JPH0324152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power conversion device using a gate turn-off thyristor (hereinafter referred to as a "GTO thyristor").

[Technical background of the invention]

GTO thyristor has self-extinguishing ability, so
There is no need for a forced commutation circuit like in conventional thyristors. Therefore, the loss of the element itself can be reduced, and the circuit configuration of the device can be simplified, making it possible to achieve smaller size, lighter weight, and improved efficiency.

By the way, GTO is used in power conversion equipment with high voltage input.
When applying a thyristor, it is necessary to connect the element configurations in series, similar to conventional thyristors.

Figure 1 shows a typical circuit diagram of an inverter circuit in which conventional GTO thyristors are connected in series.

In FIG. 1, a smoothed DC voltage is obtained from a DC power supply 1 via a filter reactor 2 and a filter capacitor 3.

In the figure, the reference numerals of symmetrical parts such as the upper and lower GTO thyristor arms are omitted for explanation.

Controlled AC power is supplied to the load 18 by controlling the conduction time of the GTO thyristors 4a and 4b.

The diode 5, which has a series connection of a resistor 13 and a capacitor 14 in parallel, is connected to the GTO thyristor 4.
This is for the flywheel when a and 4b are off. Anode reactor 6 is GTO thyristor 4
The rise of the current immediately after a and 4b are turned on (di/
dt) and the time derivative of current).

The saturable reactor 7 is a GTO thyristor 4a,
The voltage imbalance between the elements due to variations in the turn-on time of 4b is alleviated. diode 2
0 and resistor 21 are GTO thyristors 4a, 4
Immediately after b is turned off, the energy of the anode reactor 6 and the saturable reactor 7 is transferred to the capacitor 1 via the diodes 9a and 9b in the snubber circuit of the GTO thyristor (diodes 9a and 9b, capacitors 10a and 10b, and resistors 11a and 11b).
Energy is circulated through a loop of anode reactor 6 → saturable reactor 7 → resistor 21 → diode 20 → anode reactor 6 so as not to flow into 0a and 10b. In addition, 10
0 and 100' are both conventional DC-AC power converters and have the same circuit configuration.

[Problems with background technology]

Here, when turning off a current of about 500A by switching the GTO thyristors 4a and 4b at about 1KHz, if the DC power supply 11 is 1500V, then
The resistors 11a and 11b each have a power of about 500W.
Further, the resistor 21 causes a loss of about 2 kW, resulting in a decrease in efficiency and an increase in resistor capacity, which is not preferable in terms of device configuration.

[Purpose of the invention]

Here, the present invention provides series-connected
The energy stored in the reactor of a power converter using a GTO thyristor is returned to the DC power supply using a DC current transformer to improve efficiency, and the energy stored in the reactor is temporarily used immediately after the GTO thyristor turns off. The object of the present invention is to provide a DC-AC power converter that absorbs surges with a surge absorption circuit.

[Summary of the invention]

The present invention provides a power conversion device consisting of upper and lower arms of GTO thyristors connected in series, in which the anode side of the upper arm GTO thyristor and the lower arm
A surge absorption circuit is provided between the cathode side of the GTO thyristor, a snubber circuit connected in parallel with the GTO thyristor has a diode of reverse polarity, and a reactor is inserted in series with the series connection of the GTO thyristor. This is a DC-AC power conversion device that includes a DC transformer connected to feed back most of the stored energy to the DC power source.

[Embodiments of the invention]

A block diagram of one embodiment of the present invention is shown in FIG.

In FIG. 2, the anode reactor 6 and the saturable reactor 7 when the GTO thyristors 4a and 4b are turned off by the feedback DC current transformer 15.
The structure is such that the accumulated energy is fed back to the DC power supply 1 side. Further, the diode 17 is for feedback.

The diode 22, resistor 24, and capacitor 23 temporarily absorb the energy stored in the anode reactor 6 and the saturable reactor 7 immediately after the GTO thyristors 4a and 4b are turned off.

Note that 25a and 25b are also the same diodes as 8a and 8b, and 200 and 200' are DC-
It is an AC power converter.

In the drawings, the same reference numerals indicate the same or corresponding parts.

The operation of the present invention will be explained using FIGS. 3 and 4.

