WO2014117608A1

WO2014117608A1 - Apparatus for breaking current of circuit and control method thereof

Info

Publication number: WO2014117608A1
Application number: PCT/CN2013/090484
Authority: WO
Inventors: 方太勋; 曹冬明; 王宇; 杨浩; 杨兵; 石巍; 吕玮
Original assignee: 南京南瑞继保电气有限公司; 南京南瑞继保工程技术有限公司
Priority date: 2013-01-31
Filing date: 2013-12-26
Publication date: 2014-08-07
Also published as: CN103971965A; CN103971965B

Abstract

An apparatus (20) for breaking a current of a circuit (44) and a control method thereof. The apparatus (20) for breaking a current of a circuit (44) comprises a unidirectional direct current breaker (10) and a bridge branch circuit. The bridge branch circuit comprises two bridge arms formed by four identical commutating branch circuits (A, B, C, D), two groups comprising two commutating branch circuits each in the four commutating branch circuits are connected in series in the same direction, two formed bridge arms are connected in parallel, and each commutating branch circuit comprises a same-direction serial connection of at least one first power semiconductor device (7). Two bridge arms of the bridge branch circuit are both connected in parallel to the unidirectional direct current breaker (10), and two ends of the circuit (44) are separately connected to bridge arm middle points (3,4) of the two bridge arms. On the premise of enough high breaking speed and low loss, the apparatus (20) for breaking a current of a circuit (44) can greatly reduce the cost of the apparatus, and reduce the layout, mounting and wiring difficult of the apparatus and the device.

Description

Device for breaking line current and control method thereof

Technical field

The present invention relates to a device for breaking a current flowing through a line, and a method of controlling the device. Background technique

In multi-terminal DC transmission systems, high-voltage DC circuit breakers are one of the most important devices. Due to the high voltage level and low line impedance, the multi-terminal HVDC transmission system will soon affect the DC transmission network and the AC network, and the fault must be quickly removed. Therefore, the high-voltage DC circuit breaker needs to have a fast moving speed, which can minimize the duration of the fault or suppress the fault current, and reduce the impact of the fault on the AC/DC transmission network. Since the high-voltage DC circuit breaker is connected in series to the transmission line, the direction of the power flow in the transmission line is uncertain, and the current may exist in two directions. Therefore, the circuit breaker is required to be able to separate the direct current in both directions.

Chinese patent application CN 102780200 A uses a conventional high-voltage DC circuit breaker to break the DC current. The structure of the conventional high-voltage DC circuit breaker is composed of three parts: an AC circuit breaker, an LC oscillation circuit and an energy consuming component. When the AC circuit breaker is separated, an arc is generated, and the arc voltage resonates with the LC oscillation circuit. When the peak value of the oscillating current reaches the DC current amplitude, the DC current can be completely cancelled, causing the circuit breaker port to have a zero-crossing point, causing the arc to extinguish and achieving the shutdown DC current. the goal of. This type of breaking does not include power semiconductor devices, and has no directionality. Therefore, the current in both directions can be separated, and the loss during normal operation is small. However, the traditional high-voltage DC circuit breaker has a long arc-extinguishing time of about several tens of milliseconds, which cannot meet the requirements of fast isolation of multi-terminal DC transmission system faults.

In order to satisfy the rapid isolation of the DC fault current and maintain a high transmission efficiency, the Chinese patent application CN 102687221 A discloses a device and method for short-circuiting the current of a transmission line or a distribution line, and a current limiting arrangement, including a main breaker, a high-speed switch. , auxiliary circuit breakers and varistor energy consuming components. In normal operation mode, the line current flows through the auxiliary circuit, and the on-state loss is small. In the fault mode, the current is switched to the main breaker, and finally the energy-consuming component absorbs the breaking capacity.

