KR20150046529A - New circuit configuration of high-voltage hybrid dc circuit breaker - Google Patents

Abstract

The present invention relates to a large capacity high voltage hybrid DC circuit breaker and a drive method thereof to reverse the polarity of a capacitor (C) voltage with LC resonance by automatically turning off thyristor (T1) and turning on thyristor (T2) when the voltage at both ends of the capacitor (C) becomes equal to a supply voltage; and to prevent a fault current from flowing upward by making a circulating current flow through a path of the thyristor (T1) - the capacitor (C) - an inductor (L) - a surge arrester (Zn02) - a diode (D1) - a mechanical circuit breaker (CB) and a path of the thyristor (T1) - the capacitor (C) - the inductor (L) - the surge arrester (Zn02) - the diode (D1) - a diode (D2) when a fault occurred in a DC line. According to the present invention, provided is a hybrid DC circuit breaker to reduce an installation cost, to reduce a conduction loss during a normal operation, to reduce an interception loss during a fault, to have a strong transient voltage, and to be applicable to DC power transmission.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-voltage high-voltage hybrid DC circuit breaker,

The present invention relates to a large-capacity high-voltage hybrid DC circuit breaker and a driving method thereof, and more particularly, to a large-capacity high-voltage hybrid DC circuit breaker which comprises a mechanical circuit breaker, a thyristor switch, a diode and an LC resonance circuit, To a new circuit configuration of a hybrid DC breaker applicable to direct current transmission.

The large capacity high voltage DC circuit breaker has been studied much since DC power distribution in the subway has been rapidly increasing and DC transmission using the Thyristor converter has been increasing.

In order to efficiently block large-capacity high-voltage DC breakers, a method of artificially interrupting the fault current passing through the '0' point using an LC resonant circuit is proposed initially, but there is a disadvantage that the breaking speed is slow.

In order to solve these problems, a large diode and a thyristor have been developed and a circuit configuration with a cut-off speed improved by combining this with a high-speed mechanical circuit breaker like a LC resonance circuit has been proposed. However, it is mainly applied to a DC transmission line There is a lack of performance in breaking capacity, breakdown voltage and breaking speed.

On the other hand, Korean Patent Laid-Open No. 10-2005-0083067 (gate cut-off circuit of voltage-driven power switching device utilizing LC resonance) includes a switching device, an inductor, a transistor and a capacitor connected in series to a gate, Although a technique for constructing a resonant circuit is disclosed, there is a disadvantage in that the conduction loss is too large in normal operation.

In addition, a semiconductor circuit breaker using a gate turn-off thyristor (GTO) for subway feeder lines has been developed at home and abroad, and has a merit that a breakdown current can reach a certain value, It has not been commercialized because of the drawbacks that the loss is too large.

Even if an IGBT (Insulated Gate Bipolar Transistor) or IGCT (Insulated Gate-Commutated Thyristor), which is a recently developed large-capacity semiconductor switching, is used, there is no economical efficiency because the conduction loss is too large.

For this reason, a hybrid circuit breaker combining a semiconductor switch and a mechanical circuit breaker has recently been proposed. The hybrid circuit breaker is connected to the mechanical circuit breaker in normal operation and in case of failure, the fault current flowing to the mechanical circuit breaker is switched to the connected semiconductor switch in parallel.

Recently, ABB has been developing a transmission-type hybrid DC circuit breaker using IGBT as a semiconductor switch. It has announced that the cutoff speed is 4ms, which is the design value, but it does not disclose information about loss and cost.

Alstom has proposed a DC DC hybrid circuit breaker that combines a high-speed mechanical circuit breaker with an auxiliary circuit consisting of diodes, thyristors, and LC resonance circuits for rapid arc extinguishing, but the specific development status is not disclosed.

Siemens has also been working with Professor Marquart of Bundeswehr University in Germany to study a DC-breaker hybrid DC-breaker that combines a high-speed mechanical breaker with an auxiliary circuit consisting of diode, thyristor and LC resonance circuit, but the specific development status is not disclosed .

In Korea, it is known that Korea Electric Research Institute and Hyosung Co. are conducting basic research on dc, dc, dc, dc, dc, dc, dc, dc, dc, dc, dc,

To summarize, various circuit configurations have been proposed so far as direct current transmission circuit breakers, but no technology has been disclosed that satisfies all of them in terms of breaking capacity, breaking speed, conduction loss, and economy.

