JP2003070255A - Three-level power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a converter and to enhance its reliability. SOLUTION: This three-level power converter comprises of a three-level converter circuit 3 which is formed by connecting a positive-side DC smoothing capacitor and a negative-side DC smoothing capacitor to a DC output portion, is connected to a three-phase AC main power source via a switch 1 for the main power source, and converts an output from the three-phase AC main power source into a DC. The power converter is fitted with a preparatorily charging circuit composed of a rectifier 7 for preparatory charging connected to the positive-electrode side of the positive-side DC smoothing capacitor and the negative-electrode side of the negative-side DC smoothing capacitor of the converter circuit 3, a step-up transformer 6 for preparatory charging connected to the primary side of the rectifier 7, a current limiting element 5 connected to the primary side of the step-up transformer 6, and a switch 4 for preparatory charging for supplying/interrupting an output from a single-phase AC power source for preparatory charging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention charges a positive side DC smoothing capacitor and a negative side DC smoothing capacitor connected to a DC output section of a three-level converter circuit and a DC input section of a three-level inverter circuit before starting the apparatus. The present invention relates to a three-level power conversion device equipped with a pre-charging circuit, and particularly to a three-level power conversion device capable of reducing the cost of the device and improving reliability by reducing the number of parts of the pre-charging circuit. .

[0002]

2. Description of the Related Art FIG. 7 is a circuit diagram showing an example of the overall configuration of a conventional three-level power converter of this type.

As shown in FIG. 7, in a three-level power converter, a DC output section is connected with a positive side DC smoothing capacitor and a negative side DC smoothing capacitor, and a main power source transformer 2 and a main power source switch 1 are provided. A three-level converter circuit 3 that is connected to a three-phase AC main power supply via the three-phase AC main power supply and converts the output from the three-phase AC main power supply into a direct current; A positive side pre-charge rectifier 7 such as a diode connected to the sex point side,
Positive side pre-charging step-up transformer 6 connected to the primary side of the pre-charging rectifier 7, positive side current such as current limiting resistance and current limiting reactor connected to the primary side of the pre-charging step-up transformer 6. It comprises a limiting element 5 and a positive side precharging switch 4 which is connected in series to the current limiting element 5 and which opens and closes an output from the precharging single-phase AC power source to precharge the positive side DC smoothing capacitor. Positive pre-charge circuit and 3
A negative side precharge rectifier 17 such as a diode connected to the negative side and the neutral side of the positive side DC smoothing capacitor of the level converter circuit 3, and a negative side connected to the primary side of the precharge rectifier 17 The pre-charging step-up transformer 16, the current limiting resistor 15 connected to the primary side of the pre-charging step-up transformer 16, the current limiting element 15 on the negative side such as a current limiting reactor, and the current limiting element 15 are connected in series, It comprises a negative side precharging switch 14 for opening and closing the output from the precharging single-phase AC power supply, and a negative side precharging circuit for precharging the negative side DC smoothing capacitor.

[0004]

However, in the conventional three-level power converter as described above, two circuits on the positive side and the negative side are required as the pre-charging circuit for the three-level power converter. There is a problem that the cost of the device is increased and the reliability is lowered.

An object of the present invention is to provide a three-level power conversion device capable of reducing the number of parts of the pre-charging circuit to reduce the cost of the device and improve the reliability.

[0006]

In order to achieve the above object, in the invention corresponding to claim 1, a positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to a DC output section, and a main power supply is provided. In a three-level power conversion device that is connected to a three-phase AC main power supply via a switch for switching, and is composed of a three-level converter circuit that converts the output from the three-phase AC main power supply into direct current, Side DC smoothing capacitor positive side and negative side DC smoothing capacitor negative side connected for pre-charging rectifier such as diode, pre-charging rectifier primary side connected for pre-charging transformer, pre-charging Output from the single-phase AC power supply for pre-charging, which is connected in series with the current limiting element such as current limiting resistance and current limiting reactor connected to the primary side of the step-up transformer And the precharging switch for opening and closing, and a pre-charging circuit composed.

Therefore, in the three-level power converter of the invention corresponding to claim 1, the positive-side DC smoothing capacitor and the negative-side DC smoothing capacitor are collectively packaged by one preliminary charging circuit by taking the above means. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved.

