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Patent Searching and Data


Title:
TRIGGERING CIRCUIT FOR THYRISTOR AND FAST BYPASS DEVICE
Document Type and Number:
WIPO Patent Application WO/2012/171891
Kind Code:
A1
Abstract:
Disclosed in the present utility model is a triggering circuit for a thyristor, comprising a first resistance and a breakover diode for connecting in series between the anode and gate of a thyristor. Also disclosed in the present utility model is a fast bypass device which comprises a thyristor, wherein the thyristor is connected with the triggering circuit. The advantages of the present utility model are: reduced costs, simplicity and reliability, and rapid response.

Inventors:
PHILIPP ANDREAS (DE)
SONG YING HUA (CN)
WU XUE ZHI (CN)
YAO JI LONG (CN)
ZHAO YAN FENG (CN)
Application Number:
PCT/EP2012/061063
Publication Date:
December 20, 2012
Filing Date:
June 12, 2012
Export Citation:
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Assignee:
SIEMENS AG (DE)
PHILIPP ANDREAS (DE)
SONG YING HUA (CN)
WU XUE ZHI (CN)
YAO JI LONG (CN)
ZHAO YAN FENG (CN)
International Classes:
H02M1/08; H02H9/04; H03K17/08
Domestic Patent References:
WO2001006610A12001-01-25
Foreign References:
US5714861A1998-02-03
US5699218A1997-12-16
Other References:
None
Attorney, Agent or Firm:
SIEMENS AKTIENGESELLSCHAFT (München, DE)
Download PDF:
Claims:
Claims

1. A triggering circuit (1) for a thyristor,

characterized in that

it comprises a first resistance (Rl) and a breakover diode

(D3) for connecting in series between the anode (P3) and gate of a thyristor (Tl) .

2. The triggering circuit (1) as claimed in claim 1,

characterized in that

the triggering circuit (1) further comprises a Zener diode (D2) for connecting between the cathode (P4) and gate of the thyristor (Tl ) . 3. The triggering circuit (1) as claimed in claim 2,

characterized in that

the triggering circuit (1) further comprises a capacitor (C) and a second resistance (R2), wherein the capacitor (C) , the second resistance (R2) and the Zener diode (D2) are connected in parallel with each other.

4. The triggering circuit (1) as claimed in claim 2 or 3, characterized in that

the triggering circuit (1) further comprises a diode (Dl), wherein the cathode of the diode (Dl) is connected to the gate of the thyristor (Tl), and the anode (P5) of the diode (Dl) is connected to the cathode (P5) of the breakover diode (D3) and the Zener diode (D2) . 5. A fast bypass device (2), comprising a thyristor (Tl), characterized in that

the thyristor (Tl) is connected with the triggering circuit (1) as claimed in any one of claims 1 to 4. 6. The fast bypass device (2) as claimed in claim 5,

characterized in that two of the thyristors (Tl, T2) are connected in reverse par¬ allel to form a pair of reverse-parallel-connected thyristors (Tl, T2) . 7. The fast bypass device (2) as claimed in claim 6,

characterized in that

the pair of reverse-parallel-connected thyristors (Tl, T2) are connected in parallel with a main capacitor (Cm) . 8. The fast bypass device (2) as claimed in claim 6 or 7, characterized in that

the main capacitor (Cm) is one or more capacitances connected in series between the neutral point (PI) and grounding elec¬ trode (P2) of a transformer.

Description:
Description

Triggering circuit for thyristor and fast bypass device Technical field

The present utility model relates to a triggering circuit, and in particular to a triggering circuit for a thyristor. The present utility model also relates to a fast bypass de- vice connected with the triggering circuit.

