Circuit breaker and junction box equipped therewith

Abstract

To provide a circuit breaker and junction box capable of reliably eliminating DC arcs. [Solution] The circuit breaker A1 comprises a plurality of circuit breakers 10 and a control unit 15. The first circuit M1 includes a positive electrode wire L11 and a negative electrode wire L21. Each circuit breaker 10 has a first switch 1, a second switch 2, and a third switch 3. The first switch 1 conducts or disconnects the positive electrode wire L11. The second switch 2 conducts or disconnects the negative electrode wire L21. The third switch 3 opens or short-circuits the positive electrode wire L11 and the negative electrode wire L21. If an arc is detected in at least one of the first circuit M1 among the plurality of first circuit M1, the control unit 15 uses the first switch 1 and the second switch 2 to disconnect at least one of the positive electrode wire L11 and the negative electrode wire L21 of the first circuit M1. Then, the third switch 3 short-circuits the positive electrode wire L11 and the negative electrode wire L21 of the first circuit M1.

Description

Technical Field

[0001] The present disclosure relates to a disconnecting device and a connection box including the same. More specifically, the present disclosure relates to a disconnecting device that disconnects an electric circuit in which a DC arc has occurred and a connection box including the same.

Background Art

[0002] Patent Document 1 discloses an arc detection circuit that detects a DC arc in a transmission line. The arc detection circuit disclosed in Patent Document 1 includes a voltage detector, a current detector, and an arc determination unit. The voltage detector detects a current supplied from a power supply device via a transmission line. The current detector detects a voltage applied to the transmission line. The arc determination unit determines the occurrence of an arc in the transmission line based on the voltage when a predetermined frequency component of the current exceeds a first threshold value. The arc detection circuit further includes a switch that switches the opening and closing of the transmission line. When it is determined that an arc has occurred, the switch is turned on, and the transmission of power from the power supply device to the power conditioner is interrupted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, DC arcs include series arcs and parallel arcs. A series arc is an arc that can occur due to an unexpected disconnection in a wire that has received a load, by the disconnected series wiring. A parallel arc is an arc that can occur when the positive and negative conductors are short-circuited due to damage to the wire. When a series arc occurs, by opening the switch in the arc detection circuit having the above configuration, the arc state can be eliminated, and it is possible to suppress the continuous transmission of power in the transmission line.

[0005] However, when a parallel arc occurs, even if the switch is opened, current continues to flow through the short-circuited portion of the transmission line between the positive and negative electrodes. This posed a problem in that it was difficult to resolve the arc condition when a parallel arc occurred.

[0006] The purpose of this disclosure is to provide a circuit breaker and a junction box capable of reliably eliminating DC arcs. [Means for solving the problem]

[0007] A circuit breaker according to one aspect of the present disclosure comprises a plurality of circuit breakers, a plurality of current sensors, an arc detection unit, and a control unit. The plurality of circuit breakers are connected to each of a plurality of first circuits that transmit DC power. The plurality of current sensors detect each current output through the plurality of first circuits. The arc detection unit detects an arc based on signals from the plurality of current sensors. Each of the plurality of first circuits includes a positive electrode wire and a negative electrode wire. Each of the plurality of circuit breakers has a first switch for conducting or interrupting the positive electrode wire, a second switch for conducting or interrupting the negative electrode wire, and a third switch for opening or short-circuiting the positive electrode wire and the negative electrode wire. When an arc is detected in at least one of the plurality of first circuits, the control unit uses the first switch and the second switch to interrupt at least one of the positive electrode wire and the negative electrode wire of the first circuit in which the arc was detected. The control unit then uses the third switch to short-circuit the positive electrode wire and the negative electrode wire of the first circuit in which the arc was detected.

[0008] A junction box according to one aspect of the present disclosure comprises the circuit breaker and a housing for housing the circuit breaker. [Effects of the Invention]

[0009] This disclosure makes it possible to provide a circuit breaker and a junction box that can reliably eliminate DC arcs. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of a DC power generation system including a circuit breaker according to an embodiment of this disclosure. [Figure 2] Figure 2 shows the configuration of the circuit breaker shown above. [Figure 3] Figure 3 is a flowchart showing the operation flow of the above-mentioned circuit breaker. [Figure 4] Figure 4 is a schematic diagram illustrating an example of the operation of a circuit breaker when an arc occurs in the first circuit. [Figure 5] Figure 5 is a graph showing an example of current-voltage fluctuations before and after arc generation in the first circuit. [Figure 6] Figure 6 is a schematic diagram illustrating an example of the operation of a circuit breaker when an arc occurs in the second circuit. [Figure 7] Figure 7 is a graph showing an example of current-voltage fluctuations before and after arcing in the second circuit. [Figure 8] Figure 8 is a schematic diagram of a DC power generation system including a circuit breaker according to a modified example of the present disclosure. [Figure 9] Figure 9 shows the configuration of the circuit breaker described above. [Figure 10] Figure 10 shows an example of a circuit diagram when a circuit breaker is configured using semiconductor switches. [Modes for carrying out the invention]

[0011] The circuit breaker and junction box according to the embodiments will be described in detail below with reference to the drawings. However, the figures described in the following embodiments are schematic diagrams, and the dimensional ratios of the sizes of each component do not necessarily reflect the actual dimensional ratios. Furthermore, the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0012] (Embodiment) (1) Overview Hereinafter, the overview of the cutoff device A1 and the connection box 70 according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram of a DC power generation system 100 including a cutoff device A1 according to an embodiment of the present disclosure. FIG. 2 is a diagram showing the configuration of the cutoff device A1.

