Circuit breaker

Abstract

To prevent a current limited to a load side from continuing to flow during a breaker operation.SOLUTION: A circuit breaker (10) includes a first circuit breaking section (11) that switches between a connected state and a disconnected state of a main line (PL), a second circuit breaking section (12) that switches between a connected state and a disconnected state between the main line (PL) and the return line (NL) on the DC power supply (PS) side of the first circuit breaking section (11), a resistor (13) that is connected in series with the second circuit breaking section (12), and a control section (15).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shutoff device. [Background technology]

[0002] Patent Document 1 discloses a DC circuit breaking device that is inserted and connected to a main circuit between a DC power source and a load. In this DC circuit breaking device, a first circuit breaking unit, a series circuit in which a second circuit breaking unit and a resistor are connected in series, and an energy absorbing device are connected in parallel. When the first circuit breaking unit and the second circuit breaking unit are turned on, DC power is supplied from the DC power source to the load.

[0003] Furthermore, to protect the main circuit from excessive short-circuit current, when the main circuit current supplied from the DC power supply to the load reaches a preset cutoff current, the first circuit breaker is turned off and the main circuit current cutoff operation begins. When the first circuit breaker is turned off, the main circuit current that had mainly flowed through the first circuit breaker is diverted to the series circuit consisting of the second circuit breaker, which is still on, and the resistor, and is therefore limited by the resistor. After that, the second circuit breaker is turned off, completing the main circuit current cutoff operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-044904 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the DC circuit breaker disclosed in Patent Document 1 has a problem in that the limited current continues to flow from the DC power supply to the load side where the fault has occurred while the second circuit breaker is on during the circuit breaker operation. One aspect of the present invention aims to prevent the limited current from continuing to flow to the load side during the circuit breaker operation. [Means for solving the problem]

[0006] In order to solve the above problems, one embodiment of the present invention provides a circuit breaker that is arranged on a DC bus consisting of a main line and a return line, and includes a first circuit breaker that switches the main line between a connected state and a disconnected state, a second circuit breaker that is located closer to the power source than the first circuit breaker and switches the main line and the return line between a connected state and a disconnected state, a resistor connected in series with the second circuit breaker between the main line and the return line, and a control unit.The control unit normally controls the first circuit breaker to a connected state and the second circuit breaker to a disconnected state, and when it detects that the current flowing through the main line has reached or exceeded a first predetermined value that exceeds the rated value, it switches the second circuit breaker to a connected state and then switches the first circuit breaker to a disconnected state. [Effects of the Invention]

[0007] According to one aspect of the present invention, it is possible to prevent the current limited to the load from continuing to flow during the interruption operation. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram showing an example of the configuration of a DC power transmission system to which a circuit breaker according to an embodiment of the present invention is applied; [Figure 2] 2 is a flowchart showing an example of processing by a control unit included in the cutoff device shown in FIG. [Figure 3] 3 is a diagram showing switching between a connected state and a disconnected state in a first disconnecting unit and a second disconnecting unit provided in the disconnecting device shown in FIG. 1, and the relationship between time and current value. FIG. [Figure 4] FIG. 2 is a circuit diagram showing an example of the configuration of a breaker device according to a comparative example of the present invention. [Figure 5] 5 is a diagram showing switching between a connected state and a disconnected state in a first disconnecting unit and a second disconnecting unit provided in the disconnecting device shown in FIG. 4, and the relationship between time and current value. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Configuration of DC Power Transmission System 1> Fig. 1 is a circuit diagram showing an example of the configuration of a DC power transmission system 1 to which a circuit breaker 10 according to an embodiment of the present invention is applied. As shown in Fig. 1, the DC power transmission system 1 transmits DC power from the primary side to the secondary side via a DC bus BL composed of a main line PL and a return line NL. That is, the DC power transmission system 1 transmits DC power from a DC power source PS, which is an example of a power source, to a load R1.

[0010] The main line PL is one of a pair of wires between the DC power supply PS and the load R1, and is a wire through which current flows from the DC power supply PS to the load R1. The return line NL is the other of the pair of wires between the DC power supply PS and the load R1, and is a wire through which current flows from the load R1 to the DC power supply PS. The inductance component L1 shown in Figure 1 corresponds to the inductance contained in the DC bus BL.

[0011] The DC power transmission system 1 includes a DC power source PS and a circuit breaker 10. In this specification, the term "connected" means "electrically connected." Furthermore, in this specification, the term "disconnected" means "electrically disconnected."