After the high-voltage DC circuit breaker turns off the fault current, the main circuit breaker is subjected to hundreds of kV voltages, and the number of power semiconductor devices connected in series is only several hundred in one current direction. Since the power semiconductor device can only be turned on in one direction, in order to enable the fault current to be turned off in both current directions, the main series circuit of the main circuit breaker in the high voltage DC circuit breaker employs two power semiconductor devices in anti-series or reverse In the parallel structure, the number of power semiconductor devices of the main circuit breaker is doubled. When the first current direction is divided, the power semiconductor device of the second current direction has no beneficial effect on breaking current or withstanding voltage, which is equivalent to the main circuit breaker power semiconductor device. The utilization rate is only 50%. Due to work The cost of semiconductor devices accounts for a large proportion of the total cost of the device, so the cost of the device is greatly increased in order to achieve the breaking function of the bidirectional current. The increase of the power semiconductor device in the second current direction of the main circuit breaker not only does not have a beneficial effect, but the power semiconductor device in the second current direction is adversely affected by the overvoltage and overcurrent generated when the first current direction is turned off. . If the power semiconductor device of the second current direction is connected in reverse parallel connection with the power semiconductor device of the first current direction, the overvoltage when the first current direction is turned off is applied to the power semiconductor device in the second current direction, The voltage is a reverse voltage for the power semiconductor device in the second current direction, causing damage to the device; if the power semiconductor device with the anti-parallel diode of the second current direction and the anti-parallel diode with the first current direction are used The power semiconductor device is connected in reverse series, and a very high abrupt current generated during the first current direction turn-off will flow through the freewheeling diode in the power semiconductor device in the second current direction, which will cause the lifetime of the device. Negative Effects.

The increased power semiconductor device in the second current direction also adversely affects the structural design and electrical design of the main circuit breaker, and the arrangement direction of the power semiconductor devices in the first current direction is uniform, so that the electrical design and the structural design are consistent. Sex. The increase in the power semiconductor device in the second current direction destroys the consistency of the original arrangement direction, resulting in an increase in the difficulty in layout, mounting, and wiring of the device. Summary of the invention

The object of the present invention is to provide a device for breaking a line current and a control method thereof, which can greatly reduce the cost of the device and reduce the layout, installation and wiring of the device under the premise of ensuring a sufficiently fast breaking speed and low loss. Difficulty.

In order to achieve the above object, the solution adopted by the present invention is:

A device for breaking a line current, comprising a unidirectional DC circuit breaker; further comprising a bridge branch, the bridge branch comprising two bridge arms composed of four identical commutation branches, the 4 a pair of commutating branches are connected in series in the same direction, and the two bridge arms formed are further connected in parallel, each of the commutating branches comprising a parallel connection of at least one first power semiconductor device; The two bridge arms of the branch are connected in parallel with the one-way DC circuit breaker, and the two ends of the line are respectively connected to the midpoints of the bridge arms of the two bridge arms of the bridge branch.

Each of the above commutation branches further includes at least one high speed isolating switch, the high speed isolating switch being connected in series in the trunk of the commutating branch.

Each of the first power semiconductor devices in each of the commutating branches is connected in parallel with a third power semiconductor device identical thereto.

Each of the first power semiconductor devices in each of the commutating branches is reversely connected in parallel with a turn-on and turn-off capability Four power semiconductor devices.

Each of the commutating branches includes a fifth power semiconductor device having the same number and type as the first power semiconductor device, and the fifth power semiconductor device is connected in series with the first power semiconductor device in series. Parallel to parallel.

The unidirectional DC circuit breaker includes a main breaker and a non-linear resistor connected in parallel with each other, the main breaker including at least one second power semiconductor device connected in series in the same direction, and opening direction of the second power semiconductor switch The line current is consistent from the midpoint of the bridge arm and flows through any of the commutation branches.

Each of the second power semiconductor devices in the main breaker described above is connected in parallel with a sixth power semiconductor device identical thereto.

The main circuit breaker further includes a seventh power semiconductor device having the same number and type as the second power semiconductor device, wherein the seventh power semiconductor device is connected in series in the same direction, and is connected in parallel with the second power semiconductor device in series. .

The unidirectional DC circuit breaker further includes a branch connected in parallel with the main breaker and the non-linear resistor, and the branch includes a high-speed switch and an auxiliary breaker connected in series with each other, wherein the high-speed switch includes at least one connected in series a high speed isolating switch, the auxiliary circuit breaker comprising at least one eighth power semiconductor device in series in the same direction, and the direction of the eighth power semiconductor device is the same as the direction of the second power semiconductor device.

