JPH0783544B2 - Failure detection method for semiconductor switching devices for high voltage circuits - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor for a high voltage circuit when a large number of anti-parallel circuits of semiconductor switching elements are connected in series and connected to a high voltage AC circuit for use. The present invention relates to a switch element failure detection method.

[Conventional technology]

It is well known that the delay reactive power of this AC circuit can be compensated by changing the capacity of the phase-advancing capacitor connected to the high-voltage AC circuit, and a static var compensator using such a phase-advancing capacitor is known. , It is not possible to compensate the reactive power, but it is often used because it has no moving parts and maintenance is easy.

In order to connect or disconnect this phase-advancing capacitor to a high-voltage AC circuit, a large number of series-connected anti-parallel connected semiconductor switching elements are used. If any one of them becomes abnormal, the operation of this static var compensator will be hindered, so it is necessary to quickly and surely detect what kind of abnormality has occurred in which element.

FIG. 4 is a circuit diagram showing a conventional example of failure detection of semiconductor switching elements connected in anti-parallel, but shows only one set of many anti-parallel connection circuits.

In FIG. 4, an anti-parallel unit is formed by connecting the thyristors 2A and 2B as semiconductor switching elements to each other in anti-parallel.
A snubber circuit including a snubber resistor 3R and a snubber capacitor 3C is connected in parallel. Further, a voltage detector 1 for detecting whether or not a voltage is applied across the anti-parallel unit.
0, and overvoltage detector 2 that detects the application of excessive voltage
0 and is equipped.

The voltage detector 10 detects that a voltage is applied to both ends of the thyristors 2A and 2B, and outputs the signal to the electrical / optical signal converter 11
After converting into an optical signal via the light guide 12, it is sent to the optical / electrical signal converter 13 provided on the ground potential side to be converted into an electrical signal again, and then input to a failure monitoring circuit (not shown). Then, if the voltage application signal does not arrive once in one cycle of the AC circuit, this thyristor is determined to be in failure.

When the overvoltage detector 20 detects that the voltage applied to both ends of the thyristors 2A and 2B is excessive, it applies a self-ignition pulse to the gate of the thyristor whose polarity is the forward voltage. While conducting this, the self-ignition signal is sent to the electrical / optical signal converter 21, so the optical signal converted by the electrical / optical signal converter 21 is
It is sent to the optical / electrical signal converter 23 on the side of the ground potential through the light guide 22, and after being converted back to an electric signal again here, it is input to the aforementioned failure monitoring circuit (not shown), and self-ignition is performed. It is detecting.

[Problems to be solved by the invention]

As shown in FIG. 4 above, in order to monitor the abnormality of one set of anti-parallel units connected to the high-voltage AC circuit on the side of the ground potential, an electrical / optical signal converter and an optical / electrical signal converter are used. Two sets of light guides are required, each using a converter and an insulating material. Therefore, when the number of thyristors used increases due to the increase in the voltage of the AC circuit,
The number of these signal converters and light guides used for fault monitoring increases, and it has a drawback of becoming an expensive device.

Therefore, an object of the present invention is to send an abnormal signal detected from an antiparallel connection unit of semiconductor switching elements connected to a high-voltage AC circuit to the ground potential side with a signal converter or a light guide that is smaller than before. To reduce the cost for fault monitoring.

[Means for solving problems]

In order to achieve the above-mentioned object, the failure detection method of the present invention is configured such that a plurality of anti-parallel units obtained by connecting two semiconductor switching elements to each other in anti-parallel are connected in series and connected to a high-voltage AC circuit. Then, for each of the anti-parallel units, the semiconductor switch element of the polarity that becomes the forward direction when the excessive voltage is applied to both ends of the anti-parallel unit is self-ignited, and the self-ignition signal is applied to the ground potential side. To the ground potential side when a voltage is applied to both ends of the anti-parallel unit, the self-ignition signal and the voltage are applied. The OR of the applied signal is calculated for each anti-parallel unit, and the calculation result is isolated and sent to the ground potential side as a return signal, and rises when the forward voltage side element is extinguished on the ground potential side. But A first pulse signal having a predetermined pulse width, a second pulse signal having a pulse width from the falling time of the first pulse signal to the passing time of the zero point of the AC high voltage, and the time when the reverse voltage side element is extinguished. A third pulse signal having a predetermined pulse width that rises and a fourth pulse signal having a pulse width from the time when the third pulse signal falls to the time when the AC high voltage passes through the zero point are generated, and the return signal and the first signal are generated. By calculating the logical product with the first, second, third or fourth pulse signal, the return signal is applied to the forward voltage side element for each anti-parallel unit, the forward voltage side element voltage application signal, the forward voltage side element self-ignition signal, The voltage application signal of the reverse voltage element and the self-ignition signal of the reverse voltage element are separately detected.

