JPH0847242A - Fault detector of voltage-type self-excited converter - Google Patents

Abstract

PURPOSE:To provide the fault detector of a voltage type self-excited converter which can detect a fault such as an arm short-circuit, an arm external short- circuit or a short-circuit between AC power lines at a high speed with a simple circuit construction and with which the voltage-type self-excited converter can be protected without preparing unnecessarily large anode reactor and self- extinguishing element. CONSTITUTION:Arms to which a same AC bus line 1A is connected consist of GTO's 2A and 2B. A first detecting means (composed of a bias detector 19A and a reversing circuit 20A) which detects the continity state of one of the GTO's 2A and 2B of which the arms consist and a second detecting means (composed of a snubber discharge detector 18B) which detects the discharge of a snubber capacitor 5B which is connected in parallel to the other of the GTO's 2A and 2B of which the arms to which the same bus line 1A is connected consist. Further, logic circuits 13A and 13B which outputs signals when the logical multiplies of the detection signals of the first and second detecting means are obtained as the fault detection signals of a converter are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is constructed by bridge-connecting a self-extinguishing semiconductor element such as a gate turn-off thyristor (hereinafter referred to as GTO), and has a DC voltage source such as a capacitor, a storage battery and a rectifier on the DC side. The present invention relates to a voltage-type self-excited converter, and particularly to an accident detection circuit for detecting a short circuit accident of the converter.

[0002]

2. Description of the Related Art FIG. 17 shows a general configuration of a voltage type self-exciting converter including a converter in which a GTO is bridge-connected and a DC voltage source. In FIG. 17, 1A, 1B, 1
C is an AC voltage source, 2A to 2F are self-arc-extinguishing type semiconductor devices such as GTO (hereinafter abbreviated as self-arc-extinguishing device), 3A to 3F
Is a diode and 4A to 4F are resistors forming a snubber circuit for absorbing energy when the GTO is turned off.
A to 5F are capacitors forming a snubber circuit, and 6A to 6F.
F is a diode that forms a snubber circuit. 7A-7
F is an anode reactor for suppressing the rising of the current when the GTO is turned on. Reference numeral 8 is a DC voltage source such as a rectifier.

Consider a case where a short-circuit accident occurs in a voltage type self-exciting converter as shown in FIG. First, consider arm short circuit. For example, in FIG. 17, consider a case where an error signal such as noise or element damage due to some cause occurs while the GTO 2A is energized, and the GTO 2B is in a conductive state. The anode reactor 7A, the GTO 2A, the anode reactor 7B, and the GTO 2B make a short-circuit path of the DC voltage source 8, and a short-circuit current flows from the DC voltage source 8 to the converter.
The rise of the short-circuit current depends on the anode reactor 7A, 7A.
It is suppressed by B.

Second, consider an arm external short circuit accident. For example, consider a case where an external short-circuit accident such as a short-circuit of an insulator occurs in a portion corresponding to an arrow 51 while the GTO 2B is energized in FIG. A short-circuit path of the DC voltage source 8 is created at the short-circuit fault part, the anode reactor 7B, and the GTO 2B, and a short-circuit current flows from the DC voltage source 8 to the converter.

Third, consider an AC line short circuit. Figure 1
7, GTO2A and GTO2D are energized, the arrow 5
Consider a case where a short circuit occurs in the portion corresponding to 2. The anode reactor 7A, the GTO 2A, the short-circuit fault portion, the anode reactor 7D, and the GTO 2D make a short-circuit path of the DC voltage source 8, and a short-circuit current flows from the DC voltage source to the converter.

A self-extinguishing element such as a GTO is damaged when a current exceeding a current value that can be interrupted is interrupted. Therefore, when the accident described above occurs, it is necessary to detect the accident promptly and perform the protective operation (OFF) during the period when the accident current is equal to or less than the current value that can be interrupted, and the anode reactors 7A to 7F. , GTO 2A to 2F, etc., have been selected to satisfy the conditions.

FIG. 18 shows a conventional arm short circuit protection circuit. 18, the same elements as those of FIG. 17 are designated by the same reference numerals and the description thereof will be omitted. 11A to 11F are current detectors, 12
A and 12B are level detectors for detecting that the arm currents detected by the current detectors 11A and 11B have reached a predetermined value, 13 is a logical product circuit, 14 is an interlock circuit, and is a snubber capacitor 5A, This is a circuit for not detecting an arm short circuit during a period in which the current detectors 11A and 11B simultaneously detect current due to charge / discharge of 5B. Further, 15 is a memory circuit of the detected accident, 16 is a pulse amplifier circuit for amplifying an electronic level signal and transmitting an OFF command to the GTOs 2A to 2F, and 101 is an ON / OFF pattern signal required for interlock.

In FIG. 18, for simplicity, GTO2
Although only the level detectors 12A and 12B for the currents A and 2B, the AND circuit 13 and the interlock circuit 14 are shown, the GTOs 2C and 2D and the GTOs 2E and 2F are also similar to the level detectors, the AND circuits and the interlock circuits. Provide a lock circuit.

