JPH04295227A - Gto thyristor inverter - Google Patents

Abstract

PURPOSE:To enhance total efficiency by reducing snubber loss. CONSTITUTION:A parallel circuit of a GTO thyristor 14 for interrupting short circuit current, a second snubber circuit and a circulation diode 2 is inserted into a power supply path from a DC voltage supply 1 to a GTO thyristor inverter comprising GTO thyristors 5A-5D for conversion, a first snubber circuit and circulation diodes 6A-6D. Since interrupting currents of the converting GTO thyristors 5A-5D can be lowered, capacitances of snubber capacitors 13A-13D associated with the converting GTO thyristors 5A-5D can be reduced and thereby snubber loss of the snubber capacitors 13A-13D can be reduced. Furthermore, since the short circuit current interrupting GTO thyristor is normally conducting, snubber loss of a snubber capacitor 15 can be substantially nullified. Consequently, total efficiency of the GTO thyristor inverter can be enhanced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage type GTO thyristor inverter using a GTO thyristor as a switching element.

0002

2. Description of the Related Art FIG. 2 shows a circuit diagram of a conventional GTO thyristor inverter. In FIG. 2, 1 is a DC voltage source, 2
is a freewheeling diode, 3 is a DC reactor for suppressing the rate of increase in short circuit current, 4A to 4D are anode reactors, 5A to 5
D is a conversion GTO thyristor, and 6A to 6D are free wheel diodes. 7A-7D are snubber capacitors, 8A-8
D is a diode, 9A to 9D are resistors, 10 is a load, 11
1 is a DC current detector for detecting short circuit current, and 12 is a DC fuse.

Reference numeral 18A is a conversion switch element consisting of a conversion GTO thyristor 5A, a freewheeling diode 6A, a snubber capacitor 7A, a diode 8A and a resistor 9A. 18B is a conversion switch element consisting of a conversion GTO thyristor 5B, a freewheeling diode 6B, a snubber capacitor 7B, a diode 8B, and a resistor 9B. 18C is a conversion switch element consisting of a conversion GTO thyristor 5C, a free wheel diode 6C, a snubber capacitor 7C, a diode 8C and a resistor 9C. 18D is a conversion GT
It is a conversion switch element consisting of an O thyristor 5D, a freewheeling diode 6D, a snubber capacitor 7D, a diode 8D, and a resistor 9D.

[0004] Such a conventional GTO thyristor inverter converts GT for conversion according to, for example, a pulse width modulation signal.
AC power is supplied to the load 10 by switching the O-thyristors 5A to 5D. Since the conversion operation by switching the conversion GTO thyristors 5A to 5D is well known, the explanation thereof will be omitted. This G
During the conversion operation, the TO thyristor inverter may fail due to some reason, for example, to the conversion GTO thyristors 5A, 5.
In some cases, GTO thyristor B or converting GTO thyristors 5C and 5D are turned on at the same time, resulting in a power short-circuit state. In this case, the current IS will increase rapidly. current I
When the DC current detector 11 detects that S exceeds the preset threshold current IS1, the gate signal to the conversion GTO thyristors 5A to 5D is cut off and the conversion GTO thyristors 5A to 5D are turned off.
The circuit is protected by cutting off the TO thyristors 5A to 5D.

[0005]

[Problem to be Solved by the Invention] However, it is difficult to cut off the GTO thyristors 5A to 5D, that is, to cut off the GTO thyristors 5A to 5D.
Due to the restriction of securing the minimum on-pulse time Tmin, the timing of generation of the off signal for ~5D is determined by the minimum on-pulse time from the time when a short circuit occurs, that is, when the current IS exceeds the threshold current IS1, until the GTO thyristors 5A to 5D are cut off. It is necessary to delay by Tmin or more.

[0006] Therefore, GTO thyristors 5A to 5D
The current IS flowing immediately before the circuit is cut off increases to the current value IS2. This current value IS2 is set to GTO thyristor 5A to prevent destruction of GTO thyristors 5A to 5D.
It must be suppressed to a controllable current value of ~5D (corresponding to the maximum rated value of the collector current in a transistor, which is generally expressed in this way for a GTO thyristor; the same applies hereinafter). For this reason, in the conventional example, a DC reactor 3 is inserted in the power supply path from the DC voltage source 1 to suppress the rate of increase in current. Therefore, in order to make the DC reactor 3 as small as possible, the final cutoff current, that is, the current value IS2, must be increased to near the controllable current values of the GTO thyristors 5A to 5D.

On the other hand, snubber capacitors 7A to 7A in the snubber circuit connected in parallel to GTO thyristors 5A to 5D
As shown in FIG. 3, the capacitance of 7D is approximately proportional to the final breaking current of GTO thyristors 5A to 5D, and if this breaking current is large, the capacitance of snubber capacitors 7A to 7D must also be set large. be. In addition, if the DC power supply voltage is the same, the loss of the snubber circuit is proportional to the capacitance of the snubber capacitors 7A to 7D.
The larger the capacitance of ~7D, the larger it becomes. Therefore, the loss of the snubber circuit is approximately proportional to the breaking current of the GTO thyristors 5A to 5D, and increases as the breaking current increases.