[Action]

According to the present invention, the voltage application signal of the semiconductor switching elements connected in anti-parallel and the self-ignition signal are ORed and returned by one signal line, and the return signal is received at the receiving side at the ground potential. It is sorted by the logic circuit that distinguishes it according to the timing, and when the corresponding return signal appears within the predetermined period, it is stored in the memory circuit, and the content of this memory circuit is latched by a constant synchronization signal and used for failure monitoring. By doing so, the number of signal lines that transmit the return signal and the number of signal converters at both ends of the signal lines are halved compared to the conventional method.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, but as in the case of the conventional circuit described in FIG. 4, only one set of a large number of series-connected anti-parallel units is shown. Shows.

In FIG. 1, two thyristors 2A and 2B as semiconductor switching elements are connected in anti-parallel to each other to form an anti-parallel unit, and the anti-parallel unit is used by being connected to a high-voltage AC circuit. However, the snubber circuit consisting of the snubber resistor 3R and the snubber capacitor 3C is connected in parallel to this anti-parallel unit, and the voltage detector 10 and the overvoltage detector 20 are applied to both ends of this anti-parallel unit. By monitoring the voltage, the voltage detector 10 gives a voltage application signal, and the overvoltage detector 20 gives a self-ignition pulse to a thyristor having a polarity in which the overvoltage becomes a forward direction when an excessive voltage is applied. As in the case of the conventional circuit described above with reference to FIG. 4, the self-ignition signal is output in addition to the conduction.

In the present invention, the diode 15 is provided in the output circuit of the voltage detector 10 and the diode 25 is provided in the output circuit of the overvoltage detector 20.
Are provided respectively, and the logical sum of both output signals is obtained by these diodes 15 and 25. Therefore, when transmitting the voltage application signal and the self-ignition signal to the ground potential side, one light guide 4B and , An electrical / optical signal converter at both ends of this
It is sufficient to prepare one set each of 4A and the optical / electrical signal converter 4C. In this way, the signal sent to the ground potential side by one set of transmission circuits is separated by the return signal separation circuit 5.

FIG. 2 is a circuit diagram showing an example of a return signal separation circuit used in the circuit of the embodiment shown in FIG. 1, in which a logical product circuit, a memory circuit and a latch circuit are provided for one set of anti-parallel units. By preparing 4 pairs each, the return signal,
The voltage application signal of the forward voltage side thyristor and the self-ignition signal, and the voltage application signal of the reverse voltage side thyristor and the self-ignition signal are separated. The second, third and fourth pulse signals, the first and second reset signals, and the first and second latch signals are generated.

The return signal separation circuit in the case where the number of the antiparallel units composed of thyristors is N is shown in this FIG. 2, and the reference numeral 511 corresponds to the No. 1 return signal returned from the first antiparallel unit. 4 sets of AND circuits and symbols 611 to 6
Signals are separated by four sets of 14 memory circuits and four sets of latch circuits 711 to 714. Similarly, for the N-number return signal returned from the N-th anti-parallel unit, the AND circuits 5N1 to 5N4, the memory circuits 6N1 to 6N4, and the latch circuits 7N1 to 7N4 are provided. prepare.

Here, the first pulse signal is a pulse signal having a pulse width of T1 which rises when the forward voltage side thyristor is extinguished,
The pulse width of T1 is set in consideration of variations in arc extinction delay time of other thyristors connected in series, signal transmission delay time, and the like. The second pulse signal is a pulse signal in which the falling time of the first pulse signal is the rising time and the pulse width is up to the time when the voltage of the high voltage AC circuit passes the first zero point. The third pulse signal rises when the reverse voltage side thyristor extinguishes.
The fourth pulse signal is a pulse signal having a pulse width of T1, and the fourth pulse signal is a pulse signal having a pulse width from the falling time of the third pulse signal to the time when the next AC circuit voltage passes through the zero point.

The first latch signal is a short-time pulse signal that occurs at the falling edge of the second pulse signal, and a short-time pulse signal is output as the first reset signal following the first latch signal. Similarly to the above, the second latch signal is further output at the trailing edge of the fourth pulse signal, and the second reset signal is subsequently output.

In the return signal separation circuit shown in FIG. 2, the first to fourth pulse signals are individually input to the four AND circuits and the common return signal is input, so that the return signals are separated. The content of this memory circuit is latched by the latch circuit of the next stage at the timing of the failure calculation start, and the memory circuit is reset by the reset signal generated immediately after that, and the next The circuit is configured so that each return signal in the cycle can be stored.