The conventional circuit shown in FIG. 18 uses the phenomenon that a high voltage side arm and a low voltage side arm (each of which is hereinafter referred to as a pair arm) connected to the same AC bus, which is not possible in normal operation, are simultaneously energized to short-circuit the arm. Is a circuit for detecting. However, even during normal operation, the snubber capacitor 5 when the self-extinguishing element that is conducting becomes non-conducting
By the charging current of A to 5F and the discharging current of the snubber capacitors 5A to 5F when the non-conducting self-extinguishing element is conducting,
A period occurs in which the pair arms are energized at the same time.

In FIG. 18, the PWM pattern signal 10
Although 1 is used for interlocking, the time required for interlocking varies depending on the load current value, so interlocking needs to be performed in the longest time, which delays detection. Further, it is necessary to change the timing of taking the interlock depending on the direction of the load current, which causes a problem that the circuit becomes complicated.

Further, in the circuit of FIG. 18, in the case of an external short circuit of the arm, the short-circuit current cannot be detected because it does not pass through the current detector of the short-circuited arm. AC output line short circuit accident cannot be detected because the paired arms do not energize.

FIG. 19 shows a conventional protection circuit for an arm external short circuit and an AC output line short circuit accident. FIG. 18 already described
The same elements as those of 1 are designated by the same reference numerals and the description thereof will be omitted. 12C
Reference numerals 12E to 12E are level detectors for detecting that the arm currents detected by the current detectors 11A, 11C and 11E have reached a predetermined value, 15A, 15B and 15C are memory circuits, and 17 is a logical sum circuit. The level detectors 12C to 12E are GTO2
Although only the positions of the arms A, 2C, and 2E are shown,
The same circuit is added to GTOs 2B, 2D, and 2F, and the output thereof is input to the OR circuit 17.

In the circuit shown in FIG. 19, when an arm external short-circuit accident or an AC output line short-circuit accident occurs, the level detectors 12C to 12E detect and protect that the current value during normal operation is exceeded. The detection level of the overcurrent at the time of an accident is usually about 1.2 to 1.4 times the peak current at the time of normal operation so as to prevent malfunction during normal operation.
In the circuit shown in FIG. 19, detection and protection are performed after the arm current exceeds the overcurrent detection level, so there is dead time before detection, and the anode reactors 7A to 7F
Alternatively, it is necessary to increase the interruptable current of GTO 2A to 2F.

[0014]

As is apparent from the above-mentioned prior art, the self-extinguishing elements 2A to 2F are bridge-connected and a converter for converting direct current to alternating current or alternating current to direct current; In the voltage type self-exciting converter composed of the voltage source 8, the detection by the simultaneous flow of current in the high voltage side arm and the low voltage side arm connected to the same AC bus is:
It is necessary to change the interlock during the period when the charge and discharge currents of the snubber capacitors 5A to 5F simultaneously flow to the upper and lower arms depending on the direction and magnitude of the load current, which complicates the circuit and causes an arm external short circuit accident and an AC output line There was a problem that a short circuit accident could not be detected.

Further, in the method of detecting the overcurrent of each arm, it is impossible to detect up to the overcurrent level.
A dead time is generated in the accident detection, and the anode reactor and G
It was necessary to increase the rated breaking current of the TO.

The object of the present invention is to eliminate the above-mentioned problems, and when an accident such as an arm short circuit, an arm external short circuit or an AC output line short circuit occurs in a voltage type self-exciting converter. Another object of the present invention is to provide a fault detection circuit of a voltage type self-exciting converter which can detect at high speed with a simple circuit and can protect the anode reactor and the self-extinguishing element without increasing the size more than necessary.

[0017]

In order to achieve the above-mentioned object, the invention corresponding to claim 1 is such that a plurality of self-extinguishing elements are bridge-connected and at least a snubber capacitor is connected in parallel to the self-extinguishing element. In the voltage type self-exciting converter for connecting a DC voltage source to the bridge and converting DC to AC or AC to DC, an arm to which the same AC bus of the self-extinguishing element is connected is connected. First detecting means for detecting that the constituent self-extinguishing element is in a conductive state, and second detecting means for detecting discharge of the snubber capacitor of the arm connected to the same AC bus as the arm to which the AC bus is connected. The output signal output when the logical product of the detection means and the detection signal of the first detection means of the one arm and the detection signal of the second detection means of the other arm is established, is used to detect an accident in the converter. A fault detection circuit of voltage-type self-commutated converter and a logic means to issue.