In FIG. 3, the feedback DC transformer 5 does not operate immediately after the GTO thyristors 4a, 4b are turned off. The magnetic flux of a current transformer is a time integral of voltage and does not increase quickly. For this reason, the feedback DC current transformer 5 does not operate until the magnetic flux becomes sufficiently large. Therefore, the energy stored in the anode reactor 6 and the saturable reactor 7 is transferred through the current i ₁ loop (6→7→9a →10a→9
b → 10b → 18), and is discharged to the load 18 side via the diodes 22, 25a, 25b and the capacitor ₂₃ .
→23→25b→25a→18) and is released to the load 18 side. Snubber circuit (diode 9a, capacitor 10a, resistor 11a) and surge absorption circuit (diode 22, capacitor 23, resistor 24)
have a common function of absorbing the energy stored in the reactor. However, the capacitance of the capacitor 10a of the snubber circuit cannot be made very large because the discharge ends during the ON period of the GTO. Actually, the discharge resistors 11a, 11b
In terms of loss, it can be kept to around 2μF. Therefore, a surge absorption circuit is used to absorb the energy accumulated in the reactor. capacitor 2
3 only needs to be discharged to the power supply voltage by the overcharge due to the accumulated energy of the anode reactor 6 and the saturable reactor 7, so its capacity is, for example,
It can be increased to about 10μF.

Next, FIG. 4 is a state diagram in which the feedback DC transformer is in operation.

The feedback DC transformer 15 is sufficiently excited with the polarity shown, and the energy stored in the anode reactor 6 and the saturable reactor 7 is transferred to the current _i3 loop (6→7→
The stored energy is released through the auxiliary diodes 16→15→6).

At this time, a voltage is induced on the primary and secondary sides of the feedback DC transformer 15 with the polarity shown in the figure, and a current i ₄ loops (3→17→15→3) against the power supply voltage. Energy is returned.

When the saturable reactor 7 completely releases the stored energy, its magnetic flux is reset.

〔Effect of the invention〕

Thus, according to the present invention, in a DC/AC power converter in which GTO thyristors are connected in series,
Immediately after the GTO thyristor turns off, the surge absorption circuits 22, 23, and 24 suppress the overvoltage applied to the GTO thyristor due to the release of the accumulated energy of the anode reactor 6 and the saturable reactor 7, and the accumulated energy of the reactor is converted into feedback DC. Since the current is fed back to the DC power source 1 side using the current transformer 15, it is possible to improve efficiency without wasting energy with a resistor. There is also the secondary effect of making the device more compact.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the conventional device, Fig. 2 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 3 is an explanatory diagram of the operation of the surge absorption circuit, etc., and Fig. 4 is the DC feedback transformer. It is an explanatory diagram of the operation of the flow vessel. 1...DC power supply, 2...Filter reactor,
3...Filter capacitor, 4a, 4b...
GTO thyristor, 5...Flywheel diode, 6...Anode reactor, 7...Saturable reactor, 8a, 8b, 25a, 25b...Auxiliary diode, 9a, 9b, 22...Surge absorption diode, 10a, 10b , 23...Surge absorption capacitor, 11a, 11b, 24...Discharge resistor, 12a, 12b...Voltage dividing resistor, 13
... Surge absorption resistor, 14 ... Surge absorption capacitor, 15 ... DC current transformer for feedback, 16 ... Auxiliary diode, 17 ... Feedback diode, 18 ...
...Load, 100,100'...Conventional DC-AC power converter, 200,200'...DC-AC converter according to the present invention.

Claims (1)

[Scope of Claims] 1. Upper and lower arms each having a plurality of GTO thyristors connected in series and connected to a DC power supply via an anode reactor and a saturable reactor; a snubber circuit connected in parallel to the GTO thyristors; The first connected in anti-parallel to the GTO thyristor
a diode, a primary winding is connected to the reactor to feed back the energy stored in the reactor when the GTO thyristor is turned off, and a secondary winding is connected between the DC power terminals via a second diode. a DC current transformer that is connected and returns the energy stored in the reactor to the DC power supply side against the power supply voltage; and a third DC current transformer in the forward direction between the anode side of the upper arm and the cathode side of the lower arm. A DC circuit comprising a parallel circuit of a diode and a resistor, and a capacitor connected in series, and a surge absorption circuit that absorbs the energy accumulated in the reactor immediately after the turn-off of the GTO thyristor before the DC current transformer operates. -AC power converter.