JPH11206011A - Protective device for power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the energy to be processed by lightning arresters. SOLUTION: In this protective device for power conversion devices, communication capacitors 11a, 11b are connected between a transformer 10 which is connected with an alternating-current system 9 side and universal converters 12a, 12b connected with a direct-current system 14 side, and the communication capacitors 11a, 11a are protected against overvoltage through lightning arresters 16a, 16b which are parallel-connected with the communication capacitors 11a, 11b. If the charging voltage of the communication capacitors 11a, 11b detected by voltage detecting means 17a, 17b exceeds a specified value, comparing means 19a, 19b output a detection signal, and electric charges are discharged from the communication capacitors 11a, 11b through discharging means 26a, 26b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for a power converter for protecting a commutation capacitor connected between a transformer and an AC / DC converter from overvoltage.

[0002]

2. Description of the Related Art FIG. 4 shows, for example, ABB Review.
(February 1997), "Capacitor comm"
mutated converters for HVD
It is a block diagram of the protection device of the conventional power converter described in "C systems". In FIG. 4, the AC power on the AC system 1 side includes a transformer 2 and a commutation capacitor 3a,
AC / DC converter 5 grounded by grounding line 4 via 3b
a, 5b, and is converted into DC power by the DC reactor 6
And transmitted to the DC system 7. The lightning arresters 8a and 8b are connected in parallel to the commutation capacitors 3a and 3b, respectively, so that the DC current continues to flow through the commutation capacitors 3a and 3b that failed in commutation at the time of an accident in each of the systems 1 and 7. This prevents the capacitors 3a and 3b from becoming overvoltage.

In the above, when the AC / DC converters 5a and 5b perform normal AC / DC conversion, the commutation capacitor 3
A rectangular current flows through the commutation operations of the AC / DC converters 5a and 5b, and a voltage obtained by integrating the current is applied between the terminals of the commutation capacitors 3a and 3b. The rectangular wave-shaped currents of the commutation capacitors 3a and 3b flow with zero as an average. Therefore, the commutation capacitors 3a, 3
Since the charge and discharge are repeated with the balance between the positive and negative polarities, b has a rectangular wave shape in which the average of the inter-terminal voltage is almost zero.

Here, for example, due to an accident, the AC / DC converter 5a
If commutation fails and DC current continues to flow in one phase of the AC / DC converter 5a, the commutation capacitor 3a is overcharged in one direction, and an overvoltage occurs between the terminals of the commutation capacitor 3a. When the voltage between the terminals of the commutation capacitor 3a reaches the protection level of the commutation capacitor 3a, the lightning arrester 8a operates to suppress the overvoltage of the terminal voltage.

[0005]

Since the conventional protection device for the power converter is constructed as described above, if the commutation capacitors 3a and 3b continue to be charged after the accident continues, the lightning arresters 8a and 8b will be turned off. There is a problem that processing energy is increased.

An object of the present invention is to provide a protection device for a power converter that can reduce the processing energy of a lightning arrester.

[0007]

According to a first aspect of the present invention, there is provided a protection device for a power conversion device, wherein a protection device is provided between a transformer connected to an AC system and an AC / DC converter connected to a DC system. A voltage detecting means for detecting a charging voltage of the commutation capacitor, wherein the protection device of the power conversion device is connected to the commutation capacitor and protects an overvoltage of the commutation capacitor by an arrester connected in parallel with the commutation capacitor; The power supply device includes a comparison unit that outputs a detection signal when the voltage exceeds a predetermined value, and a discharge unit that discharges the charge of the commutation capacitor according to the detection signal.

According to a second aspect of the present invention, there is provided a protection device for a power converter, wherein a commutation capacitor is connected between a transformer connected to an AC system and an AC / DC converter connected to a DC system. In a protection device of a power converter in which an overvoltage of a commutation capacitor is protected by an arrester connected in parallel with a commutation capacitor, a current detection means for detecting a current of the arrester and a current of the arrester exceed a predetermined value. And a discharging means for discharging the electric charge of the commutation capacitor in accordance with the detection signal.

According to a third aspect of the present invention, there is provided a protection device for a power converter, comprising: a resistor connected in parallel with a commutation capacitor;
Series circuit with a circuit breaker, and a second circuit connected in parallel with a resistor.
The discharge means is constituted by the circuit breaker described above, and the second circuit breaker is closed after a predetermined time after the first circuit breaker is closed.

