WO2019227995A1

WO2019227995A1 - Mechanical high-voltage direct-current circuit breaker device and breaking method thereof

Info

Publication number: WO2019227995A1
Application number: PCT/CN2019/076818
Authority: WO
Inventors: 司马文霞; 付峥争; 杨鸣; 袁涛; 孙魄韬; 段盼; 韩雪; 司燕
Original assignee: 重庆大学
Priority date: 2018-06-01
Filing date: 2019-03-04
Publication date: 2019-12-05
Also published as: CN108649544A

Abstract

The present invention relates to the technical field of topological design of key equipment in a direct-current system, and particularly relates to a mechanical high-voltage direct-current circuit breaker device and a breaking method thereof. The device comprises: a main branch circuit, used for bearing a normal working current of a direct-current line and overvoltages at two ends of a direct-current circuit breaker when a fault current is broken, and implementing bidirectional conduction of the current on the direct-current line; a transfer branch circuit, used for generating an oscillating current opposite to the current of the main branch circuit in direction, and superimposing the opposite oscillating current onto the main branch circuit to enable the fault current on the main branch circuit to forcedly cross zero, so as to implement transfer of the fault current from the main branch circuit to the transfer branch circuit; an absorption branch circuit, used for absorbing and discharging energy accumulated when fault breaking; and a residual current breaking component, connected in series to the main branch circuit and used for breaking a residual current.

Description

Mechanical high-voltage DC circuit breaker device and its breaking method

Technical field

The invention relates to the technical field of topology design of key equipment in a DC system, and in particular, to a mechanical high-voltage DC circuit breaker device and an opening method thereof.

Background technique

Flexible DC transmission technology is an effective means to solve large-capacity, long-distance transmission and achieve modern power transmission. Because of its advantages of flexible and independent adjustment of active and reactive power, flexible DC transmission technology is widely used in large-scale renewable energy transmission. However, the flexible DC transmission technology itself cannot handle DC-side line failures. After the DC-side fault occurs, the fault current in the converter station increases sharply, which may cause electrical breakdown or thermal breakdown to the equipment in the converter station, such as power electronic equipment. Therefore, the use of a DC circuit breaker to break the DC side fault has an important role in the further development of flexible DC transmission technology.

DC circuit breakers can be divided into mechanical DC circuit breakers, hybrid DC circuit breakers, and solid state DC circuit breakers. Among them, since the mechanical DC circuit breaker does not contain power electronic devices, compared with the hybrid DC circuit breaker and the solid state DC circuit breaker, it has the advantages of low cost and small on-state loss. Further, mechanical DC circuit breakers can be divided into passive mechanical DC circuit breakers and active mechanical DC circuit breakers. Among them, since the active mechanical DC circuit breaker has the advantage of shorter opening time than the passive mechanical DC circuit breaker, the active mechanical DC circuit breaker has a good application prospect.

Active mechanical DC circuit breaker is generally composed of four parts: residual current circuit breaker, main branch, transfer branch and absorption branch. The main breaking principle is: when opening, the transfer branch generates an oscillating current in the direction opposite to the fault current of the main branch. The fault current is gradually transferred from the main branch to the transfer branch first. When the oscillation capacitance of the transfer branch is After the discharge is over, the fault current reversely charges the oscillating capacitor. When the reverse charging voltage reaches the operating voltage of the arrester on the absorption branch, the fault current is transferred from the transfer branch to the absorption branch for energy absorption and discharge. The circuit breaker breaks and absorbs the residual current in the branch circuit to complete the DC interruption. However, the existing active mechanical DC circuit breakers have the following disadvantages: (1) the DC side fault cannot be continuously opened in a short time; (2) the failure to effectively use the fault current to react to the oscillating capacitance on the transfer branch To charge voltage.

Summary of the Invention

In view of this, the present invention provides a mechanical high-voltage DC circuit breaker device with continuous self-charging and continuous breaking capabilities.

