 1/2 or less, and the protection by the short-circuit protection circuit is achieved. Possible methods are considered.

The rate of increase in current at the time of short circuit is calculated using the following formula (the sum of the inductance of the smoothing capacitor charging voltage Vcc and the main circuit inductance Ls (the inductance of the smoothing capacitor and two series power semiconductors and the wiring connecting them): 1).
di / dt = Vcc / Ls (1)

  From equation (1), if Ls is increased more than twice, di / dt is reduced to 1/2 or less, and the overcurrent at the time of short-circuit can be suppressed to 1/2 or less. I understand that I can do it. On the other hand, if Ls is increased more than twice, the voltage generated in Ls is increased more than twice due to the current change when the power semiconductor cuts off the current, and an overvoltage is applied to the wide bandgap semiconductor, resulting in destruction. Therefore, Ls cannot be simply increased.

  As a method of suppressing di / dt, a method of reducing Vcc is also conceivable. For this purpose, it is necessary to reduce the capacity of the smoothing capacitor to at least 1/2 or less, and when a short circuit occurs and an overcurrent flows, the smoothing capacitor is quickly discharged to reduce Vcc to 1/2 or less. is there. However, if the capacity of the smoothing capacitor is reduced, the fluctuation amount ΔVcc of the Vcc generated in the smoothing capacitor due to the power consumed during normal motor driving increases, and the operation of the motor controlled according to Vcc becomes unstable. Causes problems such as motor vibration and wheel slipping.

  As described above, in the case of an inverter using a wide band gap semiconductor, there is a problem that it is difficult to protect by a protection circuit when a short circuit occurs.

  The present invention provides a means for solving the above-mentioned problems, and does not increase the main circuit inductance, impairs the control stability, suppresses the short-circuit current at the time of short-circuit, and applies a wide band gap semiconductor or the like. An object of the present invention is to provide a railway power converter that can protect an arm short circuit of an inverter.

  A power conversion device according to the present invention includes a pair of DC terminals connected to a DC power source, an AC terminal connected to a load, an inverse conversion circuit configured of a plurality of semiconductor elements and converting DC power into AC power, and a semiconductor element. An inverter power unit having a switching capacitor connected to the input side of the inverse conversion circuit in order to supply electric charge during switching, and a smoothing capacitor provided between the pair of DC terminals and the input side of the inverter power unit. The smoothing capacitor is connected to the inverter power unit from the smoothing capacitor via a wiring having an inductance greater than or equal to a predetermined value.

  ADVANTAGE OF THE INVENTION According to this invention, even when a power semiconductor device with short short circuit tolerance, such as a wide band gap semiconductor, is used for a power converter, short circuit protection is attained without impairing the control stability of a system. Configurations and effects other than those described above will become apparent from the following description of embodiments.

It is a figure explaining the structure of the power converter device which concerns on Example 1. FIG. It is an example of the circuit diagram of the conventional power converter device. It is the figure which showed the time change of the short circuit current of the conventional inverter power unit and the inverter power unit in Example 1. FIG. It is a figure explaining the structure of the power converter device which concerns on Example 2. FIG. It is a figure explaining the structure of the power converter device which concerns on Example 3. FIG.

  Hereinafter, Examples 1 to 3 will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a power conversion device for a railway vehicle according to a first embodiment. In FIG. 1, the same components as those of the conventional power converter for a railway vehicle shown in FIG.

The power converter according to the first embodiment is different from the conventional power converter for a railway vehicle shown in FIG. 2 in that it has an inverter power unit 13 and a smoothing capacitor 14 for stabilizing a DC voltage. The inverter power unit 13 includes an inverse conversion circuit 10 for converting DC power into AC and a switching capacitor 12.
The power conversion device according to the first embodiment converts the DC power supplied from the overhead line 20 into a three-phase AC having an arbitrary frequency and an arbitrary voltage, and supplies the AC power to the motor (AC motor) 22. The supplied DC power is input to the terminal pair (P, N), and AC power is supplied to the motor 22 connected to the AC terminal A.

  In FIG. 1, 21 is a current collector (pantograph), 24 is a high-speed circuit breaker, 25 is a current breaker, 26 is a charging resistor, 11 is a reactor, 23 is a wheel, and 27 is a rail. The DC power obtained from the overhead line 20 is collected by the pantograph 21 and input to the terminal pair (P, N) via the high-speed circuit breaker 24, the circuit breaker 25, and the reactor 11. A charge resistor 26 is connected in parallel to the circuit breaker 25 in order to suppress an inrush current when the power is turned on. The reactor 11 is disconnected to limit the current increase rate di / dt so that an overcurrent does not flow from the substation when a so-called ground fault occurs in which a part of the main circuit is short-circuited to the ground potential. Connected in series with the vessel.

