JPH03118723A - Snubber circuit - Google Patents

Abstract

PURPOSE:To reduce power consumption by connecting a regenerative circuit between the connection of a capacitor and a forward diode of a first snubber circuit and the connection of a forward diode and a capacitor of a second snubber circuit. CONSTITUTION:A pair of gate turn-off thyristors(GTO) 1a and 1b are connected with diodes 5a and 5b between their anodes and cathodes to form inverse parallel circuits. A series circuit of snubber capacitors 2a and 2b and forward snubber diodes 3a and 3b is connected across the pair of thyristors. A regenerative circuit 9a is connected at its one terminal with the connection between the snubber capacitor 2a and forward snubber diode 3a, and at the other terminal to the connection between the snubber capacitor 2b and forward snubber diode 3b. Therefore, the energy stored in the capacitors 2a and 2b flows into the regenerative circuits 9a and 9b where it is consumed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a snubber circuit for a power converter configured by connecting a plurality of power elements in series.

(Prior Art) Devices that convert power by configuring power converters using power elements are used in many fields.

In such power converters, a snubber circuit is used to suppress the rate of increase in voltage applied to the power elements, and generally has a configuration as shown in FIG. 6. In FIG. 6, 1 is a gate turn-off resistance (hereinafter referred to as GTO), 2 is a snubber capacitor, 3 is a snubber diode, and 4 is a snubber resistor. This snubber circuit consists of a snubber capacitor 2, a snubber diode 3, and a G
This is provided to suppress the rate of voltage increase when the TO is turned off. That is, when GTOl is turned on and the voltage of snubber capacitor 2 is 0, when GTOl is turned off, the current that has been flowing through GTOl flows through snubber diode 3 to snubber capacitor 2. At this time, the rate of voltage increase in GTOl is suppressed by the rate of voltage increase due to charging of the snubber capacitor 2, so that no sudden voltage change occurs in GTOl. Then, when GTOl is turned on, the charging energy of the snubber capacitor 2 is consumed through the snubber resistor 4. The power consumption of the resistor due to this operation depends on the charging voltage of snubber capacitor 2,
It is determined by the capacity of GTOl and the number of switching times of GTOl.

By the way, as a snubber circuit that eliminates power consumption due to resistance, for example, US Pat. No. 4,568.051 (19
1988), etc. Figure 7 shows an example of the circuit configuration of the voltage type inverter shown in the publication, in which one phase of AC,
This shows the lower arm. In the figure, la and lb are GT
O12 is a snubber capacitor, 3 is a snubber diode, 5
a, 5b are anti-parallel diodes, 6 is a diode, 7 is a capacitor, 8 is a DC power supply, 9 is a regeneration circuit, 10 is a beam/acdle, 11 is a positive side DC terminal, 12 is a negative side DC terminal, 1
3 is an AC output terminal.

Here, the reactor 10 is GTO1a.

This has the effect of suppressing the current change rate so that a sudden current does not flow when each GTOlb is switched on. In addition, the anti-parallel diodes 5a and 5b are G
By connecting TOla and GTOlb in opposite directions and in parallel, GTOla.

This is to prevent reverse voltage from occurring in GT0lb.

In the snubber circuit having such a configuration, the positive side DC terminal 1
The potential of 1 is V d cs The potential of negative DC terminal 12 is 0
, the potential at point A is set to Vdc+Δe. Now, GTOla
Let us consider the state in which GTOlb is on and GTOlb is off. In this state, GTOl is in a conductive state, so
The potential of the AC output terminal 13 is equal to that of the positive DC terminal 11,
The terminal voltage of GTola is 0, and the terminal voltage of GTolb is V.
It becomes d.c.

From this state, when GTOla is turned off and GTOlb is turned on, the potential of the AC output terminal 13 gradually decreases and becomes equal to the potential of the negative side DC terminal 12. At this time, the terminal voltage of GTOla increases from O to Vdc, but the rate of voltage increase is suppressed by the voltage change due to charging of the snubber capacitor 2, so a sudden voltage increase does not occur.

