DC circuit breaker system, control method for DC circuit breaker, and control program for DC circuit breaker

Abstract

According to an embodiment of the present invention, a DC interruption system 200 comprises a main circuit breaker (10) installed on a DC line (11), a commutation circuit (20) which is connected in parallel to the main circuit breaker (10) and which supplies a resonant current to the main circuit breaker (10) when the main circuit breaker (10) is opened, a rectification circuit (40) which is connected in parallel to the commutation circuit (20) and which can maintain a conduction state until the insulation performance of the main circuit breaker (10) is recovered when the main circuit breaker (10) is opened, and a control device which controls the main circuit breaker (10), the commutation circuit (20), and the rectifier circuit (40).

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a DC circuit breaker system, a control method for a DC circuit breaker, and a control program for a DC circuit breaker. [Background Art]

[0002] In recent years, development of high-voltage DC circuit breakers (hereinafter, DC circuit breakers including such high-voltage DC circuit breakers are simply referred to as "DC circuit breakers") has been progressing toward the realization of high-voltage direct current power transmission. Some DC circuit breakers are provided with a main circuit breaker that performs fault interruption to isolate a fault point when a fault occurs in a DC line, and a commutation circuit (also referred to as a resonance circuit) that supplies a high-frequency current that cancels out the current flowing through the main circuit breaker. This method is called a forced arc extinction method. Some DC circuit breakers of this type perform high-speed reclosing. As forced arc extinction type DC circuit breakers that perform fault interruption after high-speed reclosing, there have conventionally been technologies providing a plurality of resonance circuits, and technologies providing a bridge circuit as the resonance circuit. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Laid-Open Publication No. 58-34526 [Patent Document 2] Japanese Patent No. 6328356 [Patent Document 3] Japanese Patent No. 6509466 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the technology including a plurality of resonance circuits, an increase in the number of resonance circuits hinders the size reduction of the device. In addition, the technology including a bridge circuit requires a plurality of switches capable of withstanding the full voltage of the capacitor, which also hinders size reduction of the device.

[0005] The object of the present invention is to provide a DC interruption system, a control method for a DC interruption device, and a control program for a DC interruption device that can be made compact in structure. [Means for solving the problem]

[0006] To achieve the above objective, the DC interruption system according to this embodiment includes a main circuit breaker provided on a DC line, a commutation circuit connected in parallel to the main circuit breaker and supplying a resonant current to the main circuit breaker when the main circuit breaker is open, and a circuit connected in parallel to the commutation circuit. It has a thyristor and is configured to be energized in both directions. The present invention is characterized by comprising a rectifier circuit capable of maintaining a conductive state until the insulation performance of the main circuit breaker is restored when the main circuit breaker is opened, and a control device that controls the main circuit breaker, the commutator circuit, and the rectifier circuit. [Brief explanation of the drawing]

[0007] [Figure 1] This is a block diagram showing the configuration of a DC interruption system according to an embodiment. [Figure 2] This is a block diagram showing the basic configuration of a DC circuit breaker according to an embodiment. [Figure 3] This is a block diagram showing a commutation circuit according to a first example of a DC circuit breaker according to an embodiment. [Figure 4] This is a block diagram showing a commutation circuit according to a second example of a DC circuit breaker according to an embodiment. [Figure 5] This is a block diagram showing a commutation circuit according to a third example of a DC circuit breaker according to an embodiment. [Figure 6] This is a block diagram showing a commutation circuit according to a fourth example of a DC circuit breaker according to an embodiment. [Figure 7] This is a block diagram showing an energy absorption circuit according to a first example of a DC circuit breaker according to an embodiment. [Figure 8] This is a block diagram showing an energy absorption circuit according to a second example of a DC circuit breaker according to an embodiment. [Figure 9]It is a block diagram showing an energy absorption circuit according to a third example of the DC circuit breaker according to the embodiment. [Figure 10] It is a block diagram showing an energy absorption circuit according to a fourth example of the DC circuit breaker according to the embodiment. [Figure 11] It is a block diagram showing an energy absorption circuit according to a fifth example of the DC circuit breaker according to the embodiment. [Figure 12] It is a block diagram showing an energy absorption circuit according to a sixth example of the DC circuit breaker according to the embodiment. [Figure 13] It is a block diagram showing a rectifier circuit according to a first example of the DC circuit breaker according to the embodiment. [Figure 14] It is a block diagram showing a rectifier circuit according to a second example of the DC circuit breaker according to the embodiment. [Figure 15] It is a block diagram showing a rectifier circuit according to a third example of the DC circuit breaker according to the embodiment. [Figure 16] It is a block diagram showing a rectifier circuit according to a fourth example of the DC circuit breaker according to the embodiment. [Figure 17] It is a block diagram showing a rectifier circuit according to a fifth example of the DC circuit breaker according to the embodiment. [Figure 18] It is a flow chart showing the procedure for performing an interruption duty in the control method for the DC circuit breaker according to the embodiment. [Figure 19] It is a graph showing an example of a temporal transition of the DC interruption system according to the embodiment. [Figure 20] It is a flow chart showing the procedure for high-speed reclosing in the control method for the DC circuit breaker according to the embodiment. [Figure 21] It is a first graph for explaining the effect of the DC interruption system according to the embodiment. [Figure 22] It is a second graph for explaining the effect of the DC interruption system according to the embodiment. DESCRIPTION OF EMBODIMENTS