Further, in the invention according to claim 2, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are connected to the DC output section, and the three-phase AC main power source is connected through the main power source switch. In the three-level power conversion device including a three-level converter circuit that converts the output from the three-phase AC main power supply into DC, a positive-side DC smoothing capacitor positive side and a negative-side DC smoothing capacitor of the three-level converter circuit are provided. A pre-charging rectifier such as a diode connected to the negative electrode side, a pre-charging step-up transformer connected to the primary side of the pre-charging rectifier, and a current limiting resistor connected to the primary side of the pre-charging step-up transformer, A current limiting element such as a current limiting reactor, a current limiting element short-circuit contactor connected in parallel with the current limiting element, a current limiting element and a current limiting element shorting connector. A precharging switch that is connected to the input side of the tactor and that opens and closes the output from the precharging single-phase AC power supply, and a contactor for short-circuiting the current limiting element after a predetermined time has elapsed after the contacts of the precharging switch are closed. It has a pre-charging circuit composed of a timer for switching from open to closed.

Therefore, in the three-level power converter of the invention according to claim 2, by taking the above means, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are combined into one pre-charging circuit. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved. Further, it is possible to reduce the current rating value of the current limiting element such as the current limiting resistance and the current limiting reactor. As a result, the outer shape of the device can be reduced, and the cost of the device can be further reduced.

Further, in the invention corresponding to claim 3, in the three-level power converter of the invention according to claim 1, the pre-charging rectifier is omitted, and the secondary side of the pre-charging step-up transformer has three levels. A pre-charge circuit is provided that is configured to use the flywheel diode built into the three-level converter circuit as a rectifier by connecting to the three-phase input of the converter circuit.

Therefore, in the three-level power converter of the invention corresponding to claim 3, by taking the above means, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are combined into one precharging circuit. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved. Further, the rectifier dedicated to the preliminary charging can be omitted. As a result, it is possible to further reduce the cost of the device and further improve the reliability.

Further, in the invention according to claim 4, in the three-level power converter of the invention according to claim 2, the pre-charging rectifier is omitted, and the secondary side of the pre-charging step-up transformer is replaced by three. A pre-charge circuit is provided which is configured to use the flywheel diode incorporated in the three-level converter circuit as a rectifier by connecting to the three-phase input of the level converter circuit.

Therefore, in the three-level power converter of the invention according to claim 4, by taking the above means, the positive-side DC smoothing capacitor and the negative-side DC smoothing capacitor are combined into one pre-charging circuit. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved. Further, it is possible to reduce the current rating value of the current limiting element such as the current limiting resistance and the current limiting reactor. As a result, the outer shape of the device can be reduced, and the cost of the device can be further reduced. Further, the rectifier dedicated to the preliminary charging can be omitted. As a result, it is possible to further reduce the cost of the device and further improve the reliability.

On the other hand, in the invention according to claim 5, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are connected to the DC output section, and the three-phase AC main power source is connected via the main power switch. The three-level converter circuit for converting the output from the three-phase AC main power source into a direct current, and the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are connected to the DC input section, and the positive electrode of the three-level converter circuit is Connected to the output DC bus of the neutral point / negative pole, and converts the DC output from the 3-level converter circuit to AC 3
In a three-level power converter configured with a level inverter circuit, connected to a pre-charging single-phase AC power supply,
A precharging switch for opening and closing the output from the precharging single-phase AC power supply, a current limiting element such as a current limiting resistor or a current limiting reactor connected to the output side of the precharging switch, and a current limiting element. Of the two output lines of the pre-charging step-up transformer and the pre-charging step-up transformer connected to the output side of the, one output line is connected to any one phase of the three-phase input of the three-level converter circuit. , The other output line is connected to any one phase of the three-phase output of the three-level inverter circuit, and any one of the two output lines of the pre-charging step-up transformer is connected via a disconnecting contactor. And a pre-charging circuit composed of the following circuit.

Therefore, in the three-level power converter of the invention according to claim 5, by taking the above means, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are combined into one precharging circuit. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved. Further, the rectifier dedicated to the preliminary charging can be omitted. As a result, it is possible to further reduce the cost of the device and further improve the reliability. Furthermore, the preliminary charging current is not consumed as the exciting current of the main power transformer, and the efficiency of the device can be improved.