The conventional GTO thyristor inverter shown in FIG.
The configuration is such that the thyristors 5A to 5D also cut off short-circuit current, and the snubber capacitor 7A is designed to cut off the maximum rated current of the GTO thyristors 5A to 5D in the event of a short circuit.
It is necessary to set a capacitance of ~7D. In other words, large capacity snubber capacitors 7A to 7D are required. Therefore, under normal conditions, a snubber capacitor with an excessive capacitance of 7A
7D, there was a problem in that the loss of the snubber circuit became extremely large.

[0009] Accordingly, an object of the present invention is to provide a GTO thyristor inverter that can be miniaturized, reduce snubber circuit loss, and increase overall efficiency.

0010

[Means for Solving the Problems] The GTO thyristor inverter of the present invention includes a converting GTO thyristor and a first
A bridge circuit is formed by connecting a plurality of conversion switch elements in which a first freewheeling diode is connected in antiparallel to the parallel circuit of the snubber circuit in a bridge configuration, and this bridge circuit is connected to a DC voltage source. In addition, a short-circuit current-blocking switch element is inserted and connected in the power supply path from the DC voltage source to the bridge circuit, and a second free-wheeling diode is connected in anti-parallel to the parallel circuit of the short-circuit current-blocking GTO thyristor and the second snubber circuit. ing.

[0011]

[Operation] According to the configuration of the present invention, the short circuit current interrupting GT
The O thyristor cuts off the short-circuit current, and the conversion GTO thyristor only interrupts the load current for conversion operation. Since the conversion GTO thyristor has a small breaking current, the first one attached to the conversion GTO thyristor The capacitance of the snubber capacitor, which is a component of the snubber circuit, can be set small, and the loss in the first snubber circuit due to the snubber capacitor can be reduced.

Furthermore, since the GTO thyristor for short-circuit current interrupting has a large interrupting current, it is necessary to increase the capacitance of the snubber capacitor that is a component of the attached second snubber circuit. Since the thyristor is normally conductive and the snubber capacitor is not charged, the loss in the second snubber circuit caused by the snubber capacitor can be reduced to substantially zero.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit diagram of a GTO thyristor inverter according to an embodiment of the present invention. This GTO thyristor inverter connects an anode reactor 4A to a DC voltage source 1 through an anti-parallel circuit of a short-circuit current interrupting GTO thyristor 14 and a freewheeling diode 2, and a DC fuse 12 in series.
, 4B and the series circuit of the conversion GTO thyristors 5A, 5B are connected, and the anode reactors 4C, 4D and the conversion GTO thyristors 5C, 5D are connected in parallel with the series circuit of the anode reactors 4A, 4B and the conversion GTO thyristors 5A, 5B. A series circuit is connected. GT for conversion
A load 10 is connected between the connection point of the O thyristors 5A and 5B and the connection point of the conversion GTO thyristors 5C and 5D.

A freewheeling diode 6A is connected in antiparallel to the converting GTO thyristor 5A, and a snubber capacitor 13
A, a snubber circuit consisting of a diode 8A and a resistor 9A are connected in parallel. Similarly, the conversion GTO thyristor 5B includes a freewheeling diode 6B and a snubber capacitor 13.
B, a snubber circuit consisting of a diode 8B and a resistor 9B, and a snubber circuit consisting of a freewheeling diode 6C, a snubber capacitor 13C, a diode 8C and a resistor 9C for the conversion GTO thyristor 5C;
A free wheel diode 6D, a snubber circuit consisting of a snubber capacitor 13D, a diode 8D and a resistor 9D are connected to the O-thyristor 5D.

[0015] Furthermore, the GTO thyristor 1 for short-circuit current interruption
A snubber circuit consisting of a snubber capacitor 15, a diode 16, and a resistor 17 is connected in parallel to 4. The conversion GTO thyristor 5A, freewheeling diode 6A, snubber capacitor 13A, diode 8A, and resistor 9A constitute a conversion switch element 19A. Similarly, the conversion GTO thyristor 5B, freewheeling diode 6B, snubber capacitor 13B, diode 8B, and resistor 9B constitute a conversion switch element 19B. Also, GTO for conversion
The thyristor 5C, freewheeling diode 6C, snubber capacitor 13C, diode 8C, and resistor 9C constitute a conversion switch element 19C. In addition, a GTO thyristor 5D for conversion, a freewheeling diode 6D, a snubber capacitor 13
D, diode 8D, and resistor 9D are conversion switch element 1
It constitutes 9D.

In this GTO thyristor inverter, the short-circuit current interrupting GTO thyristor 14 is in a conductive state under normal conditions, and the freewheeling diode 2 is connected in antiparallel to the short-circuit current interrupting GTO thyristor 14, so that the short-circuit current interrupting GTO thyristor 14 is in a conductive state. This is equivalent to the state in which the thyristor 14 and the freewheeling diode 2 are omitted, and the conversion switch elements 19A to 19
D is turned on and off according to the pulse width modulation signal, and supplies AC power to the load 10.

