JP6823573B2 - Power converter - Google Patents

Description

The present invention relates to a power converter.

FIG. 2 shows a configuration example of the power conversion device for railway vehicles. In FIG. 2, 21 is a current collector (pantograph), 24 is a high-speed circuit breaker, 25 is a breaker, 26 is a charging resistor, 11 is a reactor, 28 is a smoothing capacitor, 22 is a motor, and 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 the current collector (pantograph) 21 and supplied to the inverter power unit 13'via the high-speed circuit breaker 24, the breaker 25 and the reactor 11.

A charging resistor 26 is connected in parallel to the breaker 25 in order to suppress an inrush current when the power is turned on. The reactor 11 is cut off 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 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 a DC voltage. Has a smoothing capacitor 28 for the purpose. The inverter power unit 13'converts the input DC power into a three-phase alternating current having an arbitrary frequency and an arbitrary voltage to drive 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) that generally uses Si (silicon) as a material is widely used as a power semiconductor. When applying the IGBT to the inverter power unit, it is necessary to design in consideration of the arm short circuit due to the malfunction of the gate drive circuit and the IGBT itself. An 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. 2 are turned on at the same time to increase the power supply. This is a phenomenon in which the minus is short-circuited. When the power supply is short-circuited, an excessive current is supplied to the semiconductor element (IGBT) from the smoothing capacitor 28, leading to destruction.

The time it takes for a power semiconductor to break when a short circuit occurs is called the short circuit tolerance. The power semiconductor can be protected by detecting a short circuit in a shorter time than this short circuit tolerance, turning off the power semiconductor, and stopping the current. In the case of an IGBT with a withstand voltage of 1.7 kV to 6.5 kV used for a power converter of a railway vehicle, it generally has a short-circuit withstand capacity of about 10 μs or more, and can be protected by a short-circuit protection circuit.

Japanese Unexamined Patent Publication No. 2016-103897

In recent years, power semiconductors using wide bandgap semiconductors such as SiC (silicon carbide) and GaN (gallium nitride) have become widespread in place of IGBTs. While wide-band gap semiconductors have the advantage of low loss, they have a short short-circuit tolerance (generally 1/2 or less of Si-IGBT), and the protection provided by the short-circuit protection circuit described above is not in time, so before the short-circuit protection circuit operates. There is a problem that the semiconductor element is destroyed.

To solve this problem, the time until failure, that is, the short-circuit withstand capability, is doubled or more by suppressing the current increase rate di / dt at the time of short-circuit to 1/2 or less, and protection by the short-circuit protection circuit is provided. A method that enables it can be considered.

The rate of increase of the current at the time of short circuit is calculated by the following equation (total of the charging voltage Vcc of the smoothing capacitor and the main circuit inductance Ls (the sum of the inductances of the smoothing capacitor and the power semiconductor in series 2 and the wiring connecting them) It is represented by 1).
di / dt = Vcc / Ls ... (1)

From the equation (1), when Ls is increased more than twice, di / dt becomes 1/2 or less, and the overcurrent at the time of short circuit can be suppressed to 1/2 or less. Therefore, the short circuit withstand capacity can be increased more than twice. I know I can do it. On the other hand, if Ls is increased more than twice, the voltage generated in Ls becomes more than twice as high due to the change in current 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 to quickly discharge the smoothing capacitor to reduce Vcc to 1/2 or less when a short circuit occurs and an overcurrent flows. is there. However, if the capacity of the smoothing capacitor is reduced, the fluctuation amount ΔVcc of Vcc generated in the smoothing capacitor due to the power consumed during normal motor driving becomes large, and the operation of the motor controlled according to Vcc becomes unstable. This causes problems such as motor vibration and wheel slippage.

As described above, in the case of an inverter using a wide bandgap 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 problems, suppresses a short-circuit current at the time of a short circuit, does not increase the main circuit inductance, does not impair control stability, and applies a wide bandgap semiconductor or the like. The purpose of the present invention is to provide a power conversion device for railways that can protect an inverter arm short circuit.