  The inverse conversion circuit 10 includes at least a plurality of power semiconductor modules 2 (PU, NU, PV, NV, PW, NW) and a gate drive circuit 15 that supplies a drive signal to these power semiconductor modules 2. The inverse conversion circuit 10 also includes a short circuit protection circuit (not shown) for preventing the power semiconductor module 2 from being destroyed when a short circuit occurs. This short circuit protection circuit may be the same circuit as that used in a known inverter. Furthermore, the inverse conversion circuit 10 may have a cooler for cooling the power semiconductor module 2, for example, as other devices.

One of the differences between the power converter according to this embodiment and the conventional power converter shown in FIG. 2 is that the power converter according to this embodiment replaces the smoothing capacitor 28 shown in FIG. One capacitor (the switching capacitor 12 and the smoothing capacitor 14) is provided.
In FIG. 1, reference numeral 142 denotes a wiring between the smoothing capacitor 14 and the inverter power unit 13, and this wiring 142 has a (parasitic) inductance greater than or equal to a predetermined value (hereinafter referred to as “parasitic” by the wiring 142. Is expressed as Lo). In FIG. 1, the wiring 142 exists on the positive electrode side (the side where the terminal P exists) and the negative electrode side (the side where the terminal N exists), but the (parasitic) inductance of the wiring on the positive electrode side and the wiring on the negative electrode side. The sum is Lo.

  An inverter circuit 10 included in the power converter according to the present embodiment includes a SiC-MOSFET (Silicon-Carbide Metal) as a power semiconductor module 2 (PU, NU, PV, NV, PW, NW) that constitutes the inverter circuit 10. -Oxide-Semiconductor Field-Effect Transistor) is different from the conventional power converter (the conventional power converter shown in FIG. 2 is an IGBT (Insulated Gate Bipolar Transistor) as the power semiconductor module 2, for example. Used). However, other points, for example, the arrangement configuration of the inverse conversion circuit 10 are the same as those of the conventional power conversion device.

  The power semiconductor module 2 includes a SiC-MOSFET and a diode connected in antiparallel to the SiC-MOSFET. In the present embodiment, an example in which the semiconductor element used in each power semiconductor module 2 is a SiC-MOSFET will be described, but a wide band gap semiconductor such as a gallium nitride material or diamond is used instead of the SiC-MOSFET. Alternatively, an IGBT may be used.

  The feature of this embodiment is that the smoothing capacitor used in the conventional power converter is arranged separately for switching and smoothing, and the smoothing capacitor 14 has a (parasitic) inductance greater than a predetermined value. The point is that it is connected to the inverse conversion circuit 10 via the wiring 142.

  Generally, the total capacity of capacitors mounted on the main circuit is about 3000 μF to 20000 μF, and is selected according to the DC voltage and the output of the connected motor.

Here, the effect obtained by providing two of the switching capacitor 12 and the smoothing capacitor 14 in place of the smoothing capacitor used in the conventional power converter as in this embodiment will be described.
FIG. 3A is a diagram illustrating an example of a time change of a current flowing through the semiconductor element (SiC-MOSFET or IGBT) of the power semiconductor module 2 (or 2 ′) when an arm short circuit occurs. In FIG. 3A, the horizontal axis represents the elapsed time since the occurrence of the short circuit, and the vertical axis represents the magnitude of the current flowing through the semiconductor element. A dotted line indicates a short circuit current that flows through the semiconductor element when a short circuit occurs in the conventional power conversion device, and a solid line indicates a short circuit current that flows through the semiconductor element when a short circuit occurs in the power conversion device according to the present embodiment. Indicates.

  In the conventional power converter (for example, FIG. 2), the smoothing capacitor 28 used in the inverter power unit 13 ′ is composed of one large-capacitance capacitor or a plurality of capacitors concentrated in one place. Since the electric charges of all these capacitors are discharged and a large current flows through the semiconductor element, as shown by the dotted line, the semiconductor element is destroyed due to heat generation or the like at time t2.