The object of the present invention is achieved by the following technical solutions:

A mechanical high-voltage DC circuit breaker device including

The main branch is used to bear the overvoltage across the DC circuit breaker when the normal working current and the fault current of the DC line are broken, and to achieve bidirectional conduction of the DC line current;

The transfer branch is used to generate an oscillating current in the direction opposite to the main branch current, and the reverse oscillating current is superimposed on the main branch to force the fault current on the main branch to zero, thereby realizing the fault current from the main branch. Transfer to transfer branch;

Absorption branch, used to absorb and release the energy accumulated when the fault is opened;

The residual current interrupting element is connected in series with the main branch to interrupt the residual current.

Further, the main branch includes a series current transformer and a mechanical switch.

Further, the transfer branch is connected in parallel with the main branch, and the transfer branch includes a spark gap switch bridge and an oscillation inductor connected in series.

Further, a stray resistance is also connected in series on the transfer branch.

Further, the spark gap switch bridge includes a bridge structure composed of a spark gap switch S ₁ , a spark gap switch S ₂ , a spark gap switch S ₃ , and a spark gap switch S ₄ in series, and the anode of the oscillation capacitor is connected to the spark gap. Between the switch S ₃ and the spark gap switch S ₄ , the negative electrode of the oscillating capacitor is connected between the spark gap switch S ₁ and the spark gap switch S ₂ .

Further, the absorption branch is connected in parallel with the main branch, and the absorption branch includes at least two groups of lightning arresters connected in series.

Further, it further includes a control system, and the current transformer of the main branch sends the collected current signal to the control system, and the control system controls the mechanical switch and the spark gap switch to be turned on or off according to the current signal.

Further, the control system includes

The fault detection unit compares the current flowing through the mechanical switch collected by the current transformer with the fault current threshold. If the collected current is greater than or equal to the fault current threshold, it is judged as a DC side fault. If the collected current is less than the fault current threshold, it is judged as a system. normal operation;

The mechanical switch control unit receives the fault judgment signal from the fault detection unit. If the fault judgment signal is a DC-side fault, the mechanical switch is controlled to be turned off. If the fault judgment signal is no DC-side fault, the mechanical switch is controlled to remain on. ;

Delay unit, which delays for a preset time after the mechanical switch is turned off;

The first triggering spark gap conducting unit is used to trigger the spark gaps S ₁ and S _{3 to be} turned on after the delay unit delays for a preset time during the first fault opening process; and

The second trigger spark gap conduction unit is used to trigger the spark gap S ₂ and S _{4 to be} turned on after the delay unit delays for a preset time during the second fault opening process.

Further, the preset time is 2 milliseconds.

The invention also discloses a method for opening and closing a mechanical high-voltage DC circuit breaker, which includes the following steps:

1) On-line monitoring of the current flowing through the mechanical switch. If the current is greater than the fault monitoring threshold current, it is judged as a fault;

2) Disconnect mechanical switch;

3) Delay 2 milliseconds after the trigger mechanical switch is turned off. The first trigger spark gap conducting unit triggers a pair of spark gap switches S ₁ and S _{3 to be} turned on;

4) The pre-charged oscillating capacitor is connected to the transfer branch through the turned-on spark gap switches S ₁ and S ₃ to generate an oscillating current in the direction opposite to the fault current flowing through the mechanical switch;

5) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch is completely opened, the fault current reversely charges the oscillating capacitor, and the oscillating capacitor is automatically charged with a reverse voltage;

6) When the voltage across the oscillating capacitor reaches the arrester operating voltage, the arrester operates and energy is released from the arrester;

7) The residual current circuit breaker opens the residual current in the arrester to complete the first fault interruption;

8) After a period of time when the fault is removed, the circuit breaker is reclosed. If the recloser is a permanent fault, the fault detection unit judges it as a fault;

9) Disconnect mechanical switch;

10) Delay 2 milliseconds after the triggering of the mechanical switch is broken, and the second triggering spark gap conducting unit triggers a pair of spark gap switches S ₂ and S _{4 to be} turned on;

11) The pre-charged oscillating capacitor is connected to the transfer branch through the conducting spark gap switches S ₂ and S ₄ , and generates an oscillating current in the direction opposite to the fault current flowing through the mechanical switch;

12) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch is completely opened, the fault current reversely charges the oscillating capacitor, and the reverse voltage is automatically charged to the oscillating capacitor;

13) When the voltage across the oscillating capacitor reaches the surge arrester operating voltage, the surge arrester operates and energy is released from the surge arrester;

14) The residual current circuit breaker interrupts the residual current in the arrester to complete the second fault interruption.