Background art

When a High Voltage Direct Current (HVDC) power transmission system is in the ground return operating mode, direct current flows through the ground and causes a change in electric po ¬ tential in the vicinity of the grounding electrode of a transformer, so that a DC potential difference will arise be ¬ tween the neutral points of two neighboring transformers. Since AC systems have relatively low resistance values, the potential difference will also give rise to a direct current in an AC system with the help of the neutral points of the transformers. If the direct current is too high, it will lead to saturation of the transformer and the occurrence of DC magnetic bias therein, resulting in an excessively high temperature in the transformer, an increase in harmonics, and increased noise, and in serious cases may even damage the transformer . In order to solve this problem, people have switched in a ca ¬ pacitor between the neutral point and the grounding electrode of a transformer. A capacitor can block direct current while allowing the passage of alternating current. However, in view of the fact that the voltage which a capacitor is able to sustain is limited, there is a necessity to use a fast bypass device in parallel, to short-circuit the capacitor in the event of an electrical system fault or a power surge in the transformer, in order to prevent the voltage or current from exceeding the limit of the capacitor.

Thyristors have been used in fast bypass devices on account of having good current control capability and a fast re ¬ sponse. Reverse-parallel-connected thyristors are widely em ¬ ployed as they can allow current to flow in both directions. An electronic drive circuit is generally used to actively in ¬ ject a certain current into the gate of a thyristor and thereby achieve triggering of the thyristor. The electronic drive circuit consists of two parts, a power supply and a signal unit, and a fault in either of these will cause trig ¬ gering of the thyristor to fail. In view of the great importance of safety and reliability with respect to devices blocking direct current in electrical systems, it is neces ¬ sary to further provide an active electronic drive circuit as a backup triggering circuit for the triggering of the thyris ¬ tor. Such a solution has the following shortcomings: 1) a backup triggering circuit requires a further power source and signal processing circuit to be additionally provided, re ¬ sulting in increased costs; 2) the triggering circuit triggers the thyristor in an active way, i.e. triggering may only be performed when the power source is working normally. If the power source should suffer paralysis as a result of a se- rious fault, triggering will be unable to be carried out.

Content of the utility model

The objective of the present utility model is achieved by way of a triggering circuit for a thyristor, in order to overcome the abovementioned deficiencies in the prior art. The trig ¬ gering circuit for a thyristor comprises a first resistance and a breakover diode for connecting in series between the anode and gate of a thyristor.

According to one aspect of the present utility model, the triggering circuit further comprises a Zener diode connected between the cathode and gate of the thyristor. According to another aspect of the present utility model, the triggering circuit further comprises a capacitor and a second resistance, wherein the capacitor, the second resistance and the Zener diode are connected in parallel with each other.

According to yet another aspect of the present utility model, the triggering circuit further comprises a diode, wherein the cathode of the diode is connected to the gate of the thyris- tor, and the anode of the diode is connected to the cathode of the breakover diode and the Zener diode.

The objective of the present utility model is further

achieved by way of a fast bypass device. The fast bypass de- vice comprises a thyristor, wherein the thyristor is connected with the triggering circuit.

According to one aspect of the present utility model, two of the thyristors are connected in reverse parallel to form a pair of reverse-parallel-connected thyristors.

According to another aspect of the present utility model, the pair of reverse-parallel-connected thyristors are connected in parallel with a main capacitor.

According to yet another aspect of the present utility model, the main capacitor is one or more capacitances connected in series between the neutral point and grounding electrode of a transformer .

The advantages of the present utility model are: 1) it avoids the additional provision of a further power supply and signal processing unit, thereby reducing costs; 2) the triggering circuit triggers the thyristor in a completely passive way, i.e. a power supply is not required for triggering to be per ¬ formed, and it can be performed as usual even if the entire electricity substation suffers a power cut, and so simple and reliable triggering is achieved; 3) it requires just a few microseconds to respond, avoiding as far as possible damage to the capacitor, etc. which would be caused by a time delay.

Description of the accompanying drawings

The features and advantages of the present utility model will become clearer with reference to the following accompanying drawings, in which identical symbols indicate identical com ¬ ponents or devices:

Fig. 1 illustratively shows a triggering circuit 1 for a thyristor of the present util ¬ ity model, in which electric potential points with the same labels are at the same poten ¬ tial ;

Fig. 2 illustratively shows a fast bypass device 2 of the present utility model, with the fast bypass device 2 being connected in parallel with a main capacitor C m .

List of reference numerals:

1 triggering circuit; 2 fast bypass device;

Dl diode; D2 Zener diode;

D3 breakover diode; Tl, T2 thyristors;

C capacitor; C m main capacitor;

PI, P2, P3, P4, P5 electric potential points;

Rl, R2 resistances. Particular embodiments

According to an embodiment of the present utility model, a triggering circuit 1 for a thyristor as shown by the dashed line in Fig. 1 comprises a resistance Rl serving as a first resistance and a breakover diode D3, wherein the resistance

Rl and the breakover diode D3 are connected in series between the anode and gate of a thyristor Tl. The breakover diode D3 is capable of developing forward bias once the forward volt- age thereon exceeds a certain value such that the voltage across it falls rapidly, generating a current which is in ¬ jected into the gate of the thyristor Tl, and thereby emit ¬ ting a signal for the thyristor Tl to conduct. The first re- sistance is used to limit the current, in order to prevent the thyristor Tl from being damaged as a result of an exces ¬ sively large current.

According to another embodiment of the present utility model, the triggering circuit 1 as shown in Fig. 1 can further comprise a Zener diode D2 connected between the cathode and gate of the thyristor Tl. Since the ability of the thyristor Tl to sustain overvoltage is poor, the provision of the Zener diode D2 can prevent the occurrence of overvoltage between the gate and cathode of the thyristor Tl, thereby protecting the thy ¬ ristor Tl .

According to yet another embodiment of the present utility model, the triggering circuit 1 as shown in Fig. 1 can fur- ther comprise a capacitor C and a resistance R2 serving as a second resistance, wherein the capacitor C, the resistance R2 and the Zener diode D2 are connected in parallel with each other. The capacitor C and resistance R2 connected in paral ¬ lel can serve the function of filtering high-frequency inter- ference signals, thereby avoiding accidental triggering of the thyristor Tl; those skilled in the art can select values for the capacitance and resistance of the capacitor C and the resistance R2 according to requirements. According to yet another embodiment of the present utility model, the triggering circuit 1 as shown in Fig. 1 can further comprise a diode Dl, wherein the cathode of the diode Dl is connected to the gate of the thyristor Tl, and the anode of the diode Dl is connected to the cathode of the breakover diode D3 and the Zener diode D2 at the electric potential point P5. The diode Dl is used to ensure that the potential at the electric potential point P5 is higher than that at the gate of the thyristor Tl, and current is only permitted to flow through the diode Dl and be injected into the gate of the thyristor Tl to make the thyristor Tl conduct when the voltage on the diode Dl reaches a certain value; in this way, accidental triggering of the thyristor Tl is avoided.

According to yet another embodiment of the present utility model, a fast bypass device 2 indicated by a dashed line in Fig. 2 is connected with a triggering circuit 1 as shown in Fig. 1. Although the triggering circuit for thyristor T2 has been omitted in Fig. 2, the triggering circuits 1 in the various embodiments above can also be connected to thyristor T2 in a similar manner to that used for thyristor Tl. The triggering circuit 1 is connected on the fast bypass device 2 via electric potential points P3 and P4 respectively. Al- though Fig. 2 shows two thyristors Tl and T2 connected in re ¬ verse parallel to form a pair of reverse-parallel-connected thyristors, the triggering circuit 1 in Fig. 1 may also be used for one or more thyristors connected in another way. According to yet another embodiment of the present utility model, the fast bypass device 2 can further be connected in parallel with a main capacitor C m as shown in Fig. 2. In this case, the main capacitor C m , which is connected between the neutral point PI and the grounding electrode P2 of a trans- former, is connected in parallel with the reverse-parallel- connected thyristors Tl and T2 in the fast bypass device 2 at electric potential points P3 and P4 respectively, wherein the main capacitor C m can be one or more capacitances connected in series between the neutral point PI and grounding elec- trode P2 of the transformer.

Although embodiments of the present utility model are set forth above, these embodiments are not intended to set forth all possible forms of the present utility model. Furthermore, the contents of this description are descriptive, not re ¬ strictive. Those skilled in the art could make various changes and amendments to the contents of this description without departing from the purport of the present utility model and the scope of the claims.