On the other hand, in the case of the power converter according to the present embodiment, current flows from both the switching capacitor 12 and the smoothing capacitor 14 when a short circuit occurs. However, since the smoothing capacitor 14 is connected to the inverse conversion circuit 10 via the (parasitic) inductance of the wiring 142, di / dt is limited, and the current value is the discharge current from the switching capacitor 12. Therefore, the total current flowing through the semiconductor element is smaller than in the conventional case.
Further, since most of the current is supplied from the switching capacitor 12, the switching capacitor 12 is discharged first, and the current starts decreasing at time t1. At time t3, since the discharge current from the smoothing capacitor 14 becomes larger than the discharge current of the switching capacitor 12, the current flowing through the semiconductor element starts to increase again. The current change rate di / dt at this time is a value determined by the (parasitic) inductance of the wiring 142. At time t4, the current is interrupted by a short-circuit protection circuit not shown in FIG. 1, and the system can be stopped without destroying the semiconductor element.

Next, FIG. 3B is a diagram illustrating an example of a waveform of a current flowing through the semiconductor element in a normal operation state where no short circuit occurs. In FIG. 3B, the horizontal axis represents the elapsed time after the current starts to flow through the semiconductor element, and the vertical axis represents the magnitude of the current flowing through the semiconductor element. In the graph of FIG. 3B, the dotted line indicates the waveform of the current flowing through the semiconductor element when a short circuit occurs in the power conversion device according to this embodiment, while the solid line indicates the semiconductor element during normal operation. The waveform of the flowing current is shown.
In a normal operation state, since the inductance of the motor 22 that is a load is large, di / dt is limited and the increase in current becomes gradual. In general, the inductance of the motor is about several mH and is sufficiently larger than the (parasitic) inductance of the switching capacitor 12 and the wiring 142, so that the current flows from both the switching capacitor 12 and the smoothing capacitor 14 almost evenly. become. As a result, when the load motor is driven, fluctuations in the DC voltage caused by torque fluctuations of the motor can be limited by both the switching capacitor 12 and the smoothing capacitor 14, and a sufficient DC voltage damping effect can be obtained. can get.

  However, the capacitance of the switching capacitor 12, the capacitance of the smoothing capacitor 14, and the (parasitic) inductance of the wiring 142 connecting them must be set appropriately.

  First, the switching capacitor 12 needs to be set to a value that can suppress the current flowing through the semiconductor element when a short circuit occurs. In the case of a wide band gap semiconductor, depending on the structure design of the semiconductor element, the short circuit tolerance is reduced to about 1/2 to 1/10 of that of a silicon element (a semiconductor element such as an IGBT made of silicon). It is necessary to suppress the current to about 1/2 to 1/10. For this reason, the capacity of the switching capacitor 12 needs to be less than or equal to the total capacity required for the inverter system, that is, the capacity of the smoothing capacitor. If a semiconductor element with a short-circuit tolerance of 1/10 is applied, the capacity of the switching capacitor 12 is also set to 1/10 of the capacity of the smoothing capacitor.

  Next, the (parasitic) inductance Lo of the wiring 142 is an inductance Ls (on the current path between the switching capacitor 12 and the inverse conversion circuit 10 so that a high di / dt current does not flow into the element when a short circuit occurs. Generally, it is referred to as “main circuit inductance” and is also referred to as “main circuit inductance Ls” below, and it is necessary to make it, for example, twice or more of Ls. In particular, considering the short-circuit tolerance, the (parasitic) inductance Lo of the wiring 142 needs to be set to at least about 10 times Ls.

  For example, in an inverter for a direct current 1500V overhead line used for a train traveling in the Tokyo metropolitan area, etc., when a SiC-MOSFET whose short-circuit withstand capability is half that of a silicon IGBT is used, a switching capacitor and a smoothing capacitor are used. Both are set to 3200 μF.

  Further, since the main circuit inductance Ls is generally about 50 nH to 200 nH, it is desirable to set the (parasitic) inductance Lo of the wiring to about 500 nH to 2000 nH as about ten times this. As the wiring length in this case, an appropriate Lo can be set by selecting about 50 cm to 2 m.

  FIG. 4 is a diagram illustrating the configuration of the power conversion apparatus according to the second embodiment. In FIG. 4, the same components as those of the power conversion apparatus according to the first embodiment shown in FIG. The difference in configuration between the second embodiment and the first embodiment is that, in the power conversion device according to the second embodiment, AC power is supplied from the overhead line, and for that reason, the main point between the pantograph 21 and the converter power unit 30 is the main point. A transformer 33 is provided, and a converter power unit 30 for converting alternating current into direct current is provided between the secondary side of the main transformer 33 and the inverter power unit 13.

