DC current interrupter

Abstract

To provide a DC current cut-off device which is applied to a DC power transmission system with multiple poles and can be achieved with a small component structure.SOLUTION: A DC current cut-off device according to an embodiment has a semiconductor breaker, a plurality of first commutation circuits, a plurality of second commutation circuits, a first current switch element, and a second current switch element. The plurality of first commutation circuits supplies a current flowing between a first positive electrode line connected with a first terminal and a second positive electrode line connected with a second terminal in a selective direction. The plurality of second commutation circuits supplies a current flowing between a first negative electrode line connected with a third terminal and a second negative electrode line connected with a fourth terminal in a selective direction. The first current switch element supplies or blocks the current flowing between the first positive electrode line and the second positive electrode line to the semiconductor breaker via the first commutation circuits. The second current switch element supplies or blocks the current flowing between the first negative electrode line and the second negative electrode line to the semiconductor breaker via the second commutation circuits.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a direct current interruption device. [Background technology]

[0002] In recent years, DC transmission systems that transmit DC electricity have been studied and introduced. Compared with conventional AC transmission systems, DC transmission systems can be installed at low cost when applied to long-distance, high-power transmission, and can be constructed as highly efficient systems with little power loss. On the other hand, in DC transmission systems that interconnect multiple power generation terminals, it is difficult to cut off and isolate the part where a grid fault occurs. This is because DC current does not have a point where the current crosses zero (zero point), so the current cannot be easily cut off by mechanical contacts. To solve this problem, DC current interrupters with various configurations have been studied. When an accident occurs in a DC transmission line, a DC current interrupter opens the contacts of a DC current interrupter belonging to the DC transmission line to isolate the faulted line and maintain power transmission through a healthy line.

[0003] One type of DC current interrupter is the hybrid type. A hybrid type DC current interrupter mainly comprises a mechanical contact and a semiconductor circuit breaker. During steady-state power transmission, a hybrid type DC current interrupter passes DC through the mechanical contact. On the other hand, when interrupting a faulty line, a hybrid type DC current interrupter diverts the DC current flowing in the DC transmission line to be interrupted to a semiconductor circuit breaker by some kind of diversion means, and interrupts the DC current using the semiconductor circuit breaker. As a result, a hybrid type DC current interrupter can reduce DC loss during steady-state power transmission, and can quickly interrupt the faulty line when interrupting.

[0004] In recent years, DC transmission systems with multiple poles, for example, positive and negative poles, have been studied and introduced. In DC transmission systems with multiple poles, for example, the ground level is used as a neutral point, and DC currents of different polarities are passed between this neutral point and the DC transmission lines of each pole. As a result, in DC transmission systems with multiple poles, no DC current flows through the neutral point, but DC current flows between each DC transmission line. In other words, DC transmission systems with multiple poles can transmit DC power for two circuits. In DC transmission systems with multiple poles, having a neutral point makes it possible to reduce (here, halve) the withstand voltage required for components connected to the DC transmission lines of each pole.

[0005] However, when a hybrid DC current interrupting device is applied to a DC transmission system having multiple poles, it is necessary to connect the hybrid DC current interrupting device to the DC transmission line of each pole. Therefore, in a DC transmission system having multiple poles, the more poles that transmit DC power, the more hybrid DC current interrupting devices there are, which can lead to a large component size of the DC transmission system. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 035180 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a DC current interrupting device that can be implemented with a small component configuration and that is applicable to a DC power transmission system having multiple poles. [Means for solving the problem]

[0008] A direct current interruption device according to an embodiment includes a semiconductor circuit breaker, a plurality of first commutation circuits, a plurality of second commutation circuits, a first current switching element, and a second current switching element. The plurality of first commutation circuits selectively pass a current between a first positive pole line, which is a direct current transmission line connected to a first terminal, and a second positive pole line, which is a direct current transmission line connected to a second terminal. The plurality of second commutation circuits selectively pass a current between a first negative pole line, which is a direct current transmission line connected to a third terminal, and a second negative pole line, which is a direct current transmission line connected to a fourth terminal. The first current switching element passes or blocks a current flowing between the first positive pole line and the second positive pole line through the first commutation circuit to the semiconductor circuit breaker. A second current switching element allows or blocks a current flowing between the first negative pole line and the second negative pole line via the second commutation circuit to flow through the semiconductor circuit breaker. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of the configuration of a DC power transmission system to which a DC current interruption device according to a first embodiment is applied. [Diagram 2] 1 is a diagram showing an example of the configuration of a direct current interruption device according to a first embodiment; [Diagram 3] 1 is a diagram showing an example of the configuration of a direct current interruption device according to a first specific example. [Figure 4] 1 is a diagram (part 1) for explaining the operation of the direct current interruption device of the first specific example. FIG. [Diagram 5] FIG. 2 is a second diagram for explaining the operation of the direct current interruption device of the first specific example. [Figure 6] FIG. 3 is a diagram (part 3) for explaining the operation of the direct current interruption device of the first specific example. [Figure 7] FIG. 4 is a fourth diagram for explaining the operation of the direct current interruption device of the first specific example. [Figure 8] FIG. 13 is a diagram showing an example of the configuration of a direct current interruption device according to a second specific example. [Figure 9] FIG. 13 is a diagram showing an example of another configuration of the commutation circuit. [Figure 10]FIG. 13 is a diagram showing an example of the configuration of a direct current interruption device according to a third specific example. [Figure 11] FIG. 13 is a diagram showing an example of the configuration of a direct current interruption device according to a fourth specific example. [Figure 12] FIG. 13 is a diagram showing an example of the configuration of a DC power transmission system to which a DC current interruption device according to a second embodiment is applied. [Figure 13] FIG. 6 is a diagram showing an example of the configuration of a direct current interruption device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a direct current interruption device according to an embodiment will be described with reference to the drawings.

[0011] (First embodiment) [DC transmission system configuration] FIG. 1 is a diagram showing an example of a configuration of a DC power transmission system to which a direct current circuit breaker (DCCB) according to a first embodiment is applied. FIG. 1 shows an example of a DC power transmission system 1 having a configuration in which a bipolar DC power transmission line connects between the transmission and reception ends of a plurality of (three in FIG. 1) AC systems that transmit power to each other. The DC power transmission system 1 is, for example, a DC power transmission system that transmits DC currents having a plurality of different polarities, i.e., positive and negative poles based on a neutral point, with a ground level as a neutral point, that is, a DC power transmission system that transmits DC power for two lines. The positive pole in the DC power transmission system 1 is a polarity that represents the potential of the neutral point as a low potential side and the potential of the DC power transmission line as a high potential side. The negative pole in the DC power transmission system 1 is a polarity that represents the potential of the neutral point as a high potential side and the potential of the DC power transmission line as a low potential side. In the DC transmission system 1, in the transmission of DC current, no DC current flows through the neutral point, and a DC current corresponding to the potential difference between the potential of the positive DC transmission line and the potential of the negative DC transmission line is transmitted. Therefore, in the DC transmission system 1, the withstand voltage required for each component to transmit DC current is the withstand voltage required to pass DC current through the corresponding one of the poles, and can be kept lower than that of a DC transmission system that does not have a neutral ground point and passes DC current corresponding to the potential difference between two DC transmission lines. More specifically, in the DC transmission system 1, the withstand voltage is half that of a DC transmission system that does not have a neutral ground point and passes DC current corresponding to the potential difference between two DC transmission lines.