[0008] Hereinafter, a DC interruption system, a control method for a DC interruption device, and a control program for a DC interruption device according to embodiments of the present invention will be described with reference to the drawings. Here, identical or similar parts are denoted by common reference numerals, and redundant descriptions are omitted. FIG. 1 is a block diagram showing the configuration of a DC interruption system 200 according to an embodiment. The DC interruption system 200 includes a DC interruption device 100 and a control device 210.

[0009] The DC interruption device 100 includes a main interrupter 10, a commutation circuit 20, an energy absorption circuit 30, and a rectifier circuit 40.

[0010] The main interrupter 10 is provided on a DC line 11. In the example of FIG. 1, a power supply source such as a power plant is connected to the left side of the main interrupter 10, and a load is connected to the right side. In the following description, the line 11a on the side to which the power supply source is connected is referred to as the upstream side, and the load-side line 11b on the side to which the load is connected is referred to as the downstream side. The DC interruption system 200 described below is also applicable when the left and right on the drawing are reversed, with the line 11a as the downstream side to which the load is connected and the line 11b as the upstream side to which the power supply source is connected.

[0011] The main interrupter 10 includes, for example, a plurality of interruption units, and the interruption unit may be configured by at least any one of a vacuum interrupter, a gas interrupter, and a gap switch, or a combination thereof. Further, a saturable reactor may be connected in series to the main interrupter 10. The saturable reactor may be one saturable reactor or a plurality of saturable reactors connected in series.

[0012] Furthermore, the main circuit breaker 10 may further include voltage divider circuits connected in parallel to the energy absorption circuit 30, which is an energy absorption unit. In this case, the voltage divider circuits may be, for example, circuits that operate to divide the inter-pole voltages generated between the poles of vacuum circuit breakers, gas circuit breakers, and gap switches in multiple interruption units equally or unevenly. Also, an interruption unit may include a circuit in which at least one of the vacuum circuit breaker, gas circuit breaker, and gap switch and an energy absorption unit are connected in parallel to each other.

[0013] The main circuit breaker 10 performs an interruption operation, for example, to isolate a fault in the system, based on a command from the circuit breaker operating circuit 1.

[0014] The commutator circuit 20 is provided to generate an AC component when the main circuit breaker 10 is interrupted. As shown in Figure 1, the commutator circuit 20 is provided in parallel with the main circuit breaker 10. The commutator circuit 20 has a switch 21 and a capacitor 22 provided in series with each other.

[0015] The energy absorption circuit 30 is an energy absorption unit provided to absorb residual energy accumulated in the DC system and DC lines when the main circuit breaker 10 trips. The energy absorption circuit 30 has a metal oxide surge arrester (MOSA) 31 and a reactor 32, both provided in parallel with the main circuit breaker 10. The reactor 32 is arranged in series with the commutation circuit 20. The surge arrester 31 is composed of zinc oxide (ZnO) elements arranged in series only, in parallel only, or in a combination of series and parallel.

[0016] The rectifier circuit 40 is provided in parallel with the main circuit breaker 10 and includes thyristors 41a and 41b arranged in parallel with each other in opposite directions.

[0017] The control device 210 receives a tripping command signal from the circuit breaker operating circuit 1 to the main circuit breaker 10, and outputs predetermined command signals to the commutation circuit 20 and the rectifier circuit 40.

[0018] The control device 210 may, for example, when a fault current is generated as the current to be interrupted due to a lightning strike, interrupt the system at the location where the fault current occurred, and then perform high-speed reclosing to quickly reconnect the system. In this case, when the main circuit breaker 10 interrupts the system and the system is reconnected by the rectifier circuit 40, the control device 210 superimposes the fault current flowing through the rectifier circuit 40 with the current from the commutator circuit 20. If the fault does not persist after high-speed reclosing, the main circuit breaker 10 is closed again. If a charging circuit such as a backup charging circuit for the capacitor 22 is provided, the control device 210 may also be responsible for controlling the charging. Note that some DC interruption systems 200 do not perform high-speed reclosing. In this case, the control device 210 does not need to control high-speed reclosing after the main circuit breaker 10 interrupts the system.