A control method for a device for breaking a line current, wherein the device is connected in series to a current path of a line at a midpoint of a bridge arm of two bridge arms in a bridge branch; a unidirectional DC circuit breaker in a closing device, a closed bridge a high speed isolation switch in the branch and a first power semiconductor device, the method comprising the steps of:

And if the disconnection signal of the unidirectional DC circuit breaker is received, determining the first power semiconductor device of the cathode connected to the current input terminal directly or indirectly connected to the current input terminal, disconnecting the first a high-speed isolating switch in which the power semiconductor device is located in the commutating branch; a first power semiconductor device defining an anode directly connected to the current output terminal on the bridge arm connected to the current output terminal, disconnecting the first power semiconductor device a high speed disconnecting switch on the commutating branch;

After that, disconnecting the one-way DC circuit breaker;

The high-speed isolating switch in the closed state is disconnected to complete the entire breaking process.

After adopting the above scheme, the invention has the following characteristics:

Compared with the conventional high-voltage DC circuit breaker, the breaking speed of the invention is relatively fast, and the power semiconductor device is used as the breaking current execution unit, and the speed is fast. Generally, the breaking speed of the power semiconductor device takes only several tens of microseconds, which can be neglected. The total breaking time is mainly due to the breaking time of the high-speed isolating switch. At present, the high-speed isolating switch is divided into The breaking speed can reach 1-3ms. It can be predicted that the total breaking time of the invention is about 3-5ms, which is much faster than the breaking speed of the conventional high voltage DC circuit breaker;

The bidirectional current breaking can be realized at a small cost: The unidirectional DC circuit breaker of the present invention can be formed by using a power switching device of the same current direction in series, and the bidirectional current flow in the line is made by the current commutating branch. The unidirectional DC circuit breakers are in the same direction. When the line current is in the first current direction, the current commutation branch (A, D) is in the same direction as the first current, and the power semiconductor device in the current commutation branch (B, C) is opposite to the first current direction, In the reverse cut-off state, the direction of flowing through the unidirectional DC breaker is from node (1) to node (2); when the line current is in the second current direction, the current commutating branch (B, C) and the second current The directions are the same, and the power semiconductor device in the current commutation branch (A, D) is opposite to the second current direction and is in the reverse cut-off state. The direction through which the unidirectional DC breaker is flowing is always from the slave node (1) to the node (2).

It can be seen that when the direction of the line current is different, the direction of current flowing through the unidirectional DC circuit breaker is uniform. The current commutating branch includes a small number of power semiconductor devices and four sets of high-speed isolating switches. The number of power semiconductor devices is small and the cost is very low. The high-speed isolating switches are only separated in the no-current state, no arc extinguishing is required, and only the blocking voltage is used. The role, the cost is lower. The overall cost is greatly reduced compared to the patent CN 102687221 A, which increases the utilization efficiency of the power semiconductor device in the device while avoiding the drawback of the bidirectional function of the patent CN 102687221A. DRAWINGS

Figure 1 is a schematic view showing the connection of the device of the present invention;

2 is a diagram showing a correspondence relationship between a first current direction and a direction of a power semiconductor device;

3 is a diagram showing a correspondence relationship between a second current direction and a direction of a power semiconductor device;

Figure 4 is a connection diagram of a first embodiment of the current commutation branch of the present invention;

Figure 5 is a connection diagram of a second embodiment of the current commutation branch of the present invention;

Figure 6 is a connection diagram of a third embodiment of the current commutation branch of the present invention. detailed description

As shown in FIG. 1, the device 20 for breaking the current of the line 44 comprises a unidirectional DC circuit breaker 10 and a bridge branch connected in parallel with each other. The two junctions are node 1 and node 2, respectively. .

The unidirectional DC circuit breaker 10 includes a main breaker 9 and a varistor 13 connected in parallel with each other, wherein the main breaker 9 includes at least one power semiconductor device 5 connected in series in the same direction, and the direction of the power semiconductor device 5 is The current flowing from node 1 to node 2 is in the same direction; the unidirectional DC breaker 10 further includes a main breaker and the aforementioned main breaker 9. The non-linear resistors 13 are respectively connected in parallel, and the branch includes a high-speed switch 11 and an auxiliary breaker 12 connected in series with each other, wherein the high-speed switch 11 includes at least one high-speed isolating switch connected in series with each other, and the auxiliary breaker 12 includes At least one power semiconductor device connected in series in the same direction, and the direction of the power semiconductor device is the same as the direction of current flowing from the node 1 to the node 2, and the on-resistance of the auxiliary circuit breaker 12 is smaller than that of the main breaker 9.