Further, in the invention according to claim 6, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are connected to the DC output section, and the three-phase AC main power source is connected via the main power switch. In the three-level power conversion device including a three-level converter circuit that converts the output from the three-phase AC main power supply into DC, the pre-charging single-phase AC power supply is connected to the pre-charging single-phase AC power supply. A pre-charging switch that opens and closes the output from the device, a current limiting element such as a current limiting resistor or current limiting reactor connected to the output side of the pre-charging switch, and a reserve connected to the output side of the current limiting element. Two boosting transformers for charging and one for precharging
One of the three output lines is connected to an arbitrary one phase of the three-phase input of the three-level converter circuit, and the other output line is connected to two diodes in series. Connect to the middle point, connect the cathode side end point of the rectifying diode to the positive electrode of the DC output section of the 3-level converter circuit, and connect the anode side end point to the negative electrode of the DC output section of the 3-level converter circuit. And a pre-charging circuit including the circuit.

Therefore, in the three-level power converter of the invention corresponding to claim 6, by taking the above means, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor are combined into one pre-charging circuit. Can be pre-charged. As a result, the number of parts of the preliminary charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved. In addition, the rectifier dedicated to the preliminary charging can be halved. As a result, it is possible to further reduce the cost of the device and further improve the reliability. Further, the preliminary charging current is not consumed as the exciting current of the transformer for the main power supply, and the efficiency of the device can be improved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment. The same elements as those in FIG. 7 are designated by the same reference numerals. There is.

As shown in FIG. 1, in the three-level power converter of this embodiment, a positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section, and
A three-level converter circuit 3 that is connected to a three-phase AC main power supply via a main power supply transformer 2 and a main power supply switch 1 and that converts the output from the three-phase AC main power supply into direct current, and the three-level converter circuit. 3, a pre-charging rectifier 7 composed of a diode or the like connected to the positive side of the positive side DC smoothing capacitor and the negative side of the negative side DC smoothing capacitor, and a pre-charging booster connected to the primary side of the pre-charging rectifier 7. A transformer 6, a current limiting element 5 including a current limiting resistor connected to the primary side of the boosting transformer 6 for the preliminary charging, a current limiting reactor, and the like, and a single-phase AC for preliminary charging connected in series to the current limiting element 5. A pre-charging circuit configured by a pre-charging switch 4 that opens and closes the output from the power source is provided.

Next, the operation of the three-level power conversion device according to this embodiment having the above-described structure will be described.

In FIG. 1, three-phase AC power is supplied from a three-phase AC main power supply to a three-level converter circuit 3 via a main power supply switch 1 and a main power supply transformer 2.

A positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section of the three-level converter circuit 3.

Then, when the switch 1 for the main power supply is turned on in the state where there is no electric charge in these DC smoothing capacitors, 3
An excessive rush current flows through the flywheel diode of the level converter circuit 3, which may damage the device.

For this reason, it is necessary to charge each DC smoothing capacitor in advance to about the rectified voltage level before turning on the switch 1 for the main power supply.

In this respect, in the present embodiment, the pre-charging rectifier 7 connected to the positive side of the positive side DC smoothing capacitor and the negative side of the negative side DC smoothing capacitor of the three-level converter circuit 3, and the pre-charging rectifier 7, a pre-charging step-up transformer 6 connected to the primary side of
Precharging circuit including a current limiting element 5 connected to the primary side of the battery and a precharging switch 4 connected in series to the current limiting element 5 to open and close the output from the precharging single-phase AC power supply With the provision of the switch 4 for precharging
By turning on, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor can be precharged together by one precharge circuit.

As a result, in the conventional case, the two circuits on the positive side and the negative side were required as the preliminary charging circuit.
Since only one pre-charging circuit is required, the number of parts of the pre-charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved.

As described above, in the three-level power converter according to the present embodiment, it is possible to reduce the number of parts of the precharge circuit, reduce the cost of the device, and improve the reliability.

(Second Embodiment) FIG. 2 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment. The same parts as those in FIG. Is omitted and only different parts will be described here.