[0019] The control device 210 performs switching control by having a hardware processor, such as a CPU (Central Processing Unit), execute a control program (software). Alternatively, the control device 210 may perform switching control using hardware (including circuitry) such as an LSI (Large Scale Integrator), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphic Processing Unit), or it may perform switching control through the cooperation of software and hardware.

[0020] The control program may be stored in advance in a storage device such as the controller's HDD or flash memory (a storage device equipped with a non-transient storage medium), or it may be stored in a removable storage medium such as a DVD or CD-ROM and installed in the storage device when the storage medium (non-transient storage medium) is inserted into the drive device. The control program may also be stored in other storage units.

[0021] Here, the currents and voltages of each part are indicated by the symbols shown in Figure 1. Specifically, the DC line current flowing through the DC line 11 is represented by I, the main circuit breaker current flowing through the main circuit breaker 10 is represented by Ib, the main circuit breaker voltage across the main circuit breaker 10 is represented by Vb, the commutation circuit current flowing through the commutation circuit 20 is represented by It, and the switch voltage across the switch 21 of the commutation circuit 20 is represented by Vt.

[0022] Figure 2 is a block diagram illustrating the basic configuration of the DC circuit breaker 100 according to this embodiment. Figure 2 is a basic configuration diagram illustrating the DC circuit breaker 100 according to this embodiment shown in Figure 1, its components, and modified examples.

[0023] The DC circuit breaker 100 includes a main circuit breaker 10, an energy absorption circuit 30 and a rectifier circuit 40 connected in parallel to the main circuit breaker 10, and a commutation circuit 20 electrically connected to the energy absorption circuit 30. The DC circuit breaker 100 according to this embodiment shown in Figure 1 is also based on this configuration.

[0024] First, a modified example of the commutation circuit 20 will be explained using Figures 3 to 6. In Figures 3 to 6, the left side of the diagram is connected to the power supply line 11a (upstream side), and the right side is connected to the load line 11b (downstream side). In any of the diagrams, the left and right sides on the paper may be reversed.

[0025] Figure 3 is a block diagram showing a commutation circuit 20 according to a first example of the DC circuit breaker 100 according to this embodiment. The first example is the commutation circuit 20 of the DC circuit breaker 100 according to this embodiment shown in Figure 1.

[0026] Figure 4 is a block diagram showing a commutation circuit 20a according to a second example of the DC circuit breaker 100 according to the embodiment. The commutation circuit 20a has a switch 21, a reactor 23, and a capacitor 22 arranged in series from the upstream side.

[0027] Figure 5 is a block diagram showing a commutation circuit 20b according to a third example of the DC circuit breaker 100 according to the embodiment. The commutation circuit 20b has a switch 21, a capacitor 22, and a reactor 23 arranged in series from the upstream side.

[0028] Figure 6 is a block diagram showing a commutation circuit 20c according to a fourth example of the DC circuit breaker 100 according to the embodiment. The commutation circuit 20c has a capacitor 22, a switch 21, and a reactor 23 arranged in series from the upstream side.

[0029] Alternatively, a commutation circuit may be formed by combining any of the commutation circuits 20, 20a, 20b, and 20c.

[0030] Next, a modified example of the energy absorption circuit 30 will be described using Figures 7 to 12. Similarly, in Figures 7 to 12, the left side of the figure is connected to the power supply line 11a (upstream side), and the right side is connected to the load line 11b (downstream side). In any of the figures, the left and right sides of the page may be reversed, and the top and bottom of the page may also be reversed.

[0031] Figure 7 is a block diagram showing an energy absorption circuit 30 according to a first example of a DC circuit breaker according to an embodiment. The first example is the energy absorption circuit 30 of the DC circuit breaker 100 according to this embodiment shown in Figure 1.

[0032] Figure 8 is a block diagram showing an energy absorption circuit 30a according to a second example of a DC circuit breaker according to an embodiment. The energy absorption circuit 30a includes a surge arrester 31 positioned between the upstream and downstream sides, and reactors 32 positioned on the connection line to the commutation circuit 20 on the upstream side and on the connection line to the load-side line 11b on the downstream side.