The bridge branch includes two bridge arms composed of four identical commutating branches eight, B, C, and D. The specific connection relationship is: commutating branch eight, B in the same direction, forming a bridge arm The commutating branches (:, D are connected in series in the same direction to form another bridge arm, and the two bridge arms are connected in parallel; one end of the line 44 is connected to the midpoint 3 of the bridge arm formed by the commutating branches A and B, The other end of the line 44 is connected to the midpoint of the bridge arm formed by the commutating branch (:, D).

Each of the commutation branches includes at least one power semiconductor device 7 connected in series in the same direction. As shown in FIG. 6, such a structure does not require a high-speed isolation switch, but the series connection of the power semiconductor device 7 is required to withstand a high voltage. , requires a large number of devices in series.

The commutating branch may also be connected in series with at least one high speed isolating switch 6, as shown in Fig. 4, the high speed isolating switch 6 functioning as a blocking voltage. After the unidirectional DC circuit breaker 10 is disconnected, a high breaking voltage is generated between the node 1 and the node 2, and the voltage is applied to the bridge branch, and the high-speed isolating switch 6 can withstand a high breaking voltage, making the commutation The power semiconductor device 7 in the branches VIII, B, C, and D can withstand a small breaking voltage, and only a small number of devices are connected in series, which saves device cost.

As shown in Fig. 5, it is a further implementation structure of the commutating branch. On the basis of the structure shown in Fig. 4, each of the power semiconductor devices 7 is connected in reverse parallel with a power semiconductor device 8 having an on-off capability.

It should be noted that the main circuit breaker 9 in the unidirectional DC circuit breaker 10 has the following two connection structures in addition to the parallel connection of the plurality of power semiconductor devices 5: (1) includes an even number of a power semiconductor device, wherein the power semiconductor devices are connected in parallel in the same direction and then connected in the same direction; (2) comprising an even number of power semiconductor devices, each of which is divided into two groups, each of which is connected in the same direction, the two groups Then parallel in the same direction. With the above connection structure, the current carrying capacity of the unidirectional DC circuit breaker 10 can be doubled.

In addition to the aforementioned concentric series, the power semiconductor device 7 in each of the commutating branches may adopt the following two connection structures: (1) including an even number of power semiconductor devices, the power semiconductor devices being the same in two groups Parallel to parallel, then parallel to the same direction; (2) Include an even number of power semiconductor devices, divided into two groups, each group is connected in series in the same direction, and the two groups are paralleled in the same direction. With the above connection structure, the current carrying capacity of the unidirectional DC circuit breaker 10 can be doubled.

The present invention also provides a control method for the foregoing device 20, wherein the device 20 is connected in series to the current path of the line 44, wherein the unidirectional DC circuit breaker 10 in the device 20 is closed, the current commutation branch A, B, C, D The high speed isolating switch 6 (if no control can be omitted, the same below) and the power semiconductor device 7 are closed, the control method comprising the following steps:

If the disconnection signal of the unidirectional DC circuit breaker 10 is received, the current direction of the line 44 is determined, and if it is the first current direction 14, the high speed isolation switch 6 of the commutating branches B, C is simultaneously disconnected;

When the first current direction is 14, as shown in FIG. 2, the commutation branches 8, C will be subjected to the high breaking voltage generated by the unidirectional DC breaker 10, so that the unidirectional DC breaker 10 must be cut before being disconnected. The high-speed isolating switches 6 of the commutating branches 13, C are separated to prevent the power semiconductor device 7 of the above-mentioned branches from being damaged by the high breaking voltage; and the commutating branches A, D and the one-way DC breaker 10 are connected in series , There is a breaking current flowing, but will not withstand high breaking voltage, should be kept closed.