When the snubber capacitor 2 is charged and the potential at point B becomes higher than the potential at point A, current flows through the diode 6 to the capacitor 7 and the regeneration circuit 9. When the current flowing in the reactor 10 becomes 0, all the current flowing out from the AC output terminal 13 flows through the anti-parallel diode 5b. At this time, the terminal voltage of the snubber capacitor 2 becomes the terminal voltage of the capacitor 7, that is, Vdc+Δe.

Next, when GTOlb is turned off and GTOla is turned on, the potential of the AC output terminal 13 gradually increases and becomes equal to that of the positive DC terminal 11. At this time, the terminal voltage of GTO1b changes from 0 to V
Although the voltage increases to dc, the rate of increase is suppressed by the voltage change due to the discharge of the capacitor 2, so a sudden voltage increase does not occur. In addition, with the voltage increase at the AC output terminal 13,
Since the voltage at point B increases, the energy of the snubber capacitor 2 passes through the diode 6 and flows to the regeneration circuit 9.

The energy thus stored in the snubber capacitor 2 is guided to the regeneration circuit 9, and its output is converted into power and then regenerated to the DC circuit of the inverter or another circuit.

Incidentally, in recent years, efforts have been made to improve the performance and increase the capacity of power converters. Therefore, in order to perform high-performance control for relatively small-capacity power converters, a method is used to increase the switching frequency of the power elements, but for large-capacity converters, the relationship between the power elements is Therefore, the switching frequency cannot be increased too much. Therefore, such large-capacity converters are now configured to be capable of outputting three or more values of output voltage instead of the conventional two values. To configure a power converter that can output voltages of three or more values, two or more inverters can be multiplexed using a transformer or an accelerator, and two or more inverters can be connected between the positive DC terminal and the negative DC terminal. There is a method that has several intermediate potentials and outputs the combinations of a positive side DC terminal, an intermediate potential, and a negative side DC terminal from an AC output terminal. For the former, for example, see Chapter 6 of Semiconductor Power Conversion Circuits (Semiconductor Power Conversion System Research Specialist Committee, Institute of Electrical Engineers of Japan), and for the latter, for example, see Paper A New Neutral-Point-Clam.
ped PνH Inverter (IEEE TRA
NSACTION ON INDUSTRY APP
LICATION, VOL, I^-17, No, 5. S
EPTEMBER10CTOBER1981; AKI
The circuit system and operation are shown in detail in RA NAABAE et al.).

FIG. 8 is an example of the latter circuit. In Figure 8, 1a~
1d is GTo, 5a to 5d are anti-parallel diodes, 6a
-6d are diodes, 7a and 7b are diodes, and the potential of the positive side DC terminal 11 is Vdc, and the potential of the negative side DC terminal 12 is 0.
, the potential at point A is V d c /2.

In the circuit shown in FIG. 8, GTOla.

When GTOlb is on and GTOlc and GTold are off, GTOla and GTOlb are conductive and the terminal voltage is 0.
Therefore, the potential of the AC output terminal 13 is the same as that of the positive DC terminal 1.
It becomes equal to the potential of 1.

GTO1b, GTOI C is on, GTO1a.

When GTold is off and the current flows from the AC output terminal 13 depending on the direction of the current, the current is A.
From the point, also diode 6a.

When flowing through GTOlc, the current flows from point A through the diode 6b and GTOlc, and in either case, the potential of AC output terminal 13 becomes equal to point A.

GTOlc, GTold on, GTOla.

When GTOlb is off, GTOIc.

Since the terminal voltage becomes 0 when GTold is in a conductive state, the potential of the AC output terminal 13 becomes equal to the potential of the negative side DC terminal 12.

Therefore, using these GTOla, GTOlb, GTOlc.