[0033] Figure 9 is a block diagram showing an energy absorption circuit 30b according to a third example of a DC circuit breaker according to an embodiment. The energy absorption circuit 30b includes a surge arrester 31 positioned between the upstream and downstream sides, and reactors 32 positioned on the connection line to the commutation circuit 20 on the upstream side and on the connection line to the power supply source side line 11a on the upstream side, respectively.

[0034] Figure 10 is a block diagram showing an energy absorption circuit 30c according to a fourth example of a DC circuit breaker according to an embodiment. The energy absorption circuit 30c includes a surge arrester 31 positioned between the upstream and downstream sides, and reactors 32 positioned on the connection line to the power supply source side line 11a and the connection line to the load side line 11b, respectively.

[0035] Figure 11 is a block diagram showing an energy absorption circuit 30d according to a fifth example of a DC circuit breaker according to an embodiment. The energy absorption circuit 30d has a reactor 32 located on the connection line to the power supply source side line 11a. Note that the energy absorption circuit 30d does not include a surge arrester 31. In the energy absorption circuit 30d, the connection line to the power supply source side line 11a connects the commutation circuit 20 and the rectifier circuit 40 to the power supply source side line 11a, and the connection line to the load side line 11b connects the commutation circuit 20 and the rectifier circuit 40 to the load side line 11b.

[0036] Figure 12 is a block diagram showing an energy absorption circuit 30e according to a sixth example of a DC circuit breaker according to the embodiment. The energy absorption circuit 30e has a surge arrester 31 positioned between the upstream and downstream sides. Note that the energy absorption circuit 30e does not have a reactor.

[0037] Alternatively, any combination of energy absorption circuits 30, 30a, 30b, 30c, 30d, and 30e may be used to form an energy absorption circuit.

[0038] Next, a modified example of the rectifier circuit 40 will be described using Figures 13 to 17. Similarly, in Figures 13 to 17, the left side of the diagram is the side connected to the power supply line 11a (upstream side), and the right side is the side connected to the load line 11b (downstream side).

[0039] Figure 13 is a block diagram showing a rectifier circuit 40 according to a first example of a DC circuit breaker according to an embodiment. The first example is the rectifier circuit 40 of the DC circuit breaker 100 according to this embodiment shown in Figure 1.

[0040] Figure 14 is a block diagram showing a rectifier circuit 40a according to a second example of a DC circuit breaker according to an embodiment. The rectifier circuit 40a has a triac (Triode for Alternating Current) 42 positioned between the upstream and downstream sides, instead of the thyristors 41a and 41b in Figure 1.

[0041] Figure 15 is a block diagram showing a rectifier circuit 40b according to a third example of a DC interruption device according to the embodiment. The rectifier circuit 40b has a diode 43 arranged in the forward direction from downstream to upstream, and a thyristor 41a arranged in parallel with the diode 43 and in the opposite direction to the diode 43.

[0042] Figure 16 is a block diagram showing a rectifier circuit 40c according to a fourth example of a DC interruption device according to an embodiment. The rectifier circuit 40c has a diode 43 arranged in reverse direction from downstream to upstream, and a self-excited semiconductor 44 arranged in parallel with the diode 43. The self-excited semiconductor 44 may be an IGBT (Insulated Gate Bipolar Transistor), IEGT (Injection Enhanced Gate Transistor), IGCT (Integrated Gate Commutated Turn-off Thyristor), or GTO (Gate Turn-Off Thyristor).

[0043] Figure 17 is a block diagram showing a rectifier circuit 40d according to a fifth example of a DC circuit breaker according to the embodiment. The rectifier circuit 40d has two self-excited semiconductors 44 arranged in parallel with each other and in opposite directions.

[0044] Alternatively, any combination of rectifier circuits 40, 40a, 40b, 40c, and 40d may be used to form a rectifier circuit.

[0045] The commutation circuit 20 and its modified form, the energy absorption circuit 30 and its modified form, and the rectifier circuit 40 and its modified form according to this embodiment have been described above, and these can be combined in any way. In the case of the combination of the commutation circuit 20 shown in Figure 3 and the energy absorption circuit 30e shown in Figure 12, a reactor is not provided, but it is possible to generate an oscillation component by the inductance (L) of the circuit.

[0046] Figure 18 is a flowchart showing the procedure for performing the interruption duty in the control method of the DC interruption device 100 according to the embodiment. In Figure 18, the area within the solid line frame shows the operation of the control device 210, and the area within the dashed line frame shows the transition of the state of the DC interruption device 100. Figure 19 is a graph showing an example of the temporal transition of the DC interruption system according to the embodiment. The procedure for performing the interruption duty shown in Figure 18 will be explained sequentially, referring to the graph in Figure 19.