If it is the second current direction 15, simultaneously disconnect the high-speed isolating switch 6 of the commutating branches A, D;

When the second current direction is 15, as shown in FIG. 3, the commutating branches VIII and D will withstand the high breaking voltage generated by the unidirectional DC circuit breaker 10, so that the unidirectional DC circuit breaker 10 must be cut before being cut off. The high-speed isolating switch 6 of the commutating branch VIII and D is separated to prevent the power semiconductor device 7 of the above-mentioned branch from being damaged by the high breaking voltage; and the commutating branches B and C and the unidirectional DC breaker 10 are connected in series , There is a breaking current flowing, but will not withstand high breaking voltage, should be kept closed.

After that, the one-way DC breaker 10 is disconnected.

When it is confirmed that the line current drop is zero, the high-speed isolating switch 6 in the closed state of the commutating branches A, B, C, D is disconnected, and the entire breaking process is completed.

The technical solution of the present invention will be described below in conjunction with specific embodiments.

The design device 20 is capable of breaking the bidirectional current of a ±200kV HVDC transmission line with a current breaking capacity of 2kA. As shown in FIG. 1, the device 20 for breaking the bidirectional current of the line includes a unidirectional DC circuit breaker 10 and a current commutating branch VIII, B, C, D, wherein the unidirectional DC circuit breaker 10 includes a main circuit breaker connected in parallel with each other. 9 and a non-linear resistor 13, wherein the main breaker 9 comprises at least one power semiconductor device 5 in one direction. For the present embodiment, the main circuit breaker 9 should be able to withstand at least a breaking voltage of 400 kV, considering a certain margin, according to the 600 kV design, two IGBTs of 4. 5 kV / l. 6 kA are connected in parallel as a unit device, considering The voltage unevenness that may occur at the time of disconnection requires a certain margin for the withstand voltage design of the device. A total of 200 unit devices are required to be connected in series to form an IGBT valve block, and the total number of components is 400. All IGBTs are arranged in the same direction.

The unidirectional DC circuit breaker 10 further includes a high speed switch 11 and an auxiliary circuit breaker 12 connected in series. The high speed switch 11 includes at least one high speed isolating switch, and the auxiliary circuit breaker 12 has a smaller on-resistance than the main circuit breaker 9, and is in one direction. At least one power semiconductor device is included. For this embodiment, the high speed isolating switch requires a faster break. Speed, the break can withstand 600kV after breaking. The auxiliary circuit breaker 12 selects two IGBTs of 4. 5kV/l. 6kA in parallel as one unit device. A total of three devices are connected in series to form a valve group. A total of six unit devices are required, and the total number of components is 12.

The device 20 further includes current reversing branches A, B, C, D, wherein the commutating branches VIII and B constitute a first bridge arm whose midpoint is connected with the midpoint 3 of the bridge arm, and the commutating branch (:, D A second bridge arm, which is connected to the midpoint 4 of the bridge arm, is formed, and both bridge arms are connected in parallel with the one-way DC breaker 10.

The device 20 requires a total of four commutation branches, the same for each branch. Each branch includes a power semiconductor device 7 and a high speed isolation switch 6.

The power semiconductor device 7 can withstand a small breaking voltage and requires a small number of series connections. The power semiconductor device 7 is selected as a 4. 5kV/1. 6kA diode. A total of three diodes are connected in series and then connected in parallel to form a diode group. Each branch requires six diodes, and four groups of current commutation branches require a total of 24 Diodes. The layout of the diodes is shown in Figures 2 and 3.

The control method includes the following steps:

Normally, the high speed switch 11 and the auxiliary circuit breaker 12 in the device 20 are closed, the high speed disconnecting switch 6 and the power semiconductor device 7 in the commutating branch VIII, B, CD are closed, and the power semiconductor in the main circuit breaker 9 Device 5 is closed, since auxiliary breaker 12 includes only three IGBTs in series, and main breaker 9 includes 200 IGBTs in series, auxiliary breaker 12 has a relatively small on-resistance, and normal line current flows through auxiliary breaker 12. The functions of the commutating branches VIII, B, C, and D are: When the direction of the line current is different, the current flowing through the main breaker 9 is the same. If it is the first current direction 14, the current flows through the branches of the commutating branches A, D and the auxiliary breaker 12, as shown in FIG. 2; if it is the second current direction 15, the current flows through the commutating branch B, The branch where C and auxiliary breaker 12 are located is shown in Figure 3.