In order to achieve the above-mentioned object, the invention according to claim 2 is characterized in that a plurality of self-extinguishing elements are bridge-connected and at least a snubber capacitor is connected in parallel to the self-extinguishing element. In a voltage type self-exciting converter that connects a direct current voltage source to the bridge and converts direct current to alternating current or alternating current to direct current, a self-extinguishing device that constitutes an arm to which the same alternating current bus bar of the self-extinguishing element is connected First detecting means for detecting that the arc element is in a conducting state, and second detecting means for detecting discharge of the snubber capacitor of an arm connected to the same AC bus as the arm to which the AC bus is connected, When an OFF command is given to the self-extinguishing element of the other arm to which the same AC bus is connected among the self-extinguishing elements, a state in which a signal output for a predetermined time is inverted is detected. 3 and the first detection means of the one arm, the second detection means of the other arm, and the output signal output when the logical product of the detection signals of the third detection means is established. A fault detection circuit for a voltage-type self-excited converter, comprising: a logic means for making a fault detection signal of the converter.

Further, in order to achieve the above-mentioned object, the invention corresponding to claim 3 is a series circuit in which a plurality of self-extinguishing elements are bridge-connected, and the self-extinguishing element comprises at least a snubber capacitor and a snubber resistor. Are connected in parallel, a DC voltage source is connected to the bridge, and a voltage type self-exciting converter for converting direct current into alternating current or alternating current into direct current is provided with first detecting means and second detecting means, The first detection means includes a logic means, and a predetermined negative bias voltage is applied between the gate and the cathode of the self-extinguishing element that constitutes one arm of the self-extinguishing element to which the same AC bus is connected. A negative bias detection circuit for detecting that the current is being applied, a first current detection circuit for detecting that the current flowing through the self-extinguishing element forming the one arm is equal to or greater than a certain value, and the negative current detection circuit. And a first AND circuit that obtains a logical product of the output obtained by inverting the detection output of the bias detection circuit by the inverting circuit and the detection output of the first current detection circuit. The second detecting means detects that the self-extinguishing element that constitutes one of the connected arms is in a conductive state, and the second detecting means is the other of the self-extinguishing elements to which the same AC bus is connected. Snubber discharge detection circuit for detecting that the voltage of the snubber resistor connected to the arm of the other is a certain value or more and the direction of the current of the snubber capacitor connected to the other arm is in the discharging direction, and the other arm. Second current detection circuit for detecting that the current flowing through the snubber capacitor connected to the capacitor is a certain value or more, and a description of the second current detection circuit and the detection output of the snubber discharge detection circuit. And a second AND circuit that takes a product to detect discharge of the snubber capacitor connected to a self-extinguishing element that constitutes another arm to which the same AC bus is connected. The means uses the output signal output when the logical product of the detection signals of the outputs of the first and second AND circuits is established as the fault detection signal of the converter. This is the accident detection circuit.

In order to achieve the above-mentioned object, the invention according to claim 4 relates to a series circuit in which a plurality of self-extinguishing elements are bridge-connected, and the self-extinguishing element comprises at least a snubber capacitor and a snubber resistor. Connected in parallel,
A direct current voltage source is connected to the bridge to convert a direct current to an alternating current or an alternating current to a direct current in a voltage type self-excited converter, which comprises a first detecting means, a second detecting means, and a logic means. The first detection means confirms that a predetermined negative bias voltage is applied between the gate and the cathode of the self-extinguishing element that constitutes one arm of the self-extinguishing element to which the same AC bus is connected. A negative bias detection circuit for detecting, a first current detection circuit for detecting that the current flowing through the self-extinguishing element forming the one arm is a certain value or more, and a detection output of the negative bias detection circuit is inverted. It is composed of an output inverted by a circuit and a first OR circuit for ORing the detection output of the first current detection circuit, and constitutes one arm of the self-extinguishing element to which the same AC bus is connected. Self-extinguishing element One of the two detecting means detects that one of them is in a conductive state, and the second detecting means detects the voltage of the snubber resistor connected to the other arm of the self-extinguishing element to which the same AC bus is connected. A snubber discharge detection circuit for detecting that the current direction of the snubber capacitor connected to the other arm is a certain value or more, and the current flowing to the snubber capacitor connected to the other arm is constant. A second current detection circuit for detecting that the value is equal to or more than a value; and a second logical sum circuit for calculating the logical sum of the detection outputs of the second current detection circuit and the snubber discharge detection circuit. The logic means detects the discharge of the snubber capacitor connected to the self-extinguishing element forming the other arm to which the AC bus is connected, and the logic means is provided for the first and second detection means. A fault detection circuit of voltage-type self-commutated converter, wherein a logical product of the output signal is an accident detection signal of said transducer output signal to be outputted when satisfied.

[0021]

According to the first aspect of the present invention, when the self-extinguishing element forming the arm is in a conductive state, the snubber capacitor of another arm connected to the same AC bus as the arm is normally discharged. By detecting a state that is impossible during operation, it is possible to detect the arm current before it reaches an overcurrent, which enables a high-speed protection device.In addition, an accident such as an arm short circuit, an arm external short circuit, or an AC output line short circuit may occur. Even if it occurs, the same phenomenon occurs, so it is possible to detect it, and the direction and magnitude of the alternating current
Since it is not necessary to take an interlock by off-timing, it can be configured with a simple circuit and reliability is improved,
An economical accident detection circuit can be provided.