Operation | movement of the power converter device which concerns on Example 2 is demonstrated.
The AC power obtained from the AC overhead wire is stepped down through the main transformer 33. The converter power unit 30 converts the stepped-down AC power into DC power and supplies the DC power to the inverter power unit 13 at the subsequent stage of the converter power unit 30. The converter power unit 30 includes a forward conversion circuit 32 including a power semiconductor module 3 (PU, NU, PV, NV), a gate drive circuit 15, and the like, and a switching capacitor 31. The inverter power unit 13 generates an arbitrary three-phase AC waveform and drives the motor. Since the configuration of the inverter power unit 13 is the same as that described in the first embodiment, a description thereof is omitted here.

A smoothing capacitor 34 is arranged between the converter power unit 30 and the inverter power unit 13. The capacity of the smoothing capacitor 34 is at least twice that of the switching capacitor 12 and the switching capacitor 31.
Further, the connection between the switching capacitor 12 and the smoothing capacitor 34 and the connection between the switching capacitor 31 and the smoothing capacitor 34 are 10 times or more of the main circuit inductance Ls of the converter power unit 30 and the inverter power unit 13, respectively. Are connected by wires or conductor bars having the inductance Lo. Here, the conductor bar is a plate-like wiring made of copper or aluminum instead of the wiring.

According to this embodiment, the capacities of the switching capacitors 31 and 12 built in the converter power unit 30 and the inverter power unit 13 are set to the minimum capacity necessary for ensuring the short-circuit resistance, and the direct current generated when the motor is driven. A capacity necessary for suppressing voltage pulsation is secured by a smoothing capacitor 34 provided between the converter power unit 30 and the inverter power unit 13.
Thereby, the increase in the jumping voltage at the time of switching can be suppressed, ensuring the short circuit tolerance at the time of using a semiconductor element with low short circuit tolerance, such as a wide band gap semiconductor. Further, by setting the (parasitic) inductance Lo of the wiring connecting the switching capacitor 12 or 31 and the smoothing capacitor 34 to about 10 times the main circuit inductance Ls of the converter power unit 30 and the inverter power unit 13, a short circuit occurs. Sometimes the inflow of a short circuit current from the smoothing capacitor can be suppressed, and a decrease in short circuit tolerance can be avoided.

  FIG. 5 is a diagram illustrating the configuration of the power conversion apparatus according to the third embodiment. In FIG. 5, the same components as those of the power conversion devices according to the first and second embodiments shown in FIGS. 1 and 4 are denoted by the same reference numerals. The difference in configuration between the third embodiment and the second embodiment is that an auxiliary power unit is added in the third embodiment.

Operation | movement of the power converter device which concerns on Example 3 is demonstrated.
The AC power obtained from the AC overhead wire is stepped down through the main transformer 33. The converter power unit 30 converts the stepped-down AC power into DC power and supplies the DC power to the inverter power unit 13 at the subsequent stage of the converter power unit 30. The inverter power unit 13 generates an arbitrary three-phase AC waveform and drives the motor.
Further, a DC circuit portion between the converter power unit 30 and the inverter power unit 13 is provided in parallel with the inverter power unit 13 through a high-speed circuit breaker 44, a current breaker 45, a reactor 46, and a backflow prevention diode 47. The power unit 40 for power supply is connected. The output of the auxiliary power supply power unit 40 is connected to a three-phase transformer 48, and the output of the three-phase transformer 48 is connected to a load (not shown) such as an air conditioner.

  Since the configurations of the converter power unit 30 and the inverter power unit 13 are the same as those described in the first and second embodiments, the description thereof is omitted here. The auxiliary power supply power unit 40 includes an inverse conversion circuit and a switching capacitor 42, and converts DC power into AC. The inverse conversion circuit included in the auxiliary power supply power unit 40 includes the plurality of power semiconductor modules 4 and the gate drive circuit 15, similar to the inverse conversion circuit 10 described in the first embodiment.

A smoothing capacitor 34 is disposed between the converter power unit 30 and the inverter power unit 13. The capacity of the smoothing capacitor 34 is larger than the capacity of any of the switching capacitors 12, 31 and 42 built in the power unit, and is set to be twice or more the capacity of the switching capacitors 12, 31 and 42.
A reactor 46 and a backflow preventing diode 47 for suppressing resonance between the converter power unit 30 and the inverter power unit 13 and the auxiliary power unit 40 are also connected in series with the current breaker 45. The connection between the switching capacitors 12, 31 and 42 and the smoothing capacitor 34 built in the power unit is 10 times or more (parasitic) of the main circuit inductance Ls of the converter power unit 30, the inverter power unit 13 and the auxiliary power supply unit 40. Each is connected by a wire or a conductor bar having inductance Lo.