That is, in the three-level power converter according to the present embodiment, as shown in FIG. 2, the current limiting element short-circuiting contactor 8 is arranged in parallel with the current limiting element 5 in FIG.
Further, a timer 9 for switching (closing) the current limiting element short-circuit contactor 8 from a closed state (closing) after a lapse of a predetermined time after the contact of the preliminary charging switch 4 is closed (closing of the preliminary charging switch 4) Is provided.

Next, the operation of the three-level power converter according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 1 will be omitted, and only the operation of the different parts will be described here.

In the above-described first embodiment, from the standpoint of the withstand voltage of the precharging switch 4, the primary side of the precharging step-up transformer 6 has a low voltage of about 220V and the secondary side has a high voltage of several KV. Therefore, the current flowing through the current limiting element 5 is several hundred A for a short time.

Therefore, it is considered that the current rating value of the current limiting element 5 also becomes large, the outer size becomes relatively large, and the cost becomes high.

In this respect, in the present embodiment, the current limiting element short-circuit contactor 8 for short-circuiting the current limiting element 5 is provided, and the current limiting element short-circuiting is performed after a predetermined time has elapsed after the precharging switch 4 is turned on. By providing the timer 9 for turning on the contactor 8, the current rating value of the current limiting element 5 can be lowered.

As a result, the outer shape of the device can be reduced, and the cost of the device can be further reduced.

As described above, in the three-level power converter according to the present embodiment, it is possible to obtain the same effects as those of the above-described first embodiment, and in addition, the external size of the device is reduced. In addition, it is possible to realize further cost reduction of the device.

(Modification) In this embodiment, the current limiting element short-circuiting contactor 8 for short-circuiting the current limiting element 5 is provided.
The configuration has been described in which the current limiting element short-circuit contactor 8 is turned on after a predetermined time has passed since the precharging switch 4 was turned on. However, the present invention is not limited to this.

For example, a direct current voltage detector is provided and the contactor 8 for shorting the current limiting element is turned on when the direct current voltage reaches a predetermined voltage value, or a charging current detector is provided so that the charging current is below a predetermined current value. Therefore, even if the current limiting element short-circuiting contactor 8 is configured to be turned on, it is possible to obtain the same operational effect as that of the above-described present embodiment.

(Third Embodiment) FIG. 3 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment. The same parts as those in FIG. Is omitted and only different parts will be described here.

That is, in the three-level power converter according to the present embodiment, as shown in FIG. 3, the precharging rectifier 7 in FIG. 1 is omitted, and the precharging step-up transformer 6 is omitted.
Pre-charging configured to use the flywheel diode built in the three-level converter circuit 3 as a rectifier by connecting the secondary side of the three-level converter circuit 3 to any two-phase input of the three-phase input. It is configured with a circuit.

Next, the operation of the three-level power conversion device according to this embodiment having the above-described structure will be described.

In FIG. 3, three-phase AC power is supplied from the three-phase AC main power supply to the three-level converter circuit 3 via the main power supply switch 1 and the main power supply transformer 2.

A positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section of the three-level converter circuit 3.

Then, when the main power switch 1 is turned on in the state where these DC smoothing capacitors have no electric charge, 3
An excessive rush current flows through the flywheel diode of the level converter circuit 3, which may damage the device.

Therefore, before the main power switch 1 is turned on, each DC smoothing capacitor must be charged in advance to a rectified voltage level.

In this respect, according to the present embodiment, the secondary side of the pre-charging step-up transformer 6 is connected to any two phases of the three-phase inputs of the three-level converter circuit 3, so that the three-level converter circuit 3 is connected. The flywheel diode built in the rectifier is used as a rectifier, and the current limiting element 5 connected to the primary side of the pre-charging step-up transformer 6 is further used.
And a pre-charging switch 4 that is connected in series to the current limiting element 5 and that opens and closes the output from the pre-charging single-phase AC power source By turning on the device 4, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor can be collectively precharged by one precharging circuit.

As a result, although the two circuits on the positive side and the negative side are conventionally required as the preliminary charging circuit,
Since only one pre-charging circuit is required, the number of parts of the pre-charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved.

Further, the rectifier dedicated to the preliminary charging can be omitted.

As a result, it is possible to further reduce the cost of the device and further improve the reliability.

As described above, in the three-level power converter according to the present embodiment, it is possible to reduce the number of parts of the preliminary charging circuit, reduce the cost of the device, and improve the reliability.

