JPH0336338B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a thyristor conversion device for direct current power transmission,
The present invention relates to a failure monitoring circuit for thyristor elements in high-voltage, large-capacity thyristor conversion devices, such as thyristor-type reactive power compensators for electric power systems and thyristor-type starters for pumped-storage power generation motor generators.

[Prior art and its problems]

Generally, these thyristor conversion devices are constructed by combining multiple thyristor bulbs, which are made up of multiple thyristor elements connected in series or parallel, because the conversion device voltage is high. , it is necessary to use a high-voltage monitoring device. The monitoring method is
Generally, when the voltage applied to each thyristor element is detected, light emitted from a light emitting element is used as a monitoring signal to pass through a light guide to control and control the low voltage side.
A fault monitoring method is used in which the signal is transmitted to a monitoring device and a fault in the thyristor element is diagnosed based on the presence or absence of the signal.

FIG. 1 is a circuit diagram showing a conventional example of a failure monitoring circuit used in this type of failure monitoring system. In the figure, 1 is a thyristor element, 2 is an ignition circuit,
3 is a resistor, 4 is a diode, 5 is an LED (light emitting diode), and 6 is a light guide (light guide device made of optical fiber).

Now, in FIG. 1, when a forward voltage is applied to the thyristor element 1 which is in a non-conducting state, a current flows to the LED 5 through the resistor 3, and the light emitted from the LED 5 is transmitted as a monitoring signal to a control signal (not shown) through the light guide 6. Transmitted to the monitoring device. Further, when a reverse voltage is applied to the thyristor element 1, the current flowing through the resistor 3 flows through the diode 4 connected in antiparallel to the LED 5, so that no current flows through the LED 5. In other words, this monitoring circuit turns on the LED only when forward voltage is applied to thyristor 1.
5 emits light, and the light generated by the emitted light is transmitted as a monitoring signal.

In addition to this example, it is also possible to connect the polarities of LED 5 and diode 4 in opposite directions so that they emit light when a reverse voltage is applied to LED 5, and transmit the light as a monitoring signal. It is also possible to configure the LED to emit light by causing current to flow in both cases where a voltage of both forward and reverse polarity is applied to the thyristor by the rectifier circuit.

FIG. 2 is a waveform diagram showing operating waveforms of each part in the circuit of FIG. 1, when thyristor 1 in FIG. 1 is considered as one thyristor element constituting a three-phase pure bridge rectifier.

In this case, the thyristor 1 in FIG.
The thyristor is conductive during the 120 degree period of the cycle, and there is no voltage applied to the thyristor during this period.
During the remaining 240 degrees, there is no conduction, so the voltage V _TH is applied to the thyristor, and the thyristor voltage is applied to the resistor 3.
A current i _R with a waveform almost similar to v _TH flows, and this current i _R
Of these, only the forward current portion flows through the LED 5 as a current i _LED , and the reverse current portion bypasses the diode 4 and flows.

Since the thyristor voltage v _TH changes depending on the control phase angle given by the ignition circuit 2, and the waveform of the forward voltage and its duration also change accordingly, the LED 5
The waveform and conduction period of the current flowing through the circuit change accordingly. When the control delay angle is small, the forward voltage period of the thyristor voltage v _TH becomes short, the voltage value of the forward voltage becomes small, and the current flowing through the LED 5 also has a short conduction period and the current value becomes small. In this case, in order to generate and transmit the monitoring signal (light emitted from LED 5) with sufficient sensitivity, it is necessary to reduce the resistance value of resistor 3 and increase the current flowing through LED 5. This results in a large power loss.

On the other hand, when the control delay angle is large, the forward voltage period of the thyristor voltage v _TH approaches 240 degrees, and the forward voltage value becomes large. This causes a large current to flow through the resistor 3, which increases the loss and causes a loss in the LED 5. Also, a large current flows and the current responsibility of LED5 increases,
There are problems in that the lifespan of the LED 5 is shortened and the failure rate increases.

Since the above-mentioned large-capacity thyristor conversion device is used in connection with an electric power system, it is required to have particularly high reliability and long life, and must be able to operate for a long period of time without maintenance. Related to this, failure of the failure monitoring circuit also leads to equipment shutdown, so
Components such as LEDs, whose lifespan and failure rate are greatly affected by usage conditions such as current duty, must be used with a sufficiently reduced duty to ensure long-life reliability.

However, from this point of view, reducing the conduction current makes it difficult to ensure sufficient transmission characteristics of the monitoring signal depending on the operating conditions as described above, and also unnecessarily reduces the sensitivity of the receiver to compensate for this. Increasing the noise level causes the problem that the device becomes susceptible to noise and has low reliability.

[Purpose of the invention]

This invention has been made to solve the problems in the prior art as described above, and the purpose of this invention is to provide a system that has a long life, does not require long-term maintenance and inspection, and has sufficient sensitivity for monitoring signals. The object of the present invention is to provide an inexpensive thyristor failure monitoring circuit that can transmit signals with high reliability and noise resistance.