By operating GTold as shown in FIG. 9, the potential of the AC output terminal 13 can be made closer to a sine wave.

(Problems to be Solved by the Invention) As described above, in conventional large-capacity power converters, GTOs are widely used, and because these GTOs have large restrictions on the rate of voltage change applied to the elements, a snubber circuit is indispensable. Become an element. Further, even when power elements other than GTO are used, it is necessary to use a snubber circuit in order to reduce the load on the power elements.

However, in the case of a power converter configured as shown in Fig. 8,
It is not possible to construct a snubber circuit as shown in FIG. Therefore, if a snubber circuit like the one shown in FIG. 6 is provided for each GTO shown in FIG. A cooling device must be provided to handle the power consumed by the resistor, which poses a problem of increasing the size of the converter.

The present invention provides a snubber with low power consumption that can effectively absorb charging energy of a snubber capacitor without using a snubber resistor for a plurality of series-connected power elements constituting a large-capacity power converter. The purpose is to provide circuits.

[Structure of the Invention] In order to achieve the above object, in the first invention, 2n power elements (where n is an integer of 2 or more) are connected in series between the positive side DC terminal and the AC output terminal, In the configured power converter, two power elements are set as one set, and a first snubber is configured by connecting a capacitor and a forward diode in this order from the anode terminal to the cathode terminal of the power element on the positive side, A forward diode and a capacitor are connected in this order from the anode terminal to the cathode terminal of the power element on the negative side to form a second snubber, and the connection point between the capacitor and the forward diode of the first snubber and the second A regeneration circuit is connected to the connection point between the snubber's forward diode and the capacitor.

In addition, in the second invention, the positive side DC terminal and AC output! 20+1 (however, n: an integer of 2 or more) between the terminal and the terminal
In a power converter in which a positive side arm and a negative side arm are configured by connecting power elements in series, the first power element connected to the positive DC terminal has an anode terminal and a cathode terminal of the element. A snubber consisting of a directional diode and a capacitor is connected, a positive regeneration circuit is connected between the connection point between the diode and the capacitor of the snubber and the positive DC terminal, and a positive regeneration circuit is connected to the negative DC terminal. A snubber consisting of a capacitor and a forward diode is connected from the anode terminal of the power element No. 1 to the cathode terminal of the element, and a negative regeneration circuit is provided between the connection point of the snubber diode and the capacitor and the negative DC terminal. For the second and subsequent power elements of the positive side arm and the negative side arm, each set of two power elements is connected, and a capacitor is connected from the anode terminal of the power element on the positive side to the cathode terminal. , a forward diode are connected in this order to form a first snubber, and a forward diode and a capacitor are connected in this order from the anode terminal to the cathode terminal of the power element on the negative side to form a second snubber. A regeneration circuit is connected to a connection point between the capacitor and the forward diode of the first snubber and a connection point between the forward diode and the capacitor of the second snubber.

(Function) Therefore, in the snubber circuit configured as in the first invention, there are 2n snubber circuits (2n pieces) between the positive side DC terminal and the AC output terminal and between the negative side DC terminal and the AC output terminal. However, if n is an integer of 2 or more) power elements are connected in series, when one set of power elements is turned on, the energy stored in the first and second snubber capacitors is transferred to the regeneration circuit. Since it flows and is consumed, there is no need for a snubber resistor as in the conventional case, thereby reducing power loss.