[0012] The DC power transmission system 1 includes, for example, three AC systems AC (AC systems AC-1 to AC-3), six power converters 10 (power converters 10-P-1 to 10-P-3, 10-N-1 to 10-N-3), and three DC current interruption devices 20 (DC current interruption devices 20-1 to 20-3). In FIG. 1, a "- (hyphen)" and a letter are added to the end of the reference numeral of each component to indicate the polarity of the DC power (DC current) to which each component corresponds. More specifically, a component with "-P" attached corresponds to a DC current on the positive pole side, and a component with "-N" attached corresponds to a DC current on the negative pole side. Furthermore, in FIG. 1, a "- (hyphen)" and a number are added to the end of the reference numeral of each component to indicate the correspondence between each component. In the DC power transmission system 1, for example, each of the power converters 10-P-1 to 10-P-3 corresponds to a positive DC current, and each of the power converters 10-N-1 to 10-N-3 corresponds to a negative DC current. In the DC power transmission system 1, for example, the power converters 10-P-1 and 10-N-1, and the DC current interrupting device 20-1 correspond to the AC system AC-1. Similarly, in the DC power transmission system 1, for example, the power converters 10-P-2 and 10-N-2, and the DC current interrupting device 20-2 correspond to the AC system AC-2, and the power converters 10-P-3 and 10-N-3, and the DC current interrupting device 20-3 correspond to the AC system AC-3. In the following description, when there is no need to distinguish the polarity of the DC power (DC current) to which each component corresponds or the corresponding relationship between each component, the hyphen and the letters or numbers attached to the symbol of each component will be omitted.

[0013] Corresponding components are arranged (installed) adjacent to each other in the DC power transmission system 1. In the DC power transmission system 1, power is transmitted and received between AC systems AC-1, AC-2, and AC-3.

[0014] Each of the AC systems AC is a power transmission facility that transmits AC power. The AC systems AC transmit the received AC power to consumers connected to the AC systems AC. The AC systems AC may be power generation facilities.

[0015] Each of the power converters 10 is a type of AC / DC converter that converts AC power (AC current) input to the AC side into DC power (DC current) and outputs it to the DC side, or converts DC power (DC current) input to the DC side into AC power (AC current) and outputs it to the AC side. Each of the power converters 10-1 to 10-3 is, for example, an AC / DC converter. The power converter 10 converts, for example, a three-phase AC current output from the AC system AC into a positive-side DC current or a negative-side DC current and outputs it to the DC current interrupter 20 side. The power converter 10 converts, for example, a positive-side DC current or a negative-side DC current supplied from the DC current interrupter 20 side into a three-phase AC current and outputs it to the AC system AC side. The power converter 10 is, for example, a modular multilevel converter (MMC) in which arms are configured using half-bridge circuits made up of semiconductor switch units each including a semiconductor switching element and a diode connected in parallel to each other.

[0016] Each of the DC current interrupting devices 20 is connected to a DC transmission line LN that transmits a DC current output by the power converter 10. In the DC power transmission system 1 shown in Fig. 1, each of the power converters 10 is connected to each other by the corresponding DC transmission lines LN via DC current interrupting devices 20-1 to 20-3. More specifically, in the DC power transmission system 1, the DC current interrupting devices 20-1 and 20-2 are connected to each other by a positive side DC transmission line LN-P-1 and a negative side DC transmission line LN-N-1. Similarly, in the DC transmission system 1, each of the power converters 10 is connected by a positive side DC transmission line LN-P-2 and a negative side DC transmission line LN-N-2 via a DC current interrupting device 20-2 and a DC current interrupting device 20-3, and is connected by a positive side DC transmission line LN-P-3 and a negative side DC transmission line LN-N-3 via a DC current interrupting device 20-1 and a DC current interrupting device 20-3. Thus, in the DC transmission system 1, each of the power converters 10 transmits DC current to each other via the DC transmission lines LN that are connected to each other via the DC current interrupting device 20-1, the DC current interrupting device 20-2, and the DC current interrupting device 20-3. The DC transmission line LN-P-1 is an example of a "first positive pole line," the DC transmission line LN-P-3 is an example of a "second positive pole line," the DC transmission line LN-N-1 is an example of a "first negative pole line," and the DC transmission line LN-N-3 is an example of a "second negative pole line."

[0017] When an accident occurs in any of the connected DC transmission lines LN, each DC current interrupting device 20 electrically interrupts a connection point (connection terminal) with the DC transmission line LN (fault line) where a system accident (hereinafter simply referred to as "fault") has occurred, in response to an instruction from, for example, a higher-level control device (not shown) in the DC transmission system 1 or a control device (not shown) of the DC current interrupting device 20. As a result, in the DC transmission system 1, the fault line is disconnected and power transmission through a healthy line is maintained.

[0018] An upper-level control device (not shown) and an unillustrated control device of the DC current interrupting device 20 (hereinafter, each control device will be referred to as an "upper-level control device" without distinguishing between them) control the respective components of the DC current interrupting device 20 to control interruption and conduction of the DC transmission line LN in the DC current interrupting device 20. The upper-level control device realizes the following functions by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of the functions of the upper-level control device may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by cooperation between software and hardware. Some or all of the functions of the upper-level control device may be realized by a dedicated LSI. The program may be stored in advance in a storage device (a storage device with a non-transient storage medium) such as an HDD (Hard Disk Drive) or flash memory equipped in the upper-level control device, or may be stored in a removable storage medium (a non-transient storage medium) such as a DVD or CD-ROM, and installed in the storage device equipped in the upper-level control device by inserting the storage medium into a drive device equipped in the upper-level control device.

[0019] [Configuration of DC current interrupter] Next, an example of the configuration of the DC current interrupting device 20 will be described. FIG. 2 is a diagram showing an example of the configuration of the DC current interrupting device 20 of the first embodiment. FIG. 2 shows an example of the DC current interrupting device 20 configured at the node portion of the corresponding DC transmission line LN. The DC current interrupting device 20 shown in FIG. 2 is, for example, an example of a DC current interrupting device 20-1. In the DC current interrupting device 20, for example, a transmission line of a positive pole side DC current converted and output by the power converter 10 (which is also the DC transmission line LN) is connected to a terminal b1 on the power converter 10 side, and a positive pole side DC transmission line LN-P is connected to a terminal a1 or a2 on the other DC current interrupting device 20 side. In the DC current interrupting device 20, for example, a negative-side DC transmission line (which is also the DC transmission line LN) converted and output by the power converter 10 is connected to terminal b2 on the power converter 10 side, and the negative-side DC transmission line LN-N is connected to terminal a3 or terminal a4 on the other DC current interrupting device 20 side. Terminal a1 is an example of a "first terminal", terminal a2 is an example of a "second terminal", terminal a3 is an example of a "third terminal", and terminal a4 is an example of a "fourth terminal".

[0020] The DC current interrupting device 20 includes, for example, a plurality of commutation circuits 201 (commutation circuits 201-1 to 201-8), a plurality of current switching elements 202 (current switching elements 202-1 to 202-4), and one semiconductor circuit breaker 203. The DC current interrupting device 20 is configured such that the semiconductor circuit breaker 203, which is a component used to interrupt the connected positive-side DC transmission line LN-P and negative-side DC transmission line LN-N, is shared by all DC transmission lines LN. With this configuration, the DC current interrupting device 20 can reduce the size (component scale) of the DC current interrupting device 20 and further the DC transmission system 1, compared to a configuration in which a plurality of semiconductor circuit breakers 203 are provided for each DC transmission line LN.

[0021] Each of the commutation circuits 201 switches (commutes) the direction or magnitude of a DC current flowing between the DC transmission lines LN connected to both ends or through the current switching element 202. The commutation circuits 201 include, as components (hereinafter referred to as "commutation elements"), a semiconductor switch unit in which a semiconductor switching element and a diode are connected in parallel to each other. The on and off states of the semiconductor switch unit included in the commutation circuits 201 are controlled, for example, by a higher-level control device (not shown) in the DC power transmission system 1. In other words, the commutation circuits 201 commutate the DC current flowing between the DC transmission lines LN connected to both ends or through the current switching element 202 in response to the control of the higher-level control device to turn the semiconductor switch unit on or off.