Since the above technical solution is adopted, the present invention has the following advantages:

The invention adopts a method in which a pre-charged oscillating capacitor is connected to a transfer branch by a spark gap switch bridge. By triggering different groups of spark gap switches during different fault opening and closing processes, the fault current is effectively used to oscillate the capacitor on the transfer branch. The reverse charging voltage is used as the pre-charging voltage of the second oscillation capacitor, which can continuously switch off the DC side fault in a short time. The reverse charging voltage of the oscillating capacitor on the transfer branch is effectively used as the pre-charging voltage of the second oscillating capacitor by the fault current, which can continuously switch off the DC side fault in a short time. The structure is simple and novel, and the cost is saved.

Other advantages, objectives, and characteristics of the present invention will be explained to some extent in the subsequent description, and to a certain extent, it will be apparent to those skilled in the art based on the following research studies, or can be obtained from It is taught in the practice of the invention. The objects and other advantages of the present invention can be achieved and obtained by the following description. .

BRIEF DESCRIPTION OF THE DRAWINGS

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the following further describes the present invention in detail with reference to the accompanying drawings:

1 is a structural diagram of a mechanical high-voltage DC circuit breaker device according to the present invention;

FIG. 2 is a capacitor voltage waveform diagram of two fault interruptions;

FIG. 3 is a fault current waveform diagram of two fault interruptions.

Detailed ways

The following describes the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Referring to FIG. 1, the mechanical high-voltage DC circuit breaker device of this embodiment includes

The main branch 1, which includes a series current transformer TA and a mechanical switch K, is used to bear the over-voltage across the DC circuit breaker when the DC line is under normal working current and open fault current, and to achieve bidirectional conduction of DC line current;

The transfer branch 2 is connected in parallel with the main branch. The transfer branch includes a spark gap switch bridge, an oscillation inductance L, and a stray resistance R connected in series. It is used to generate an oscillating current in the opposite direction of the main branch current, and superimpose the reverse oscillating current on the main branch to force the fault current on the main branch to zero, thereby realizing the transfer of the fault current from the main branch to the transfer branch. The spark gap switch bridge includes a bridge structure composed of a spark gap switch S ₁ , a spark gap switch S ₂ , a spark gap switch S ₃ , and a spark gap switch S ₄ connected in series, and the anode of the oscillation capacitor C is connected to the spark. Between the gap switch S ₃ and the spark gap switch S ₄ , the negative electrode of the oscillation capacitor C is connected between the spark gap switch S ₁ and the spark gap switch S ₂ .

Absorption branch 3 is connected in parallel with the main branch. The absorption branch includes at least two groups of arresters F connected in series, which are used to absorb and release the energy accumulated when the fault is opened;

The residual current interrupting element K1 is connected in series with the main branch and is used for interrupting the residual current in the absorbing branch arrester.

The control system (not shown in the figure), the current transformer TA of the main branch sends the collected current signal to the control system, and the control system controls the mechanical switch K and the spark gap switch to be turned on or off according to the current signal. The control system includes:

The fault detection unit compares the current flowing through the mechanical switch K collected by the current transformer with the fault current threshold. If the collected current is greater than or equal to the fault current threshold, it is judged to be a DC-side fault. The system is running normally;

The control unit of the mechanical switch K receives the fault judgment signal from the fault detection unit. If the fault judgment signal is a DC-side fault, the mechanical switch K is turned off. If the fault judgment signal is no DC-side fault, the mechanical switch K is maintained. On state

Delay unit, delay 2 milliseconds after mechanical switch K is turned off;

The first triggering spark gap conducting unit is used to trigger the spark gaps S ₁ and S _{3 to be} turned on after a delay of 2 milliseconds in the delay unit; and

The second trigger spark gap conduction unit is used for triggering the spark gap S ₂ and S _{4 to} switch on after the delay unit is delayed by 2 milliseconds during the second fault opening and closing process.