Also, omitting the rectifier dedicated to the preliminary charging,
It is possible to further reduce the cost of the device and further improve the reliability.

(Fourth Embodiment) FIG. 4 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment, and the same parts as those in FIG. Is omitted and only different parts will be described here.

That is, in the three-level power converter according to the present embodiment, as shown in FIG. 4, the current limiting element short-circuiting contactor 8 is arranged in parallel with the current limiting element 5 in FIG.
Further, a timer 9 for switching (closing) the current limiting element short-circuit contactor 8 from a closed state (closing) after a lapse of a predetermined time after the contact of the preliminary charging switch 4 is closed (closing of the preliminary charging switch 4) Is provided.

Next, the operation of the three-level power converter according to the present embodiment configured as described above will be described.

The description of the operation of the same parts as in FIG. 3 will be omitted, and only the operation of the different parts will be described here.

In the above-described third embodiment, from the viewpoint of the withstand voltage of the pre-charging switch 4, the primary side of the pre-charging step-up transformer 6 has a low voltage of about 220V and the secondary side has a high voltage of several KV. Therefore, the current flowing through the current limiting element 5 is several hundred A for a short time.

Therefore, it is considered that the current rating value of the current limiting element 5 also becomes large, the outer size becomes relatively large, and the cost becomes high.

In this respect, in the present embodiment, the current limiting element short-circuit contactor 8 for short-circuiting the current limiting element 5 is provided, and the current limiting element short-circuiting is performed after a predetermined time has elapsed since the precharging switch 4 was turned on. By providing the timer 9 for turning on the contactor 8, the current rating value of the current limiting element 5 can be lowered.

As a result, the outer shape of the device can be reduced, and the cost of the device can be further reduced.

As described above, in the three-level power converter according to the present embodiment, it is possible to obtain the same effects as those of the third embodiment described above, and in addition, the external size of the device is reduced. In addition, it is possible to realize further cost reduction of the device.

(Modification) In this embodiment, the current limiting element short-circuiting contactor 8 for short-circuiting the current limiting element 5 is provided.
The configuration has been described in which the current limiting element short-circuit contactor 8 is turned on after a predetermined time has passed since the precharging switch 4 was turned on. However, the present invention is not limited to this.

For example, a configuration is provided in which a DC voltage detector is provided and the contactor 8 for short-circuiting the current limiting element is turned on when the DC voltage reaches a predetermined voltage value, or a charging current detector is provided so that the charging current is less than or equal to a predetermined current value. Therefore, even if the current limiting element short-circuiting contactor 8 is configured to be turned on, it is possible to obtain the same operational effect as that of the above-described present embodiment.

(Fifth Embodiment) FIG. 5 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment. The same elements as those in FIG. 7 are designated by the same reference numerals. There is.

As shown in FIG. 5, in the three-level power converter of the present embodiment, a positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section, and
A three-level AC main power supply is connected via a main power supply transformer 2 and a main power supply switch 1, and a three-level converter circuit 3 for converting the output from the three-phase AC main power supply into a direct current, and a positive input to the direct current input part. Side DC smoothing capacitor and negative side DC smoothing capacitor are connected, and also connected to the positive / neutral / negative output DC bus of the 3-level converter circuit 3 to convert the DC output from the 3-level converter circuit 3 to AC. And a three-level inverter circuit 10 that supplies the load 17 to the load 17, and a pre-charging switch 7 that is connected to the pre-charging single-phase AC power supply to open and close the output from the pre-charging single-phase AC power supply, A current limiting element 5 including a current limiting resistance and a current limiting reactor connected to the output side of the switch 7, a pre-charging step-up transformer 6 connected to the output side of the current limiting element 5, and the spare. One of the two output lines of the electric booster transformer 6 is connected to an arbitrary one phase of the three-phase input of the three-level converter circuit 3, and the other output line is connected to the three-level inverter circuit 10. Precharging composed of a circuit connected to any one phase output and one of two output lines of the precharging step-up transformer 6 being connected via a disconnecting contactor 11 And a circuit.

Next, the operation of the three-level power converter according to the present embodiment configured as described above will be described.

In FIG. 5, three-phase AC power is supplied from the three-phase AC main power supply to the three-level converter circuit 3 and the three-level inverter circuit 10 via the main power supply switch 1 and the main power supply transformer 2. .