According to a fourth aspect of the present invention, there is provided a protection device for a power conversion device, comprising: a resistor connected in parallel with a commutation capacitor;
The discharging means is constituted by a series circuit with the circuit breaker of the first embodiment and a second circuit breaker connected in parallel with the series circuit, and the second circuit breaker is closed after a predetermined time from when the first circuit breaker is closed. It was made.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram of the first embodiment. In FIG. 1, 9 is an AC system on the AC voltage side, 10 is a transformer for transforming the AC voltage, 11a, 1
Reference numeral 1b denotes a commutation capacitor, which is an AC / DC converter 1 to be described later.
2a and 12b. 12a, 12b
Is an AC / DC converter, which converts between AC and DC. 13 is a DC reactor for smoothing a DC current, 14 is a DC system on the DC voltage side, and 15 is a ground line. 16a and 16b are lightning arresters connected in parallel to the commutation capacitors, 17a and 17b are voltage detection means connected in parallel to the commutation capacitors 11a and 11b, and detect the charging voltage of the commutation capacitors 11a and 11b to detect a voltage signal 18a, 18b is output.

19a and 19b are voltage signals 18a and 18b
A comparison means for outputting detection signals 20a and 20b when the value exceeds a predetermined value, and outputs short-circuit signals 21a and 21b after a predetermined time from the detection signals 20a and 20b. 22a, 22b
Are resistors, 23a and 23b are resistors 22a and 22b, respectively.
Are connected in parallel, and are turned on by the detection signals 20a and 20b. The resistor 22a and the circuit breaker 23a form a series circuit 24a, and the resistor 22b and the circuit breaker 23b
Form a series circuit 24b. The series circuits 24a and 24b are respectively connected to commutation capacitors 11a and 11b.
b is connected in parallel. Circuit breakers 25a and 25b are connected in parallel with the resistors 22a and 22b, respectively, and are turned on by short-circuit signals 21a and 21b. Note that the series circuit 24
a and the circuit breaker 25a constitute discharge means 26a, respectively, and the series circuit 24b and the circuit breaker 25b constitute discharge means 26b.
Is composed.

Next, the operation will be described. In FIG. 1, the circuit breakers 23a, 23b, 25a, and 25b are normally open. The AC power on the AC system 9 side is
Then, the power is converted into DC power by the AC / DC converters 12a and 12b via the commutation capacitors 11a and 11b and transmitted to the DC system 14 side. And the commutation condenser 11
a, 11b are AC-DC converters 12a, 1b during the operation of AC-DC conversion.
2b to supply reactive power required by the AC / DC converter 1
A margin angle associated with the commutation operations 2a and 12b is secured.

In a normal operation, it is assumed that the commutation failure of the AC / DC converter 12a occurs due to, for example, an accident or the like, and DC current continues to flow in one phase of the AC / DC converter 12a. In this case, the commutation capacitor 11a is charged in one direction, and an overvoltage occurs between the terminals. The voltage detecting means 17a detects an overvoltage of the commutation capacitor 11a and outputs a voltage signal 18a. The comparing means 19a, to which the voltage signal 18a has been input, outputs a detection signal 20a when the voltage between the terminals of the commutation capacitor 11a stored in advance exceeds a predetermined value defined as a protection level. The circuit breaker 23a of the discharging means 26a is turned on by the detection signal 20a, and the commutation capacitor 1
The charge 1a is discharged via the resistor 22a. Depending on the time constant of the discharging means, for example, the detection signal 20
a short-circuit signal 2 which is output 10 ms to 20 ms later than a
The circuit breaker 25a is turned on by 1a, and the circuit breakers 23a, 2
The terminals of the commutation capacitor 11a are short-circuited by 5a. Thereby, the charge of the commutation capacitor 11a is discharged.

As described above, the commutation capacitors 11a, 1a
1b is detected by voltage detecting means 17a and 17b, and the charging voltages are compared by comparing means 19a and 19b. When the charging voltage exceeds a predetermined value, discharging means 26a and 26b are detected.
By discharging the charges of the commutation capacitors 11a and 11b by b, the processing energy of the lightning arresters 16a and 16b can be reduced.

The resistors 22a and 22b and the circuit breakers 23a and 23 connected in parallel to the commutation capacitors 11a and 11b
b and series circuits 24a and 24b, and resistors 22a and 22
b in parallel with the circuit breakers 25a and 25b.
6a and 26b, and the circuit breakers 25a and 25b are turned on a predetermined time after the circuit breakers 23a and 23b are turned on so that the commutation capacitors 11a and 11b are short-circuited. Can be quickly discharged.