It is an object of the present invention to provide a hybrid DC circuit breaker which is constituted by a mechanical circuit breaker, a Thyristor switch, a diode and an LC resonance circuit, has less conduction loss in normal operation, have.

In order to accomplish the above object, a large capacity high voltage hybrid DC circuit breaker according to the present invention comprises a thyristor (T1) turned on to charge a capacitor (C), and when a voltage across a capacitor (C) (T1) is automatically turned off and the thyristor (T2) is turned on so that the polarity of the capacitor (C) voltage is reversed by the LC resonance. When a fault occurs in the DC line, the thyristor (T1) The surge arrester (ZnO2) is conducted by the voltage of the capacitor (C) charged in the reverse direction and the thyristor (T1), the capacitor (C), the inductor (L), the surge arrester The path of the mechanical circuit breaker CB and the path of the diode D1 are connected to the path of the diode D2 through the path of the thyristor T1, the capacitor C, the inductor L, the surge arrester Zn02, So that the fault current can not rise any more.

The method for driving a high capacity high voltage hybrid DC circuit breaker according to the present invention includes the steps of: (a) charging a capacitor C by turning on a thyristor T1; (B) when the charging of the capacitor (C) is completed and the voltage across the capacitor (C) becomes equal to the supply voltage, the thyristor (T1) is automatically turned off; (C) the thyristor (T2) is turned on and the polarity of the voltage of the capacitor (C) is reversed by the L-C resonance; (D) when the failure occurs in the DC line, the surge arrester (ZnO2) is conducted by the voltage of the capacitor (C) charged in the reverse direction by turning on the thyristor (T1); And Thyristor (T1) → Capacitor (C) → Inductor (L) → Surge Arrester (Zn02) → Diode (D1) → Mechanical Circuit Breaker (CB) (E) so that a circulating current flows through the path of the inductor (L) -> the surge arrester (ZnO2) -> the diode (D1) -> the diode (D2) .

According to the present invention, by constituting the mechanical circuit breaker, the thyristor switch, the diode and the LC resonance circuit, it is possible to reduce the conduction loss in normal operation with low installation cost, It is effective to provide an applicable (less than 4 ms) hybrid DC circuit breaker.

Specifically, according to the present invention, it is possible to reduce the conduction loss in the normal operation and to set the cut-off speed in the fault within 4ms, which is smaller in size and less in loss than the circuit breaker proposed by ABB Co., and is manufactured by Alstom and Siemens As the performance and efficiency are excellent, it can be applied in a timely manner to the rapidly increasing demand for DC transmission.

1 is a circuit diagram showing a high capacity high voltage hybrid DC circuit breaker according to the present invention;
BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a high-capacity high-voltage hybrid DC circuit breaker, and more particularly,
FIG. 3 is a graph showing the relationship between the voltage of the main portion (high-voltage high-voltage hybrid DC circuit breaker) and the voltage applied to the high-voltage high-voltage hybrid DC circuit breaker according to the present invention Of the voltage and current.
4 is a graph showing the relationship between the voltage of the main part and the voltage of the main part of the high-voltage high-voltage hybrid DC circuit breaker according to the present invention in order to confirm the response speed until the faulty current is generated by turning on the thyristor (T1) An enlarged view of the waveform of the current.
5 is a diagram showing a bi-directional circuit configuration of a large capacity high voltage hybrid DC circuit breaker according to the present invention.
6 is a flowchart showing a method of driving a large-capacity high-voltage hybrid DC circuit breaker according to the present invention.

Specific features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings. Prior to this, terms and words used in the present specification and claims are to be interpreted in accordance with the technical idea of the present invention based on the principle that the inventor can properly define the concept of the term in order to explain his invention in the best way. It should be interpreted in terms of meaning and concept. It is to be noted that the detailed description of known functions and constructions related to the present invention is omitted when it is determined that the gist of the present invention may be unnecessarily blurred.

As shown in FIG. 1, when the circuit of the high capacity high voltage hybrid DC circuit breaker 10 according to the present invention is examined, power is supplied from the DC power source on the left side to the load on the right side through the power source resistance, the breaker, and the transmission line.

The hybrid DC circuit breaker 10 according to the present invention includes two thyristors T1 and T2 and two diodes D1 and D2 as auxiliary circuits for increasing the breaking speed of the mechanical circuit breaker CB and the mechanical circuit breaker CB. , Two surge arresters (Zn01 and Zn02), and a capacitor (C) and an inductor (L) used in the LC resonant circuit. At this time, the resistance connected in series with the inductor L represents the coil resistance of the inductor L.

In the case of DC, the mechanical breaker (CB) can not be directly cut off because the fault current does not exceed '0', unlike AC, and various studies have been made to improve the cut-off speed have.

Specifically, when the mechanical circuit breaker CB is closed to supply the rated power from the power source to the load, the operation modes (MODE1 to MODE4) of the hybrid DC circuit breaker 10 according to the present invention are as follows.

MODE1

First, the capacitor C is charged by turning on the thyristor T1, the charging speed is determined by the Rs-LC constant, and charging is completed in accordance with the application of the current to the capacitor C, When the voltage becomes equal to the supply voltage, the thyristor (T1) is automatically turned off.

MODE2

가 되고, 공진시 피크전류는

가 된다. 또한, 피크전류가 고장전류의 최대치에 약 1.3 내지 1.5배 되도록 설정한다. 실제 반전된 커패시터(C)의 전압은 인덕터(L)의 저항에 의해 공급전압보다 낮아진다.Subsequently, when the thyristor (T2) is turned on, the voltage of the capacitor (C) is reversed by the LC resonance. At this time,

And the peak current at the resonance is

. Also, the peak current is set to be about 1.3 to 1.5 times the maximum value of the fault current. The voltage of the actually inverted capacitor C becomes lower than the supply voltage by the resistance of the inductor L. [

As the voltage polarity of the capacitor C is inverted, the supply voltage and the inverted voltage of the capacitor C are applied to the thyristor T1 and the surge arrester (Zn01) is applied across the thyristor T1 Connect.

MODE3

When a failure occurs in the DC line, when the thyristor (T1) is turned on, the surge arrester (Zn02) is turned on by the voltage of the capacitor (C) charged in the reverse direction, (C) -> Inductor (L) -> Surge Arrester (Zn02) -> Diode (D1) -> Mechanical Circuit Breaker (CB) path and Thyristor ) -> Surge Arrester (Zn02) -> Diode (D1) -> Diode (D2), the fault current can no longer rise.

At this time, when the mechanical circuit breaker CB is opened, all the circulating currents are shared by the diodes D2, which facilitates arc extinguishing.

MODE4

When the mechanical circuit breaker (CB) is opened, the magnetic energy stored in the inductance of the transmission line is gradually reduced while free-wheeling through the transmission line, surge arrester (ZnO2) and diode (D1) in the form of current, That is, it is affected by the line resistance.

Meanwhile, FIG. 2 is a diagram showing a simulation model composed of PSCAD / EMTDC software for verifying the operation of the high-capacity high-voltage hybrid DC circuit breaker 10 according to the present invention.

The input voltage is 200kV, the power resistance is 2.0Ω, the load is 100Ω, and the capacity is set to 400MW. The line is assumed to be 200 km, divided into four, and the line resistance of each part is set to 0.872 Ω and the line inductance to 31.5 mH. In addition, a ground fault was simulated by connecting breakers (BRK1 to BRK5) in parallel at the end of each line to simulate various line faults.

The simulation scenario first turns off the thyristor (T1) when the capacitor (C) is fully charged by turning on the thyristor (T1) at 0.1s.

Then, the polarity of the capacitor C is inverted by turning on the thyristor (T2) at 0.2s.

Subsequently, the circuit breaker (BRK3) connected in parallel to the line at 0.3S is closed to artificially generate a fault.

Then, when the fault current rises to 10 kA, the fault is detected and the thyristor (T1) is turned on.

When the current flowing through the thyristor (T1) reaches 10 kA, the current flowing through the mechanical circuit breaker (CB) decreases, and when this current reaches zero, the mechanical circuit breaker (CB) opens.

3 shows the voltage and current waveforms of the main portion in order to confirm the overall operation until the fault transistor T1 is turned on and the mechanical breaker CB is fully opened to interrupt the fault current FIG.

3 (a) shows a voltage waveform appearing in the thyristor (T1). When the thyristor (T1) is turned on and the capacitor (C) is fully charged, the voltage appearing at both ends becomes '0' and the thyristor When the voltage of the capacitor C becomes the opposite polarity, a voltage nearly twice as high as the supply voltage is generated.

3 (b) shows a voltage waveform to be charged in the capacitor C. When the thyristor T1 is turned on for 0.1 s, a positive voltage is charged. When the thyristor T2 is turned on for 0.2 s, the polarity of the voltage is reversed . The fault current reaches 10kA to turn off the thyristor (T1) in order to shut off the fault occurring at 0.3s.

Therefore, the path of the Thyristor (T1) -> Capacitor (C) -> Inductor (L) -> Surge Arrester (Zn02) -> Diode (D1) (C) -> inductor (L) -> surge arrester (Zn02) -> diode (D1) -> diode (D2), the capacitor C is completely discharged and the inductor And is charged with an initial polarity.

FIG. 3C shows a voltage waveform appearing in the mechanical circuit breaker CB. In a normal state, the voltage is '0'. In the case of a fault, the mechanical circuit breaker CB is opened and a supply voltage of 200kV appears.

3 (d) shows the waveform of the current flowing through the mechanical circuit breaker CB. In the normal state, the rated current flows during the normal state. When the mechanical circuit breaker CB is open, After that, the current flowing becomes '0'.

3E shows a current waveform flowing in the diode D1 and the surge arrester (ZnO2). When the thyristor T1 is turned on at the time of fault, a circulating current by the capacitor C flows, and the mechanical circuit breaker CB is opened The current stored as magnetic energy is free-wheeled by the line inductance.

3F shows the waveform of the fault current flowing through the line at the time of fault. When the mechanical circuit breaker CB is completely cut off, it is free-wheeled through the surge arrester (ZnO 2) and the diode D 1 by the inductance of the line, .

Meanwhile, FIG. 4 is an enlarged view of voltage and current waveforms of a main part in order to check the response speed until the thyristor (T1) is turned on and the mechanical breaker (CB) is completely opened to break the fault current when a fault is generated .

The simulation results show that the 4ms cutoff speed required for current DC transmission can be sufficiently achieved.

Specifically, FIG. 4A shows a waveform in which the current flowing through the thyristor (T1) is enlarged. After a fault occurs at 0.3s and a fault current reaches 10kA, a fault is detected at 0.3028s, It can be seen that it operates.

Fig. 4 (b) shows an enlarged waveform of the voltage applied to the mechanical circuit breaker CB. At 0. 038 s, the mechanical circuit breaker CB is opened and the voltage appearing at both ends gradually rises to become equal to the supply voltage.

4C shows a waveform in which the current flowing through the mechanical circuit breaker CB is enlarged. A fault is generated in 0.3s and the fault current gradually increases. The fault reference current is set to 10kA to reach 10kA at 0.3028s .

When the thyristor (T1) turns on, the surge arrester (Zn02) is turned on by the voltage of the capacitor (C) charged in the reverse direction, and the path of T1 - C - L - Zn02 - D1 - CB reaches 0.3033s At 0.3035 s, when the reverse current gradually increases and this current becomes equal to the fault current, the mechanical breaker (CB) current decreases and falls to '0'.

In addition, the current flowing in the mechanical circuit breaker CB flows continuously by the magnetic energy stored in the inductor L, and is shut off at 0.3038 s. By this current, the capacitor C is again charged in the forward direction.

FIG. 4F shows an enlarged waveform of the voltage applied to the surge arrester (ZnO2). In a normal state, most of the supply voltage is applied to the diode D1, so a low voltage appears. When the thyristor T1 is turned ON, A voltage of '0' is applied, and a current of the mechanical circuit breaker CB is reduced, and a reverse voltage of 10 kA is applied.

5 is a diagram showing a bi-directional circuit configuration of the high capacity high voltage hybrid DC circuit breaker 10 according to the present invention.

In the transmission line consisting of the power source and the load, it is possible to shut off when a fault occurs with a single circuit breaker. However, in the case of normal DC transmission in which two DC power sources are connected to the line, if a fault occurs in the line, it is required to cut off both ends, and a circuit breaker is installed in both the transmission and reception ends.

If a fault occurs at the center of the line, the left and right hybrid DC circuit breakers operate in the same manner as described above and can interrupt the fault current in both directions.

Hereinafter, a method of driving a large capacity high voltage hybrid DC circuit breaker according to the present invention will be described with reference to FIG.

First, the thyristor (T1) is turned on to charge the capacitor (C) (S10).

Subsequently, when the charging of the capacitor C is completed and the voltage across the capacitor C becomes equal to the supply voltage, the thyristor T1 is automatically turned off (S20).

Subsequently, the thyristor (T2) is turned on, and the polarity of the voltage of the capacitor (C) is inverted by L-C resonance (S30). At this time, the supply voltage and the inverted voltage of the capacitor C are applied to the thyristor (T1), and a surge arrester (Zn01) is connected to both ends of the thyristor (T1) in order to generate an overvoltage.

Then, when a failure occurs in the DC line, the surge arrester (ZnO2) is turned on by the voltage of the capacitor (C) charged in the reverse direction by turning on the thyristor (T1) (S40).

The path of Thyristor (T1) -> Capacitor (C) -> Inductor -> Surge Arrester (Zn02) -> Diode (D1) -> Mechanical Circuit Breaker (CB) The loop current is caused to flow through the path of the inductor L-> the inductor L-> the surge arrester (ZnO 2) -> the diode D 1 -> the diode D 2 (S 50).

In this case, when the mechanical breaker CB is opened, the magnetic energy stored in the inductance of the transmission line is gradually reduced while free-wheeling via the transmission line, the surge arrester (ZnO 2) and the diode D 1.

As described above, according to the present invention, a charged capacitor is used to inject a discharge current in a direction opposite to a fault current to reduce a fault current. When the mechanical breaker is opened, the electric energy stored in the inductance of the faulty line is divided into ZnO and a diode By cutting through free-wheeling, the cut-off speed of the mechanical breaker has been greatly improved.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be appreciated by those skilled in the art that numerous changes and modifications may be made without departing from the invention. And all such modifications and changes as fall within the scope of the present invention are therefore to be regarded as being within the scope of the present invention.

10: High capacity high voltage hybrid DC circuit breaker
CB: Mechanical breaker T1, T2: Thyristor
D1, D2: diode Zn01, Zn02: Surge Arrester
C: Capacitor L: Inductor

Claims (6)

When the voltage across the capacitor C becomes equal to the supply voltage by charging the capacitor C by turning on the thyristor T1, the thyristor T1 is automatically turned off and the thyristor T2 is turned on Thereby inverting the polarity of the voltage of the capacitor C by LC resonance,
If a failure occurs in the DC line, the surge arrester (ZnO2) is conducted by the voltage of the capacitor (C) charged in the reverse direction by turning on the thyristor (T1) Inductor (L) -> Surge Arrester (Zn02) -> Diode (D1) -> Mechanical Circuit Breaker (CB) path and Thyristor (T1) -> Capacitor (C) -> Inductor (L) -> Surge Arrester ) -> diode (D1) -> diode (D2) so that the fault current can not rise any more. The high-capacity high-voltage hybrid DC circuit breaker according to claim 1, The method according to claim 1,
In the LC resonance,
That cycle

, And the resonance peak current is

, Wherein the peak current is configured to be 1.3 to 1.5 times the maximum value of the fault current and the voltage of the inverted capacitor (C) is configured to be lower than the supply voltage by the resistance of the inductor (L). breaker. The method according to claim 1,
A surge arrester (Zn01) is connected to both ends of the thyristor (T1) in order to prevent an overvoltage generated by the voltage of the capacitor (C) being inverted and the voltage of the capacitor (C) Voltage high-voltage hybrid DC circuit breaker. The method according to claim 1,
When the mechanical circuit breaker (CB) is opened, the magnetic energy stored in the inductance of the transmission line is reduced in a current form by free-wheeling through a transmission line, a surge arrester (ZnO 2) and a diode (D 1) DC breaker. (a) charging the capacitor (C) by turning on the thyristor (T1);
(b) when the charging of the capacitor C is completed and the voltage across the capacitor C becomes equal to the supply voltage, the step (a) of turning off the thyristor T1 is automatically turned off;
(c) the thyristor (T2) is turned on so that the polarity of the voltage of the capacitor (C) is reversed by LC resonance;
(d) conducting a surge arrester (ZnO2) by the voltage of the capacitor (C) charged in the reverse direction when the thyristor (T1) is turned on when a fault occurs in the DC line; And
(e) Thyristor (T1) -> Capacitor (C) -> Inductor (L) -> Surge Arrester (Zn02) -> Diode (D1) -> Path of mechanical breaker (CB) (C) -> inductor (L) -> surge arrester (Zn02) -> diode (D1) -> diode (D2) so that the fault current does not rise anymore Voltage high-voltage hybrid DC circuit breaker. 6. The method of claim 5,
After the step (e)
(f) When the mechanical circuit breaker (CB) is opened, the magnetic energy stored in the inductance of the transmission line is gradually reduced while free-wheeling via the transmission line, the surge arrester (ZnO2) and the diode Voltage hybrid hybrid DC circuit breaker.

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