DC output section of the three-level converter circuit 3,
And the DC input section of the three-level inverter circuit 10,
A positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected.

Then, when the switch 1 for the main power supply is turned on in the state where there is no electric charge in these DC smoothing capacitors, 3
An excessive rush current flows through the flywheel diode of the level converter circuit 3, which may damage the device.

Therefore, before the main power switch 1 is turned on, each DC smoothing capacitor must be charged in advance to a rectified voltage level.

In this respect, in the present embodiment, any one line on the secondary side of the pre-charging step-up transformer 6 is connected to any one of the three-phase inputs of the three-level converter circuit 3, and the other one is connected. The flywheel diode is used as a rectifier by connecting one wire to any one of the three-phase outputs of the three-level inverter circuit 10 via the disconnecting contactor 11, and the boosting transformer 6 for precharging is also used. Precharging circuit including a current limiting element 5 connected to the primary side of the battery and a precharging switch 4 connected in series to the current limiting element 5 to open and close the output from the precharging single-phase AC power supply Since the pre-charging current does not act as the exciting current of the transformer 2 for the main power source by turning on the switch 4 for pre-charging, the positive side DC smoothing capacitor and the negative side DC flat capacitor are provided. It can be pre-charged in a lump capacitor in one pre-charging circuit.

As a result, in the conventional circuit, two circuits, a positive side circuit and a negative side circuit, were required as the preliminary charging circuit.
Since only one pre-charging circuit is required, the number of parts of the pre-charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved.

Further, the rectifier dedicated to the preliminary charging can be omitted.

As a result, the cost of the device can be further reduced and the reliability can be further improved.

Further, the preliminary charging current is not consumed as the exciting current of the main power source transformer.

As a result, the efficiency of the device can be increased.

As described above, in the three-level power converter according to the present embodiment, it is possible to reduce the number of parts of the preliminary charging circuit, reduce the cost of the device, and improve the reliability.

Further, omitting the rectifier dedicated to the preliminary charging,
It is possible to further reduce the cost of the device and further improve the reliability.

Further, the preliminary charging current is not consumed as the exciting current of the main power supply transformer 2 and the efficiency of the device can be improved.

(Sixth Embodiment) FIG. 6 is a circuit diagram showing a configuration example of a three-level power converter according to the present embodiment. The same parts as those in FIG. Is omitted and only different parts will be described here.

That is, in the three-level power converter according to the present embodiment, as shown in FIG. 6, the pre-charging rectifier 7 in FIG. 1 is omitted, and two diodes are replaced with each other. The rectifying diode 12 is connected in series, and one of the two output lines of the pre-charging step-up transformer 6 is connected to any one of the three-phase input of the three-level converter circuit 3. At the same time, the other output line is connected to the middle point of the rectifying diode 12, the cathode side end point of the rectifying diode 12 is connected to the positive electrode of the DC output section of the three-level converter circuit 3, and the anode side end point. Is provided with a precharge circuit configured to be connected to the negative electrode of the DC output section of the three-level converter circuit 3.

Next, the operation of the three-level power converter according to the present embodiment configured as described above will be described.

In FIG. 6, three-phase AC power is supplied from the three-phase AC main power supply to the three-level converter circuit 3 via the main power supply switch 1 and the main power supply transformer 2.

A positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section of the three-level converter circuit 3.

When the switch 1 for the main power supply is turned on in the state where there is no electric charge in these DC smoothing capacitors, 3
An excessive rush current flows through the flywheel diode of the level converter circuit 3, which may damage the device.

For this reason, it is necessary to charge each DC smoothing capacitor in advance to a level of a rectified voltage before turning on the switch 1 for the main power supply.

In this respect, in the present embodiment, any one line on the secondary side of the pre-charging step-up transformer 6 is connected to any one of the three-phase inputs of the three-level converter circuit 3, and the other one is connected. One line is connected to the middle point of the rectifying diode 12, the cathode side end point of this rectifying diode 12 is connected to the positive electrode of the DC output of the three-level converter circuit 3, and the anode side end point is connected to the three-level converter circuit 3. The current limiting element 5 connected to the negative side of the DC output of the precharging, and further connected in series to the current limiting element 5 connected to the primary side of the precharging step-up transformer 6, By providing the pre-charging circuit including the pre-charging switch 4 that opens and closes the output, the pre-charging current does not act as the exciting current of the main power source transformer 2 and the pre-charging switching is performed. 4 By introducing, can be pre-charged at once positive side DC smoothing capacitor and the negative side DC smoothing capacitor in a single pre-charging circuit.