Embodiment 2 FIG. FIG. 2 is a configuration diagram of the second embodiment. In FIG. 2, 9, 10, 11a, 11b,
Reference numerals 12a, 12b, 13 to 15, 16a, and 16b are the same as those in the first embodiment. 27a and 27b are current detecting means for detecting the current of the lightning arresters 16a and 16b,
It outputs current signals 28a and 28b. 29a and 29b are current signals 28 when the lightning arresters 16a and 16b operate.
When a and 28b exceed a predetermined value, comparing means for outputting detection signals 30a and 30b,
0a, 30b after a predetermined time from the short-circuit signals 31a, 31b
Is output. 32a and 32b are resistors, and 33a and 33b are circuit breakers connected in series with the resistors 32a and 32b, respectively, which are turned on by detection signals 30a and 30b. The resistor 32a and the circuit breaker 33a form a series circuit 34a, and the resistor 32b and the circuit breaker 33b form a series circuit 34b. The series circuits 34a and 34b are connected in parallel to the commutation capacitors 11a and 11b, respectively. Circuit breakers 35a and 35b are connected in parallel with the resistors 32a and 32b, respectively, and are turned on by short-circuit signals 31a and 31b. The discharging means 36a is composed of the series circuit 34a and the circuit breaker 35a, and the series circuit 34b and the circuit breaker 35a.
and b constitute the discharging means 36b.

Next, the operation will be described. In FIG. 2, the circuit breakers 33a, 33b, 35a, and 35b are normally open. The operation of converting AC power to DC power is the same as in the first embodiment. During normal operation, for example, due to the occurrence of an accident or the like, the AC / DC converter 1
Suppose that commutation failure occurred in 2a, and DC current continued to flow in one phase of AC / DC converter 12a. In this case, the commutation capacitor 11a is charged in one direction, and an overvoltage occurs between the terminals. Here, when the terminal voltage of the commutation capacitor 11a exceeds a predetermined value defined as a protection level, the surge arrester 16a operates and an operating current flows. This operating current is detected by the current detecting means 27a, and a current signal 28a is output. In the comparison means 29a to which the current signal 28a is input, the lightning arrester 16
When the current of “a” exceeds a predetermined value, a detection signal 30a is output. Circuit breaker 3 according to detection signal 30a
3a is charged, and the charge of the commutation capacitor 11a is discharged via the resistor 32a. Then, for example, the circuit breaker 35a is turned on by a short-circuit signal 31a output with a delay of 10 ms to 20 ms from the detection signal 30a, and the terminals of the commutation capacitor 11a are short-circuited. Thereby, the charge of the commutation capacitor 11a is discharged.

As described above, when the current of the lightning arresters 16a, 16b exceeds a predetermined value, the commutation capacitors 11a, 11b
Of the lightning arrester 16
The processing energy of a and 16b can be reduced.

The resistors 32a and 32b and the circuit breakers 33a and 33 are connected in parallel with the commutation capacitors 11a and 11b.
b, and circuit breakers 35a, 35b connected in parallel to the respective resistors 32a, 32b to discharge means 36a, 36b.
The circuit breakers 33a and 33b are turned on, and the circuit breakers 35a and 35b are turned on a predetermined time after the circuit breakers 33a and 33b are turned on, so that the charges of the commutation capacitors 11a and 11b can be quickly discharged.

Embodiment 3 FIG. 3 is a configuration diagram of the third embodiment. In FIG. 3, 9, 10, 11a, 11b,
12a, 12b, 13-15, 16a-24a, 16b
24b are the same as those of the first embodiment. 3
7a and 37b are commutation capacitors 11a and 11b, respectively.
Are connected in parallel with each other, and are turned on by short-circuit signals 21a and 21b. The series circuit 24a and the circuit breaker 37a
Constitute the discharging means 38a, and the series circuit 24b and the circuit breaker 37b constitute the discharging means 38b.

Next, the operation will be described. In FIG. 3, the circuit breakers 23a, 23b, 25a, and 25b are normally open. The operation of converting AC power to DC power is the same as in the first embodiment. further,
When a commutation failure occurs in the AC / DC converter 12a due to, for example, an accident during normal operation and an overvoltage occurs between the terminals of the commutation capacitor 11a, the circuit breaker 23a of the series circuit 24a is turned on by the detection signal 20a. The operation until the charge of the commutation capacitor 11a is discharged via the resistor 22a is the same as in the first embodiment. Next, although it depends on the time constant of the discharging means, for example, 10 ms from the detection signal 20a.
The circuit breaker 37a is turned on by the short-circuit signal 21a output with a delay of about 20 ms, and the terminals of the commutation capacitor 11a are short-circuited by the circuit breaker 37a. Thereby, the charge of the commutation capacitor 11a is discharged.