At this time, the ON voltage of the freewheeling diode 2 is applied as a reverse voltage between the anode and cathode of the GTO thyristor 14 for short circuit current interruption, and the ON voltage of the GTO thyristor 14 itself for short circuit current interruption is applied as a forward voltage. Only voltage is applied. Therefore, the snubber capacitor 15 has almost no accumulated charge in normal times. Therefore, even if the capacitance of the snubber capacitor 15 is increased, the loss of the snubber circuit does not increase.

Furthermore, during the conversion operation, if for some reason, for example, the conversion GTO thyristors 5A and 5B or the conversion GTO thyristors 5C and 5D are turned on at the same time and the power supply is short-circuited, the current IS suddenly changes. It will increase to . When the DC current detector 11 detects that the current IS exceeds the preset threshold current IS1, if the short-circuit current interrupting GTO thyristor 14 is in a conductive state, the short-circuit current interrupting GTO thyristor 14
Immediately give an off signal to the gate of G
The TO thyristor 14 is shut off, and the supply of subsequent ON signals is stopped. In addition, GTO thyristor 1 for short circuit current interruption
4 is in the cutoff state (a state in which regenerative current is flowing through the freewheeling diode 2), the supply of subsequent ON signals is stopped.

At this time, the conversion GTO thyristor 5A~
The gate signal to 5D is continuously supplied as it is, and the on state of the conversion GTO thyristors 5A to 5D is maintained. Therefore, there is no problem in securing the minimum on-pulse time. As mentioned above, since the short circuit current is interrupted by the short circuit current interrupting GTO thyristor 14,
There is no need to shut off the conversion GTO thyristors 5A to 5D. Therefore, the capacitance of the snubber capacitors 13A to 13D attached to the conversion GTO thyristors 5A to 5D, respectively, may be set based on the breaking current corresponding to the peak value of the current flowing through the load 10 during normal times, and the capacitance of the snubber capacitor 13A to The capacitance of 13D to 13D can be set small, and the loss of the snubber circuit caused by the snubber capacitors 13A to 13D can be reduced.

[0020] Furthermore, the GTO thyristor 1 for short-circuit current interruption
Since the snubber capacitor 4 is normally in a conductive state and the snubber capacitor 15 is not charged, the loss of the snubber circuit due to the snubber capacitor 15 can be reduced to substantially zero. Therefore, the loss of both snubber circuits can be reduced, and the overall efficiency can be increased. In addition, instead of using a DC reactor like the conventional example, G
Since the TO thyristor 14 and the snubber circuit are used, miniaturization can be achieved.

[0021]

According to the GTO thyristor inverter of the present invention, the short circuit current is interrupted by the GTO thyristor for short circuit current interruption, and the conversion GTO thyristor only interrupts the load current for conversion operation. Since the breaking current of the thyristor is small, the capacitance of the snubber capacitor that is a component of the snubber circuit attached to the conversion GTO thyristor can be set small, and the loss of the snubber circuit due to the snubber capacitor can be reduced.

Furthermore, since the GTO thyristor for short-circuit current interruption has a large interruption current, it is necessary to increase the capacitance of the snubber capacitor that is a component of the attached snubber circuit, but the GTO thyristor for short-circuit current interruption is in a conductive state and the snubber capacitor is not charged, so the loss of the snubber circuit due to the snubber capacitor can be reduced to substantially zero. Therefore, the loss of both snubber circuits can be reduced, and the overall efficiency can be increased.

Furthermore, since a short-circuit current interrupting GTO thyristor and a snubber circuit are used instead of using a DC reactor as in the conventional example, miniaturization can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a GTO thyristor inverter according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing the configuration of a conventional GTO thyristor inverter.

FIG. 3 is a characteristic diagram showing the relationship between capacitance and peak cut-off current of a snubber capacitor.

[Explanation of symbols]

1 DC voltage source 2 Freewheeling diode 4A to 4D Anode reactor 5A to 5D
Conversion GTO thyristor 6A to 6D Freewheeling diode 8A to 8D Diode 9A to 9D Resistor 10 Load 11 DC current detector 12 DC fuse 13A to 13D Snubber capacitor 14
GTO thyristor for short circuit current interruption 15 Snubber capacitor 16 Diode 17 Resistor

Claims (1)

[Claims] 1. A bridge circuit is formed by connecting in a bridge configuration a plurality of sets of conversion switch elements each including a first freewheeling diode connected in anti-parallel to a parallel circuit of a conversion GTO thyristor and a first snubber circuit; In a GTO thyristor inverter whose circuit is connected to a DC voltage source,
A short-circuit current-blocking switch element having a second freewheeling diode connected in antiparallel to a parallel circuit of a short-circuit current-blocking GTO thyristor and a second snubber circuit was inserted and connected in a power supply path from the DC voltage source to the bridge circuit. The GTO thyristor inverter is characterized by: