JPH1042462A - Capacitor protective device for dc filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitor bank for DC filter used for the DC power source of a power converter which can make a system to be operated continuously, even when a failure occurs in a capacitor by only disconnecting the capacitor from a power source circuit by using the failure detecting signal of the capacitor without stopping the entire system. SOLUTION: An expulsion fuse 4 composed of a fusible piece 12 and a spring 13 which pulls the piece 12 is connected in series with a capacitor 11, and a commutation circuit 2 composed of a commutation capacitor 21, a charging power source, and an inductance 24 is connected to both ends of the piece 12, and then a semiconductor switch element or switch 15 which is conducted by the failure detecting signal of the capacitor 21 is connected in series between the piece 12 and circuit 2, so that when a failure occurs in the capacitor 11, only the capacitor 11 can be disconnected from the power source by fusing the piece 12 by making a large oscillating current to flow to the piece 12 by means of the failure detecting signal of the capacitor 21 and, at the same time, separating the piece 12 by means of the spring 13.

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 capacitor bank for a DC filter used on the DC side, such as a large-capacity self-excited inverter device used mainly in a reactive power compensator or a frequency converter. is there.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a circuit breaker on a power supply side of a power converter is opened by a failure detection signal of a capacitor.

[0003]

As described above, conventionally, when a capacitor has failed, a system in which the power supply side of the power converter is opened and the power converter is completely stopped has been used, but several to several tens of MVA have been used. In the large-capacity converter, the DC filter capacitor bank is composed of several tens of capacitors, and it is unreasonable considering the effect of the failure of one of these capacitors to stop the entire system.
There is a strong demand that only the faulty capacitor be separated and the operation continued.

For this reason, there is a case where a DC fuse is attached to each capacitor in a relatively small-capacity converter having a relatively low DC voltage, but when a large-capacity DC voltage is high, Since there was no DC fuse available for this, there was no other way but to stop the entire system as described above.

[0005]

As a method of detecting an internal failure of a capacitor, a method of detecting imbalance of current or voltage or a method of detecting an increase in internal pressure of a case has been considered and put to practical use. DC capacitors have difficulty blocking high voltage DC current. For this reason, the present invention employs a method of generating a large oscillation current using a commutation circuit using a discharge current of a capacitor, thereby fusing the fusible pieces and generating a current zero point to interrupt the current.

That is, according to the present invention, the capacitor 11
A capacitor bank 1 for a DC filter of a power converter including a fuse 4 formed of a fusible piece, a spring and a fuse tube, a semiconductor switching element or switch 15, a commutation circuit 2 composed of a commutation capacitor, an inductance and a charging power source. Each of the capacitors 11 is a capacitor having a function of detecting an internal failure and generating a signal. The discharging fuse 4 having a capacitor 11, a fusible piece 12, a spring 13 for cutting the fusible piece, and a fuse cylinder 14 is connected in series. A commutation capacitor and a commutation circuit 2 composed of an inductance and a charging power supply are connected in parallel to the fusible piece 12, and a semiconductor switching element or a switching element that allows commutation current to flow according to a signal for detecting an internal failure of the capacitor 11. The devices 15 are connected in series between the fusible pieces 12 and the commutation circuit 2, respectively, A DC filter characterized in that, when an internal failure occurs in the sensor, the fusible piece is blown off by a commutation current, the fusible piece is separated by the spring and cut off, and a connection point with the commutation circuit 2 is cut off. It is a protection device for capacitors.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The DC filter capacitor protection device of the present invention reliably disconnects this capacitor from the power supply in accordance with the capacitor internal detection signal. Only the failed capacitor is disconnected, and the entire system operates without any trouble. Can be continued.