[0047] In the following explanation, we will use the DC circuit breaker 100 having the configuration shown in Figure 1 as an example. However, even if modified versions are used for at least one or all of the elements, the control method will be the same if the equivalent parts are substituted.

[0048] First, the control device 210 sets the gate signals of each thyristor 41a and 41b of the rectifier circuit 40 to ON (step S11). That is, in preparation for a fault, the rectifier circuit 40 is in parallel with the main circuit breaker 10 and conducts between the power supply source line 11a and the load line 11b.

[0049] Meanwhile, the switch 21 of the commutation circuit 20 is in the open state. In this state, with the commutation circuit 20 disconnected from the main circuit breaker 10, the capacitor 22 is charged via, for example, a pre-charging circuit (not shown in Figure 1) so that it has a potential opposite to that of the DC line 11. In other words, the commutation circuit 20 is set to a charged state for the capacitor 22.

[0050] At time t2 (Figure 19), an accident occurs (event progression W1). When an accident occurs, the control device 210 receives an accident occurrence signal (step S12). Here, an accident refers to a situation where an accident occurs in the DC line 11 or the circuit or power system to which it is connected, causing the main circuit breaker 10 to open. The accident occurrence signal may be caused by, for example, a ground fault, overcurrent, three-phase current, voltage imbalance, etc., and may be a direct or indirect output from these relays, or a command from another protection system.

[0051] When the control device 210 receives a fault signal, it outputs an open command for the main circuit breaker 10 (step S13). Upon receiving the open command from the control device 210, the main circuit breaker 10 transitions to the open state at time t2 (Figure 19). As the main circuit breaker 10 opens, an arc discharge occurs in the main circuit breaker 10, and the main circuit breaker 10 remains energized (event transition W2).

[0052] The control device 210 outputs a closing command to the switch 21 of the commutation circuit 20 immediately after outputting an opening command to the main circuit breaker 10 (step S14). The closing command may be output to the switch 21 of the commutation circuit 20 simultaneously with the output of the opening command to the main circuit breaker 10. Alternatively, the closing command may be output to the switch 21 of the commutation circuit 20 before the output of the opening command to the main circuit breaker 10. Upon receiving the closing command from the control device 210, the switch 21 of the commutation circuit 20 transitions to the closed state at time t3.

[0053] When the switch 21 of the commutation circuit 20 closes, an alternating current is applied from the commutation circuit 20 to the main circuit breaker 10 (event transition W3). That is, charge is released from the pre-charged capacitor 22 into the loop including the capacitor 22, the reactor 32, and the main circuit breaker 10, and an oscillating current in the opposite direction to the direction in which the fault current Ib flows is supplied to the main circuit breaker 10 and superimposed on the fault current. As a result, a current zero is formed in the main circuit breaker 10, and the current interruption is completed (time t4 in Figure 19).

[0054] When a current zero is formed in the main circuit breaker 10 at time t4 and current interruption is completed, the resonant current that flowed in the loop including capacitor 22, reactor 41, and main circuit breaker 10 between time t3 and time t4 flows in the loop including capacitor 22, reactor 41, and thyristors 41a and thyristor 41b that constitute the rectifier circuit 40 after time t4. Also, the fault current Ib that flowed in the main circuit breaker 10 between time t1 and time t4 flows in the thyristors 41a and thyristor 41b that constitute the rectifier circuit 40 after time t4. Therefore, both the fault current Ib and the resonant current flowing in the loop including capacitor 22, reactor 23, and thyristors 41a and thyristor 41b flow through the thyristors 41a and thyristor 41b that constitute the rectifier circuit 40 (event transition W4).

[0055] After this, the insulation performance of the main circuit breaker 10 returns to the recovered state (event transition W5). During this time, the control device 210 continues to check the insulation performance of the main circuit breaker 10 (step S15). That is, if it is not determined that the insulation performance has recovered (step S16 NO), steps S15 and S16 are repeated.

[0056] The insulation performance of the main circuit breaker 10 may be determined, for example, by calculating the resistance value obtained by dividing the estimated voltage of the main circuit breaker 10 by the measured value of the current flowing through the main circuit breaker 10. Alternatively, it may be determined by the measured value of the voltage applied across the main circuit breaker and the estimated value of the current. Alternatively, it may be determined from the measured value of the current flowing through the main circuit breaker 10 and the measured value of the voltage applied across the main circuit breaker. Furthermore, while the thyristors 41a and thyristors 41b constituting the rectifier circuit 40 are conducting, the voltage applied across the main circuit breaker 10 may be determined as the sum of the ON voltage of the thyristors and the product of the rate of change of current and the inductance component of the circuit.