According to the invention of claim 2, claim 1
In addition to the function of the invention described above, the output signal output when the logical product of the detection signals of the first detection means of one arm, the second detection means and the third detection means of the other arm is established is converted. It is possible to provide an accident detection circuit capable of preventing erroneous detection even when there is a variation in the delay time between the detection of the conduction state of the self-extinguishing element and the detection of the discharge of the snubber capacitor by using the accident detection signal of the device.

Further, according to the invention of claim 3, in addition to the operation of the invention of claim 1, a signal for detecting the conduction state of the self-extinguishing element forming one arm and the other arm are formed. When the logical product of the signals that detect the discharge of the snubber capacitor connected to the self-extinguishing element is established, by using the fault detection signal of the converter, the detector may fail,
A highly reliable accident detection circuit that does not malfunction even if noise is mixed in any of the detection signals can be provided.

According to the invention corresponding to claim 4,
When the logical product of the signal that detects the conduction state of the self-extinguishing element that constitutes one arm and the signal that detects the discharge of the snubber capacitor connected to the self-extinguishing element that constitutes the other arm, is converted It is possible to provide an accident detection circuit that always operates when an accident occurs even if the detector fails and does not operate by using the accident detection signal of the device.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. (Structure of First Embodiment) FIG. 1 is a view for explaining the first embodiment (an embodiment corresponding to claim 1), but here, the same elements as those of FIGS. 18 and 19 are the same. The reference numerals will be given, and the points different from those in FIGS. 18 and 19 will be mainly described. Snubber discharge detection circuits 18A and 18B, negative bias detection circuit 19
A, 19B, inverting circuits 20A, 20B, AND circuit 13
A, 13B and storage circuits 15A, 15B are newly provided.

The negative bias detection circuits 19A and 19B detect that the self-extinguishing elements, such as GTOs (hereinafter referred to as GTOs) 2A and 2B, which form the arm, are in a non-conducting state (off state). The snubber discharge detection circuits 18A and 18B are
The discharge of the snubber capacitors 5A and 5B of the arm is detected. The AND circuits 13A and 13B convert the signals detected by the negative bias detection circuits 19A and 19B into an inverting circuit 20.
The signal inverted by A and 20B and the detection signal of the snubber discharge detection circuits 18A and 18B (the discharge detection signal of the snubber capacitor connected to the same AC bus as the arm) are input and the logical product of both signals is obtained. Then, the memory circuits 15A, 1
5B stores the output signals of the AND circuits 13A and 13B, outputs the signals stored in the storage circuits 15A and 15B through the logical sum circuit 17 as a fault signal of the converter, and outputs this as a pulse. The signal is amplified by the amplifier circuit 16 and given as an off-gate signal for the self-extinguishing elements 2A and 2B.

Although the structure described above is only for the arm connected to the AC voltage source 1A, it goes without saying that the arms connected to the other AC voltage sources 1B and 1C are the same. Yes.

Thus, when the self-extinguishing element on one side of the pair arm is in the conducting state, which is not possible during the operation of the normal voltage type self-exciting converter, it is detected that the snubber capacitor on the remaining side is discharged. However, it is used as an accident detection signal of the converter.

(Operation of First Embodiment) The operation of the first embodiment will be described below. Before that, the commutation operation of the voltage type self-exciting converter in the normal operation will be described with reference to FIGS. Explain.

FIG. 2 corresponds to FIG. 17 which has already been described.
The waveform of each part when commutating from GTO2B to the diode 3A is shown. The direction of current is GTO, the direction of current flowing in the diode is positive, and the snubber capacitor is positive in charging.

In FIG. 2, the energized state until time t1 is shown in FIG. The current is flowing through GTO2B. The snubber capacitor 5A is charged to a value equal to the DC voltage. FIG. 3B shows the energized state immediately after the OFF instruction is given to the GTO 2B at time t1. When the OFF command is given, the energization current of the GTO 2B becomes zero, the snubber capacitor 5B is charged, and the snubber capacitor 5A is discharged. At time t2, when the snubber capacitor 5B is charged to a value equal to the DC voltage, a forward voltage is applied to the diode 3A and the diode 3A becomes conductive as shown in FIG. 3 (c). Discharge current of snubber capacitor 5A and diode 3A
The sum of the current values of is equal to the alternating current. When the discharge of the snubber capacitor 5A is completed, all the alternating current flows through the diode 3A.

Next, the operation when commutating from the diode 3B to the GTO 2A will be described. Figure 4 shows the waveform of each part during commutation
Shown in In FIG. 4, the off-gate signal is applied to the GTO 2B at time t0, but since the diode 3B is energized as shown in FIG. 5A, there is no change in the waveform of each part.
When an on-gate signal is applied to the GTO 2A at time t1 in FIG. 4, the snubber capacitor 5A as shown in FIG.
Discharges through GTO 2A, and the current in diode 3B gradually decreases.