The power conversion device according to the present invention includes a pair of DC terminals connected to a DC power supply, an AC terminal connected to a load, and an inverse conversion circuit composed of a plurality of wideband gap semiconductor elements to convert DC power into AC power. A wide band gap is provided between an inverter power unit having a switching capacitor connected to the input side of the inverse conversion circuit to supply charge when switching the semiconductor element, and a pair of DC terminals and the input side of the inverter power unit. and a capacitor for smoothing the capacitance of the switching capacitor is less than half of the capacitance of the capacitor for smoothing, the capacitor and the inverter power unit for smoothing, via a wiring having a predetermined value or more inductance characterized in that it is connected.

According to the present invention, even when a power semiconductor element having a short short circuit tolerance such as a wide bandgap semiconductor is used for the power conversion device, short circuit protection can be performed without impairing the control stability of the system. Configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a figure explaining the structure of the power conversion apparatus which concerns on Example 1. FIG. This is an example of a circuit diagram of a conventional power converter. It is a 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 conversion apparatus which concerns on Example 2. FIG. It is a figure explaining the structure of the power conversion apparatus which concerns on Example 3. FIG.

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

FIG. 1 is a diagram showing a configuration of a power conversion device for a railway vehicle according to the first embodiment. In FIG. 1, the same components as those of the conventional power conversion device for railway vehicles shown in FIG. 2 are designated by the same reference numerals.

The power conversion device according to the first embodiment differs from the conventional power conversion device for railway vehicles 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 has an inverse conversion circuit 10 for converting DC power into alternating current, and a switching capacitor 12.
The power conversion device according to the first embodiment converts the DC power supplied from the overhead wire 20 into a three-phase AC of an arbitrary frequency and an arbitrary voltage, and supplies the AC power to the motor (AC motor) 22 from the overhead wire 20. The supplied DC power is input to the terminal pair (P, N), and the AC power is supplied to the motor 22 connected to the AC terminal A.

Further, in FIG. 1, 21 is a current collector (pantograph), 24 is a high-speed circuit breaker, 25 is a 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 wire 20 is collected by the pantograph 21 and input to the terminal pair (P, N) via the high-speed circuit breaker 24, the breaker 25, and the reactor 11. A charging resistor 26 is connected in parallel to the breaker 25 in order to suppress an inrush current when the power is turned on. The reactor 11 is disconnected in order 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 has at least a plurality of power semiconductor modules 2 (PU, NU, PV, NV, PW, NW) and a gate drive circuit 15 that supplies drive signals 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. Further, the inverse conversion circuit 10 may have, for example, a cooler for cooling the power semiconductor module 2 as other equipment.

One of the differences between the power conversion device according to this embodiment and the conventional power conversion device shown in FIG. 2 is that the power conversion device according to this embodiment replaces the smoothing capacitor 28 shown in FIG. This is a point that two capacitors (switching capacitor 12 and smoothing capacitor 14) are provided.
Further, in FIG. 1, 142 represents a wiring between the smoothing capacitor 14 and the inverter power unit 13, and the wiring 142 has a (parasitic) inductance of a predetermined value or more (hereinafter, parasitic by the wiring 142). Inductance of 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 total is Lo.

The reverse conversion circuit 10 of the power conversion device according to the present embodiment is a SiC-MOSFET (Silicon-Carbide Metal) as a power semiconductor module 2 (PU, NU, PV, NV, PW, NW) constituting the reverse conversion circuit 10. -Oxide-Semiconductor Field-Effect Transistor) is used, which is different from the conventional power converter (the conventional power converter shown in FIG. 2 uses, for example, an IGBT (Insulated Gate Bipolar Transistor) as the power semiconductor module 2. I'm using it). However, other points, such as 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 is composed of a SiC-MOSFET and a diode connected to the SiC-MOSFET in antiparallel. In this embodiment, an example in which the semiconductor element used in each power semiconductor module 2 is a SiC-MOSFET will be described, but instead of the SiC-MOSFET, a wide bandgap semiconductor such as a gallium nitride based material or diamond is used. You may use it, or you may use an IGBT.

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

Generally, the total capacity of the 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 of providing two switching capacitors 12 and smoothing capacitors 14 instead of the smoothing capacitors used in the conventional power conversion device as in the present embodiment will be described.
FIG. 3A is a diagram showing an example of a time change of the 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 short circuit occurred, and the vertical axis represents the magnitude of the current flowing through the semiconductor element. The dotted line indicates the short-circuit current flowing through the semiconductor element when a short circuit occurs in the conventional power conversion device, and the solid line indicates the short-circuit current flowing through the semiconductor element when a short circuit occurs in the power conversion device according to the present embodiment. Is shown.