[0012] <Configuration of circuit breaker 10> The circuit breaker 10 is a device that interrupts an excessive current (fault current) that occurs when a short circuit or other fault occurs on the load R1 side of the DC bus BL. The circuit breaker 10 is inserted into the DC bus BL. The circuit breaker 10 includes a first circuit breaker unit 11, a second circuit breaker unit 12, a resistor 13, and a control unit 15.

[0013] <Configuration of first interrupter unit 11> The first circuit breaker 11 is a switch provided on the main line PL. The first circuit breaker 11 switches between a connected state and a disconnected state of the main line PL. The first circuit breaker 11 is connected to the DC power supply PS via the main line PL on the DC power supply PS side, and is connected to the load R1 via the main line PL on the load R1 side.

[0014] The first cutoff unit 11 is configured with a semiconductor switch element such as an IGBT (Insulated Gate Bipolar Transistor). However, without being limited thereto, the first cutoff unit 11 may be configured with a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). As shown in FIG. 1, the semiconductor switch element may be provided with a freewheeling diode. Furthermore, the first cutoff unit 11 may be a mechanical switch.

[0015] <Configuration of second cutoff unit 12 and resistor 13> The second circuit breaker 12 is a switch provided in a parallel section 14 that connects the main line PL and the return line NL. Like the first circuit breaker 11, the second circuit breaker 12 is configured with a semiconductor switch element such as an IGBT. However, the present invention is not limited to this, and the second circuit breaker 12 may be configured with a MOSFET. The second circuit breaker 12 may also be a mechanical switch.

[0016] When only one of the first and second circuit breakers 11 and 12 is a mechanical switch, it is preferable to use a mechanical switch for the first circuit breaker 11. This is because it is preferable to use a mechanical switch with low resistance when conducting, thereby reducing power loss during normal operation. The second circuit breaker 12 is included in a parallel part 14 connected in parallel with the DC power supply PS and the load R1.

[0017] The parallel portion 14 is connected between the main line PL and the return line NL and includes a line CL, and the second circuit breaker 12 and resistor 13 connected to the line CL. The line CL branches off from a branch point P1 of the main line PL between the DC power supply PS and the first circuit breaker 11. The line CL is also a line branching off from a branch point P2 of the return line NL between the DC power supply PS and the load R1.

[0018] The parallel part 14 is a current limiting circuit for limiting a fault current that occurs when a short-circuit fault or the like occurs on the load R1 side of the DC bus BL relative to the circuit breaker 10. The DC power supply PS and the load R1 are located on opposite sides of the parallel part 14. The second circuit breaker 12 switches between a connected state and a disconnected state between the main line PL and the return line NL on the DC power supply PS side relative to the first circuit breaker 11.

[0019] The resistor 13 is connected in series with the second circuit breaker 12 between the main line PL and the return line NL. Specifically, the resistor 13 is included in the parallel portion 14 and is connected in series with the second circuit breaker 12 in the parallel portion 14.

[0020] <Configuration of control unit 15> The control unit 15 controls the first interrupting unit 11 and the second interrupting unit 12. The control unit 15 can control the first interrupting unit 11 to a connected state by outputting a connection command to the first interrupting unit 11. The control unit 15 can control the first interrupting unit 11 to a disconnected state by outputting a disconnection command to the first interrupting unit 11. Furthermore, the control unit 15 can control the second interrupting unit 12 to a connected state by outputting a connection command to the second interrupting unit 12. The control unit 15 can control the second interrupting unit 12 to a disconnected state by outputting a disconnection command to the second interrupting unit 12.

[0021] The control unit 15 changing the first circuit breaking unit 11 or the second circuit breaking unit 12 from the cut-off state to the connected state can be said to be the control unit 15 turning on the first circuit breaking unit 11 or the second circuit breaking unit 12. In addition, the control unit 15 changing the first circuit breaking unit 11 or the second circuit breaking unit 12 from the connected state to the cut-off state can be said to be the control unit 15 turning off the first circuit breaking unit 11 or the second circuit breaking unit 12.

[0022] The control unit 15 acquires the current value of the current IP from a current measuring unit such as an ammeter (not shown). The current measuring unit is connected, for example, between the DC power supply PS and the branch point P1. The current measuring unit measures the current value of the current IP flowing through the main line PL. The current IP is a main circuit current flowing through the wiring of the main line PL between the DC power supply PS and the branch point P1.