When the current of the diode 3B becomes zero, as shown in FIG.
As shown in (c), the snubber capacitor 5B is charged from the DC side via the GTO 2A. Snubber capacitor 5B
At the time point when the charging of the capacitor and the discharging of the snubber capacitor 5A are completed, all the alternating current flows through the GTO 2A.

In the commutation phenomenon during normal operation, the snubber capacitors 5A and 5B are discharged after time t1 in FIG.
And as you can see from time t1 onwards in FIG.
G of the other arm (paired arm) connected to the same bus
Occurs when TO is off.

Next, while the GTO 2B is energized, the GTO 2A is erroneously ignited or damaged for some reason and becomes conductive, and the waveforms of the respective parts are shown in FIG.
Shown in When the GTO 2A becomes conductive at time t1 in FIG. 6, the GTO 2A, 2B are turned on from the DC voltage source as shown in FIG.
At the same time that a short-circuit current flows through the snubber capacitor 5A, the snubber capacitor 5A discharges through the snubber resistor 4A and the GTO 2A.

Next, FIG. 8 shows an explanation of the operation when a short circuit accident occurs outside the arm while the GTO 2B is energized. When a short circuit occurs, a short circuit current flows from the DC voltage source through the fault point and GTO2B, and at the same time, the snubber capacitor 5
A discharges through the snubber resistor 4A, the anode reactor 7A, and the accident point. The waveform of each part at this time is the same as that at the time of arm short circuit if the current of GTO 2A is replaced with the fault point current in FIG.

Next, FIG. 9 shows the waveform of each part when a short circuit accident between the AC output lines occurs while the GTO 2A and GTO 2D are energized, and FIG. 10 shows the operation of the converter. Before the line short circuit occurs, the current flows as shown in FIG. Figure 9
When a short circuit occurs at time t1, a short circuit current flows from the DC voltage source via the fault point and GTO2A and GTO2D as shown in FIG. 10 (b). The snubber capacitor 5C is
It discharges through GTO2A and the accident point. The snubber capacitor 5B discharges via the GTO 2D and the accident point.

As described above with reference to FIGS. 6 to 10, a phenomenon common to each accident is that when the accident occurs, the snubber capacitors of the paired arms are discharged while the GTO is conducting. This phenomenon does not occur during normal operation. The present invention utilizes this feature to detect an accident at high speed.

In FIG. 1, the gate-cathode of the GTO (hereinafter referred to as GK) is used as the GTO conduction detection.
The negative bias voltage detection circuits 19A and 19B are used. A negative bias voltage of about −10 V is applied between the GK and GK of the GTO in order to prevent false ignition. GT
When O becomes conductive, the voltage across GK becomes zero or a positive value. Therefore, by detecting the voltage between GK, GT
The conduction state of O can be detected.

Further, in FIG. 1, the snubber discharge detection circuit 1
8A and 18B detect the discharge of the snubber capacitors 5A and 5B by the voltage generated in the snubber resistors 4A and 4B. When the snubber capacitors 5A and 5B are discharged,
Since it always passes through the snubber resistors 4A and 4B, the snubber capacitors 5A and 5B can be provided by providing a voltage detecting means having a polarity generated when a current in the discharging direction flows through the snubber resistors 4A and 4B.
The discharge of B can be detected.

In FIG. 1, when the GTO 2A is off,
When the output of the negative bias voltage detection circuit 19A is "1", the output of the inverting circuit 20A is "0", and the GTO 2A is on, the output of the negative bias voltage detection circuit 19A is "0" and the output of the inverting circuit 20A is " Since it becomes 1 ”, the inverting circuit 20
The output of A can detect the on / off state of the GTO.

By logically ANDing the conduction state signal of the GTO 2A and the discharge detection signal of the snubber capacitor 5B of the paired arm by the AND circuit 13B, the snubber capacitor 5B of the paired arm is discharged while the GTO 2A is energized. Detect what you have done and detect an accident. Similarly, GTO2B
Continuity signal and snubber capacitor 5 of paired arm
The discharge detection signal of A is ANDed by the AND circuit 13A to detect the accident.

Although only the arms of GTOs 2A and 2B are shown in FIG. 1, GTOs 2C to 2F are similarly detected. A logical sum circuit 17 takes the logical sum of the respective accident detection signals, and the pulse amplification circuit 16 outputs an off-gate signal to the GTO for protection.

(Effect of First Embodiment) According to the first embodiment described above, one GTO connected to the same AC bus is connected.
2A conduction state detection signal (by the negative bias detection circuit 19A and the inverting circuit 20A) and a discharge detection signal (by the snubber discharge detection circuit 18B) of the snubber capacitor 5B of the GTO 2B of the other arm connected to the same AC bus. An AND circuit 13B for input is provided, and the conduction state detection signal of the other GTO 2B connected to the same AC bus (by the negative bias detection circuit 19B and the inverting circuit 20B) and one arm connected to the same AC bus. An AND circuit 13A that receives the discharge detection signal of the snubber capacitor 5A of the GTO 2A (by the snubber discharge detection circuit 18A) is provided, and an accident is detected by the output signals of the AND circuits 13A and 13B, thereby causing an arm short circuit and an outside arm. It is also possible to detect accidents such as short circuits and short circuits between AC output lines. Ri interlock without requiring, also, since it is possible prior to detection leading to an overcurrent, it is possible to obtain the fault detection circuit of the economical and reliable and fast.