As a result, in the conventional circuit, two circuits on the positive side and the negative side were required as the preliminary charging circuit.
Since only one pre-charging circuit is required, the number of parts of the pre-charging circuit can be reduced, and the cost of the device can be reduced and the reliability can be improved.

Further, the rectifying diode 1 for exclusive use in the preliminary charging
The number of 2 can be halved.

As a result, it is possible to further reduce the cost of the device and further improve the reliability.

Further, the preliminary charging current is not consumed as the exciting current of the main power supply transformer.

As a result, the efficiency of the device can be increased.

As described above, in the three-level power converter according to the present embodiment, it is possible to reduce the number of parts of the preliminary charging circuit, reduce the cost of the device, and improve the reliability.

In addition, the rectifier dedicated to the preliminary charging is halved,
It is possible to further reduce the cost of the device and further improve the reliability.

Further, the preliminary charging current is not consumed as the exciting current of the main power source transformer 2, and the efficiency of the device can be improved.

(Other Embodiments) It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified and implemented at the stage of implementation without departing from the spirit thereof. Is. In addition, the respective embodiments may be implemented in combination as appropriate as possible, and in that case, combined operation effects can be obtained. Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent features. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problem (at least one) described in the section of the problem to be solved by the invention can be solved, and When the effect (at least one) described in the section can be obtained, a structure in which this constituent element is deleted can be extracted as an invention.

[0097]

As described above, according to the three-level power converter of the present invention, the positive side DC smoothing capacitor and the negative side DC smoothing capacitor can be precharged together by one precharging circuit. .

As a result, it is possible to reduce the number of parts of the pre-charge circuit, reduce the cost of the apparatus, reduce the size of the apparatus, improve reliability, and improve efficiency of the apparatus.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of a three-level power conversion device according to the present invention.

FIG. 2 is a circuit configuration diagram showing a second embodiment of a three-level power conversion device according to the present invention.

FIG. 3 is a circuit configuration diagram showing a third embodiment of a three-level power converter according to the present invention.

FIG. 4 is a circuit configuration diagram showing a fourth embodiment of a three-level power conversion device according to the present invention.

FIG. 5 is a circuit configuration diagram showing a fifth embodiment of a three-level power conversion device according to the present invention.

FIG. 6 is a circuit configuration diagram showing a sixth embodiment of a three-level power conversion device according to the present invention.

FIG. 7 is a circuit diagram showing a configuration example of a conventional three-level power conversion device.

[Explanation of symbols]

1 ... Switch for main power supply 2 ... Transformer for main power supply 3 ... 3 level converter circuit 4 ... Switch for pre-charging 5 ... Current limiting element 6 ... Shosho transformer for pre-charging 7 ... Rectifier for pre-charging 8 ... Contactor for current limiting element short circuit 9 ... Timer 10 ... 3 level inverter circuit 11 ... disconnector contactor 12 ... Rectifying diode 14 ... Switch for precharge on the negative side 15 ... Negative side current limiting element 16 ... Step-up transformer for negative side preliminary charging 17 ... Load.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Sei Miyazaki             No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation             Fuchu Office (72) Inventor Masahiko Tsukoshi             No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation             Fuchu Office F-term (reference) 5H006 AA00 CA01 CA07 CB01 CC01                       CC08 FA02 GA01                 5H007 AA17 CA01 CB02 CB05 CC01                       FA03 FA12 FA17 GA03

Claims (6)

[Claims] 1. A DC output section is connected to a positive side DC smoothing capacitor and a negative side DC smoothing capacitor, and is also connected to a three-phase AC main power source via a switch for the main power source. In a three-level power conversion device configured by a three-level converter circuit for converting the output of the above into a direct current, a diode connected to the positive side of the positive side DC smoothing capacitor and the negative side of the negative side DC smoothing capacitor of the three level converter circuit. Rectifier for pre-charging, etc., a boosting transformer for pre-charging connected to the primary side of the rectifier for pre-charging, current limiting resistor, current limiting transformer, etc. connected to the primary side of the boosting transformer for pre-charging Pre-charging composed of a limiting element and a pre-charging switch connected in series with the current limiting element to open and close the output from the pre-charging single-phase AC power supply 3-level power converting apparatus which is characterized in that it comprises an road. 2. A positive side direct current smoothing capacitor and a negative side direct current smoothing capacitor are connected to the direct current output part, and are also connected to a three-phase alternating current main power source via a switch for the main power source, and from the three-phase alternating current main power source. In a three-level power conversion device configured by a three-level converter circuit for converting the output of the above into a direct current, a diode connected to the positive side of the positive side DC smoothing capacitor and the negative side of the negative side DC smoothing capacitor of the three level converter circuit. Rectifier for pre-charging, etc., a boosting transformer for pre-charging connected to the primary side of the rectifier for pre-charging, current limiting resistor, current limiting transformer, etc. connected to the primary side of the boosting transformer for pre-charging A limiting element, a current limiting element short-circuiting contactor connected in parallel with the current limiting element, and a current limiting element and a current limiting element shorting contactor A pre-charging switch connected to the power side for opening and closing the output from the pre-charging single-phase AC power supply; and a contactor for short-circuiting the current limiting element after a lapse of a predetermined time after the contacts of the pre-charging switch are closed. A three-level power conversion device comprising a timer for switching from open to closed, and a pre-charging circuit composed of. 3. The three-level power converter according to claim 1, wherein the pre-charging rectifier is omitted, and the secondary side of the pre-charging step-up transformer is connected to the three-phase input of the three-level converter circuit. By doing so, a three-level power conversion device comprising a precharge circuit configured to use the flywheel diode built in the three-level converter circuit as a rectifier. 4. The three-level power converter according to claim 2, wherein the pre-charging rectifier is omitted, and the secondary side of the pre-charging step-up transformer is connected to the three-phase input of the three-level converter circuit. By doing so, a three-level power conversion device comprising a precharge circuit configured to use the flywheel diode built in the three-level converter circuit as a rectifier. 5. A DC output section is connected to a positive side DC smoothing capacitor and a negative side DC smoothing capacitor, and is also connected to a three-phase AC main power source via a switch for the main power source. 3 level converter circuit for converting the output of DC to DC, and a positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC input section, and the positive / neutral point / negative side output DC of the 3 level converter circuit is connected. A three-level power converter comprising a three-level inverter circuit that is connected to a bus bar and that converts a DC output from the three-level converter circuit to an AC, and is connected to a pre-charging single-phase AC power source for the pre-charging. A precharging switch for opening and closing the output from the single-phase AC power supply, and a current limiting resistor connected to the output side of the precharging switch,
A current limiting element such as a current limiting reactor, a pre-charging step-up transformer connected to the output side of the current limiting element, and one output line of the two output lines of the pre-charging step-up transformer While connecting to any one phase of the three-phase input of the level converter circuit, the other output line is connected to any one phase of the three-phase output of the three-level inverter circuit,
Further, any one of the two output lines of the pre-charging step-up transformer is provided with a circuit which is connected through a disconnecting contactor, and a pre-charging circuit comprising: Three-level power converter. 6. A positive side DC smoothing capacitor and a negative side DC smoothing capacitor are connected to the DC output section, and are connected to a three-phase AC main power source via a switch for the main power source. In a three-level power conversion device composed of a three-level converter circuit for converting the output of the above into a direct current, for pre-charging, which is connected to a single-phase AC power supply for pre-charging and opens and closes the output from the single-phase AC power supply for pre-charging A switch, and a current limiting resistor connected to the output side of the switch for precharging,
A current limiting element such as a current limiting reactor, a pre-charging step-up transformer connected to the output side of the current limiting element, and one output line of the two output lines of the pre-charging step-up transformer It is connected to any one of the three-phase inputs of the level converter circuit, the other output line is connected to the middle point of a rectifying diode formed by connecting two diodes in series, and the cathode of the rectifying diode is connected. Side end point is connected to the positive electrode of the DC output section of the three-level converter circuit, and the anode side end point is connected to the negative electrode of the DC output section of the three-level converter circuit. A three-level power conversion device comprising a circuit.