JPS6074927A - Defect monitoring circuit of thyristor element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to high voltage converters for DC power transmission, thyristor-type reactive power compensators for electric power systems, thyristor-type starting devices for motor generators for pumped storage power generation, etc. -Relates to a failure monitoring circuit for a thyristor element in a large-capacity thyristor conversion device, which is suitable for use in the device.

[Prior art and its problems]

Generally, these thyristor conversion devices are constructed by combining multiple thyristor valves, each of which is made up of a large number of thyristor elements connected in series or in parallel, because the voltage of the conversion device is high. , it is necessary to use a high-voltage monitoring device. The monitoring method generally involves transmitting light from a light-emitting element that emits light when it detects the voltage applied to each thyrisk element as a monitoring signal to a control/monitoring device on the low-voltage side through a light guide. A fault monitoring method is used in which a fault in a thyristor element is diagnosed based on its presence or absence.

FIG. 1 is a circuit diagram showing a conventional example of a fault monitoring circuit used in this type of fault monitoring system. In the same 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 (a light guide device made of an 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 LBD 5 is transmitted as a monitoring signal to the light guide 6 for control and control (not shown). 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. That is, this monitoring circuit is configured such that the LED 5 emits light only when a forward voltage is applied to the thyristor 1, 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 a current to flow in both cases where a voltage of forward polarity or forward 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 the thyristor 1 in FIG. 1 is considered as one thyristor element constituting a three-phase line bridge rectifier.

In this case, thyristor 1 in fan 1i is conductive for a period of 120 degrees in one cycle, and there is no voltage applied to the thyristor during this period, but it is not conductive for the remaining 240 degrees, so no voltage is applied to the thyristor. VT)T is applied, a current jH with a waveform almost similar to this sirisk voltage VTII flows through the resistor 3, and of this current iH, only the M current portion flows to the LED 5 as a current 1LaD, and the reverse current portion flows through the diode 4. flow bypassing.

Since the thyristor voltage "TH changes according to the control phase angle provided by the ignition circuit 2, and the waveform and duration of the forward voltage also change accordingly, the waveform and conduction period of the current flowing through the LED s also change accordingly. When the control delay angle is small, the forward voltage period of the thyristor voltage VTHO becomes short, the voltage value of the forward voltage becomes small, and the current flowing through LED 5 also has a short conduction period and the current value becomes small. In order to generate and transmit a 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'D5. The loss will be huge.

Conversely, if the control delay angle is large, the thyristor voltage VT
Since the HO forward voltage period approaches 240 degrees and the forward voltage value increases, a large current flows through the resistor 3, resulting in a large loss, and a large current also flows through the LED 5, causing the L
There is a problem that the current duty of the ED5 increases, the life of the LED5 becomes short, 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, a failure in the failure monitoring circuit can also lead to equipment shutdown, so long life and reliability are especially important for components such as LEDs, whose lifespan and failure rate are greatly affected by usage conditions such as current duty. It is necessary to reduce the liability sufficiently in order to ensure that

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 increases the sensitivity of the receiver to compensate for this. This poses a problem in that the device becomes susceptible to noise and has low reliability.

[Purpose of the invention]

This invention was made to solve the problems in the prior art as described above, and therefore, an object of the invention is to provide a system that has a long life, does not require long-term maintenance and inspection, and provides monitoring signals with sufficient sensitivity. An object of the present invention is to provide an inexpensive thyristor fault monitoring circuit that can transmit data using a thyristor and has high reliability and noise resistance. Stop passing current to the LED, and store the charge of the current flowing through the resistor in the capacitor.
The L E D
The light emitted from the capacitor is transmitted as a monitoring signal.0 Once the switch element is turned on and a discharge current flows to the LED, the current flowing to the capacitor through the resistor is passed through the switch element. By bypassing the capacitor and not recharging the capacitor, the number of times the monitoring signal consisting of light emitted from the LED is transmitted is no more than once or several times in one cycle of thyristor operation, so that the floor monitoring signal is not transmitted without interruption. By doing so, the operating responsibility of the LED is reduced.

[Embodiments of the invention]

The present invention will now be described in detail with reference to the drawings.

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

FIG. 4 is a waveform diagram showing the operating waveforms of each part of the circuit shown in FIG. 3, when the 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 Figure 4 of the 3IA.

First, during period A when a reverse voltage is applied to the thyristor 1, the voltage causes a current 1l11εiH to flow through the path from the diode 4 to the resistor 3, and the LED 5 for generating a monitoring signal
No current flows through.

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 diac 7 also rises, and when it reaches the breakover voltage of the diac 7, the diac 7 is turned on, and the current IC with an exponential waveform as shown in the period flows in 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 resulting light signal from the LEDs causes light guide 6 to emit light. transmitted via.

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

During the period E after the diac 7 is once turned on, the current iH 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, the circuit including the capacitor 9 is bypassed, and the current iH flows through the diac 7. Since this state continues as long as the holding current is greater than or equal to the holding current, the capacitor 9 is not recharged, and therefore no current flows through LBD5. In the example shown in the figure, the monitoring signal is transmitted only once per operation cycle of thyristor 1, but depending on the control phase angle, the thyristor's
The voltage waveform VTR of VTR may alternate between positive and negative during one cycle, turning off the diac and recharging the capacitor, so the monitoring signal may be transmitted two or several times in one cycle. However, in any case, since small pulse currents do not flow through LEDs, their operating duties are significantly reduced.