In addition, in the snubber circuit configured as in the second invention, there are 2n+1 snubber circuits (however, n
; an integer of 2 or more) are connected in series, when the first power element connected to the positive side DC terminal and the negative side DC terminal is turned off, the element and the positive side DC terminal, Since the energy of the accelerator provided between the connection with the negative side DC terminal flows into the regeneration circuit, the excess energy existing in the reactor can be effectively used, and the power from the second and subsequent of the positive side arm and the negative side arm is Regarding the elements, as in the first invention, when a set of power elements is turned on, the energy stored in the first and second snubber capacitors flows to the regeneration circuit and is consumed, resulting in power loss. can be made smaller.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows one inverter as an example of the configuration of a snubber circuit according to the present invention. In Figure 1,
1a to 1d are GTO12a to 2d are snubber capacitors, 3a to 3d are snubber diodes, 5a to 5d are anti-parallel diodes, 6a to 6d are diodes, 7a and 7b are capacitors, 8 is a DC power supply, 9a and 9b are regeneration circuits ,1
1 is a positive DC terminal, 12 is a negative DC terminal, and 13 is an AC output terminal. Further, the potential of the positive side DC terminal 11 is Vdc
, the potential of the negative side DC terminal 12 is 0, and the potential of point A is V d
c/2, and the regeneration circuits 9a and 9b are controlled so that the terminal voltage is sufficiently lower than the DC voltage Vdc.

Here, GTO1a to GTO1d are connected in series, one end of which is connected to a positive DC terminal 11 connected to DC type R8, and the other end connected to a negative DC terminal 12 connected to DC power supply 8. Further, capacitors 7a and 7b are connected in series between the positive side DC terminal 11 and the negative side DC terminal 12, and the voltage dividing point A is connected to c'ro through the diode 6a.
It is connected between the connection between ia and GTOlb, and between the connection between GTOIC and GTOld via the diode 6b. Furthermore, if GTOla and GTO1b are a pair, an anti-parallel diode 5a is connected between the anode terminal and cathode terminal of GTOla on the positive side, and a series circuit of snubber capacitor 2a and snubber diode 3a in the l1li direction is connected. , and GTOl on the negative side
An anti-parallel diode 5b is connected between the anode terminal and the cathode terminal of b, and a series circuit of a forward snubber diode 3b and a snubber capacitor 2b is connected. Then, the connection point between the snubber capacitor 2a and the forward snubber diode 3b is connected to one end of the regeneration circuit 9a via the diode 6c of the illustrated polarity, and the connection point between the forward snubber diode 3b and the snubber capacitor 2b is It is connected to the other end of the regeneration circuit 9a.

Since the configuration is similar to that described above in the case where GTOlc and GTold are combined as one set, the explanation thereof will be omitted here.

Next, the operation of the snubber circuit configured as described above will be described.

Now, in FIG. 1, it is assumed that the upper arms, that is, GTOla and GTOlb, are in the on state, and the lower arms, GTOlc and GTOld, are in the off state. At this time, GTOL a.

Since GTOlb is in a conductive state, the potential of the AC output terminal 13 is equal to the potential of the positive DC terminal 11, and GTOla,
The terminal voltage of GTOlb is 01GTO1c, and the terminal voltage of GTOld is Vdc/2. Also, a snubber capacitor 5a.

5b terminal voltage is 0, snubber capacitor 5c,
The terminal voltage of 5d is V d c /2, respectively.

When GTOla is turned off and GTOIC is turned on from this state, the terminal voltage of GTo 1 a gradually increases. At this time, the voltage increase rate of GTOla is the snubber capacitor 2a
Since the voltage change is suppressed to the voltage change due to charging, a sudden voltage increase does not occur.

Also, by turning on GTOlc, GTOl
c, diode 3d, regeneration circuit 9b, diode 6d,
Since a circulating current flows through the snubber capacitor 2c,
All of the energy in the snubber capacitor 2c is transferred to the regeneration circuit 9b.
guided by. Then, the potential of the AC output terminal 13 becomes equal to point A, and the terminal voltage of the snubber capacitor 2a becomes Vcd.
/2, the terminal voltage of the snubber capacitor 2c becomes 0.

Next, when GTO1b is turned off and GTOld is turned on from the low state, the terminal voltage of GTOlb gradually increases. At this time, the rate of voltage increase of GTOlb is suppressed by the voltage change due to charging of the snubber capacitor 2b, so a sudden voltage increase does not occur. Further, by turning on GTold, a circulating current flows through GTold, the snubber capacitor 2d, the regeneration circuit 9b, the diode 6d, and the snubber diode 3C, so that all the energy of the snubber capacitor 2d is guided to the regeneration circuit 9b.