[0022] The commutation circuit 201-1 is connected in series between the terminal a1 and the current switching element 202-1, and commutates the positive DC current flowing between the terminal a1 and the current switching element 202-1 in response to control by a higher-level control device (not shown). The commutation circuit 201-2 is connected in series between the terminal a1 and the current switching element 202-2, and commutates the positive DC current flowing between the terminal a1 and the current switching element 202-2 in response to control by the higher-level control device. The commutation circuit 201-3 is connected in series between the terminal a2 and the current switching element 202-1, and commutates the positive DC current flowing between the terminal a2 and the current switching element 202-1 in response to control by the higher-level control device. The commutation circuit 201-4 is connected in series between the terminal a2 and the current switching element 202-2, and commutates the positive DC current flowing between the terminal a2 and the current switching element 202-2 in response to control by the higher-level control device. The commutation circuit 201-5 is connected in series between the terminal a3 and the current switching element 202-3, and commutates the negative DC current flowing between the terminal a3 and the current switching element 202-3 in response to the control by the upper control device. The commutation circuit 201-6 is connected in series between the terminal a3 and the current switching element 202-4, and commutates the negative DC current flowing between the terminal a3 and the current switching element 202-4 in response to the control by the upper control device. The commutation circuit 201-7 is connected in series between the terminal a4 and the current switching element 202-3, and commutates the negative DC current flowing between the terminal a4 and the current switching element 202-3 in response to the control by the upper control device. The commutation circuit 201-8 is connected in series between the terminal a4 and the current switching element 202-4, and commutates the negative DC current flowing between the terminal a4 and the current switching element 202-4 in response to the control by the upper control device. The commutation circuit 201-1, the commutation circuit 201-2, the commutation circuit 201-3, and the commutation circuit 201-4 are examples of a "first commutation circuit," and the commutation circuit 201-5, the commutation circuit 201-6, the commutation circuit 201-7, and the commutation circuit 201-8 are examples of a "second commutation circuit."

[0023] Each of the current switching elements 202 allows (restricts the direction in which the DC current flows) or blocks the DC current flowing between the DC transmission lines LN connected to both ends. The open and closed states of the current switching elements 202 are controlled, for example, by a higher-level control device (not shown) in the DC power transmission system 1. That is, the current switching elements 202 allow (restricts the direction in which the DC current flows) or block the flow of the DC current between the DC transmission lines LN connected to both ends, depending on the control by the higher-level control device to either the open state or the closed state.

[0024] Current switching element 202-1 is connected in series between commutation circuit 201-1 and commutation circuit 201-3 and current switching element 202-3 and semiconductor circuit breaker 203, and allows positive DC current to flow from commutation circuit 201-1 and commutation circuit 201-3 to semiconductor circuit breaker 203, and prevents current from flowing from current switching element 202-3 or semiconductor circuit breaker 203 to commutation circuit 201-1 and commutation circuit 201-3, depending on the control by a higher-level control device. Current switching element 202-2 is connected in series between commutation circuit 201-2 and commutation circuit 201-4 and current switching element 202-4 and semiconductor circuit breaker 203, and allows positive DC current to flow from the semiconductor circuit breaker 203 side to the commutation circuit 201-2 and commutation circuit 201-4 side, and prevents current from flowing from the commutation circuit 201-2 and commutation circuit 201-4 side to the semiconductor circuit breaker 203 side or the current switching element 202-4 side, in accordance with the control by the higher-level control device. Current switching element 202-3 is connected in series between commutation circuit 201-5 and commutation circuit 201-7 and current switching element 202-1 and semiconductor circuit breaker 203, and allows negative DC current to flow from commutation circuit 201-5 and commutation circuit 201-7 to semiconductor circuit breaker 203, and prevents current from flowing from current switching element 202-1 or semiconductor circuit breaker 203 to commutation circuit 201-5 and commutation circuit 201-7, depending on the control by the higher-level control device. The current switching element 202-4 is connected in series between the commutation circuit 201-6 and the commutation circuit 201-8 and the current switching element 202-2 and the semiconductor circuit breaker 203, and allows a negative DC current to flow from the semiconductor circuit breaker 203 side to the commutation circuit 201-6 and the commutation circuit 201-8 side, and prevents a current from flowing from the commutation circuit 201-6 and the commutation circuit 201-8 side to the semiconductor circuit breaker 203 side or the current switching element 202-2 side, according to the control by the higher-level control device. The current switching element 202-1 and the commutation circuit 201-2 are an example of a "first current switching element", and the current switching element 202-3 and the commutation circuit 201-4 are an example of a "second current switching element". The current switching element 202-1, the commutation circuit 201-2, the current switching element 202-3, and the commutation circuit 201-4 are an example of a "current switching element".

[0025] The semiconductor circuit breaker 203 allows or blocks (cuts off) a direct current flowing between both ends. FIG. 2 shows a part of the configuration of the semiconductor circuit breaker 203. The semiconductor circuit breaker 203 shown in FIG. 2 has a configuration in which, for example, a series circuit of a plurality of semiconductor switch units (only two semiconductor switch units are shown in FIG. 2) connected in series in the same direction and an arrester are connected in parallel. Each of the semiconductor switch units includes, for example, a semiconductor switching element and a diode connected in parallel to each other. The on and off states of the semiconductor switch units included in the semiconductor circuit breaker 203 are controlled, for example, by a host control device (not shown) in the DC power transmission system 1. That is, the semiconductor circuit breaker 203 allows or blocks (cuts off) a direct current flowing between both ends in response to the control of the semiconductor switch units to either the on or off state by the host control device (not shown). The semiconductor switching element is, for example, a switching element such as an insulated gate bipolar transistor (IGBT). The semiconductor switching element is not limited to an IGBT, and may be any semiconductor switching element capable of realizing self-extinguishing. The arrester consumes (absorbs) surge energy generated due to the energy of the inductance of the connected DC transmission line LN when a plurality of semiconductor switch units included in a series circuit of the semiconductor switch units are controlled to an off state. With this configuration, the semiconductor circuit breaker 203 allows or prevents (cuts off) a DC current flowing between both ends in response to the control of the semiconductor switch units to either an on or off state by the upper control device.

[0026] In DC current interruption device 20, current switching elements 202-1 and 202-3 are connected to the cathodes of diodes constituting a semiconductor switch unit included in semiconductor circuit breaker 203, and current switching elements 202-2 and 202-4 are connected to the anodes of the diodes. Therefore, semiconductor circuit breaker 203 allows DC current flowing from current switching elements 202-1 and 202-3 to current switching elements 202-2 and 202-4 when in the on state, and interrupts it when in the off state.

[0027] [First specific example of a direct current interrupter] Next, a configuration of a first specific example of the DC current interrupting device 20 will be described. FIG. 3 is a diagram showing an example of the configuration of the DC current interrupting device 20 of the first specific example. In the DC current interrupting device 20 of the first specific example shown in FIG. 3, the commutation circuit 201 is configured to include, for example, a parallel circuit 2011 in which a mechanical contact and a bidirectional H-bridge circuit are connected in parallel, and a mechanical contact is connected in series, and the current switching element 202 is a mechanical contact. The bidirectional H-bridge circuit of the parallel circuit 2011 includes four semiconductor switch units and one capacitor connected to each other. The semiconductor switching element of the bidirectional H-bridge circuit is also a switching element such as an insulated gate bipolar transistor (IGBT) like the semiconductor switching element of the semiconductor switch unit of the semiconductor circuit breaker 203. However, the semiconductor switching element of the semiconductor switch unit of the commutation circuit 201 may have a lower withstand voltage than the semiconductor switching element of the semiconductor switch unit of the semiconductor circuit breaker 203. The semiconductor switching element is not limited to an IGBT, and may be any switching element as long as it is a semiconductor switching element capable of realizing self-extinguishing. The parallel circuit 2011 is an example of a "parallel circuit," the mechanical contacts constituting the parallel circuit 2011 are an example of a "first mechanical contact," and the bidirectional H-bridge circuit constituting the parallel circuit 2011 is an example of a "bridge circuit." The semiconductor switch unit included in the bidirectional H-bridge circuit is an example of a "semiconductor switching element," and the capacitor included in the bidirectional H-bridge circuit is an example of a "voltage source."