In a conventional power converter (for example, FIG. 2), the smoothing capacitor 28 used in the inverter power unit 13'is composed of one large-capacity capacitor or a plurality of capacitors integrated in one place, so that a short circuit occurs. 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 conversion device 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, the 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 before.
Further, since most of the current is supplied from the switching capacitor 12, the switching capacitor 12 is discharged first, and the current starts to decrease at time t1. When the time t3 is reached, the discharge current from the smoothing capacitor 14 becomes larger than the discharge current of the switching capacitor 12, so that 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 cut off 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 showing an example of a waveform of a current flowing through a semiconductor element in a normal operating state in which a short circuit does not occur. In FIG. 3B, the horizontal axis represents the elapsed time from the start of current flowing through the semiconductor element, and the vertical axis represents the magnitude of the current flowing through the semiconductor element. Further, in the graph of FIG. 3B, the dotted line shows the waveform of the current flowing through the semiconductor element when the power conversion device according to the present embodiment is short-circuited, while the solid line shows the semiconductor element during normal operation. The waveform of the flowing current is shown.
In a normal operating state, since the inductance of the motor 22, which is a load, is large, di / dt is limited and the increase in current becomes slow. Generally, the inductance of the motor is about several mH, which is sufficiently larger than the (parasitic) inductance of the switching capacitor 12 and the wiring 142, so that the current flows almost evenly from both the switching capacitor 12 and the smoothing capacitor 14. become. As a result, when driving a load motor, fluctuations in 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 bandgap semiconductor, although it depends on the structural design of the semiconductor element, the short-circuit tolerance is reduced to about 1/2 to 1/10 of that of a silicon element (semiconductor element such as an IGBT made of silicon), resulting in a short circuit. It is also necessary to suppress the current to about 1/2 to 1/10. Therefore, the capacity of the switching capacitor 12 needs to be 1/2 or less of the total capacity required for the inverter system, that is, the capacity of the smoothing capacitor. When a semiconductor element having 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 the inductance Ls (on the current path between the switching capacitor 12 and the reverse conversion circuit 10) so that a high di / dt current at the time of a short circuit does not flow into the element. Generally, it is called "main circuit inductance", and it is necessary to make it larger than "main circuit inductance Ls"), 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 DC 1500V overhead wire used for a train traveling in a metropolitan area or the like, when a SiC-MOSFET having a short circuit tolerance of 1/2 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 10 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 showing a configuration of a power conversion device according to a second embodiment. In FIG. 4, the same components as those of the power conversion device according to the first embodiment shown in FIG. 1 are designated by the same reference numerals. The structural difference 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 wire, and therefore, mainly between the pantograph 21 and the converter power unit 30. A transformer 33 is provided, and a converter power unit 30 that converts alternating current into direct current is provided between the secondary side of the main transformer 33 and the inverter power unit 13.

The operation of the power conversion device according to the second embodiment will be described.
The AC power obtained from the AC overhead line is stepped down via the main transformer 33. The converter power unit 30 converts the stepped-down AC power into DC power and supplies it to the inverter power unit 13 in the subsequent stage of the converter power unit 30. The converter power unit 30 is composed of a forward conversion circuit 32 composed of 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, the description here is omitted.

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 the capacity of the switching capacitor 12 and the switching capacitor 31.
Further, regarding 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, the main circuit inductance Ls of the converter power unit 30 and the inverter power unit 13 is 10 times or more, respectively. Connect with a wire or conductor bar that has an inductance Lo of. Here, the conductor bar is a plate-shaped wiring made of copper, aluminum, or the like 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 capacities required to secure the short-circuit withstand capability, and the direct current generated when the motor is driven is set. The capacity required for suppressing the pulsation of the voltage is secured by the smoothing capacitor 34 provided between the converter power unit 30 and the inverter power unit 13.
As a result, it is possible to suppress an increase in the flip-up voltage during switching while ensuring the short-circuit tolerance when a semiconductor element having a low short-circuit tolerance such as a wide bandgap semiconductor is used. Further, a short circuit occurs 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. Occasionally, the inflow of short-circuit current from the smoothing capacitor can be suppressed, and a decrease in short-circuit withstand capability can be avoided.

