JPH11178358A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a harmonic current when supplying power from an AC power supply to a power-converting device, in the power conversion device as a DC power supply with a regenerating function. SOLUTION: One terminal of a series circuit of a DC reactor 31 and a resistor 18 is connected to one terminal of the DC output of a circuit where semiconductor switches 11-16 are bridge-connected, a diode 20 is connected to both terminals of the series circuit, a thyristor 19 is connected to both terminals of the resistor 18, and an electrolytic capacitor 21 is connected between the other terminal of the series circuit and the other terminal of the DC output of a circuit being connected in a bridge, thus suppressing a harmonic current when power from the AC power supply 1 is to supplied a power conversion device 30 through the use of the DC reactor 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, connecting an AC motor to an output of a power converter via an inverter,
The present invention relates to a power conversion device that supplies power to an inverter from an AC power supply via a power conversion device during power running operation of the electric motor and regenerates power from the inverter to the AC power supply via the power conversion device during regenerative operation of the motor.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a conventional example of this type of power converter. In FIG. 2, 1 is an AC power supply such as a commercial power supply, 2 is a three-phase AC reactor, 3 is a power converter, and 4 is a DC voltage input from the power converter 3 into an AC voltage having a desired frequency and voltage. And 5, an AC motor driven by the output of the inverter 4.

The power converter 3 has transistors 11a to 16a as self-extinguishing elements and a diode 11b.
16b, anti-parallel semiconductor switches 11-16, a snubber capacitor 17, and a resistor 18
Thyristor 19, diode 20, electrolytic capacitor 21 as a smoothing capacitor, transistor 11
a to 16a and a control circuit 22 for controlling the thyristor 19, respectively, and each of the semiconductor switches 11 to 16 constitutes a three-phase bridge connection circuit as shown.

The operation of the power converter 3 shown in FIG. 2 will be described below. FIG. 3 is a waveform chart showing a method of controlling the transistors 11a to 16a by the control circuit 22.
3A shows the phase voltages of the input terminals R, S, and T of the power converter 3 from the AC power supply 1 via the AC reactor 3, and FIG. 3B shows the transistor 11a for the R, S, and T phase voltages. 16a shows the ON state section, for example, the transistor 11a is in the ON state in the section where the R phase voltage is the highest in the + polarity compared to the S and T phase voltages, and the transistor 14a is the R phase voltage having the S and T phases. The ON state is set in a section having the lowest polarity with respect to the phase voltage.

First, the input terminals R, S,
When an AC voltage is applied to T from the AC power supply 1 via the AC reactor 3, the transistors 11a to 16a are all turned off by the control circuit 22 and the thyristor 19 is turned off. The AC voltage applied to S and T is rectified by the diodes 11b to 16b, and the rectified voltage charges the electrolytic capacitor 21 via the resistor 18. This charging current is suppressed by the resistor 18 to prevent an excessive rush current from flowing through the diodes 11b to 16b.

Next, the thyristor 19 is turned on by the control circuit 22 at the timing when the voltage across the electrolytic capacitor 21 has almost risen to the rated voltage to short-circuit the resistor 18, and the transistors 11a to 16a are also shown in FIG. When the operation is started, the activation of the power converter 3 is completed,
Thereafter, the thyristor 19 is kept on by the control circuit 22, and the transistors 11a to 16a also continue the operation shown in FIG.

When the activation of the power converter 3 is completed by the above-described operation, the inverter 4 starts operating and converts the DC voltage between the output terminals P and N of the power converter 3 to an AC voltage having a desired frequency and voltage. After the conversion, the AC motor 5 is driven. After that, the AC power supply 1
Power is supplied to the inverter 4 via the reactor 2 and further via the diodes 11b to 16b and the thyristor 19 of the power converter 3, and when the AC motor 5 is in a regenerative operation, the inverter 4 supplies the power to the diode 20 of the power converter 3. Transistors 11a-1a that operate as shown in FIG.
The power is regenerated to the AC power supply 1 via the AC reactor 2 via the AC reactor 2.

The AC reactor 2 is provided to suppress the current flowing through the diode 20 and the transistors 11a to 16a during the regenerative operation described above. The snubber capacitor 17 is used for snubber for the switching operation of the transistors 11a to 16a.

[0009]

The main circuit configuration of the power converter 3 shown in FIG. 2 is similar to the configuration of a so-called PWM control self-excited rectifier, except that the switching operation of the transistors 11a to 16a by the control circuit 22 is performed. As described above, a simple switching operation based on only the phase of the voltage of the AC power supply 1 is performed.