[Key points of the invention]

This invention uses the voltage applied to the thyristor as a power source, stops flowing current directly to the LED through a resistor, stores the charge of the current flowing through the resistor in a capacitor, and when the capacitor is charged to a predetermined voltage. By turning on the switch element, the charge stored in the capacitor is discharged through the LED, and the light emitted from the LED is transmitted as a monitoring signal.

Also, once the switch element is turned on and a discharge current flows to the LED, the current flowing to the capacitor through the resistor bypasses the capacitor through the switch element and prevents the capacitor from being recharged. This is intended to reduce the operational responsibility of the LED by reducing the number of times the monitoring signal consisting of light emitted from the LED is transmitted no more than once or several times in one cycle of thyristor operation so that the monitoring signal is not transmitted frequently. .

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a circuit diagram showing one embodiment of the present invention. In the embodiment shown in the figure, between the anode and cathode of the thyristor 1, there is a parallel circuit consisting of a diode 4 and a diac (bidirectional two-terminal thyristor) 7, and a resistor 3 connected in series with the parallel circuit. In addition to the series circuit connected, a series circuit consisting of a parallel circuit of a diode 10 and an LED 5, a resistor 8, and a capacitor 9 is also connected to both ends of the diode 7.

FIG. 4 is a waveform diagram showing the operating waveforms of each part of the circuit of FIG. 3 when thyristor 1 is considered as one of the thyristor elements constituting a three-phase pure bridge rectifier.

The circuit operation will be explained with reference to FIGS. 3 and 4. First, during a period A in which a reverse voltage is applied to the thyristor 1, a current i _R flows through the path from the diode 4 to the resistor 3 due to the voltage, and no current flows through the LED 5 for generating a monitoring signal.

Next, during the period B during which the forward voltage is applied to the thyristor 1, in the first period C, a current flows through the path of the resistor 3, the resistor 8, the capacitor 9, and the diode 10, and the capacitor 9 is charged.
As the capacitor 9 is charged, the voltage applied to the diode 7 also rises, and when it reaches the breakover voltage of the diode 7, the diode 7 is turned on, and the current i with an exponential waveform as shown in period D. _C flows through the path of capacitor 9 → resistor 8 → diagonal 7 → LED 5 → capacitor 9, discharging the capacitor 9, and the discharge current i _LED causes LED 5 to emit light, and the light signal from LED 5 is transmitted to the light guide 6. transmitted via.

Here, the resistor 8 is a resistor for limiting this discharge current.

During the period E after the diagonal 7 is turned on, the current i _R flowing through the resistor 3 flows through the path from the resistor 3 to the diac 7 to the cathode side of the thyristor 1, bypassing the circuit including the capacitor 9, and the current i R flowing through the diac 7. Since this state continues as long as the holding current of 7 is greater than or equal to the holding current of 7, the capacitor 9 is not recharged and therefore no current flows through the LED 5. The example in the figure shows a case where the monitoring signal is transmitted only once per operation cycle of thyristor 1, but depending on the control phase angle, the voltage waveform v _TH of thyristor 1 may change during one cycle. Since the diac may be turned off and the capacitor may be recharged by alternating between positive and negative, the monitoring signal may be transmitted two or several times in one cycle, but in any case, a small pulse current is applied to LED5. Since only a small amount of current flows, its operating duties are significantly reduced.

FIG. 5 is a circuit diagram showing another embodiment of the present invention. In the embodiment shown in the figure, a switch element consisting of a thyristor 11 and a Zener diode 12 connected between its anode and gate is used in place of the diode 7 in FIG. When the voltage exceeds the Zener voltage of the Zener diode 12, current is supplied to the gate of the thyristor 11, and the thyristor 11
turns on. This switch element therefore has a similar function to the dial 7. Other than that, the circuit operation is the same as that shown in FIG. 3, so the explanation will not be repeated.

FIG. 6 is a circuit diagram showing still another embodiment of the present invention.

The embodiment shown in the figure is an embodiment in which the monitoring circuit according to the present invention is applied to a reactive power compensation device that controls a reactor current by a thyristor switch configured by connecting thyristors in antiparallel.
This is an embodiment in which a monitoring circuit according to the present invention is provided for each thyristor consisting of a total of four elements connected in two series and anti-parallel.

In this embodiment, the resistor 3a and the resistor 3b provide
Thyristor voltages v _TH1 and v _TH2 applied to thyristors 1a, 1b and thyristors 1c, 1d, respectively, are detected and used as AC input terminals of a rectifier consisting of diodes 4a to 4d. A diagonal 7 is connected to its DC terminal, so that the circuit on the right is similar to the corresponding circuit in FIG. Further, a negative terminal of the DC terminals of the rectifier is connected to an intermediate point to which the thyristors 1a to 1d are commonly connected.

FIG. 7 is a waveform diagram showing operating waveforms of each part in the circuit of FIG. 6. The circuit operation will be explained with reference to FIGS. 6 and 7.