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

The operation of the power conversion device according to the third embodiment will be described.
The AC power obtained from the AC overhead line is stepped down via the main transformer 33. The converter power unit 30 converts the stepped-down AC power into DC power and supplies it to the inverter power unit 13 in 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, the DC circuit portion between the converter power unit 30 and the inverter power unit 13 is assisted in parallel with the inverter power unit 13 via a high-speed circuit breaker 44, a breaker 45, a reactor 46, and a diode 47 for preventing backflow. The power unit 40 for power supply is connected. The output of the auxiliary power supply power unit 40 is connected to the three-phase transformer 48, and the output of the three-phase transformer 48 is connected to a load (not shown) such as air conditioning.

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 has an inverse conversion circuit and a switching capacitor 42, and converts DC power into AC power. The reverse conversion circuit included in the auxiliary power supply power unit 40 has a plurality of power semiconductor modules 4 and a gate drive circuit 15 as in the reverse conversion circuit 10 described in the first embodiment.

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

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

According to this 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 power unit 40 are set to the minimum capacities required to secure the short-circuit withstand capability. The smoothing capacitor 34 secures the capacity required to suppress the pulsation of the DC voltage generated when the motor is driven.
As a result, it is possible to suppress an increase in the flip-up voltage during switching while ensuring the short-circuit tolerance when a semiconductor element having a low short-circuit tolerance such as a wide bandgap semiconductor is used. 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, the inflow of short-circuit current from the smoothing capacitor can be suppressed when a short-circuit occurs, and a decrease in short-circuit withstand capability can be avoided.

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, but a wide bandgap semiconductor such as a gallium nitride based 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 having a short short-circuit tolerance is applied.

Further, in Examples 1 to 3, the two-level circuit has been described, but it is clear to those skilled in the art that the same effect can be obtained even if the circuit is 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: Reverse 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: Breaker 26: Charging resistance 27: Rail 28: Smoothing capacitor 30: Converter power unit 31: Switching capacitor 32: Forward conversion circuit 33: Main transformer 34: Smoothing Capacitors 35 and 36: Electromagnetic contactor 40: Power unit for auxiliary power supply 42: Capacitor for switching 44: High-speed circuit breaker 45: Breaker 46: Reactor 47: Diode (diode for preventing backflow)
48: Three-phase transformer 142: Wiring

Claims (4)

A pair of DC terminals connected to a DC power supply,
AC terminal connected to the load and
A reverse conversion circuit composed of a plurality of wideband gap semiconductor elements that converts DC power into AC power, and a switching circuit connected to the input side of the reverse conversion circuit to supply electric charges when the wideband gap semiconductor element is switched. An inverter power unit with a capacitor and
A smoothing capacitor provided between the pair of DC terminals and the input side of the inverter power unit is provided.
The capacity of the switching capacitor is 1/2 to 1/10 of the capacity of the smoothing capacitor in consideration of the difference between the short-circuit withstand capability of the wide bandgap semiconductor element and the short-circuit withstand capability of the silicon semiconductor element .
A power conversion device characterized in that the smoothing capacitor and the inverter power unit are connected via wiring having an inductance of a predetermined value or more. The power conversion device according to claim 1, wherein the predetermined value of the inductance is set to a value at least twice the inductance on the current path between the switching capacitor and the reverse conversion circuit. The power conversion device is a power conversion device for railway vehicles.
The power conversion device according to claim 1 or 2, further comprising a converter power unit that converts the AC power into DC power between the pantograph that collects AC power from the overhead wire and the pair of DC terminals. Further, an auxiliary power supply power unit having a second inverse conversion circuit and a second switching capacitor connected in parallel to the input side of the second inverse conversion circuit is provided.
The auxiliary power supply power unit is connected in parallel between the inverter power unit and the smoothing capacitor.
The power conversion device according to claim 3, wherein the smoothing capacitor and the auxiliary power supply power unit are connected via wiring having an inductance of a predetermined value or more.

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