However, during the power running operation of the AC motor 5 described above, the power converter 3 is equivalent to a capacitor-input three-phase full-wave rectifier circuit comprising bridge-connected diodes 11b to 16b and an electrolytic capacitor 21. A large amount of harmonic current flows from the AC power supply 1 to the converter 3, and there is a problem that the AC power supply 1 is disturbed by the harmonic current.

An object of the present invention is to solve the above-mentioned problems and to provide a power converter in which the harmonic current is suppressed.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a power converter for converting an AC voltage input from an AC power supply to a DC voltage and outputting the DC voltage, wherein a plurality of sets of self-extinguishing elements and diodes are connected in anti-parallel. A semiconductor switch is bridge-connected, one end of a series circuit of a DC reactor and a resistor is connected to one end on the DC side of the bridge-connected circuit, a diode is connected to both ends of the series circuit, and both ends of the resistor are connected. A power converter having a configuration in which a thyristor is connected to the DC-side of the bridge-connected circuit and a smoothing capacitor is connected between the other end of the series circuit and a voltage across the smoothing capacitor as an output. I do.

According to the present invention, as described later, the harmonic current can be suppressed by inserting the DC reactor into a conventional circuit.

[0014]

FIG. 1 is a circuit diagram of a power converter showing an embodiment of the present invention.
Reference numeral 0 denotes semiconductor switches 11 to 16, snubber capacitors 17, and resistors 1 having the same functions as those of the conventional circuit shown in FIG.
8, a rectifier 19, a diode 20, an electrolytic capacitor 21, a control circuit 22 and a DC reactor 31 are provided.

That is, as shown in FIG. 1, one end of a series circuit of a DC reactor 31 and a resistor 18 is connected to the + side of the DC output of a three-phase bridge connection circuit composed of semiconductor switches 11 to 16, and An electrolytic capacitor 21 is connected between the other end of the bridge connection circuit and the negative side of the DC output of the bridge connection circuit.
Thyristor 19 is connected to both ends of the resistor 18.
Is connected.

The operation of the power converter 30 shown in FIG. 1 will be described below. First, the operation up to the completion of the activation of the power converter 30 is the same as the operation of the power converter 3 described above. Next, when the activation of the power conversion device 30 is completed, the inverter 4 starts operating and converts the DC voltage between the output terminals P and N of the power conversion device 3 into an AC voltage having a desired frequency and voltage, thereby obtaining an AC motor. 5 is driven. Thereafter, during power running operation of the AC motor 5, the diodes 11 b to 16 b of the power converter 3 are further switched from the AC power supply 1 via the AC reactor 2.
And supplies the power to the inverter 4 via the DC reactor 31 and the thyristor 19. When the AC motor 5 is in the regenerative operation, the inverter 4 supplies the diode 20 of the power converter 3 and the transistor which operates as shown in FIG. 11
a to 16a, and further, to the AC power supply 1 via the AC reactor 2.

In the above-described power running operation, the DC reactor 3
1 suppresses a harmonic current flowing from the AC power supply 1 to the power converter 30. During regenerative operation, the diode 2
0 causes no current to flow in the DC reactor 31, so that the DC reactor 31 is irrelevant to the aforementioned switching operations of the transistors 11a to 16a.

[0018]

According to the power converter of the present invention, when power is supplied from the AC power supply to the power converter using the DC reactor, the harmonic current of the AC power supply is suppressed, and the operation of the control circuit is simplified. An inexpensive and high-quality power converter as a DC power supply can be provided.

[Brief description of the drawings]

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

FIG. 2 is a circuit configuration diagram of a power converter showing a conventional example.

FIG. 3 is a waveform chart for explaining the operation of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... AC reactor, 3 ... Power converter, 4 ... Inverter, 5 ... AC motor, 11-16 ... Semiconductor switches, 11a-16a ... Transistors, 11b
~ 16b ... diode, 17 ... snubber capacitor, 18
... Resistance, 19 ... Thyristor, 20 ... Diode, 21 ...
Electrolytic capacitor, 22: control circuit, 30: power converter, 31: DC reactor.

Claims (1)

[Claims] 1. A power converter for converting an AC voltage input from an AC power supply into a DC voltage and outputting the DC voltage, wherein a plurality of sets of self-extinguishing elements and diodes are connected in anti-parallel by bridge-connecting a semiconductor switch. Connecting one end of a series circuit of a DC reactor and a resistor to one end on the DC side of the bridge-connected circuit; connecting a diode to both ends of the series circuit; connecting a thyristor to both ends of the resistor; A power converter, wherein a smoothing capacitor is connected between the other end of the connected circuit on the DC side and the other end of the series circuit, and a voltage between both ends of the smoothing capacitor is output.