[0028] [Operation of interrupting DC transmission line LN in DC current interrupting device 20 of first specific example] Here, referring to Figs. 4 to 7, an example of the operation of the DC current interrupter 20 to interrupt the DC transmission line LN-P-1 will be described by taking as an example a case where the DC current interrupter 20 of the first specific example is the DC current interrupter 20-1, and a positive DC current flows from the DC transmission line LN-P-3 connected to the terminal a2 to the DC transmission line LN-P-1 connected to the terminal a1, and an accident occurs in the DC transmission line LN-P-1. At this time, it is assumed that no accident occurs in the path of the negative DC current flowing through the DC transmission line LN-N-1 connected to the terminal a3 and the DC transmission line LN-N-3 connected to the terminal a4. Figs. 4 to 7 show the flow of DC current in the DC current interrupter 20 of the first specific example when the DC current interrupter 20 interrupts the DC transmission line LN-P-1. 4 to 7, the direct currents flowing through terminals b1 and b2, that is, the direct currents flowing on the respective power converter 10 sides of power converter 10-P-1 and power converter 10-N-1, are omitted from illustration.

[0029] In a steady power transmission state (initial state) in DC current interrupting device 20, the mechanical contacts of all commutation circuits 201 are closed, and the mechanical contacts of all current switching elements 202 are open. In this case, in DC current interrupting device 20, as shown in Fig. 4, a positive DC current input to terminal a2 flows through each of positive commutation circuits 201-1 to 201-4 to terminal a1, and a negative DC current input to terminal a3 flows through each of negative commutation circuits 201-5 to 201-8 to terminal a4.

[0030] Here, if an accident occurs on the DC transmission line LN-P-1, an upper control device (not shown) cuts off the DC transmission line LN-P-1 where the accident has occurred by controlling the opening, closing, on, and off of each component of the DC current interruption device 20 in the following procedure.

[0031] (Step 1): First, the upper control device closes the pole of the DC transmission line LN-P-1 where the fault has occurred, that is, the current switching element 202-1 and the current switching element 202-2 on the positive pole side. Then, the upper control device opens the mechanical contacts of the commutation circuits 201-1 and 201-4. That is, the upper control device opens two mechanical contacts, that is, the mechanical contact in the parallel circuit 2011 of the commutation circuits 201-1 and 201-4 and the mechanical contact connected in series to the parallel circuit 2011. Even in this case, in the DC current interruption device 20, as shown in FIG. 5, the DC current on the positive pole side where the fault has occurred flows from the terminal a2 to the terminal a1 through each of the commutation circuits 201-1 to 201-4. This is because simply opening each of the mechanical contacts does not electrically interrupt (cut off) the DC transmission line LN-P-1 due to the arcs generated between the contacts of each of the mechanical contacts. Even in this case, in the DC current interrupting device 20, as shown in Fig. 5, the DC voltage on the negative pole side on the side where no fault has occurred remains unchanged from the normal power transmission state and flows from terminal a3 to terminal a4 through each of the commutation circuits 201-5 to 201-8.

[0032] (Step 2): Next, the upper control device turns on two of the semiconductor switching elements constituting the bidirectional H-bridge circuits in the parallel circuit 2011 provided in the commutation circuits 201-1 and 201-4, thereby canceling the current flowing through the mechanical contacts in the parallel circuit 2011. As a result, in the DC current interrupter 20, the arc generated between the mechanical contacts in the parallel circuit 2011 provided in the commutation circuits 201-1 and 201-4 is extinguished.

[0033] (Step 3): Next, the upper control device turns off each of the semiconductor switching elements constituting the bidirectional H-bridge circuit in the parallel circuit 2011 included in the commutation circuit 201-1 and the commutation circuit 201-4, and turns on each of the semiconductor switching elements included in the semiconductor circuit breaker 203. As a result, in the direct current interrupting device 20, as shown in FIG. 6, the positive direct current input to the terminal a2 flows to the terminal a1 through the commutation circuit 201-3, the current switching element 202-1, the semiconductor circuit breaker 203, the current switching element 202-2, and the commutation circuit 201-2. That is, in the direct current interrupting device 20, the positive direct current input to the terminal a2 is commutated to the semiconductor circuit breaker 203. In other words, in the direct current interrupting device 20, the fault current due to the fault that has occurred is commutated to the semiconductor circuit breaker 203. Even in this case, in DC current interruption device 20, as shown in FIG. 6, the DC voltage on the negative electrode side on the side where no accident has occurred remains unchanged from the steady power transmission state and flows from terminal a3 to terminal a4 through each of commutation circuits 201-5 to 201-8.

[0034] (Step 4): Next, the upper control device turns off each semiconductor switching element included in the semiconductor circuit breaker 203. As a result, in the DC current interrupting device 20, the DC transmission line LN-P-1 where the fault has occurred is interrupted as shown in FIG. 7. That is, in the DC current interrupting device 20, the flow of the positive DC current from the terminal a2 to the terminal a1 to which the DC transmission line LN-P-1 where the fault has occurred is interrupted. Then, the upper control device completes the operation of electrically isolating the DC transmission line LN-P-1 where the fault has occurred. Even in this case, in the DC current interrupting device 20, as shown in FIG. 7, the negative DC voltage on the side where the fault has not occurred remains unchanged from the normal power transmission state and flows from the terminal a3 to the terminal a4 through each of the commutation circuits 201-5 to 201-8. That is, in the DC current interrupting device 20, power transmission on the side where the fault has not occurred is maintained.

[0035] According to such a procedure, in the DC current interrupting device 20, a higher-level control device (not shown) controls opening, closing, on and off of the respective components of the commutation circuit 201 and the current switching element 202 belonging to the pole connected to the DC transmission line LN where the fault has occurred, and the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred. Even in this case, the DC current interrupting device 20 can maintain power transmission in the pole on the side where the fault has not occurred. Here, if the DC current interrupting device 20 is configured to be able to connect further another DC transmission line LN to the positive and negative pole sides, for example, power transmission not passing through the DC transmission line LN where the fault has occurred can be maintained even on the pole side where the fault has occurred.

[0036] Furthermore, in the DC current interrupting device 20, the semiconductor circuit breaker 203 is shared between the positive and negative sides, so the number of parts and size of the DC current interrupting device 20 and the DC power transmission system 1 can be significantly reduced compared to a configuration in which multiple semiconductor circuit breakers 203 are provided for each DC power transmission line LN.

[0037] In the above-mentioned example of the interruption operation of the DC transmission line LN-P-1 in the DC current interruption device 20, the case where the positive DC current flows from the terminal a2 to the terminal a1 has been described. However, the positive DC current may flow in the opposite direction to the direction shown in Figs. 4 to 7, that is, from the terminal a1 to the terminal a2. Even in this case, the upper control device may control the fault current caused by the fault to be commutated to the semiconductor circuit breaker 203. More specifically, in step 1, the upper control device opens the mechanical contacts of the commutation circuits 201-2 and 201-3, and in step 2, turns on the semiconductor switching elements constituting the bidirectional H-bridge circuits in the parallel circuits 2011 of the commutation circuits 201-2 and 201-3. Then, in step 3, the upper control device turns off each of the semiconductor switching elements constituting the bidirectional H-bridge circuits in the parallel circuit 2011 included in the commutation circuits 201-2 and 201-3, and turns on each of the semiconductor switching elements included in the semiconductor circuit breaker 203, thereby commutating the fault current to the semiconductor circuit breaker 203. Thereafter, in step 4, the upper control device turns off each of the semiconductor switching elements included in the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred.

[0038] [Second specific example of a direct current interrupter] Next, a configuration of a second specific example of the direct current interrupting device 20 will be described. FIG. 8 is a diagram showing an example of the configuration of the direct current interrupting device 20 of the second specific example. In the direct current interrupting device 20 of the second specific example shown in FIG. 8 (hereinafter referred to as "direct current interrupting device 21"), the configuration of the commutation circuit 201 is different from the configuration of the commutation circuit 201 included in the direct current interrupting device 20 of the first specific example. The commutation circuit 201 included in the direct current interrupting device 21 (hereinafter referred to as "commutation circuit 211") is configured, for example, by connecting a series circuit 2111 in which a plurality of semiconductor switch units (only two semiconductor switch units are shown in FIG. 8) are connected in series in the opposite directions to each other, and a mechanical contact is connected in series. The semiconductor switching element constituting the semiconductor switch unit included in the series circuit 2111 is also a switching element such as an insulated gate bipolar transistor (IGBT), similar to the semiconductor switching element of the semiconductor switch unit included in the commutation circuit 201 of the direct current interrupting device 20 of the first specific example. The semiconductor switching element in this case is not limited to an IGBT, and may be any switching element that can realize self-extinguishing. The series circuit 2111 is an example of a "series circuit", the semiconductor switch unit that constitutes the series circuit 2111 is an example of a "self-extinguishing semiconductor switching element", and the mechanical contact is an example of a "mechanical contact".