[0023] <Processing of the control unit 15> Fig. 2 is a flowchart showing an example of processing by the control unit 15 included in the circuit breaker 10 shown in Fig. 1. Fig. 3 is a diagram showing switching between a connected state and a disconnected state in the first circuit breaker 11 and the second circuit breaker 12 included in the circuit breaker 10 shown in Fig. 1, and the relationship between time and current value.

[0024] Graph G1 shown by a solid line in Fig. 3 is a graph showing the current value of current IR flowing through main line PL on the load R1 side of circuit breaker 10. Graph G2 shown by a dotted line in Fig. 3 is a graph showing the current value of current IP flowing through main line PL on the DC power supply PS side of circuit breaker 10. Between time 0 and time t2, graphs G1 and G2 overlap each other, and the current value of current IP is the same as the current value of current IR.

[0025] Control unit 15 normally controls first circuit breaker 11 to be connected and second circuit breaker 12 to be disconnected. In other words, control unit 15 normally maintains first circuit breaker 11 in the connected state and second circuit breaker 12 in the disconnected state. This makes it possible to prevent power loss due to resistor 13 connected in series with second circuit breaker 12. Therefore, current can be efficiently passed through main line PL under normal circumstances.

[0026] Note that normal operation refers to a state in which no short-circuit fault or the like has occurred on the load R1 side of the DC bus BL. In Fig. 3, normal operation occurs before time t1. When a short-circuit fault or the like occurs on the load R1 side of the DC bus BL, the current values ​​of the currents IP and IR gradually increase from time t1 when the fault occurs, as shown in graphs G1 and G2 in Fig. 3. In this way, it is assumed that the current IP reaches the first predetermined value at time t2.

[0027] 2, when the DC power supply PS transmits DC power to the load R1, the control unit 15 determines whether the current IP flowing through the main line PL is equal to or greater than a first predetermined value (S1). The first predetermined value is a current value that serves as a criterion for determining whether the current IP needs to be interrupted. The first predetermined value for the current IP flowing through the main line PL is a predetermined value that exceeds the rating of the DC power transmission system 1 or the DC bus BL.

[0028] If the control unit 15 has not detected that the current IP has become equal to or greater than the first predetermined value (NO in S1), that is, if the control unit 15 has detected that the current IP has become less than the first predetermined value, it repeats step S1. If the control unit 15 has detected that the current IP has become equal to or greater than the first predetermined value (YES in S1), it changes the second circuit breaker 12 from the cut-off state to the connect state (S2). Therefore, the control unit 15 changes the second circuit breaker 12 from the cut-off state to the connect state at time t2 in FIG. 3.

[0029] After switching second cutoff unit 12 to the connected state, control unit 15 switches first cutoff unit 11 from the connected state to the cutoff state (S3). Specifically, control unit 15 switches first cutoff unit 11 from the connected state to the cutoff state at time t3. The time difference between time t2 and time t3 is, for example, several μs.

[0030] When the first circuit breaker 11 is in the circuit breaker state, the current IP is limited and the value of the current IP gradually decreases, as shown in graph G2 of Fig. 3. At this time, the current IP output from the DC power supply PS flows to the parallel part 14 as the current IC. The current value of the current IC flowing through the parallel part 14 is the same as the current value of the current IP. Furthermore, as shown in graph G1 of Fig. 3, the current value of the current IR becomes 0, that is, the current IR does not flow from the circuit breaker 10 to the load R1.

[0031] The control unit 15 determines whether a predetermined time has elapsed since the first circuit breaker 11 was switched to the interrupted state (S4). If the control unit 15 determines that the predetermined time has not elapsed since the first circuit breaker 11 was switched to the interrupted state (NO in S4), the control unit 15 repeats step S4. If the control unit 15 determines that the predetermined time has elapsed since the first circuit breaker 11 was switched to the interrupted state (YES in S4), the control unit 15 switches the second circuit breaker 12 from the connected state to the interrupted state (S5). Specifically, the control unit 15 switches the second circuit breaker 12 from the connected state to the interrupted state at time t4. At this time, as shown in graph G2 in FIG. 3, the current value of the current IP becomes 0. The time difference between time t3 and time t4 is, for example, several tens of microseconds.

[0032] In this way, when control unit 15 detects in step S1 that current IP has become equal to or greater than the first predetermined value, it causes second circuit breaker 12 to be in the cutoff state in step S5 after a predetermined time has elapsed since first circuit breaker 11 was brought into the cutoff state in step S3. As a result, after the predetermined time has elapsed, current IP in DC power supply PS can be made zero, and current IC between main line PL and return line NL can also be made zero, completing the cutoff process.