As described above, the commutation capacitors 11a, 1
1b is detected by the voltage detecting means 17a, 17b, and the charging voltages are compared by the comparing means 19a, 19b. When the charging voltage exceeds a predetermined value, the discharging means 38a, 38b
By discharging the charges of the commutation capacitors 11a and 11b by b, the processing energy of the lightning arresters 16a and 16b can be reduced.

The resistors 22a and 22b and the circuit breakers 23a and 23 connected in parallel to the commutation capacitors 11a and 11b
b and the serial circuits 24a and 24b, and the serial circuit 24a,
Discharge means 38a and 38b are constituted by circuit breakers 37a and 37b connected in parallel to 24b, respectively.
By turning on the circuit breakers 37a and 37b a predetermined time after the switch 3b is turned on to short-circuit the commutation capacitors 11a and 11b, the charges of the commutation capacitors 11a and 11b can be quickly discharged.

In the third embodiment, the description has been given of the case where the charging voltages of the commutation capacitors 11a and 11b are detected by the voltage detecting means 17a and 17b as in the first embodiment. Current detection means 27
A similar effect can be expected even if the detection is performed by using a and 27b.

[0026]

According to the first aspect of the present invention, the charging voltage of the commutation capacitor detected by the voltage detecting means is compared by the comparing means, and when the charging voltage exceeds a predetermined value, the discharging means is used by the discharging means. By discharging the electric charge, the processing energy of the lightning arrester can be reduced.

According to the second aspect of the present invention, the current of the lightning arrester detected by the current detecting means is compared by the comparing means, and when the current of the lightning arrester exceeds a predetermined value, the charge of the commutation capacitor is discharged by the discharging means. By doing so, the processing energy of the lightning arrester can be reduced.

According to the third aspect of the present invention, the discharging means is constituted by the series circuit of the resistor and the first circuit breaker connected in parallel to the commutation capacitor, and the second circuit breaker connected in parallel to the resistor. However, since the commutation capacitor is short-circuited by turning on the second circuit breaker a predetermined time after the first circuit breaker is turned on, the charge of the commutation capacitor can be quickly discharged.

According to the fourth aspect of the present invention, the discharging means is connected to the series circuit of the resistor and the first circuit breaker connected in parallel to the commutation capacitor and the second circuit breaker connected in parallel to the series circuit. With the configuration, the second circuit breaker is turned on a predetermined time after the first circuit breaker is turned on so that the commutation capacitor is short-circuited, so that the charge of the commutation capacitor can be quickly discharged. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional protection device for a power conversion device.

[Explanation of symbols]

9 AC system, 10 transformer, 11a, 11b commutation capacitor, 12a, 12b AC / DC converter, 14 DC system, 16a, 16b surge arrester, 17a, 17b Voltage detection means, 19a, 19b, 29a, 29b Comparison means,
22a, 22b, 32a, 32b Resistance, 23a, 23
b, 25a, 25b, 33a, 33b, 35a, 35
b, 37a, 37b Circuit breaker, 24a, 24b, 34
a, 34b Series circuit, 26a, 26b, 36a, 36
b, 38a, 38b discharging means, 27a, 27b current detecting means.

Claims (4)

[Claims] A commutation capacitor is connected between a transformer connected to an AC system and an AC / DC converter connected to a DC system, and the rectifier is connected in parallel with the commutation capacitor. In a protection device of a power conversion device configured to protect an overvoltage of a current capacitor, a voltage detection unit that detects a charging voltage of the commutation capacitor and a comparison that outputs a detection signal when the charging voltage exceeds a predetermined value. And a discharging means for discharging the electric charge of the commutation capacitor in accordance with the detection signal. 2. A commutation capacitor is connected between a transformer connected to the AC system and an AC / DC converter connected to the DC system, and the lightning arrester connected in parallel to the commutation capacitor. In a protection device of a power conversion device configured to protect an overvoltage of a current capacitor, a current detection unit that detects a current of the lightning arrester, and a comparison unit that outputs a detection signal when the current of the lightning arrester exceeds a predetermined value. And a discharging means for discharging the charge of the commutation capacitor in accordance with the detection signal. 3. The discharging means comprises a series circuit of a resistor and a first circuit breaker connected in parallel to a commutation capacitor, and a second circuit breaker connected in parallel to the resistor. The protection device for a power converter according to any one of claims 1 and 2, wherein the second circuit breaker is turned on a predetermined time after the circuit breaker is turned on. . 4. The discharging means comprises a series circuit of a resistor and a first circuit breaker connected in parallel to a commutation capacitor, and a second circuit breaker connected in parallel to the commutation capacitor.
The protection device for a power conversion device according to claim 1, wherein the second circuit breaker is turned on a predetermined time after the first circuit breaker is turned on.