FIG. 5 is a circuit diagram showing another embodiment of the present invention. In the embodiment shown in FIG. 3, a Zener diode 12 is connected between the thyristor 1, its anode, and gate instead of the diac 7 in FIG. 3, and a terminal switch element is used. When the cathode 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 diac 7. Other than that, the circuit operation is the same as that 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 compensator 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 parallel.

In this embodiment, thyristor voltages VTH□ and vTH2 applied to thyristors 1a and Ib and thyristors 1c and 1d, respectively, are detected by resistors 3a and 3b, and are used as AC input terminals of a rectifier consisting of diodes 4a to 4d. A diac 7 is connected to the DC terminal, and the circuit to the right is the same as the corresponding circuit in the third path. 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 6a → diode 4a → resistor 8 → capacitor 9 → diode 10 using vT1□1 as the power supply (period C), and the diac When the voltage of 7 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 flows through the LED (period EDD).

After that, the current of the resistor 6a changes from the resistor 6a to the diode 4a.
→The flow capacitor 9 is not recharged in the path of the discharge charge 7 (period E). On the other hand, the current of resistor 3b is
Since the current flows through the path from the diode 4d to the resistor 5b using rH2 as the power source, it is unrelated to the charging and discharging of the capacitor 9.

Next, during period B when a reverse voltage is applied to the thyristor, the resistor 3b → diode 4b is connected using VTyo2 as the power source.
→ Capacitor 9 is charged in the path of resistor 8 → capacitor 9 → diode 10 (period F), and when the voltage of diac 7 reaches the breakover voltage, capacitor 9 → resistor 8 →
The capacitor 9 is discharged along the path of the diagonal 7 → LED 5 → capacitor 9, and the LED Ka flow iI flows (
Period G).

Thereafter, the current in the resistor 6b flows through the path of the resistor 5b, the diode 4b, and the diode 7, and the capacitor 9 is never recharged (period H). On the other hand, the current of the resistor 6a is vT
Since the current flows through the path from the diode 4° to the resistor 5a using H□ as the power source, it is unrelated to the charging and discharging of the capacitor 9.

As mentioned above, when the sirisk voltage is positive and negative,
The capacitor is charged one by one, and the discharge current is LE
D, a monitoring signal is generated and transmitted.

Also, during these periods, vTH□ and vTH2 are used alternately as a power source to charge the capacitor, so the monitoring signal transmitted during period A
3. This indicates that the voltage VT y is applied to ib, and the monitoring signal transmitted in period B indicates that the thyristor 1° is applied, and the voltage vTI (2) is applied to ld. This means that a monitoring signal indicating that 1b and thyristor 1゜Id is 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. be able to.

〔Effect of the invention〕

According to this invention, the detection current flowing through the resistor for detecting the syrisk voltage is temporarily stored in the capacitor, and when a predetermined capacitor voltage is reached, the accumulated charge in the capacitor is discharged by a switch element such as a diac, and the monitoring result display means The detection current is then passed through the capacitor by the switch element so that the capacitor is not recharged, so that no large current flows through the LED for a long period of time, and pulse current is passed through the LED. Since only a small amount of current flows, the operational responsibility of the LED can be significantly reduced, and its lifespan can be expected to be extended.In addition, there is no need to use large-capacity, special, and expensive LEDs, so it is inexpensive, has a long life, and is highly reliable. This has the advantage that it can provide a fault monitoring circuit.

In addition, the voltage detection resistor does not directly determine the LED current as in the conventional method, but only needs to charge the capacitor within a predetermined time, so it is possible to select a resistor with a large resistance value. Loss becomes smaller. 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]

FIG. 1 is a circuit diagram showing a conventional example of a failure monitoring circuit, FIG. 2 is a waveform diagram showing operating waveforms of each part in the circuit of FIG. 1, and FIG. 6 is a circuit diagram showing an embodiment of the present invention. 4 is a waveform diagram showing operation waveforms of each part in the circuit of FIG. 3, FIG. 5 is a circuit diagram showing another embodiment of the present invention, and FIG. 6 is a circuit diagram showing still another embodiment of the present invention. FIG. 7 is a waveform diagram showing operating waveforms of each part in the circuit of FIG. 6. Code explanation 1.1a-1d... Cyrisk, 2...
・Ignition circuit, 3.5at3b...Resistance, 4,4
a~4d...Diode, 5,...L E
D' (light emitting diode), 6...Light guide, 7...Diac, 8...Resistor, 9...Capacitor, 10...・Diode, 11...Thyristor, 12...
Zener Diode Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Figure 4 Figure 5 (Go to Figure 1 I l Figure

Claims (1)

[Claims] 1) In a thyristor conversion device including a thyristor element that alternately undergoes conduction periods and non-conduction periods, a charging circuit that extracts the voltage applied to the thyristor element during the non-conduction period to charge a capacitor. a discharge circuit including a switch means that detects when the charging pressure of the capacitor reaches a certain limit and discharges the capacitor by turning on the switch means, which is inserted into the discharge circuit and is operated by the discharge current. 1. A failure monitoring circuit for a thyristor element, comprising: display means for detecting a failure. 2. In the fault monitoring circuit according to claim 1, the switching means is a diac or a thyristor, which continues to be in an on state until the current flowing therethrough decreases below a certain holding current. A failure monitoring circuit for a cyrisk element, characterized by comprising a switch element.