Then, the potential of the AC output terminal 13 becomes equal to that of the negative DC terminal 12, and the terminal voltage of the snubber capacitor 2b becomes Vdc.
/2, the terminal voltage of the snubber capacitor 2d becomes O.

The same operation applies to other switching modes.
The voltage increase rate when the GTO is off is suppressed by charging the corresponding snubber capacitor, and when the GTO is on, all the energy of the snubber capacitor is transferred to the regeneration circuit 9a or 9b.
guided by.

As described above, in this embodiment, the charging energy of the capacitor can be effectively guided to the regeneration circuit by the snubber circuit consisting of a pair of GTO diodes and capacitors connected in series.

Next, other embodiments of the present invention will be described.

FIG. 2 shows an example of a configuration in which four sets are connected in series when the number of series is two. In Figure 2, 8a-8
d is a DC power supply, and since the other components correspond to the corresponding symbols in FIG. 1, their explanation will be omitted here.

As for the operation of the main circuit, when GTO1a to GTO1d are on and the other GTOs are off, the potential of the AC output terminal 13 becomes equal to that of the positive DC terminal 11.
When GTO1b to GTO1e are on and the other GTOs are off, the potential of the AC output terminal 13 becomes equal to point A.

When GTOlcmGTOlf is on and the other GTOs are off, the potential of the AC output terminal 13 becomes equal to point B.

When GTold-GTOlg are on and the other GTOs are off, the potential of the AC output terminal 13 becomes equal to point C'.

When GTOle-GTOl,h is on and the other GTOs are off, the potential of the AC output terminal 13 becomes equal to that of the negative DC terminal 12.

Regarding the regenerative operation, when the GTO is turned off, the rate of voltage increase of the GTO is suppressed by the snubber capacitor, and when the GTO is turned on, the energy of the snubber capacitor is guided to the regeneration circuit, as in the previous embodiment.

Moreover, FIG. 3 shows a configuration example in which two sets are connected in series when the number of series is three, and the same symbols are attached to the same components as in FIG. 2.

In this case, as shown in FIG. 3, in a set of GTO series circuits connected to the positive DC terminal 11 side,
A series circuit of an antiparallel diode 5a% snubber diode 3a and a snubber capacitor 2a is connected between the anode and cathode of GTOla, and the anode side of GTOla is connected to the regeneration circuit 9a via a diode 6e with the polarity shown. At the same time, the connection point between the snubber diode 3a and the snubber capacitor 2a is connected to the regeneration circuit 9a. Also, the other 2
The configuration for the GTOlb and GTOlc is similar to the case where the two GTOlb and GTOlc are combined into one set as shown in FIG. Another set of GTO series circuits connected to the negative DC terminal 12 side are also configured in the same manner as described above.

Even when the number of series connections is odd, the operation of the main circuit is the same as that of the embodiment shown in FIG. 2, so a description thereof will be omitted here.

Further, in FIG. 4, when the number of GTOs in series is three, two sets are connected in series, and a reactor 10a, a reactor 10a, and a 10b, and the same components as in FIG. 3 are given the same symbols and their explanations will be omitted. In the embodiment shown in FIG. 4, the rate of change in voltage is limited by a snubber capacitor, and the rate of change in current is limited by a reactor.

Next, the operation of the embodiment shown in FIG. 4 will be described.

Now, in FIG. 4, it is assumed that the positive side arms, that is, GTO1a to GTO1c, are on, and the negative side arms, GTO1d to GTO1f, are in the off state.