[0039] [Operation of interrupting DC transmission line LN in DC current interrupting device 21 of second specific example] The operation of the DC current interrupting device 21 to interrupt the DC transmission line LN where a fault has occurred is the same as the operation of the DC current interrupting device 20 of the first specific example described with reference to Figs. 4 to 7 to interrupt the DC transmission line LN where a fault has occurred. That is, in the DC current interrupting device 21, the upper control device may also divert the fault current to the semiconductor circuit breaker 203 as shown in Figs. 4 to 7 to interrupt the DC transmission line LN where a fault has occurred. Therefore, a detailed description of the operation of interrupting the DC transmission line LN in the DC current interrupting device 21 will be omitted. However, in the DC current interrupting device 21, the commutation circuit 201 provided in the DC current interrupting device 20 of the first specific example is replaced with a commutation circuit 211. And the series circuit 2111 in the commutation circuit 211 does not include the mechanical contacts and the H-bridge circuit provided in the parallel circuit 2011 in the commutation circuit 201. For this reason, in the DC current interruption device 21, the control of opening the mechanical contacts in the parallel circuit 2011 of the commutation circuit 201, which was controlled by the higher-level control device in the DC current interruption device 20 of the first specific example, is omitted, and the on / off control of the semiconductor switching elements of the H-bridge circuit is replaced with off control of the series circuit 2111.

[0040] In this manner, in the DC current interrupting device 21, similarly to the DC current interrupting device 20 of the first specific example, a host control device (not shown) controls the opening, closing, on and off of the respective components of the commutation circuit 211 and the current switching element 202 belonging to the pole connected to the DC transmission line LN where the fault has occurred, and the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred. At this time, the DC current interrupting device 21 can also maintain power transmission in the pole on the side where the fault has not occurred.

[0041] The configuration of the commutation elements provided in the commutation circuit 201 and the commutation circuit 211 is not limited to the configuration provided in the commutation circuit 201 in the first specific example of the DC current interrupting device 20 shown in Figure 3 in which a parallel circuit 2011 in which a mechanical contact and a bidirectional H-bridge circuit are connected in parallel and a mechanical contact are connected in series, or the configuration provided in the commutation circuit 211 in the DC current interrupting device 21 shown in Figure 8 in which a series circuit 2111 of a plurality of semiconductor switch units and a mechanical contact are connected in series.

[0042] Here, another configuration of the commutation element included in the commutation circuit will be described. FIG. 9 is a diagram showing an example of another configuration of the commutation circuit 201 (which may be the commutation circuit 211). The commutation circuit 221 shown in FIG. 9 is configured such that, for example, a parallel circuit 2211 in which a mechanical contact and a unidirectional H-bridge circuit are connected in parallel, and a mechanical contact are connected in series. The unidirectional H-bridge circuit included in the parallel circuit 2011 has two semiconductor switch units, two diodes, and one capacitor connected to each other. The semiconductor switching element constituting the semiconductor switch unit included in the unidirectional H-bridge circuit is also a switching element such as an insulated gate bipolar transistor (IGBT), similar to the semiconductor switching elements of the semiconductor switch units included in the commutation circuit 201 of the direct current interrupting device 20 of the first specific example and the commutation circuit 211 of the direct current interrupting device 21. The semiconductor switching element in this case is not limited to an IGBT, and may be any switching element as long as it is a semiconductor switching element capable of realizing self-extinguishing. The parallel circuit 2211 is an example of a “parallel circuit”, the mechanical contacts constituting the parallel circuit 2211 are an example of a “first mechanical contact”, and the unidirectional H-bridge circuit constituting the parallel circuit 2211 is an example of a “bridge circuit”. The semiconductor switch unit included in the unidirectional H-bridge circuit is an example of a “semiconductor switching element”, and the capacitor included in the unidirectional H-bridge circuit is an example of a “voltage source”.

[0043] Even if the commutation circuit is replaced with the configuration of the commutation circuit 221 shown in Fig. 9, the DC current interrupting device 20 (including the DC current interrupting device 21) of the first embodiment can interrupt the DC transmission line LN where an accident has occurred by an upper control device (not shown) controlling the opening, closing, on and off of the respective components of the commutation circuit 221 and the current switching element 202 belonging to the pole on the side where the DC transmission line LN where an accident has occurred, and the semiconductor circuit breaker 203. At this time, the DC current interrupting device 20 (including the DC current interrupting device 21) equipped with the commutation circuit 221 can also maintain power transmission at the pole on the side where no accident has occurred.

[0044] [Third specific example of a DC current interrupter] Next, a configuration of a third specific example of the direct current interruption device 20 will be described. FIG. 10 is a diagram showing an example of the configuration of the direct current interruption device 20 of the third specific example. In the direct current interruption device 20 of the third specific example shown in FIG. 10 (hereinafter referred to as "direct current interruption device 22"), the configuration of the current switching element 202 is different from the configuration of the current switching element 202 included in the direct current interruption device 20 of the first specific example. The current switching element 202 included in the direct current interruption device 22 (hereinafter referred to as "current switching element 222") is composed of, for example, a thyristor. The current switching element 222 may be composed of a plurality of thyristors connected in series in the same direction. The direction of the thyristor, that is, the direction in which the anode and cathode are connected, is the same direction as the direction in which the semiconductor circuit breaker 203 passes a direct current. That is, the cathodes of the current switching elements 222-1 and 222-3 arranged on the side where the DC current flows into the semiconductor circuit breaker 203 are connected to the semiconductor circuit breaker 203 side, and the anodes of the current switching elements 222-2 and 222-4 arranged on the side where the DC current flows out from the semiconductor circuit breaker 203 are connected to the semiconductor circuit breaker 203 side. The gates of the thyristors are controlled, for example, by a higher-level control device (not shown) in the DC power transmission system 1. The current switching element 222 allows or blocks a DC current flowing between the DC transmission lines LN connected to both ends, depending on the control of the gates of the thyristors by the higher-level control device.

[0045] The operation of interrupting the DC transmission line LN in the DC current interrupting device 22 may be equivalent to the operation of interrupting the DC transmission line LN in the DC current interrupting device 20 of the first specific example or the DC current interrupting device 21 of the second specific example by the upper control device. Therefore, a detailed description of the operation of interrupting the DC transmission line LN in the DC current interrupting device 22 will be omitted.

[0046] In the DC current interrupting device 22, similarly to the DC current interrupting device 20 of the first specific example and the DC current interrupting device 21 of the second specific example, a host control device (not shown) controls the opening, closing, on and off of the respective components of the commutation circuit 201 and the current switching element 222 belonging to the pole connected to the DC transmission line LN where the fault has occurred, and the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred. At this time, the DC current interrupting device 22 can also maintain power transmission in the pole on the side where the fault has not occurred.

[0047] [Fourth specific example of a DC current interrupter] Next, the configuration of a fourth specific example of the DC current interrupting device 20 will be described. Fig. 11 is a diagram showing an example of the configuration of the DC current interrupting device 20 of the fourth specific example. In the DC current interrupting device 20 of the fourth specific example shown in Fig. 11 (hereinafter referred to as "DC current interrupting device 23"), one of the two current switching elements 222 on the positive side and one of the two current switching elements 222 on the negative side provided in the DC current interrupting device 22 of the third specific example are replaced with a current switching element 232. In the DC current interrupting device 23 shown in Fig. 11, the positive side current switching element 222-1 provided in the DC current interrupting device 22 is replaced with a current switching element 232-1, and the negative side current switching element 222-3 is replaced with a current switching element 232-3. In the DC current interrupting device 23, the positive electrode side current switching element 222-2 of the DC current interrupting device 22 may be replaced by a current switching element 232-2, and the negative electrode side current switching element 222-4 may be replaced by a current switching element 232-4. The current switching element 232 may be composed of, for example, a diode. The current switching element 232 may be configured such that a plurality of diodes are connected in series in the same direction. The direction of the diodes in the current switching element 232, that is, the direction in which the anode and cathode are connected, is the same as that of the current switching element 222 at the corresponding position in the DC current interrupting device 22. That is, in the DC current interrupting device 23, the direction of the diodes in the current switching element 232 is the same as the current that flows when the semiconductor circuit breaker 203 passes a DC current. That is, the current switching element 232 replacing the current switching elements 222-1 and 222-3 arranged on the side where the DC current flows into the semiconductor circuit breaker 203 has a cathode connected to the semiconductor circuit breaker 203 side, and the current switching element 232 replacing the current switching elements 222-2 and 222-4 arranged on the side where the DC current flows out from the semiconductor circuit breaker 203 has an anode connected to the semiconductor circuit breaker 203 side. The current switching element 232 allows or blocks a DC current flowing between the DC transmission lines LN connected to both ends without being controlled by a higher-level control device.