[0033] As described above, when the control unit 15 detects that the current IP flowing through the main line PL has reached or exceeded the first predetermined value, it brings the second circuit breaker 12 into the connected state and then brings the first circuit breaker 11 into the interrupted state. This makes it possible to prevent an overcurrent from flowing to the side of the first circuit breaker 11 opposite to the DC power supply PS side in the event of a short-circuit accident or the like occurring on the load R1 side of the DC bus BL. Furthermore, at the moment the first circuit breaker 11 is brought into the interrupted state, the current IP output from the DC power supply PS can be made to flow between the main line PL and the return line NL, making it possible to prevent arc discharge from occurring in the first circuit breaker 11.

[0034] Furthermore, the current IP output from the DC power supply PS is caused to flow between the main line PL and the return line NL, and the current IC flowing between the main line PL and the return line NL can be limited by the resistor 13. Moreover, the current IC being limited by the resistor 13 can be prevented from flowing to the side of the first breaker unit 11 opposite to the DC power supply PS side (the load R1 and the short-circuit point).

[0035] <Variation 1> In step S4 described above, the control unit 15 may determine whether the current IP flowing through the main line PL has become less than a second predetermined value that is lower than the first predetermined value, instead of determining whether a predetermined time has elapsed.

[0036] That is, in Modification 1, when control unit 15 detects in step S1 that current IP flowing through main line PL is equal to or greater than a first predetermined value, control unit 15 causes first circuit breaker 11 to be in an interrupted state in step S3. Furthermore, after causing first circuit breaker 11 to be in an interrupted state, when control unit 15 detects in step S4 that current IP flowing through main line PL is less than a second predetermined value, control unit 15 causes second circuit breaker 12 to be in an interrupted state in step S5.

[0037] As a result, when the current IP flowing through the main line PL becomes sufficiently small, the current IP in the DC power supply PS can be set to zero, and the current IC between the main line PL and the return line NL can be set to zero, thereby completing the interruption process.

[0038] <Variation 2> The circuit breaker 10 may further include a first snubber circuit (not shown) connected in parallel with the first circuit breaker 11, and a second snubber circuit (not shown) connected in parallel with the second circuit breaker 12. The first snubber circuit and the second snubber circuit are each a circuit in which a capacitor and a resistor are connected in series.

[0039] The first snubber circuit is a circuit for protecting the first circuit breaker 11. One end of the first snubber circuit is connected to the wiring between the branch point P1 and the first circuit breaker 11, and the other end of the first snubber circuit is connected to the wiring between the first circuit breaker 11 and the load R1. The second snubber circuit is a circuit for protecting the second circuit breaker 12. One end of the second snubber circuit is connected to the wiring between the branch point P1 and the second circuit breaker 12, and the other end of the second snubber circuit is connected to the wiring between the branch point P2 and the resistor 13. The branch point P2 is a point where the wiring CL branches off from the wiring between the DC power supply PS and the load R1.

[0040] When the first circuit breaker 11 and the second circuit breaker 12 are in the cutoff state, the first snubber circuit and the second snubber circuit can suppress the peak of the transient back electromotive force generated by the wiring inductance components of the first circuit breaker 11 and the second circuit breaker 12. This prevents the semiconductor switch elements of the first circuit breaker 11 and the second circuit breaker 12 from being destroyed by an overvoltage, and improves the reliability of the circuit breaker 10.

[0041] <Variation 3> The circuit breaker 10 may further include a first energy absorption unit (not shown) connected in parallel to the first circuit breaker 11, and a second energy absorption unit (not shown) connected in parallel to the second circuit breaker 12 and the resistor 13 in the parallel portion 14. The first energy absorption unit and the second energy absorption unit are surge absorbers that absorb the energy stored in the inductance component L1.

[0042] When first circuit breaker 11 is brought into an interrupted state, current IR is commutated from first circuit breaker 11 to the first energy absorption unit. One end of the first energy absorption unit is connected to the wiring between branch point P1 and first circuit breaker 11, and the other end of the first energy absorption unit is connected to the wiring between first circuit breaker 11 and load R1.

[0043] When the second circuit breaker 12 is turned off, the current IC is commutated from the second circuit breaker 12 to the second energy absorption unit. One end of the second energy absorption unit is connected to the wiring between the branch point P1 and the second circuit breaker 12, and the other end of the second energy absorption unit is connected to the wiring between the branch point P2 and the resistor 13.