At this time, GTO1a to GTO1c are in a conductive state, so the potential of the AC output terminal 13 is equal to the potential of the positive DC terminal 11, the terminal voltage of GTO1a to GTO1c is 0, and the terminal voltage of GTO1d to GTO1f is Vd.
c/3. Further, the terminal voltages of the snubber capacitors 2a to 2C are each 0, and the terminal voltages of the snubber capacitors 2d to 2f are each Vdc/3.

From this state, turn off GTO1a to GTO1c, and
When 1d to 1f are turned on, the current flowing in the reactor 10a flows through the snubber diode 3a s snubber capacitor 28.2b% snubber diode 3b = 3cs snubber capacitor 2C, and the positive side snubber capacitor 2a.
Charge ~2C.

At this time, the terminal voltages of GTO1a to GTO1c increase, but the rate of voltage increase is respectively from snubber capacitors 2a to
Since the voltage change is suppressed to 2C charging, a sudden voltage increase does not occur in the GTO.

The charging voltage of snubber capacitors 2a to 2C is V, respectively.
When dc/3 is exceeded, the load current begins to flow through the GTO1d to GTO1f on the negative side arm, and the current in the reactor 10a circulates through the accelerator 10a, snubber diode 3A, S diode 6A, and regeneration circuit 9A, and decreases. . At this time, GTO1d.

By turning on GTole, GTO1d.

GTO1e, snubber capacitor 2 e s regeneration circuit 9
A circulating current flows through the cs diode 6c and the snubber capacitor 2d, and the snubber capacitor 2d.

The energy of 2e is guided to the regeneration circuit 9C. Also, GT
By turning on Olf, GTOlf.

A circulating current flows through the reactor 10b1 regeneration circuit 9d, diode 6d, and snubber capacitor 2f, and the energy of the snubber capacitor 2f is guided to the regeneration circuit 9d.

From this state, when GTO1d to GTO1f on the negative side arm are turned off and GTO1a to GTO1c on the positive side arm are turned on, the current flowing in the reactor 10b is transferred to the snubber capacitor 2d, snubber diode 3d, 3es snubber capacitor 2e.

2f and snubber diode 3f, charging the negative side snubber capacitors 2d to 2f. At this time, GTO1d-
Although the terminal voltage of the GTO 1f increases, the rate of voltage increase is suppressed by the voltage change due to charging of the snubber capacitors 2d to 2f, so that no sudden voltage increase occurs in the GTO. When the charging voltage of snubber capacitors 2d to 2f exceeds Vdc/3, the load current starts to flow through the GTO on the positive side arm, and the reactor 10b
current beam accelerator 10b1 snubber diode 3f.

It circulates through the diode 6d and the regeneration circuit 9d and decreases. At this time, GTO1b and GTO1c are turned on by turning on GTO1b and GTO1c.

Snubber capacitor 2c, diode 6d, regeneration circuit 9b
, a circulating current flows through the snubber capacitor 2b, and the energy of the snubber capacitors 2b, 2c is guided to the regeneration circuit 9b. Also, by turning on GTola, GT
A circulating current flows through the o 1 g, reactor 10a, regeneration circuit 9 a s diode 6a, and snubber capacitor 2a, and the energy of the snubber capacitor 2a is transferred to the regeneration circuit 9.
guided by a.

In the embodiment shown in FIG. 4, when the number of GTOs in series is three, two sets are connected in series, and the positive side DC terminal 11 and negative side DC terminal derived from one DC power supply 8 are connected in series. In the configuration in which the voltage change rate and current change rate applied to each GTOI a to GTOI f are suppressed by being connected to the terminal 12 via reactors 10a and 10b, respectively, the snubber capacitors 28 to 2f and the reactor 10a used for suppression are , 10b can be effectively utilized and guided to the regeneration circuits 9a to 9d.

In addition, Fig. 5 shows 2 for the case where the number of GTOs in series is 5.
This shows an example of a configuration in which the sets are connected in series and connected to the positive side DC terminal 11 and negative side DC terminal 12 derived from one DC power supply 8 via reactors 10a and 10b, respectively. Parts corresponding to the shown components are given the same symbols. Also, regarding the operation of the main circuit, the fifth
Since it is similar to the figure, its explanation will be omitted.