[0057] If it is determined that the insulation performance has been restored (step S16 YES), the control device 210 turns OFF the gate signals of thyristors 41a and 41b of the rectifier circuit 40 (step S17). The rectifier circuit 40 maintains its conduction state until the current flowing through thyristors 41a and 41b becomes zero. This corresponds to time t5 in Figure 19.

[0058] When the sum of the fault current Ib flowing through thyristors 41a and 41b of the rectifier circuit 40 and the resonant current flowing through the loop including capacitor 22, reactor 23, and main circuit breaker 10 of the commutator circuit 20 becomes zero, the current flowing through thyristors 41a and 41b of the rectifier circuit 40 becomes zero. As a result, thyristors 41a and 41b transition to a non-conducting state. Consequently, the DC interruption system 200 completes its interruption duty by interrupting the current (event transition W6). This corresponds to time t6 in Figure 19.

[0059] Furthermore, forcibly interrupting the fault current through such control may leave residual electromagnetic energy in the system. This residual electromagnetic energy charges the capacitor 22 that constitutes the commutation circuit 20 and is processed by the energy absorption circuit 30. When the DC interruption system 200 completes current interruption at time t6, the fault current becomes current Ir and flows into the commutation circuit 20, which consists of the circuit excluding the main circuit breaker 10 and the rectifier circuit 40.

[0060] The current Ir due to the fault current flowing through the commutation circuit 20 charges the capacitor 22 in the opposite direction to the direction it was previously charged, while the switch 21 is "closed". If we ignore the voltage induced in the reactor 32, the charging voltage Vc of the capacitor 22 is approximately equal to the voltage Vb across the main circuit breaker 10, and the surge arrester 31, which is a unit of the energy absorption circuit 30, begins processing energy from the time when Vb rises to a certain voltage value.

[0061] The control device 210 outputs an "open" command to the switch 21 again (step S18). Based on this, the switch 21 opens again at time t7 in Figure 19, and the capacitor 22 is disconnected from the DC system. If a high-speed reclosing step is required, the switch 21 opening again allows the charging voltage Vc of the capacitor 22 to be maintained at the voltage value necessary for further fault handling.

[0062] If a high-speed reclosing step is required, the voltage value may, of course, be increased or maintained by charging the capacitor 22 from a circuit not shown. Note that time t7 in Figure 19 may be before event transition W6, when the DC interruption system 200 completes the current interruption and fulfills its interruption duty. In addition, if the switch 21 automatically opens after closing due to electromagnetic or mechanical repulsion, the control device 210 does not need to output an "open" command to the switch 21.

[0063] Next, the procedure for the high-speed reclosing step S20 will be described. Figure 20 is a flowchart showing the procedure for high-speed reclosing in the control method of the DC circuit breaker 100 according to the embodiment.

[0064] First, the control device 210 turns ON the gate signal of the thyristor 41a of the rectifier circuit 40 (step S21, time t8 in Figure 19). Furthermore, it may also turn ON the gate signal of the thyristor 41b of the rectifier circuit 40.

[0065] If the fault is not still present when the thyristor 41a constituting the rectifier circuit 40 is turned ON in order to achieve high-speed reclosing, the control device 210 outputs a "close" command to the main circuit breaker 10 again (step S22). As a result, high-speed reclosing is achieved.

[0066] On the other hand, when the thyristor 41a constituting the rectifier circuit 40 is turned ON in order to reclose the circuit at high speed, the fault may persist. This case will be explained below. Note that the response in this case is shown from time t8 onwards in Figure 19.

[0067] After high-speed reclosing, a fault current flows through the thyristor 41a that constitutes the rectifier circuit. At this time, the direction of the fault current Ib is the same as the direction of the first fault current before the high-speed reclosing was performed.

[0068] In response to the continued fault and the re-flow of current Ib, the control device 210 turns OFF the gate signals of thyristors 41a and 41b at time t9. The conduction state is maintained until thyristors 41a and 41b are turned off.

[0069] Next, at time t10, the switch 21 constituting the commutation circuit 20 is closed. By closing the switch 21, charge is released from the pre-charged capacitor 22 into the loop including the capacitor 22, the reactor 32, and the rectifier circuit 40. As a result of the charge being released from the capacitor 22, a resonant current flows from the capacitor 22 through the reactor 32 and the thyristor 41a. Consequently, in the DC circuit breaker 100, an oscillating current in the same direction as the fault current Ib is superimposed on the fault current, and then, due to resonance, an oscillating current in the opposite direction is superimposed on the fault current. As a result, the thyristor 41a turns off at time t11. After that, as in the case of the first fault interruption, the electromagnetic energy remaining in the system is processed.