(Second Embodiment) FIG. 11 is a diagram showing a second embodiment (an embodiment corresponding to claim 1) of the present invention. Instead of providing the snubber discharge detection circuits 18A and 18B of FIG. 1, instead of this, current detectors 11A and 11B that detect the current flowing through the snubber circuit and level detection that detects the level of the detection value by the current detectors 11A and 11B. 12A and 12B are provided to detect the discharge of the snubber capacitors 5A and 5B by detecting the level of the current flowing through the snubber capacitors 5A and 5B with polarity. It is configured to input to the input terminal. The other points are the same as those of the first embodiment shown in FIG.

(Third Embodiment) FIG. 12 is a diagram showing a third embodiment (an embodiment corresponding to claim 1) of the present invention. The negative bias detection circuits 19A and 19B of FIG. 1 are not provided, but instead of this, current detectors 12A and 12B that detect the current flowing through the GTOs 2A and 2B are provided, whereby the GTOs 2A and 2B are provided.
The conduction of B is detected, and this detection signal is output to the AND circuit 13
It is input to one of the input terminals of A and 13B. The other configuration is the same as that of FIG.

(Fourth Embodiment) FIG. 13 is a diagram showing a fourth embodiment (an embodiment corresponding to claim 2) of the present invention, in which the AND circuit 13A of the embodiment of FIG. 1 has three input terminals. The one-shot circuit 21 and the inverting circuit 20 are newly provided at this one input terminal. When the one-shot circuit 21 inputs the GTO 2B off command 102,
A pulse having a predetermined width (one shot time) T is output. The output pulse of the one-shot circuit 21 is inverted by the inversion circuit 20, and this is input to one input terminal of the AND circuit 13A. Similarly, the AND circuit 13B of the embodiment of FIG.
Is changed to the one with 3 input terminals, and to this one input terminal,
The one-shot circuit 21 and the inverting circuit 20 are newly provided. The other structure is the same as that of the embodiment of FIG.

The operation of the circuit of FIG. 13 configured as above will be described with reference to FIG. In this embodiment, the problem in the case where the one-shot circuit 21 and the inverting circuit 20 are not provided can be eliminated. That is, after the OFF command is output to the GTO 2B and the GTO 2B is turned off and before the negative bias detection circuit 19B of the GTO 2B detects that the GTO 2B is turned off, the operation time of the circuit and the filter circuit for preventing malfunctions are different. There is a certain delay time. On the other hand, the snubber capacitor discharge detection circuit 18A has a similar delay time. When the delay times of the conduction detection circuit and the discharge detection circuit are different and the discharge detection is shorter, as can be seen from FIG. 14, the conduction of the arms and the discharge of the snubber capacitors of the pair arms are detected at the same time during the period from time t1 to t2. However, the accident is erroneously detected.

Therefore, as shown in FIG. 13, the OFF command 102 of the GTO 2B is input to the one-shot circuit 21, the output of the one-shot circuit 21 is inverted by the inverting circuit 20A, and the AND circuit 13 for detecting an accident is provided. input. FIG.
With the configuration shown in, even if there is a variation in the operation time of the GTO conduction detection and the snubber capacitor discharge detection,
It is possible to prevent erroneous detection. However, if the one-shot time T is too long, the period in which the failure cannot be detected increases, so it is desirable to check the time for detecting the conduction of the GTO and the detection of the discharge of the snubber capacitor and set it to the shortest possible value.

(Fifth Embodiment) FIG. 15 is a view showing a fifth embodiment of the present invention (an embodiment corresponding to claim 3). The difference from the embodiment of FIG. 1 is that the current detectors 11A and 1A are newly added.
1B, level detectors 12A and 12B, inverting circuit 20D,
The AND circuits 13D, 13E and 13C are provided. That is, the current flowing through the snubber capacitor 5A is detected by the current detector 11A, and the detected value is detected by the level detector 1A.
2A and a signal generated when the voltage exceeds a predetermined level are input to one input terminal of the AND circuit 13D, and the snubber discharge detection circuit 18 is input to the other input terminal of the AND circuit 13D.
Input the detection signal of A. Further, the detection signal of the negative bias detection circuit 19B is inverted by the inversion circuit 20D and input to one input terminal of the AND circuit 13E, and the GTO 2B
The current flowing through the current detector 11B is detected by the current detector 11B, the detected value is input to the level detector 12B, and the signal generated when the value exceeds a predetermined level is input to the other input terminal of the AND circuit 13E. The configurations of the AND circuits 13D and 13E are the same as those of the embodiment of FIG. 1 except that the outputs of the AND circuits 13C and 13C are input to the storage circuit 15A. Although only the GTO 2A detection circuit is shown in FIG. 15, it goes without saying that the GTO 2B to GTO 2F are similarly configured.