  The feature of the third embodiment is that a smoothing capacitor 34 is arranged in a DC circuit between the converter power unit 30, the inverter power unit 13, and the auxiliary power supply power unit 40.

According to the present embodiment, the capacities of the switching capacitors 12, 31, and 42 built in the converter power unit 30, the inverter power unit 13, and the auxiliary power supply unit 40 are set to the minimum capacity necessary for ensuring the short-circuit tolerance, The smoothing capacitor 34 secures the capacity necessary for suppressing the pulsation of the DC voltage generated when the motor is driven.
Thereby, the increase in the jumping voltage at the time of switching can be suppressed, ensuring the short circuit tolerance at the time of using a semiconductor element with low short circuit tolerance, such as a wide band gap semiconductor. Further, the (parasitic) inductance Lo of the wiring connecting the switching capacitors 12, 31 and 42 and the smoothing capacitor 34 is set to 10 of each main circuit inductance Ls of the converter power unit 30, the inverter power unit 13, and the auxiliary power supply power unit 40. By setting it to about twice, it is possible to suppress the inflow of a short-circuit current from the smoothing capacitor when a short-circuit occurs, and to avoid a decrease in short-circuit tolerance.

  As described above, in Examples 1 to 3, the example in which the SiC-MOSFET module is used for the power conversion circuit such as the inverse conversion circuit has been described. However, a wide band gap semiconductor such as a gallium nitride material or diamond, or an IGBT is used. It may be a power conversion circuit. That is, the same effect can be obtained when a power semiconductor element with a short circuit resistance is applied.

  Further, although the two-level circuit has been described in the first to third embodiments, it is obvious to those skilled in the art that the same effect can be obtained even when applied to a three-level circuit or a multi-level circuit having four or more levels. .

2 (PU, NU, PV, NV, PW, NW): Power semiconductor module 3 (PU, NU, PV, NV): Power semiconductor module 4 (PU, NU, PV, NV, PW, NW): Power semiconductor module 10: Inverse conversion circuit 11: Reactor 12: Switching capacitor 13: Inverter power unit 14: Smoothing capacitor 15: Gate drive circuit 21: Current collector (pantograph)
22: Motor 23: Wheel 24: High-speed circuit breaker 25: Circuit breaker 26: Charging resistor 27: Rail 28: Smoothing capacitor 30: Converter power unit 31: Switching capacitor 32: Forward conversion circuit 33: Main transformer 34: Smoothing Capacitors 35, 36: Electromagnetic contactor 40: Power unit for auxiliary power supply 42: Switching capacitor 44: High-speed circuit breaker 45: Current breaker 46: Reactor 47: Diode (diode for backflow prevention)
48: Three-phase transformer 142: Wiring

Claims (6)

A pair of DC terminals connected to a DC power source;
An AC terminal connected to the load;
Inverter power unit comprising an inverter circuit composed of a plurality of semiconductor elements for converting DC power into AC power, and a switching capacitor connected to the input side of the inverter circuit for supplying electric charge when the semiconductor elements are switched When,
A smoothing capacitor provided between the pair of DC terminals and the input side of the inverter power unit;
The smoothing capacitor is connected to the inverter power unit from the smoothing capacitor via a wiring having an inductance of a predetermined value or more. 2. The power conversion device according to claim 1, wherein a capacitance of the switching capacitor is ½ or less of a capacitance of the smoothing capacitor. The power converter according to claim 1 or 2, wherein the predetermined value of the inductance is set to a value that is twice or more of an inductance on a current path between the switching capacitor and the inverse conversion circuit. . The power conversion device according to any one of claims 1 to 3, wherein the semiconductor element is a wide band gap semiconductor. The power converter is a railway vehicle power converter,
The converter power unit which converts alternating current power into direct current power is provided between the pantograph which collects alternating current power from an overhead line, and the pair of direct current terminals. Power conversion device. And a power unit for auxiliary power having a second inverse conversion circuit and a second switching capacitor connected in parallel to the input side of the second inverse conversion circuit,
The auxiliary power unit is connected in parallel between the inverter power unit and the smoothing capacitor,
6. The power converter according to claim 5, wherein the smoothing capacitor is connected from the smoothing capacitor to the auxiliary power unit through a wiring having an inductance of a predetermined value or more.

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