[0048] The operation of interrupting the DC transmission line LN in the DC current interrupting device 23 may be equivalent to the operation of interrupting the DC transmission line LN in the DC current interrupting device 20 of the first specific example, the DC current interrupting device 21 of the second specific example, and the DC current interrupting device 22 of the third specific example by the upper control device. Therefore, a detailed description of the operation of interrupting the DC transmission line LN in the DC current interrupting device 23 will be omitted.

[0049] In the DC current interrupting device 23, similarly to the DC current interrupting device 20 of the first specific example, the DC current interrupting device 21 of the second specific example, and the DC current interrupting device 22 of the third specific example, a higher-level control device (not shown) controls the opening, closing, on, and off of the respective components of the commutation circuit 201 and the current switching element 222 belonging to the pole on the side to which the DC transmission line LN where the fault has occurred is connected, and the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred. At this time, the DC current interrupting device 23 can also maintain power transmission in the pole on the side where the fault has not occurred.

[0050] As described above, the DC current interrupting device 20 of the first embodiment is disposed at a node of the corresponding DC transmission line LN in the DC power transmission system 1 configured to connect the power transmitting and receiving ends with a bipolar DC transmission line LN having a positive pole and a negative pole. The DC current interrupting device 20 of the first embodiment interrupts the DC transmission line LN in which the fault has occurred by controlling the opening, closing, on and off of the respective components of the commutation circuit 201 and the current switching element 202 belonging to the pole connected to the DC transmission line LN in which the fault has occurred, and the semiconductor circuit breaker 203 by the upper control device. At this time, the DC current interrupting device 20 of the first embodiment maintains the power transmission at the pole on the side where the fault has not occurred.

[0051] Moreover, in the DC current interrupting device 20 of the first embodiment, the semiconductor circuit breaker 203 is shared between the path of the positive-side DC transmission line LN and the path of the negative-side DC transmission line LN. In other words, the DC current interrupting device 20 of the first embodiment is not configured to have a plurality of semiconductor circuit breakers 203 for each DC transmission line LN, but is configured to share one semiconductor circuit breaker 203 for each pole. As a result, in the DC current interrupting device 20 of the first embodiment, it is possible to reduce at least the number of parts (parts size) required to configure the semiconductor circuit breaker 203. As a result, in the DC power transmission system 1 to which the DC current interrupting device 20 of the first embodiment is applied, the number of parts can be significantly reduced, and the size can be reduced, thereby making it possible to reduce the area required for installation.

[0052] The configuration of the DC current interrupting device 20 is not limited to the configuration shown in FIG. 2. The DC current interrupting device 20 may have any configuration as long as it can pass a current through a path similar to that shown in FIG. 4 in a steady power transmission state, and when an accident occurs in any DC transmission line LN, it commutates the fault current to the semiconductor circuit breaker 203 through a path as shown in FIGS. 5 to 7, and then cuts off the DC transmission line LN where the accident occurred. In other words, the DC current interrupting device 20 may have components other than those shown in FIG. 2 in the path as long as it can conduct current through a path similar to that shown in FIGS. 4 to 7. For example, the commutation circuit 201, the current switching element 202, and the semiconductor circuit breaker 203 may be connected in series or in parallel.

[0053] In the DC current interrupting device 20, the number of DC transmission lines LN on each of the positive and negative poles is two, that is, a configuration in which there are two circuits is shown, but the number of circuits for each pole may be three or more. In the DC current interrupting device 20, the configuration in which the DC current has two poles, that is, a positive pole and a negative pole, is shown, but the number of poles of the DC current may be three or more. In the DC current interrupting device 20, the configuration in which the semiconductor circuit breaker 203 is shared by each of the positive and negative poles is shown, but when the number of circuits for each pole is three or more, or when the number of poles of the DC current is three or more, the configuration in which the semiconductor circuit breaker 203 is shared by all the circuits or poles is not required. In other words, as long as the semiconductor circuit breaker 203 is shared by at least two circuits or two poles, the number of parts when configuring the DC current interrupting device 20 and the DC power transmission system 1 can be reduced, and the size can be reduced.

[0054] Second embodiment The second embodiment will be described below. Fig. 12 is a diagram showing an example of the configuration of a DC power transmission system to which a direct current circuit breaker (DCCB) according to the second embodiment is applied. Fig. 12(a) shows an example of the configuration of a DC power transmission system 1 according to the first embodiment for comparison, and Fig. 12(b) shows an example of the configuration of a DC power transmission system 2 according to the second embodiment. However, Fig. 12(a) and Fig. 12(b) show an example of a DC power transmission system in which two AC systems AC are connected by a bipolar DC transmission line LN to facilitate comparison.

[0055] As described above, the DC current interruption device 20 of the first embodiment is configured to correspond to a DC transmission system in which a bipolar DC transmission line LN having a positive electrode and a negative electrode, such as the DC transmission system 1 shown in FIG. 12(a), in other words, one DC transmission line LN on each of the positive electrode side and the negative electrode side transmits power to each other.

[0056] In contrast, the DC transmission system 2 shown in Fig. 12(b) has two DC transmission lines LN on the positive and negative sides, that is, a two-circuit configuration. In the following description, this configuration of the DC transmission system 2 is also referred to as "two-bipolar."

[0057] The DC power transmission system 2 includes, for example, two AC systems AC (AC systems AC-1 and AC-2), eight power converters 10 (power converters 10-P1-1, 10-P2-1, 10-P1-2, 10-P2-2, 10-N1-1, 10-N2-1, 10-N1-2, and 10-N2-2), and two DC current interruption devices 25 (DC current interruption devices 25-1 and 25-2). In the DC power transmission system 2, components having the same functions as those included in the DC power transmission system 1 of the first embodiment are denoted by the same reference numerals. Therefore, detailed description of components included in the DC power transmission system 2 that have the same configurations and operations as those included in the DC power transmission system 1 of the first embodiment will be omitted, and only different configurations and operations will be described.

[0058] In the DC power transmission system 2 shown in FIG. 12(b), a "- (hyphen)", a letter, and a number are added to the end of the symbol of each component to indicate the polarity and number of poles of the DC power (DC current) to which each component corresponds. More specifically, the component with "-P1" attached corresponds to the first DC current on the positive side, the component with "-P2" attached corresponds to the second DC current on the positive side, the component with "-N1" attached corresponds to the first DC current on the negative side, and the component with "-N2" attached corresponds to the second DC current on the negative side. In FIG. 12(b), the "- (hyphen)" and the number added to the end of the symbol of each component also indicate the corresponding relationship of each component, as in the first embodiment. In the following description, when the polarity and number of poles of the DC power (DC current) to which each component corresponds, or the corresponding relationship of each component is not to be distinguished, the hyphen and the letter or number added to the symbol of each component are omitted.

[0059] In the DC power transmission system 2, corresponding components are arranged (installed) adjacent to each other, similarly to the DC power transmission system 1. In the DC power transmission system 2, power is transmitted and received between the AC system AC-1 and the AC system AC-2 in a bipolar manner.