With this configuration, a failure of the detection circuit,
Even if the detector malfunctions due to noise, etc., the AND circuit 1
Since the outputs of 3D and 13E are zero, erroneous detection is not performed, and a highly reliable accident detection circuit can be provided.

(Sixth Embodiment) FIG. 16 is a diagram showing a sixth embodiment of the present invention (an embodiment corresponding to claim 4). The difference from the embodiment of FIG. 1 is that the current detectors 11A and 1A are newly added.
1B, level detectors 12A and 12B, inverting circuit 20D,
The logical sum circuits 17A and 17B and the logical product circuit 13F are provided.

That is, the current flowing through the snubber capacitor 5A is detected by the current detector 11A, the detected value is input to the level detector 12A, and a signal generated when the value exceeds a predetermined level is input to one input terminal of the OR circuit 17A. In addition, the detection signal of the snubber discharge detection circuit 18A is input to the other input terminal of the OR circuit 17A. Negative bias detection circuit 1
The detection signal of 9B is inverted by the inverting circuit 20D and input to one input terminal of the OR circuit 17B.
The current flowing through the current detector 11B is detected by the current detector 11B, the detected value is input to the level detector 12B, and a signal generated when the value exceeds a predetermined level is input to the other input terminal of the logical sum circuit 17B. The outputs of the logical sum circuits 17A and 17B are input to the logical product circuit 13F, and the output of the logical product circuit 13F is input to the storage circuit 15A, which is the same as the embodiment of FIG. Although only the GTO 2A detection circuit is shown in FIG. 16, it goes without saying that GTO 2B to GTO 2F are similarly configured.

With such a configuration, even if the detection circuit fails, the outputs of the OR circuits 17A and 17B operate with sound detectors, so that there is no malfunction and a highly reliable accident detection circuit. Can be provided.

[0055]

According to the present invention, in a voltage type self-exciting converter, when an accident such as an arm short circuit, an arm external short circuit, or a short circuit between AC output lines occurs, it can be detected at high speed with a simple circuit. It is possible to provide an accident detection circuit for a voltage type self-excited converter that can protect the anode reactor and the self-extinguishing element without making them unnecessarily large.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of an accident detection circuit of a voltage type self-exciting converter according to the present invention.

FIG. 2 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 during normal operation.

FIG. 3 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 during normal operation.

FIG. 4 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 during normal operation.

5 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 during normal operation.

FIG. 6 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 in the event of an accident.

FIG. 7 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 in the event of an accident.

FIG. 8 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 in the event of an accident.

FIG. 9 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 in the event of an accident.

FIG. 10 is a diagram for explaining the operation of the voltage type self-exciting converter of FIG. 1 in the event of an accident.

FIG. 11 is a diagram showing a second embodiment of the accident detection circuit of the voltage type self-exciting converter of the present invention.

FIG. 12 is a diagram showing a third embodiment of the fault detection circuit of the voltage type self-exciting converter of the present invention.

FIG. 13 is a diagram showing a fourth embodiment of the accident detection circuit of the voltage type self-exciting converter of the present invention.

FIG. 14 is a diagram for explaining the operation of FIG.

FIG. 15 is a diagram showing a fifth embodiment of the accident detection circuit of the voltage type self-exciting converter of the present invention.

FIG. 16 is a diagram showing a sixth embodiment of the fault detection circuit of the voltage type self-exciting converter of the present invention.

FIG. 17 is a diagram showing a configuration of a general voltage type self-excited converter.

FIG. 18 is a diagram showing a conventional arm short circuit detection circuit.

FIG. 19 is a diagram showing a conventional arm external short circuit and AC output line short-circuit detection circuit.

[Explanation of symbols]

1A-1C ... AC voltage source, 2A-2F ... Self-extinguishing element such as GTO, 3A-3F ... Diode, 4A-4F ... Snubber resistance, 5A-5F ... Snubber capacitor, 6A-6F
... Snubber diode, 7A to 7F ... Anode reactor, 8 ... DC voltage source, 11A to 11F ... Current detector, 1
2A to 12E ... Level detector, 13, 13A, 13B,
13C, 13D, 13E, 13F ... AND circuit, 14 ...
Interlock, 15, 15A to 15C ... Memory circuit, 16
... pulse amplifier circuit, 17, 17A, 17B ... OR circuit, 18A, 18B ... snubber discharge detection circuit, 19A, 1
9B ... Negative bias detection circuit, 20, 20A, 20B, 2
0D ... Inversion circuit, 21 ... One shot circuit, 51, 52
… Accident point, 101… GTO ON / OFF pattern signal, 102
... GTO off command, 103 ... GTO on command.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruhisa Inoguchi No.1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu factory

Claims (4)