FIG. 3 is a time chart showing the aforementioned various signals for separation given to the return signal separation circuit shown in FIG. 2, and FIG. 3 (a) shows synchronization in synchronization with the voltage of the high voltage AC circuit. Fig. 3 (b) shows the voltage applied to the thyristor, Fig. 3 (c) shows the current, and Fig. 3 (d), (e),
(F) and (g) show the first to fourth pulse signals, FIG. 3 (h) shows the first latch signal, and FIG.
Represents the first reset signal, FIG. 3 (u) represents the second latch signal, and FIG. 3 (l) represents the second reset signal. Note that T1 is the pulse width of the first and third pulse signals, and T2 is the pulse width of the second and fourth pulse signals.

As described above, the signals returned from the anti-parallel unit by the signals shown in FIG. 3 are the voltage application signal and the self-ignition signal of the forward voltage side thyristor, and the voltage application signal and the self-ignition signal of the reverse voltage side thyristor. Since it is separated into an arc signal, by sending these separated signals to a fault monitoring circuit (not shown), the thyristor at any position among the many thyristors connected to the high voltage AC circuit It is possible to immediately identify what kind of abnormality has occurred.

2 and 3, in order to reset the memory circuit after sending the contents of the memory circuit to the latch circuit, the first latch signal and the first latch signal for the forward voltage side are used.
Although the reset signal and the second latch signal and the second reset signal for the reverse voltage side are used, one of the first latch signal and the second latch signal, the first reset signal and the second reset signal is used. It is needless to say that either of them can latch or reset the return data from both the forward voltage side and the reverse voltage side thyristors.

〔The invention's effect〕

According to the present invention, when a large number of anti-parallel connection units of semiconductor switching elements are connected in series and used by connecting them to an AC high voltage circuit, a voltage application signal and a self-ignition signal for each anti-parallel unit are provided. Collectively, the signal is returned to the ground potential side through a set of signal transmission paths, and the signal separation is performed by a logic circuit that can classify the content of the returned signal according to its timing, so that a circuit configuration can be constantly monitored for abnormalities in each thyristor. Therefore, the number of expensive light guides, electric / optical signal converting means, and optical / electrical signal converting means used for transmitting signals from the high potential side to the ground potential side is smaller than the conventional one. Since it can be halved by
Although it has the effect of significantly reducing the cost for failure monitoring, the number of semiconductor switching elements used to connect to this AC circuit increases rapidly as the voltage and capacity of the AC circuit increase. Therefore, the effect of reducing the cost required for failure monitoring will be significantly increased.

[Brief description of drawings]

1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of a return signal separation circuit used in the embodiment circuit shown in FIG. 1, and FIG. 3 is shown in FIG. FIG. 4 is a time chart showing various signals for separation given to the return signal separation circuit, and FIG. 4 is a circuit diagram showing a conventional example of failure detection of semiconductor switch elements connected in antiparallel. 2A, 2B ... Thyristor as semiconductor switching element, 3C
...... Snubber capacitor, 3R …… Snubber resistor, 4A, 11,21…
… Electric / optical signal converter, 4B, 12,22 …… Light guide, 4
C, 13,23 …… Optical / electrical signal converter, 5 …… Return signal separation circuit, 10 …… Voltage detector, 15,25 …… Diode, 20…
… Overvoltage detector, 511 to 514,5N1 to 5N4 …… AND circuit, 6
11 to 614,6N1 to 6N4 ... Memory circuit, 711 to 714,7N1 to 7N4
...... Latch circuit.

Claims (1)

[Claims] 1. A plurality of anti-parallel units obtained by connecting two semiconductor switching elements to each other in anti-parallel are connected in series and connected to a high-voltage AC circuit. When an excessive voltage is applied to both ends of the parallel unit, the semiconductor switch element of the polarity that becomes the forward direction is self-ignited, this self-ignition signal is sent to the ground potential side, and both ends of this anti-parallel unit are In the method of monitoring the abnormality of each semiconductor switching element by sending a voltage application signal to the ground potential side when a voltage is applied to the anti-parallel unit, the logical sum of the self-ignition signal and the voltage application signal is calculated for each anti-parallel unit. The first pulse signal of a predetermined pulse width which rises when the forward voltage side element is extinguished on the ground potential side, and the first pulse signal A second pulse signal having a falling pulse width to zero-axis crossing point of the AC high voltage from a time point of the pulse signal, a third predetermined pulse width which rises when the reverse voltage side element is extinguished
A pulse signal and a fourth pulse signal having a pulse width from the falling time of the third pulse signal to the passing time of the zero point of the AC high voltage are generated, and the return signal and the first, second, and third signals are generated. Alternatively, by calculating the logical product with the fourth pulse signal, the return signal is applied to each anti-parallel unit for the voltage application signal of the forward voltage side element, the self-ignition signal of the forward voltage side element, and the voltage application of the reverse voltage side element. A method of detecting a failure of a semiconductor switch element for a high voltage circuit, characterized by detecting the signal and a self-ignition signal of a reverse voltage element separately.