[0060] Each of the DC current interrupting devices 25 is connected to a DC transmission line LN that transmits the DC current output by the corresponding power converter 10, similarly to the DC current interrupting device 20. The DC current interrupting device 25 is configured so that each of the positive and negative sides corresponds to two DC transmission lines LN. In the DC power transmission system 2 shown in FIG. 12(b), the corresponding power converters 10 are connected to each other by the corresponding DC transmission lines LN via the DC current interrupting device 25-1 and the DC current interrupting device 25-2. More specifically, in the DC power transmission system 2, each of the power converters 10 is connected to the first DC transmission line LN-P1 and the second DC transmission line LN-P2 on the positive side and the first DC transmission line LN-N1 and the second DC transmission line LN-N2 on the negative side via the DC current interrupting device 25-1 and the DC current interrupting device 25-2. As a result, in the DC transmission system 2, the power converters 10 transmit DC current to each other via the DC current interruption devices 25-1 and 25-2 and the two bipolar DC transmission lines LN connected to each other.

[0061] When an accident occurs in any of the connected DC transmission lines LN, each DC current interrupting device 25 also electrically interrupts a connection point (connection terminal) with the DC transmission line LN where the accident has occurred (fault line) in response to an instruction from a higher-level control device, such as a higher-level control device (not shown) in the DC transmission system 2 or a control device (not shown) of the DC current interrupting device 25. As a result, the DC transmission system 2 also disconnects the fault line and maintains power transmission through a healthy line.

[0062] [Configuration of DC current interrupter] Next, an example of the configuration of the DC current interrupting device 25 will be described. FIG. 13 is a diagram showing an example of the configuration of the DC current interrupting device 25 of the second embodiment. FIG. 13 shows an example of the DC current interrupting device 25 configured at the node portion of the corresponding DC transmission line LN. The DC current interrupting device 25 shown in FIG. 13 is, for example, an example of the DC current interrupting device 25-1. In the DC current interrupting device 25, for example, a transmission line of a first DC current on the positive pole side (which is also the DC transmission line LN) converted and output by the power converter 10-P1-1 is connected to a terminal b1 on the power converter 10-P1-1 side, and a first DC transmission line LN-P1 on the positive pole side is connected to a terminal a1 or a2 on the other DC current interrupting device 25 side. In the DC current interrupting device 25, for example, a positive-side second DC transmission line (also the DC transmission line LN) converted and output by the power converter 10-P2-1 is connected to the terminal b3 on the power converter 10-P2-1 side, and a positive-side second DC transmission line LN-P2 is connected to the terminal a5 or a6 on the other DC current interrupting device 25 side. In the DC current interrupting device 25, for example, a negative-side first DC transmission line (also the DC transmission line LN) converted and output by the power converter 10-N1-1 is connected to the terminal b2 on the power converter 10-N1-1 side, and a negative-side first DC transmission line LN-N1 is connected to the terminal a3 or a4 on the other DC current interrupting device 25 side. In the DC current interrupter 25, for example, a second DC current transmission line (which is also a DC transmission line LN) on the negative side converted and output by the power converter 10-N2-1 is connected to terminal b4 on the power converter 10-N2-1 side, and a second DC transmission line LN-N2 on the negative side is connected to terminal a7 or terminal a8 on the other DC current interrupter 25 side.

[0063] The DC current interruption device 25 includes, for example, a plurality of commutation circuits 201 (commutation circuits 201-1 to 201-16), a plurality of current switching elements 202 (current switching elements 202-1 to 202-8), and one semiconductor circuit breaker 203. In the DC current interruption device 25, components having the same functions as those included in the DC current interruption device 20 of the first embodiment are denoted by the same reference numerals. The DC current interruption device 25 includes different numbers of components, but the components are the same as the corresponding components included in the DC current interruption device 20. Therefore, detailed explanations of the components included in the DC current interruption device 25 will be omitted.

[0064] In DC current interrupting device 25, the configuration of commutation circuits 201-1 to 201-8 and current switching elements 202-1 to 202-4 is a DC current interrupting device configuration corresponding to the first positive DC transmission line LN-P1 and the first negative DC transmission line LN-N1. In DC current interrupting device 25, the configuration of commutation circuits 201-9 to 201-16 and current switching elements 202-5 to 202-8 is a DC current interrupting device configuration corresponding to the second positive DC transmission line LN-P2 and the second negative DC transmission line LN-N2. In the DC current interrupting device 25, the semiconductor circuit breaker 203, which is a component used to interrupt the first DC transmission line LN-P1 and the second DC transmission line LN-P2 on the positive electrode side and the first DC transmission line LN-N1 and the second DC transmission line LN-N2 on the negative electrode side, is shared by all the DC transmission lines LN. With this configuration, the DC current interrupting device 25 can reduce the size (component scale) of the DC current interrupting device 25 and the DC transmission system 2 as well, compared to a configuration in which a plurality of semiconductor circuit breakers 203 are provided for each DC transmission line LN.

[0065] The operation of interrupting the DC transmission line LN in the DC current interrupting device 25 may be equivalent to the operation of interrupting the DC transmission line LN in the DC current interrupting device 20 of the first embodiment by the upper control device. Therefore, a detailed description of the operation of interrupting the DC transmission line LN in the DC current interrupting device 25 will be omitted.

[0066] In the DC current interrupting device 25, as in the DC current interrupting device 20 of the first embodiment, an upper control device (not shown) controls the opening, closing, on and off of the respective components of the commutation circuit 201 and the current switching element 202 belonging to the pole connected to the DC transmission line LN where the fault has occurred, and the semiconductor circuit breaker 203, thereby interrupting the DC transmission line LN where the fault has occurred. At this time, the DC current interrupting device 25 can also maintain power transmission in the pole on the side where the fault has not occurred. Furthermore, since the DC current interrupting device 25 has a bipolar configuration, that is, the positive and negative DC transmission lines LN are configured as two circuits, even if one of the DC transmission lines LN is interrupted due to an accident occurring in that DC transmission line LN, the remaining DC transmission line LN can be used to maintain power transmission equivalent to that when no accident has occurred.

[0067] As described above, the DC current interrupting device 25 of the second embodiment is disposed at a node of the corresponding DC transmission line LN in the DC power transmission system 2 having a two-bipolar configuration in which the DC transmission line LN having a positive pole and a negative pole is connected by two circuits between the transmitting and receiving ends. In the DC current interrupting device 25 of the second embodiment, as in the DC current interrupting device 20 of the first embodiment, the upper control device also interrupts the DC transmission line LN in which the accident has occurred by controlling the opening, closing, on and off of the respective components of the commutation circuit 201 and the current switching element 202 belonging to the pole connected to the DC transmission line LN in which the accident has occurred, and the semiconductor circuit breaker 203. At this time, the DC current interrupting device 25 of the second embodiment maintains the power transmission at the pole on the side where the accident has not occurred. Furthermore, in the DC current interruption device 25 of the second embodiment, the DC transmission line LN of the two-circuit DC transmission line LN, which is the circuit in which no fault occurs, is used to maintain power transmission equivalent to that when no fault occurs.

[0068] Moreover, in the DC current interrupting device 25 of the second embodiment, similar to the DC current interrupting device 20 of the first embodiment, the semiconductor circuit breaker 203 is shared between the path of the two-circuit DC transmission line LN on the positive side and the path of the two-circuit DC transmission line LN on the negative side. That is, similar to the DC current interrupting device 20 of the first embodiment, the DC current interrupting device 25 of the second embodiment does not have a configuration in which a plurality of semiconductor circuit breakers 203 are provided for each DC transmission line LN, but has a configuration in which one semiconductor circuit breaker 203 is shared by each pole. As a result, similar to the DC current interrupting device 20 of the first embodiment, the DC current interrupting device 25 of the second embodiment can reduce the number of parts (parts size) required to configure at least the semiconductor circuit breaker 203. As a result, in the DC transmission system 2 employing the DC current interruption device 25 of the second embodiment, similarly to the DC transmission system 1 employing the DC current interruption device 20 of the first embodiment, the number of parts can be significantly reduced and the size can be reduced, thereby making it possible to reduce the area required for installation.