[0070] The above describes the processing flow when a fault persists while the thyristor 41a constituting the rectifier circuit 40 is turned ON in order to reclose the circuit at high speed.

[0071] Another possible scenario is when the fault current Ib flowing through the main circuit breaker 10 due to a fault flows in the opposite direction to the arrow in Figure 1. In this case, as the first fault interruption, the switch 21 is closed at time t3. As a result, an oscillating current in the same direction as the fault current Ib is superimposed on the fault current in the main circuit breaker 10, and then, due to resonance, an oscillating current in the opposite direction to the fault current Ib is superimposed on the fault current. Consequently, the main circuit breaker 10 completes its interruption by forming a current zero at time t4.

[0072] When the main circuit breaker 10 is tripped, the fault current and oscillating current that were flowing through the main circuit breaker 10 flow to the thyristors 41a and 41b of the rectifier circuit 40. By turning off the gate signals of the thyristors 41a and 41b of the rectifier circuit 40 at time t5, the thyristors 41a and 41b turn off at time t6 when the sum of the fault current and oscillating current becomes zero, and the DC circuit breaker 100 completes the fault interruption. After that, the electromagnetic energy remaining in the DC system is processed.

[0073] The above explanation describes the case where interruption is successful at the first current zero point formed in the main circuit breaker 10 by the resonant current superimposed from the commutation circuit 20 to the main circuit breaker 10. In contrast, the main circuit breaker 10 may fail to interrupt the current at the first current zero point, but may succeed at the second or third current zero point.

[0074] In this case, the operation to interrupt the load current as the current to be interrupted is the same as the operation for the first fault interruption. That is, by opening the main circuit breaker 10 and closing the switch 21 of the commutation circuit 20, charge is released from the capacitor 22 into the loop including the capacitor 22, switch 21, reactor 32, and main circuit breaker 10, causing a resonant current to flow. As the resonant current flows, a current zero point is formed in the main circuit breaker 10, completing the current interruption and thus fulfilling its interruption duty.

[0075] When the current flowing through the main circuit breaker 10 becomes zero, the resonant current that was flowing through the loop including the capacitor 22, switch 21, reactor 32, and main circuit breaker 10 flows through the loop including the capacitor 22, switch 21, reactor 32, and rectifier circuit 40. The control device 210 of the DC circuit breaker 100 turns OFF the gate signals of the thyristors 41a and 41b of the rectifier circuit 40 at an appropriate time after a current zero point is formed in the main circuit breaker 10, so that the thyristors 41a and 41b turn off at the time when the sum of the load current and the resonant current flowing through the thyristors 41a and 41b becomes zero. As a result, the rectifier circuit 40 becomes non-conductive and fulfills its interruption duty. The energy remaining in the system is processed by the energy absorption circuit 30. As a result, the DC circuit breaker 100 fulfills its current interruption duty.

[0076] Figure 21 is a first graph illustrating the effects of the DC interruption system according to the embodiment. Figure 22 is a second graph illustrating the effects of the DC interruption system according to the embodiment.

[0077] The first graph shows the response in this embodiment, and the second graph shows the response in a conventional example shown as a comparative example. In Figures 21 and 22, the horizontal axis represents time (msec), and the vertical axis represents the voltage and current values ​​at the main circuit breaker 10, both of which are relative values ​​(pu).

[0078] In Figure 21, p1a represents the point where the current Ib of the main circuit breaker 10 is zero, and p2a represents the point where the absolute value of the voltage of the main circuit breaker 10 is maximum in the negative direction. Similarly, in Figure 22, p1b represents the point where the current Ib of the main circuit breaker 10 is zero, and p2b represents the point where the absolute value of the voltage of the main circuit breaker 10 is maximum in the negative direction.

[0079] In this case, comparing the time interval Δt1 from point p1a to point p2a in Figure 21 (this embodiment) with the time interval Δt2 from point p1b to point p2b in Figure 22 (comparative example), the time interval Δt1 is approximately 100 times or more than the time interval Δt2, indicating that the time interval Δt1 is significantly larger than the time interval Δt2.

[0080] Furthermore, the voltage change rate (ΔVcb / Δt), which is the slope connecting the point where the current value Ib of the main circuit breaker 10 is zero and the point where the absolute value of the voltage of the main circuit breaker 10 is maximum in the negative direction, is approximately 1 / 100th or less in the case of Figure 22 (comparative example) in the case of Figure 21 (this embodiment), and is significantly smaller in this embodiment compared to the comparative example.