[Claims] 1. A bridge connection of a plurality of self-extinguishing elements,
And a self-extinguishing element in which at least a snubber capacitor is connected in parallel, a DC voltage source is connected to the bridge, and a direct current to an alternating current or an alternating current to a direct current is converted into a voltage type self-exciting converter, First detecting means for detecting that the self-extinguishing element forming an arm to which the same AC bus is connected is in a conducting state; and an arm connected to the same AC bus as the arm to which the AC bus is connected. Is output when the logical product of the detection signals of the second detection means for detecting the discharge of the snubber capacitor, the first detection means of the one arm and the second detection means of the other arm is established. A fault detection circuit for a voltage-type self-excited converter, comprising: a logic unit that uses an output signal as a fault detection signal of the converter. 2. A plurality of self-extinguishing elements are bridge-connected,
And a self-extinguishing element in which at least a snubber capacitor is connected in parallel, a DC voltage source is connected to the bridge, and a direct current to an alternating current or an alternating current to a direct current is converted into a voltage type self-exciting converter, First detecting means for detecting that the self-extinguishing element forming an arm to which the same AC bus is connected is in a conducting state; and an arm connected to the same AC bus as the arm to which the AC bus is connected. When a turn-off command is given to the second detection means for detecting the discharge of the snubber capacitor and the self-extinguishing element of the one arm to which the same AC bus is connected among the self-extinguishing elements, Third detecting means for detecting a state in which a signal output in time is inverted, first detecting means of the one arm, second detecting means of the other arm, and the third detecting hand. A fault detection circuit for a voltage-type self-excited converter, comprising: logic means for using an output signal output when a logical product of the detection signals of the stages is established as a fault detection signal of the converter. 3. A plurality of self-extinguishing elements are bridge-connected,
A voltage-type self-exciting converter for connecting a series circuit composed of at least a snubber capacitor and a snubber resistor in parallel to the self-extinguishing element, connecting a direct current voltage source to the bridge, and converting direct current to alternating current or converting alternating current to direct current In, a first detection means, a second detection means, and a logic means are provided, and the first detection means constitutes one arm to which the same AC bus is connected among the self-extinguishing elements. A negative bias detection circuit that detects that a predetermined negative bias voltage is applied between the gate and the cathode of the self-extinguishing element, and the current that flows through the self-extinguishing element that constitutes the one arm is a certain value or more. And a first current detection circuit for detecting the above, and a logical product of the output obtained by inverting the detection output of the negative bias detection circuit by the inverting circuit and the detection output of the first current detection circuit. A second AND detection circuit configured to detect that the self-extinguishing element, which comprises one of the self-extinguishing elements and constitutes one arm to which the same AC bus is connected, is in a conductive state. The means has a voltage of a snubber resistor connected to the other arm connected to the same AC bus of the self-extinguishing element is equal to or higher than a certain value, and a current direction of a snubber capacitor connected to the other arm. Is a discharging direction, a second current detection circuit for detecting that the current flowing through the snubber capacitor connected to the other arm is a fixed value or more, and a second current detection circuit A current detection circuit and a second AND circuit that obtains a logical product of the detection outputs of the snubber discharge detection circuit,
The logic means detects the discharge of the snubber capacitor connected to the self-extinguishing element forming the other arm to which the same AC bus is connected, and the logic means is provided for the first and second AND circuits. An accident detection circuit for a voltage type self-excited converter, wherein an output signal output when a logical product of output detection signals is established is an accident detection signal of the converter. 4. A bridge connection of a plurality of self-extinguishing elements,
A voltage-type self-exciting converter for connecting a series circuit composed of at least a snubber capacitor and a snubber resistor in parallel to the self-extinguishing element, connecting a direct current voltage source to the bridge, and converting direct current to alternating current or converting alternating current to direct current In, a first detection means, a second detection means, and a logic means are provided, and the first detection means constitutes one arm to which the same AC bus is connected among the self-extinguishing elements. A negative bias detection circuit that detects that a predetermined negative bias voltage is applied between the gate and the cathode of the self-extinguishing element, and the current that flows through the self-extinguishing element that constitutes the one arm is a certain value or more. And a first current detection circuit for detecting the above, and a first logical OR of an output obtained by inverting a detection output of the negative bias detection circuit by an inverting circuit and a detection output of the first current detection circuit. A second circuit for detecting that one of the self-extinguishing elements of the self-extinguishing element, which constitutes one arm to which the same AC bus is connected, is in a conducting state. Among the self-extinguishing elements, the voltage of the snubber resistor connected to the other arm to which the same AC bus is connected is a certain value or more, and the direction of the current of the snubber capacitor connected to the other arm is A snubber discharge detection circuit for detecting that the current is in the discharge direction, a second current detection circuit for detecting that the current flowing through the snubber capacitor connected to the other arm is a certain value or more, and the second current A detection circuit and a second OR circuit for ORing the detection outputs of the snubber discharge detection circuit,
The logic means detects a discharge of the snubber capacitor connected to a self-extinguishing element forming another arm to which the same AC bus is connected, and the logic means detects the first and second detection means. An accident detection circuit for a voltage-type self-excited converter, wherein an output signal output when a logical product of signals is established is used as an accident detection signal for the converter.