1) Online monitoring the current flowing through the mechanical switch K. If the current is greater than the fault monitoring threshold current, it is judged as a fault;

2) Disconnect mechanical switch K;

3) After the mechanical switch K is triggered, the delay is 2 milliseconds. The first trigger spark gap conducting unit triggers a pair of spark gap switches S ₁ and S _{3 to be} turned on;

4) The pre-charged oscillating capacitor C is connected to the transfer branch through the turned-on spark gap switches S ₁ and S ₃ and generates an oscillating current in the direction opposite to the fault current flowing through the mechanical switch K;

5) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch K is completely opened, the fault current reversely charges the oscillating capacitor C, and the oscillating capacitor C is automatically charged with a reverse voltage;

6) When the voltage across the oscillating capacitor C reaches the operating voltage of the arrester F, the arrester F operates and energy is discharged from the arrester F;

7) The residual current circuit breaker opens the residual current in the arrester F to complete the first fault interruption;

9) Disconnect mechanical switch K;

10) After the mechanical switch K is triggered, the delay is 2 milliseconds. The second trigger spark gap conduction unit triggers a pair of spark gap switches S ₂ and S _{4 to be} turned on.

11) The pre-charged oscillating capacitor C is connected to the transfer branch through the turned-on spark gap switches S ₂ and S ₄ to generate an oscillating current in the direction opposite to the fault current flowing through the mechanical switch K;

12) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch K is completely opened, the fault current reversely charges the oscillating capacitor C, and the oscillating capacitor C is automatically charged with a reverse voltage;

13) When the voltage across the oscillating capacitor C reaches the operating voltage of the arrester F, the arrester F operates and energy is discharged from the arrester F;

14) The residual current circuit breaker opens the residual current in the arrester F, and completes the second fault opening.

Use the mechanical high-voltage DC circuit breaker device of this embodiment and its breaking method in a double-end flexible DC power transmission system with a DC voltage level of ± 200kV. The rated DC current is 1kA. At t = 0s, exit at the unilateral converter station. A metal-to-electrode short circuit occurred at the site and was a permanent fault. The time to remove the line fault was 140 milliseconds. At t = 150ms, the DC circuit breaker was reclosed. The stray resistance R = 0.01Ω of the transfer branch of the circuit breaker was set. = 10μF, oscillation inductance L = 200μH, first pre-charge voltage VC1 = 100kV of the oscillation capacitor, PSCAD simulation results are shown in Figures 2 and 3 below. Figure 2 is a capacitor voltage waveform diagram of two fault interruptions, and Figure 3 is a fault current waveform diagram of two fault interruptions. It can be seen in the figure that the mechanical high-voltage DC circuit breaker device and the breaking method provided by the present invention with continuous self-charging and continuous breaking capacity can effectively use the fault current to reversely charge the oscillating capacitor on the transfer branch. The voltage is used as the precharge voltage of the second oscillation capacitor, which can achieve two consecutive fault interruptions in a short reclosing time.

Finally, it is explained that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Although the present invention is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention Modifications or equivalent replacements without departing from the spirit and scope of the technical solution should be covered by the protection scope of the present invention.

Claims

A mechanical high-voltage DC circuit breaker device, comprising:

The main branch is used to bear the overvoltage across the DC circuit breaker when the normal working current and the fault current of the DC line are broken, and to achieve bidirectional conduction of the DC line current;

The transfer branch is used to generate an oscillating current in the direction opposite to the main branch current, and the reverse oscillating current is superimposed on the main branch to force the fault current on the main branch to zero, thereby realizing the fault current from the main branch. Transfer to transfer branch;

Absorption branch, used to absorb and release the energy accumulated when the fault is opened;