If the disconnection signal of the one-way DC breaker 10 is received, the auxiliary breaker 12 is first disconnected, and the current is switched to the main breaker 9;

Judging the current direction of the line 44, if it is the first current direction 14, simultaneously disconnecting the high-speed isolating switch 6 of the commutating branches B, C and the high-speed switch 11 of the auxiliary branch; if it is the second current direction 15, simultaneously switching High-speed isolating switch 6 to branch roads A, D and high-speed switch 11 of auxiliary branch;

After that, the main breaker 9 of the one-way DC breaker 10 is disconnected, and the current is switched to the varistor 13. The high-speed disconnecting switch 6 in the closed state is disconnected to complete the entire breaking process.

The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to be limiting, although those skilled in the art can make various modifications or changes to the present invention with reference to the above embodiments, but the modifications or changes are It is intended to be within the scope of the claims of the invention.

Claims

Claim

1. A device for breaking a line current, comprising a unidirectional DC circuit breaker; characterized in that:

A bridge branch is further included, the bridge branch includes two bridge arms composed of four identical commutating branches, and the four commutating branches are formed in series in the same direction. The two bridge arms are further connected in parallel, and each of the commutating branches includes a parallel connection of at least one first power semiconductor device; the two bridge arms of the bridge branch are all connected in parallel with the one-way DC breaker. And the two ends of the line are respectively connected to the midpoints of the bridge arms of the two bridge arms of the bridge branch.

2. The device for breaking a line current according to claim 1, wherein: each of the commutating branches further comprises at least one high speed isolating switch, wherein the high speed isolating switch is connected in series with the commutating branch In the road.

3. The device for breaking a line current according to claim 1 or 2, wherein: each of the first power semiconductor devices in each of the commutating branches is connected in parallel with a third power semiconductor device identical thereto .

4. The device for breaking a line current according to claim 1 or 2, wherein: each of the first power semiconductor devices in each of the commutating branches is reversely connected in parallel with a turn-on and turn-off capability. Fourth power semiconductor device.

5. The apparatus for breaking a line current according to claim 1 or 2, wherein: each of the commutating branches includes a fifth power semiconductor device having the same number and type as the first power semiconductor device. After the fifth power semiconductor device is connected in series, the first power semiconductor device connected in series is connected in parallel in the same direction.

6. The apparatus for breaking a line current according to claim 1, wherein: the one-way DC circuit breaker includes a main breaker and a non-linear resistor connected in parallel with each other, and the main breaker includes at least one The second power semiconductor device is connected in series in the same direction, and the opening direction of the second power semiconductor switch is consistent with the flow direction of the line current from the midpoint of the bridge arm and flowing through any of the commutation branches.

7. A device for breaking a line current according to claim 6, wherein: each of the second power semiconductor devices in the main circuit breaker is connected in parallel with a sixth power semiconductor device identical thereto.

8. The apparatus for breaking a line current according to claim 6, wherein: said main circuit breaker further comprises a seventh power semiconductor device having the same number and type as said second power semiconductor device, said After the seven power semiconductor devices are connected in series in the same direction, they are connected in parallel in the same direction as the second power semiconductor devices in series.

9. The device for breaking a line current according to any one of claims 6 to 8, wherein: the one-way DC circuit breaker further comprises a parallel connection with the main breaker and the nonlinear resistor. a branch circuit comprising a high speed switch and an auxiliary circuit breaker connected in series with each other, wherein the high speed switch comprises at least one high speed isolating switch connected in series with each other, the auxiliary circuit breaker comprising at least one eighth power semiconductor device connected in series in the same direction, and The direction of the eighth power semiconductor device is the same as the direction of the second power semiconductor device.

10. A control method for a device for breaking a line current according to claim 2, wherein said device is connected in series to a current path of the line at a midpoint of a bridge arm of the two bridge arms in the bridge branch; A unidirectional DC circuit breaker in the closing device, a high speed isolating switch in the closed bridge branch and a first power semiconductor device, the method comprising the steps of:

After that, disconnecting the one-way DC circuit breaker;