[0069] The configuration of the DC current interrupting device 25 is not limited to the configuration shown in FIG. 13. As with the DC current interrupting device 20, the DC current interrupting device 25 may have any configuration as long as it can pass a current through a path equivalent to the path shown in FIG. 4 in a steady power transmission state, and when an accident occurs in any DC transmission line LN, it can commutate the fault current to the semiconductor circuit breaker 203 through a path equivalent to the paths shown in FIGS. 5 to 7, and then cut off the DC transmission line LN where the accident occurred. In other words, as with the DC current interrupting device 20, as long as it can conduct current through a path equivalent to the paths shown in FIGS. 4 to 7, other components other than those shown in FIG. 13 may be provided in the path. For example, the DC current interrupting device 25 may also have a configuration in which the commutation circuit 201, the current switching element 202, and the semiconductor circuit breaker 203 are connected in series or in parallel.

[0070] In the DC current interrupting device 25, the number of circuits for each of the positive and negative poles may be three or more, as in the DC current interrupting device 20. In the DC current interrupting device 25, the configuration in which the DC current has two poles, that is, a positive pole and a negative pole, has been shown, as in the DC current interrupting device 20, but the number of poles of the DC current may be three or more. In the DC current interrupting device 25, the configuration in which the semiconductor circuit breaker 203 is shared between the positive and negative poles has been shown, as in the DC current interrupting device 20, but when the number of circuits for each pole is three or more, or when the number of poles of the DC current is three or more, the configuration in which the semiconductor circuit breaker 203 is shared between all the circuits or poles is not required. In other words, as long as the semiconductor circuit breaker 203 is shared between at least two poles and two circuits, the number of parts required to configure the DC current interrupting device 25 and the DC power transmission system 2 can be reduced, and the size can be reduced.

[0071] As described above, the DC current interrupting device of each embodiment is disposed at a node of a corresponding DC transmission line in a DC power transmission system configured to connect power transmitting and receiving ends with a bipolar DC transmission line having a positive pole and a negative pole. In the DC current interrupting device of each embodiment, a host control device (not shown) controls opening, closing, on, and off of the respective components of the commutation circuit and current switching element belonging to the pole connected to the DC transmission line where the fault has occurred, and the semiconductor circuit breaker, thereby interrupting the DC transmission line where the fault has occurred. At this time, the DC current interrupting device of each embodiment maintains power transmission at the pole on the side where the fault has not occurred.

[0072] Moreover, in the DC current interrupting device of each embodiment, the semiconductor circuit breaker is shared between the path of the positive pole side DC transmission line and the path of the negative pole side DC transmission line. In other words, the DC current interrupting device of each embodiment is configured to share one semiconductor circuit breaker between the respective poles, rather than having a plurality of semiconductor circuit breakers for each DC transmission line. This makes it possible to reduce at least the number of parts (parts size) required to configure the semiconductor circuit breaker in the DC current interrupting device of each embodiment. As a result, in a DC transmission system to which the DC current interrupting device of each embodiment is applied, the number of parts can be significantly reduced, and the size can be reduced, thereby making it possible to reduce the area required for installation.

[0073] According to at least one of the embodiments described above, there is provided a semiconductor circuit breaker (203), a plurality of first commutation circuits (201-1, 201-2, 201-3, and 201-4) that selectively pass a current flowing in a direction between a first positive pole line (LN-P-1) that is a DC transmission line (LN) connected to a first terminal (a1) and a second positive pole line (LN-P-3) that is a DC transmission line connected to a second terminal (a2), and a plurality of second commutation circuits (201-1, 201-2, 201-3, and 201-4) that selectively pass a current flowing in a direction between a first negative pole line (LN-N-1) that is a DC transmission line connected to a third terminal (a3) ​​and a second negative pole line (LN-N-3) that is a DC transmission line connected to a fourth terminal (a4). By providing the above-mentioned commutation circuits (201-5, 201-6, 201-7, and 201-8), a first current switching element (202-1 and 201-2) that causes or blocks a current flowing between the first positive pole wire and the second positive pole wire via the first commutation circuit to flow to the semiconductor circuit breaker, and a second current switching element (202-3 and 201-4) that causes or blocks a current flowing between the first negative pole wire and the second negative pole wire via the second commutation circuit to flow to the semiconductor circuit breaker, it is possible to realize a DC current interruption device that is applicable to a DC transmission system having multiple poles with a small component configuration.

[0074] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0075] 1,2···DC transmission system, 10,10-P-1,10-P-2,10-P-3,10-N-1,10-N-2,10-N-3,10-P1-1,10-P2-1,10-P1-2,10-P2-2,10-N1-1,10-N2-1,10-N1-2,10-N2-2···Power converter, 20,20-1,20-2 ,20-3,21,22,23,25,25-1,25-2···DC current interrupter, 201,201-1,201-2,201-3,201-4,201-5,201-6,201-7,201-8,201-9,201-10,201-11,201-12,201-13,201-14,201-15,201-1 6,211,211-1,211-2,211-3,211-4,211-5,211-6,211-7,211-8,221... Commutation circuit, 2011,22 11...Parallel circuit, 2111...Series circuit, 202,202-1,202-2,202-3,202-4,222,222-1,222-2,222-3, 222-4, 232, 232-1, 232-3... Current switching element, 203... Semiconductor circuit breaker, LN, LN-P-1, LN-P-2, LN-P-3, LN-N-1, LN-N-2, LN-N-3, LN-P1, LN-P2, LN-N1, LN-N2... DC transmission line, AC, AC-1, AC-2, AC-3... AC system

Claims

1. A semiconductor circuit breaker; a plurality of first commutation circuits for allowing a current to flow in a selective direction between a first positive pole line which is a DC transmission line connected to the first terminal and a second positive pole line which is a DC transmission line connected to the second terminal; a plurality of second commutation circuits for allowing a current to flow in a selective direction between a first negative pole line which is a DC transmission line connected to the third terminal and a second negative pole line which is a DC transmission line connected to the fourth terminal; a first current switching element that allows or blocks a current flowing between the first positive pole line and the second positive pole line through the first commutation circuit to the semiconductor circuit breaker; a second current switching element that allows or blocks a current flowing between the first negative pole line and the second negative pole line via the second commutation circuit to flow through the semiconductor circuit breaker; A direct current interrupting device comprising:

2. When an accident occurs on any of the DC transmission lines, A current is caused to flow from either the first current switching element or the second current switching element connected to a fault line, which is a DC transmission line in which the fault has occurred, to the semiconductor circuit breaker; Either the first commutation circuit or the second commutation circuit connected to the fault line directs the current flowing in the fault line toward the semiconductor circuit breaker. The direct current interruption device according to claim 1 .

3. the first current switching element is at least one mechanical contact; the second current switching element is at least one mechanical contact; The direct current interruption device according to claim 1 or 2.

4. the first current switching element is at least one thyristor; the second current switching element is at least one thyristor; The direct current interruption device according to claim 1 or 2.

5. Each of the first current switching element and the second current switching element has at least one diode disposed on a side where a current flows into the semiconductor circuit breaker, and at least one thyristor disposed on a side where a current flows out from the semiconductor circuit breaker. The direct current interruption device according to claim 1 or 2.

6. Each of the first current switching element and the second current switching element has at least one thyristor disposed on a side where a current flows into the semiconductor circuit breaker, and at least one diode disposed on a side where a current flows out from the semiconductor circuit breaker. The direct current interruption device according to claim 1 or 2.

7. Each of the first commutation circuit and the second commutation circuit is configured by connecting in series a parallel circuit in which a first mechanical contact and a bridge circuit are connected in parallel, and at least one first mechanical contact, The bridge circuit is configured by connecting at least one semiconductor switching element and a voltage source to each other. The direct current interruption device according to any one of claims 1 to 6.

8. Each of the first commutation circuit and the second commutation circuit is a series circuit in which a mechanical contact and at least one self-extinguishing semiconductor switching element are connected in series. The direct current interruption device according to any one of claims 1 to 6.

9. Each of the first commutation circuit and the second commutation circuit is configured by connecting in series a parallel circuit in which a first mechanical contact and a bridge circuit are connected in parallel, and at least one first mechanical contact, The bridge circuit is configured by connecting at least one semiconductor switching element, at least one diode, and a voltage source to each other. The direct current interruption device according to any one of claims 1 to 6.

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