The residual current interrupting element is connected in series with the main branch to interrupt the residual current. .
The mechanical high-voltage DC circuit breaker device according to claim 1, wherein the main branch comprises a series current transformer and a mechanical switch.
The mechanical high-voltage DC circuit breaker device according to claim 2, wherein the transfer branch is connected in parallel with the main branch, and the transfer branch includes a series-connected spark gap switch bridge and an oscillation inductor.
The mechanical high-voltage DC circuit breaker device according to claim 3, wherein a stray resistance is further connected in series on the transfer branch.
A mechanical high-voltage DC circuit breaker apparatus according to claim 3, characterized in that the switching bridge comprises a spark gap spark gap switches S 1, spark gap switches S 2, spark gap switches S 3, spark gap switches S 4 is a bridge structure in series. The anode of the oscillation capacitor is connected between the spark gap switch S 3 and the spark gap switch S 4. The anode of the oscillation capacitor is connected between the spark gap switch S 1 and the spark gap switch S 2 . .
The mechanical high-voltage DC circuit breaker device according to claim 5, wherein the absorption branch is connected in parallel with the main branch, and the absorption branch includes at least two groups of lightning arresters connected in series.
The mechanical high-voltage DC circuit breaker device according to any one of claims 2 to 6, further comprising a control system, and the current transformer of the main branch sends the collected current signal to the control system to control The system controls the mechanical switch and spark gap switch to be turned on or off according to the current signal.
The mechanical high-voltage DC circuit breaker device according to claim 7, wherein the control system comprises

The fault detection unit compares the current flowing through the mechanical switch collected by the current transformer with the fault current threshold. If the collected current is greater than or equal to the fault current threshold, it is judged as a DC side fault. If the collected current is less than the fault current threshold, it is judged as a system. normal operation;

The mechanical switch control unit receives the fault judgment signal from the fault detection unit. If the fault judgment signal is a DC-side fault, the mechanical switch is controlled to be turned off. If the fault judgment signal is no DC-side fault, the mechanical switch is controlled to remain on. ;

Delay unit, which delays for a preset time after the mechanical switch is turned off;

The first triggering spark gap conducting unit is used to trigger the spark gaps S 1 and S 3 to be turned on after the delay unit delays for a preset time during the first fault opening process; and

The second trigger spark gap conduction unit is used to trigger the spark gap S 2 and S 4 to be turned on after the delay unit delays for a preset time during the second fault opening process.
The mechanical high-voltage DC circuit breaker device according to claim 8, wherein the preset time is 2 milliseconds.
A method for opening a mechanical high-voltage DC circuit breaker according to any one of claims 1-9, comprising the following steps:

1) On-line monitoring of the current flowing through the mechanical switch. If the current is greater than the fault monitoring threshold current, it is judged as a fault;

2) Disconnect mechanical switch;

3) Delay 2 milliseconds after the trigger mechanical switch is turned off. The first trigger spark gap conducting unit triggers a pair of spark gap switches S 1 and S 3 to be turned on;

4) The pre-charged oscillating capacitor is connected to the transfer branch through the turned-on spark gap switches S 1 and S 3 to generate an oscillating current in the direction opposite to the fault current flowing through the mechanical switch;

5) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch is completely opened, the fault current reversely charges the oscillating capacitor, and the oscillating capacitor is automatically charged with a reverse voltage;

6) When the voltage across the oscillating capacitor reaches the arrester operating voltage, the arrester operates and energy is released from the arrester;

7) The residual current circuit breaker opens the residual current in the arrester to complete the first fault interruption;

8) After a period of time when the fault is removed, the circuit breaker is reclosed. If the recloser is a permanent fault, the fault detection unit judges it as a fault;

9) Disconnect mechanical switch;

10) Delay 2 milliseconds after the triggering of the mechanical switch is broken, and the second triggering spark gap conducting unit triggers a pair of spark gap switches S 2 and S 4 to be turned on;

11) The pre-charged oscillating capacitor is connected to the transfer branch through the conducting spark gap switches S 2 and S 4 , and generates an oscillating current in the direction opposite to the fault current flowing through the mechanical switch;

12) When the amplitude of the oscillating current is equal to the fault current, the mechanical switch is completely opened, the fault current reversely charges the oscillating capacitor, and the reverse voltage is automatically charged to the oscillating capacitor;

13) When the voltage across the oscillating capacitor reaches the surge arrester operating voltage, the surge arrester operates and energy is released from the surge arrester;

14) The residual current circuit breaker interrupts the residual current in the arrester to complete the second fault interruption.