[0008]

Embodiment 1 FIG. 1 shows an embodiment of the configuration of a capacitor protecting device for a DC filter according to the present invention. In FIG. 1, reference numeral 1 denotes a DC filter capacitor bank used for a DC power supply such as a power converter, 11 denotes a capacitor constituting the DC filter capacitor bank, 12 denotes a fusible piece connected in series to the capacitor, and 13 denotes a fusible piece. And 14 is a fuse cylinder for accommodating the spring. Reference numeral 2 denotes a commutation circuit that supplies a commutation current to the fusible piece 12, and includes a commutation capacitor 21, a rectification circuit 22,
It is composed of a charging resistor 23 and an inductance 24 and is supplied with power from the AC power supply 3. Reference numeral 15 denotes a semiconductor switching element such as a thyristor that is turned on by an internal failure detection signal of the capacitor 11.

When an internal failure occurs in the capacitor 11,
The thyristor 15 is turned on by this detection signal, and the accumulated charge of the commutation capacitor 21 is discharged to the fusible piece 12 through the inductance 24, so that a large oscillating current flows. The fusible piece is blown off by the current energy, separated from the blown portion by the spring 13, cut off at the current zero point, and the connection line from the commutation circuit 2 is also cut off. FIG. 2 shows this state. In this state, the faulty capacitor 11 is completely opened from the power supply circuit, so that the entire system can continue to operate as it is.

[0010]

According to the protection device for a DC filter capacitor of the present invention, only a failed capacitor can be disconnected from a power supply by a failure detection signal without stopping the entire system due to failure of one capacitor. Since the operation can be continued, there is a great effect on improving the reliability of the system without affecting the system.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing one embodiment of the configuration of a DC filter capacitor protection device of the present invention.

FIG. 2 is an explanatory diagram showing a state of a fusible piece of the present invention after fusing.

FIG. 3 is a connection diagram showing an embodiment of a conventional application method of a capacitor protection device for a DC filter.

[Explanation of symbols]

 1: DC filter capacitor bank 2: Commutation circuit 3: AC power supply 4: Discharge fuse 5: Power converter 6: Power supply circuit breaker 11: Capacitor 12: Soluble piece 13: Spring 14: Fuse cylinder 15: Semiconductor switching element or Switch 21: Commutation capacitor 22: Rectifier circuit 23: Charging resistor 24: Inductance

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H02M 7/06 8726-5H H02M 7/06 G 7/48 8110-5H 7/48 M (72) Inventor Koji Morita Nichicon Co., Ltd., 3rd floor of 4 Uehara Bldg., 191 Nakabori-cho, 1st line, Oike-dori Karasuma Higashi-iri, Nakagyo-ku, Kyoto-shi, Kyoto

Claims (3)

[Claims] 1. A capacitor (11), a discharge fuse (4) comprising a fusible piece, a spring and a fuse tube, a semiconductor switching element or switch (15), a commutation circuit comprising a commutation capacitor, an inductance and a charging power supply. (2)
A DC filter capacitor bank (1) for a power converter, wherein each capacitor (11) has a function of detecting an internal failure and generating a signal, and includes a capacitor (11) and a fusible piece ( 12), a discharge fuse (4) having a spring (13) for cutting the fusible piece and a fuse cylinder (14) are connected in series, and the fusible piece (12) has a commutation circuit comprising a commutation capacitor, an inductance and a charging power supply. (2) are connected in parallel, and a semiconductor switching element or switch (15) through which commutation current flows according to a signal for detecting an internal failure of the capacitor (11).
Are connected in series between the fusible piece (12) and the commutation circuit (2), respectively, when the internal failure of the capacitor occurs, the fusible piece is blown off by the commutation current, and the fusible piece is separated by the spring and cut off. A protection device for a capacitor for a DC filter, wherein a connection point with a commutation circuit (2) is also disconnected. 2. The protection device for a DC filter capacitor according to claim 1, wherein the semiconductor switching elements or switches respectively connected in series between the fusible piece and the commutation circuit are thyristors or transistors that are turned off by a gate signal. 3. The protection device for a DC filter capacitor according to claim 1, wherein the semiconductor switching element or switch connected in series between the fusible piece and the commutation circuit is an electromagnetic switch that is closed by a signal current.