[Effects of the Invention] As described above, according to the present invention, charging energy of a snubber capacitor can be reduced without using a snubber resistor for a plurality of series-connected power conversion elements constituting a large-capacity power converter. It is possible to provide a snubber circuit with low power consumption that can effectively absorb energy.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of a snubber circuit according to the present invention, FIGS. 2 to 5 are circuit diagrams showing other embodiments of the present invention, and FIG. 6 is a circuit diagram showing a conventional snubber circuit. The circuit configuration diagram; Figure 7 is a configuration diagram of a conventional snubber circuit including a regenerative circuit; Figure 8 is a circuit diagram showing an example of the configuration of an inverter that can output three values to the AC output terminal; FIG. 2 is a time chart for explaining the effect of FIG. 1a-1h...GTo, 2a-2h...snubber capacitor, 3a-3h...snubber diode, 58-5
h...Anti-parallel diode, 6a-6j...Diode, 7, 7a, 7b/w capacitor, 8.8a-8
d...DC power supply, 9a to 9f...Regeneration circuit, 10a
. 10b...Reactor, 11...Positive DC terminal, 1
2...Negative side DC terminal, 13...AC output terminal.

Claims (3)

[Claims] (1) 2n (n: an integer greater than or equal to 1) power elements are connected in series between the positive DC terminal and the AC output terminal, and 2n (n is an integer greater than or equal to 1) power elements are connected in series between the negative DC terminal and the AC output terminal. However, in a power converter configured by connecting power elements in series (n: an integer of 1 or more), two power elements are considered as one set, and a capacitor is connected from the anode terminal to the cathode terminal of the power element on the positive side. , a forward diode are connected in this order to form a first snubber, and a forward diode and a capacitor are connected in this order from the anode terminal to the cathode terminal of the power element on the negative side to form a second snubber. A snubber circuit characterized in that a regeneration circuit is connected to a connection point between a capacitor and a forward diode of a first snubber and a connection point between a forward diode and a capacitor of a second snubber. (2) 2n+1 (where n is an integer greater than or equal to 1) power elements are connected in series between the positive DC terminal and the AC output terminal,
In a power converter in which 2n+1 (where n is an integer of 1 or more) power elements are connected in series between a negative DC terminal and an AC output terminal to form a positive arm and a negative arm,
A snubber consisting of a forward diode and a capacitor is connected from the anode terminal of the first power element connected to the positive side DC terminal to the cathode terminal of the element, and the connection point between the diode and the capacitor of the snubber and the A positive side regeneration circuit is connected between the positive side DC terminal, and a capacitor and a forward diode are connected from the anode terminal of the first power element connected to the negative side DC terminal to the cathode terminal of the element. A snubber is connected, a negative regeneration circuit is connected between the connection point of the snubber's diode and the capacitor, and the negative DC terminal, and a negative regeneration circuit is connected between the second and subsequent power elements of the positive arm and the negative arm. The first snubber is formed by connecting a capacitor and a forward diode from the anode terminal to the cathode terminal of the power element on the positive side, respectively, as a set of two power elements, and the power element on the negative side. A forward diode from the anode terminal to the cathode terminal of the device,
The capacitors are connected in this order to form a second snubber, and a regeneration circuit is connected to the connection point between the capacitor and the forward diode of the first snubber and the connection point between the forward diode and the capacitor of the second snubber, respectively. A snubber circuit characterized by: (3) Among the 2n+1 power elements (where n is an integer greater than or equal to 1) connected in series between the positive DC terminal and the AC output terminal and between the negative DC terminal and the AC output terminal, 3. The snubber circuit according to claim 2, wherein a reactor is provided between the connections between each first power element and the positive DC terminal and the negative DC terminal.