First, in period A when a forward voltage is applied to the thyristor, capacitor 9 is charged through the path of resistor 3a → diode 4a → resistor 8 → capacitor 9 → diode 10 using v _TH1 as a power source (period C), and diode 7 When the voltage reaches the breakover voltage, the capacitor 9 is discharged along the path of capacitor 9 → resistor 8 → diode 7 → LED 5 → capacitor 9, and a current i _LED flows through the LED (period D).

Thereafter, the current in the resistor 3a flows along the path of the resistor 3a, the diode 4a, and the diode 7, and the capacitor 9 is not recharged (period E). On the other hand, the current of resistor 3b flows through diode 4 using v _TH2 as the power source.
Since the current flows through the path from d to the resistor 3b, it has no relation to the charging and discharging of the capacitor 9.

Next, during period B when a reverse voltage is applied to the thyristor, capacitor 9 is charged through the path of resistor 3b → diode 4b → resistor 8 → capacitor 9 → diode 10 using v _TH2 as the power source (period F),
When the voltage of diac 7 reaches the breakover voltage, capacitor 9 → resistor 8 → diac 7 →
The capacitor 9 is discharged along the path from the LED 5 to the capacitor 9, and a current i _LED flows through the LED (period G).
After that, the current of resistor 3b is from resistor 3b to diode 4
b → dielectric 7, and capacitor 9 is not recharged (period H). On the other hand, the current of resistor 3a is diode 4c → with v _TH1 as the power source.
Since it flows through the path of the resistor 3a, it has no relation to the charging and discharging of the capacitor 9.

As described above, the capacitor is charged once each during the positive and negative periods of the thyristor voltage, and the discharge current flows to the LED to generate and transmit a monitoring signal.

Also, during those periods, v _TH1 and v _TH2 are used alternately as a power source to charge the capacitor, so the monitoring signal transmitted in period A indicates that voltage v _TH1 is applied to thyristors 1a and 1b. The monitoring signal transmitted in period B indicates that the voltage v _TH2 is applied to the thyristors 1c and 1d. That is, thyristor 1
This means that a monitoring signal indicating that thyristors a, 1b and thyristors 1c, 1d are normal is transmitted alternately every half cycle, and it is determined which set of thyristors has failed based on the presence or absence of this signal and its phase. can do.

〔Effect of the invention〕

According to this invention, a detection current flowing through a resistor for detecting a thyristor voltage is temporarily stored in a capacitor, and when a predetermined capacitor voltage is reached, the accumulated charge in the capacitor is discharged by a switch element such as a diagonal, thereby monitoring results. as a means of display
By making the detection current flow through the LED, and then bypassing the capacitor by using the switch element to prevent the capacitor from being recharged, a large current will not flow through the LED for a long period of time, and the pulse current will flow through the LED. Because only the flow is
The operational responsibility of the LED can be significantly reduced,
It can be expected to have a longer lifespan, and since there is no need to use large-capacity, special, and expensive LEDs, it is inexpensive and has the advantage of providing a fault monitoring circuit with a long life and high reliability.

Also, the resistor for voltage detection is the same as in the conventional method.
Since it does not directly determine the LED current and only needs to charge the capacitor within a predetermined time, a large resistance value can be selected, and the loss due to the resistance will be reduced. Furthermore, unlike conventional methods, a pulse current of a fixed magnitude can always be passed through the LED without depending on the thyristor voltage waveform, so if the waveform is selected appropriately, sufficient transmission characteristics of the monitoring signal can always be obtained. This has the advantage of providing a failure monitoring circuit with excellent noise resistance.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional example of a failure monitoring circuit.
Fig. 2 is a waveform diagram showing the operating waveforms of each part in the circuit of Fig. 1, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a waveform diagram showing the operating waveforms of each part in the circuit of Fig. 3. 5 is a circuit diagram showing another embodiment of the present invention, FIG. 6 is a circuit diagram showing still another embodiment of the present invention, and FIG. 7 shows operating waveforms of each part in the circuit of FIG. 6. FIG. Code explanation, 1, 1a to 1d...Thyristor, 2
...Ignition circuit, 3, 3a, 3b...Resistance, 4, 4
a to 4d...Diode, 5...LED (light emitting diode), 6...Light guide, 7...Diac, 8...Resistor, 9...Capacitor, 10...Diode, 11...Thyristor, 12... Zener diode.

Claims (1)

[Scope of Claims] 1. A failure monitoring circuit for a thyristor element constituting a thyristor device, comprising a series connection of a resistor, a capacitor, and a diode, wherein when the thyristor element is in a non-conducting period, the capacitor connects to the anode of the thyristor element. A resistor/capacitor/diode series connection circuit is charged by the voltage applied between the capacitor and the cathode, and the capacitor is connected in parallel to this series connection circuit, and when the charging voltage of the capacitor exceeds a certain limit, it is detected and turned on. recharging the capacitor by discharging the capacitor and by bypassing the anode and cathode of the thyristor element and keeping it on until the bypass current flowing therethrough drops below a certain limit; and display means connected in parallel to the diode to detect and display only the presence or absence of discharge current of the capacitor, thereby indicating the presence or absence of a failure in the thyristor element. A failure monitoring circuit for a thyristor element, characterized by: