JP3068968B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter for regenerating snubber energy to a DC capacitor, and more particularly to a power converter having a circuit for initially charging a DC capacitor.

[0002]

2. Description of the Related Art FIG. 5 shows a circuit of a conventional inverter.

There is provided a power conversion circuit 3 for inputting the main AC power supply 1 and converting it to DC, and a DC voltage source circuit having a capacitor 4 connected in parallel to the DC output section. And an inverter device having an inverter circuit 5 that outputs AC by controlling the inverter circuit. As a power conversion device for converting to direct current, it is inexpensive to use a diode, and it is generally used. In such a circuit, when the power is turned on, an inrush current flows through the capacitor. To prevent this, a resistor 10 and a contact 11 are inserted in series with the capacitor 4, and the resistor 1 is turned on when the power is turned on.
The capacitor 4 is charged via 0, and after a predetermined time has elapsed, the contact 11 is turned on, and the operation is started in a manner unrelated to the resistor 10. Further, as another conventional method, as shown in FIG. 6, a thyristor converter 3 is used as a power converter to control a charging current.

[0004]

In a conventional initial charging circuit using a resistor, if the voltage is relatively low, such as about 400 V, the cost of the articles is low and there is no problem.
Inverter devices that handle DC voltages as high as the above, it is difficult to obtain contacts suitable for such applications.
There was a disadvantage that it would be expensive even if it was.

In the case of controlling with a thyristor converter, there is a problem that a converter applicable to a high voltage circuit is expensive and is not always practical as a method for overcoming the problem of initial charging.

Recently, a converter using a switching device conventionally used for an inverter is used on the power supply side,
The current on the power supply side is also controlled.In this case, the inrush current flows through a freewheel diode connected in parallel to the switching device. As in the case, there is a problem that another initial charging circuit is required. An object of the present invention is to provide a power conversion device having an inexpensive initial charging circuit applicable to a high-voltage inverter.

[0007]

In a high-voltage inverter device using a switching element such as a GTO, a method of regenerating energy of a snubber circuit for protecting the GTO element to a DC capacitor is known. A step-up chopper circuit is used for the portion that regenerates the DC capacitor. However, if this is added to each capacitor, it becomes expensive, so it is once collected in another chopper capacitor and then regenerated by the step-up chopper. The present invention provides a DC auxiliary power supply circuit, which is connected in parallel with a chopper capacitor. The boost chopper circuit is operated to initially charge a capacitor serving as a DC voltage source with power from the DC auxiliary power supply circuit.

[0008]

The DC capacitor is discharged before receiving the AC power. First, the DC auxiliary power supply circuit is operated to supply power to the chopper capacitor. Next, the step-up chopper circuit is operated to charge the DC capacitor to a predetermined voltage, and thereafter, the AC main power supply is received. As a result, no rush current is generated when the AC main power is received.

[0009]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

An AC main power supply is received via an AC switch 2. This switch is connected to the diode converter 3,
Furthermore, it is connected to a DC capacitor 4. The inverter part is a converter 5 using GTO (51U, 51X,...).
A snubber capacitor 55 and a snubber capacitor charging diode 54 are connected to each GTO.
A chopper capacitor is connected. The DC auxiliary power supply circuit 8 is connected in parallel to the chopper capacitor 64. A step-up chopper circuit 6 for transferring the energy of the chopper capacitor 64 to the DC capacitor 4 is connected. FIG. 2 shows an example of a specific circuit of the DC auxiliary power supply circuit of FIG.

A single-phase AC power source 7 is received, and power is input to a thyristor converter 82 via a transformer 81. The DC output of this thyristor converter is connected in parallel with the chopper capacitor. An impedance 83 (resistor or D) is provided between the thyristor converter and the chopper capacitor.
CL) may be provided to suppress the current.

Before turning on the AC switch 2, the DC capacitor 4 is discharged. In this state, first, the DC auxiliary power supply device 8 is operated, and the chopper capacitor 64 is operated.
Supply DC power to Next, the regenerative chopper circuit 6 is operated to charge the DC capacitor 4 to a predetermined voltage. Thereafter, the AC switch 2 is turned on to operate the inverter. As a result, no rush current is generated when the AC main power is received.

According to the present invention, since the DC capacitor can be charged to a predetermined value before the AC main power supply is turned on, it is possible to provide an inverter device which does not generate an inrush current when the AC main power supply is turned on.

FIG. 3 shows an example of another embodiment of the present invention.
An example of application to an inverter in which O is connected in series will be described. Even such a circuit connected in series can be applied to an inverter having a regenerative circuit for snubber energy to a DC capacitor using a boost chopper without changing the gist of the present invention.

FIG. 4 shows an example of another embodiment of the present invention, in which the present invention is applied to a neutral point clamp type GTO inverter. Even such a circuit can be applied to an inverter having a circuit for regenerating snubber energy to a DC capacitor using a boost chopper without changing the gist of the present invention. In the description, an inverter device using a GTO element has been described, but the present invention can also be applied to an inverter device including a switching element such as a GTR or an IGBT. In the description, the inverter device has been described, but the present invention can also be applied to an uninterruptible power supply device without changing the gist of the present invention.

[0016]

As described above, according to the present invention, the initial charging function is realized by using the snubber energy regenerating circuit, and there is an advantage that the initial charging circuit can be formed relatively inexpensively. Since this circuit only needs to increase the breakdown voltage of the DC auxiliary power supply according to the voltage of the DC capacitor, there is an advantage that an initial charging circuit that can be easily applied to a high-voltage circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a configuration diagram showing a specific example of the DC auxiliary power supply circuit of FIG. 1;

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional device.

FIG. 6 is another configuration diagram of a conventional device.

[Explanation of symbols]

 1. 1. AC main power supply AC switch 3. 3. AC / DC converter (converter) DC capacitor 5. 5. DC / AC converter (inverter) 6. Step-up chopper circuit AC auxiliary power supply 8. 8. DC auxiliary power supply circuit AC motor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-133668 (JP, A) JP-A-63-283469 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/48

Claims (2)

(57) [Claims] 1. A power conversion circuit for inputting a main AC power and converting it to DC, comprising a capacitor connected in parallel to the DC output section and operating as a DC voltage source, and a plurality of switching elements connected thereto. In the inverter device that outputs an AC of variable frequency, a snubber capacitor is connected in parallel with the switching element that constitutes the inverter circuit, and a circuit that absorbs energy when the switching element is off is provided. A circuit for transferring the energy charged in the capacitor to another integration capacitor after the switching element is turned on next, and adding a boost chopper circuit to the integration capacitor to boost the energy collected in the integration capacitor. Snubber energy regenerated by the chopper circuit to the capacitor as the DC voltage source In the inverter device with formic regeneration function, it provided the auxiliary DC power supply circuit, the power conversion apparatus characterized by connecting the DC output to the accumulation capacitor. 2. The power converter according to claim 1,
Prior to receiving the AC main power, the DC auxiliary power supply circuit supplies power to the integration capacitor, and further controls the boost chopper circuit to control the charging of the capacitor voltage to a predetermined voltage. A power converter characterized by the above-mentioned.