[0044] <Comparative Example> FIG. 4 is a circuit diagram showing an example of the configuration of a circuit breaker 10A according to a comparative example of the present invention. The comparative example is not included in the technical scope of the present invention. The following describes the differences between the circuit breaker 10A and the circuit breaker 10. The circuit breaker 10A is connected to the main line PL and includes a first circuit breaker unit 11A, a second circuit breaker unit 12A, and a resistor 13A. The first circuit breaker unit 11A is connected between the DC power supply PS and the load R1 on the main line PL. The second circuit breaker unit 12A is connected in parallel with the first circuit breaker unit 11A, and the resistor 13A is connected in series with the second circuit breaker unit 12A.

[0045] Fig. 5 is a diagram showing the relationship between time and current value and switching between the connected state and the disconnected state in the first circuit breaker 11A and the second circuit breaker 12A included in the circuit breaker 10A shown in Fig. 4. In Fig. 5, graph G3 is a graph showing the current value of the current IP flowing through the main line PL in a comparative example.

[0046] In the circuit breaker 10A, the current value of the current IR flowing through the load R1 is always the same as the current value of the current IP. Also, times t1, t3, and t4 shown in Figure 5 are the same as times t1, t3, and t4 shown in Figure 3, in that order.

[0047] If a short circuit or the like occurs on the load R1 side at time t1, the current values ​​of currents IP and IR gradually increase, as shown in graph G3 of Figure 5. If current IP exceeds a third predetermined value exceeding the rated value at time t3, first circuit breaker 11A changes from the connected state to the disconnected state. When first circuit breaker 11A changes to the disconnected state, currents IP and IR are limited, and the current values ​​of currents IP and IR gradually decrease. When second circuit breaker 12 changes from the connected state to the disconnected state at time t4, the current values ​​of currents IP and IR become zero.

[0048] In the circuit breaker 10A, the first circuit breaker 11A is in a connected state from time 0 to time t3, and the second circuit breaker 12A is in a connected state from time 0 to time t4. Therefore, although the current is limited, even after the first circuit breaker 11A is switched to the disconnected state at time t3, the current continues to flow to the load where the fault has occurred for a while. Therefore, compared to the circuit breaker 10, the current supply to the fault point is not interrupted as quickly. Furthermore, in the circuit breaker 10A, the resistor 13A is connected in parallel with the first circuit breaker 11A connected to the main line PL, and therefore, even under normal circumstances, a power loss occurs due to the resistor 13A.

[0049] <Software implementation example> The functions of the control unit 15 can be realized by a program that causes a computer to function as the control unit 15. In this case, the control unit 15 includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each of the functions described in the above embodiment.

[0050] The program may be stored non-transitory on one or more computer-readable storage media. The storage media may or may not be included in the control unit 15. In the latter case, the program may be supplied to the control unit 15 via any wired or wireless transmission medium.

[0051] Furthermore, some or all of the functions of the control unit 15 can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as the control unit 15 is formed is also included in the scope of the present invention. In addition, the functions of the control unit 15 can also be realized by, for example, a quantum computer.

[0052] <Additional Notes> The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Configurations obtained by appropriately combining multiple technical means disclosed in the embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0053] 10. Circuit Breaker 11 First interrupter 12 Second interrupter 13 Resistor 15 Control Unit BL DC bus PL Main Line NL return line PS DC power supply IP current

Claims

1. A circuit breaker disposed on a DC bus consisting of a main line and a return line, a first breaker that switches between a connected state and a cutoff state of the main line; a second circuit breaker that switches between a connection state and a disconnection state between the main line and the return line, the second circuit breaker being located closer to the power source than the first circuit breaker; a resistor connected in series with the second interrupter between the main line and the return line; a control unit, The control unit Normally, the first cutoff unit is controlled to a connected state and the second cutoff unit is controlled to a cutoff state; A circuit breaker characterized in that, when it detects that the current flowing through the main line has reached a first predetermined value that exceeds the rated value, it brings the second circuit breaker into a connected state and then brings the first circuit breaker into a cut-off state.

2. The control unit 2. The circuit breaker according to claim 1, wherein when it is detected that the current flowing through the main line has reached or exceeded the first predetermined value, the second circuit breaker is brought into the cut-off state after a predetermined time has elapsed since the first circuit breaker was brought into the cut-off state.

3. The control unit When it is detected that the current flowing through the main line has reached or exceeded the first predetermined value, the first interrupter is brought into an interrupted state, and then:

2. The circuit breaker according to claim 1, wherein the second circuit breaker is brought into a circuit break state when it is detected that the current flowing through the main line has become less than a second predetermined value that is lower than the first predetermined value.

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