[0081] As shown in the comparative example, in the conventional technology, the transient recovery voltage is applied immediately after the current flowing through the main circuit breaker becomes zero. On the other hand, in the DC circuit breaker 100 according to this embodiment, the transient recovery voltage is applied after a predetermined time has elapsed since the current flowing through the main circuit breaker became zero. Therefore, the voltage change rate (ΔVcb / Δt), which is the slope connecting the point where the current value Ib of the main circuit breaker 10 becomes zero and the point where the absolute value of the voltage of the main circuit breaker 10 becomes maximum in the negative direction, is significantly reduced compared to the conventional example. As a result, the risk of tripping failure can be reduced.

[0082] Furthermore, in this embodiment, since the fault current and oscillating current are commutated to the rectifier circuit 40 after a current zero point is formed in the main circuit breaker 10, the transient recovery voltage applied after the current zero point in the main circuit breaker 10 can be reduced. Therefore, the number of circuit breakers in series that make up the main circuit breaker 10 can be reduced, making miniaturization easier.

[0083] Furthermore, in conventional systems, after the first fault interruption, it is necessary to drive the main circuit breaker multiple times to perform high-speed reclosing and re-interruption, resulting in a complex drive mechanism and making miniaturization difficult. In this respect, the DC interruption system 200 of this embodiment can perform high-speed reclosing and re-interruption using the rectifier circuit 40 and the commutator circuit 20, so it is not necessary to operate the main circuit breaker 10 for re-interruption. As a result, the drive mechanism and control circuit are simplified. In addition, since it is not necessary to operate the main circuit breaker 10, there is no need to wait for the electrodes of the main circuit breaker 10 to open sufficiently, allowing for high-speed re-interruption and reducing the number of capacitors required for re-interruption. As a result, the overall size of the device can be made more compact.

[0084] According to the embodiments described above, it is possible to provide a DC interruption system, a control method for a DC interruption device, and a control program for a DC interruption device that can be made compact in structure.

[0085] [Other embodiments] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. Furthermore, the features of each of these embodiments may be combined. Moreover, the 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. Embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0086] 1... Circuit breaker operating circuit, 10... Main circuit breaker, 11... DC line, 11a... Power supply side line, 11b... Load side line, 20, 20a, 20b, 20c... Commutation circuit, 21... Switch, 22... Capacitor, 23... Reactor, 30, 30a, 30b, 30c, 30d, 30e... Energy absorption circuit, 31... Surge arrester, 32... Reactor, 40, 40a, 40b, 40c, 40d... Rectifier circuit, 41a, 41b... Thyristor, 42... Triac, 43... Diode, 44... Self-excited semiconductor, 100... DC interruption device, 200... DC interruption system, 210... Control device

Claims

1. The main circuit breaker installed on the DC line, A commutation circuit connected in parallel to the main circuit breaker, which supplies a resonant current to the main circuit breaker when the main circuit breaker is open, A rectifier circuit is connected in parallel to the commutation circuit, has a thyristor, is configured to be able to conduct electricity in both directions, and is capable of maintaining a conductive state until the insulation performance of the main circuit breaker recovers when the main circuit breaker is opened. A control device that controls the main circuit breaker, the commutation circuit, and the rectifier circuit, A DC interruption system characterized by comprising the following features.

2. The DC interruption system according to claim 1, further comprising an energy absorption circuit electrically connected to the commutation circuit.

3. The DC circuit breaker according to claim 1, characterized in that the main circuit breaker is composed of a plurality of units.

4. The main circuit breaker is further equipped with an ammeter installed in series with the main circuit breaker. The control device calculates the insulation performance of the main circuit breaker from the value of the current flowing through the ammeter. The DC interruption system according to feature 1.

5. The step of making a rectifier circuit having a thyristor and configured to be energized in both directions conduct electricity, The steps include: opening the main circuit breaker upon receiving a fault signal, The steps include: receiving the fault signal and supplying a resonant current from the commutation circuit to the main circuit breaker; A step of determining whether the insulation performance of the main circuit breaker has been restored, If it is determined that the insulation performance has been restored, the rectifier circuit is set to a non-conductive state. A control method for a DC circuit breaker, characterized by having the following features.

6. On the computer, The steps include: bringing a rectifier circuit, which has a thyristor and is configured to be energized in both directions, into a conductive state; The steps include:

1. Receiving a fault signal and opening the main circuit breaker; The steps include: receiving the fault signal and supplying a resonant current from the commutation circuit to the main circuit breaker; A step of determining whether the insulation performance of the main circuit breaker has been restored, If it is determined that the insulation performance has been restored, the rectifier circuit is made non-conductive. A control program for a DC circuit breaker to execute the operation.

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