[0013] As shown in FIG. 1, the DC power generation system 100 includes a plurality (three in FIG. 1) of power generation devices 30 that generate DC power, a power conditioner (hereinafter also referred to as "PCS") 40, and a connection box 70.

[0014] In this embodiment, the DC power generation system 100 is a solar power generation system, and the power generation device 30 is a solar power generation device in which a plurality (nine in FIG. 1) of solar panels (also referred to as solar cell modules) 5 are connected in series to form a string. The DC power generation system 100 of this embodiment is applicable to a large-scale solar power generation system, so-called megasolar, in which thousands to tens of thousands of solar cell modules are arranged side by side.

[0015] The DC power generated by the plurality (three in FIG. 1) of power generation devices 30 is supplied to the PCS 40. The PCS 40 converts the DC power generated by the plurality of power generation devices 30 into AC power and outputs it. In this embodiment, the PCS 40 employs MPPT (maximum power point tracking) control, and adjusts the current and voltage of the DC power supplied from the plurality of power generation devices 30 to values at which the power is maximized. The PCS 40 converts the input DC power into, for example, a voltage of 100V and a frequency of 50Hz or 60Hz. Thereby, the AC power output from the PCS 40 can be used by household electrical appliances and the like. The PCS 40 of this embodiment is a so-called centralized power conditioner that combines the inputs from the plurality of power generation devices 30 and performs power conversion. Therefore, the plurality of power generation devices 30 are connected to the PCS 40 via the connection box 70.

[0016] Each of the plurality of power generation devices 30 is connected to the connection box 70 via the first circuit M1. The DC power generated by the power generation device 30 is transmitted via the first circuit M1. Each of the plurality (three in FIG. 2) of the first circuits M1 includes a first positive electrode wire L11 and a first negative electrode wire L21. The first positive electrode wire L11 and the first negative electrode wire L21 are conducting wires made of a conductive member such as copper. The first circuit M1 is a wire including a coating made of an insulating member that protects the first positive electrode wire L11 and the first negative electrode wire L21.

[0017] The connection box 70 is connected to the PCS 40 via the second circuit M2. The second circuit M2 is connected in series with the plurality (three in FIG. 2) of the first circuits M1 connected in parallel. The DC power generated by the plurality of power generation devices 30 is transmitted to the PCS 40 via the second circuit M2. The second circuit M2 includes a second positive electrode wire L12 and a second negative electrode wire L22. The second positive electrode wire L12 and the second negative electrode wire L22 are conducting wires made of a conductive member such as copper. The second circuit M2 is a wire including a coating made of an insulating member that protects the second positive electrode wire L12 and the second negative electrode wire L22.

[0018] As shown in FIG. 2, the connection box 70 includes a cutoff device A1 according to the present embodiment and a housing 19 that houses the cutoff device A1.

[0019] The cutoff device A1 is a device that cuts off a circuit in which a DC arc has occurred in the DC power generation system 100. The cutoff device A1 includes a plurality (three in FIG. 2) of circuit breakers 10, a plurality (three in FIG. 2) of current detection units 12, an arc detection unit 14, and a switch control unit 15.

[0020] Multiple (three in Figure 2) circuit breakers 10 are connected to each of the multiple first circuits M1 that transmit DC power. Each of the multiple circuit breakers 10 has a first switch 1, a second switch 2, and a third switch 3. The first switch 1 conducts or disconnects the first positive wire L11. The second switch 2 conducts or disconnects the first negative wire L21. The third switch 3 opens or short-circuits the first positive wire L11 and the first negative wire L21. In this disclosure, "switch" refers to a switch that can electrically open or close contacts. A switch is, for example, an electromagnetic relay, an electromagnetic switch, an electromagnetic contactor, a remotely operated circuit breaker, or a semiconductor switch.

[0021] Multiple current detection units 12 are connected to each of the multiple first circuits M1. The current detection units 12 are "current sensors" as defined in this disclosure. Therefore, the multiple current detection units 12 detect each of the currents output through the multiple first circuits M1.

[0022] The arc detection unit 14 detects a DC arc based on signals from multiple current detection units 12.

[0023] The switch control unit 15 controls multiple (three in Figure 2) circuit breakers 10 according to the control signal from the arc detection unit 14.

[0024] Incidentally, there are two types of DC arcs: series arcs and parallel arcs. A series arc is an arc that can occur when an unexpected break occurs in a loaded wire, resulting in a broken series connection. A parallel arc is an arc that can occur when damage to a wire causes a short circuit between the positive and negative conductors. In this disclosure, "arc" refers to a DC arc. Hereafter, a DC arc may be simply referred to as "arc".

[0025] In the circuit breaker A1 of this embodiment, if an arc is detected in at least one of the three first circuits M1, the switch control unit 15 uses the first switch 1 to shut off the first positive electrode wire L11 of the first circuit M1 in which the arc was detected. Then, the second switch 2 shuts off the first negative electrode wire L21 of the first circuit M1 in which the arc was detected.

[0026] If the generated arc is a series arc, the arc may occur at the point of breakage in at least one of the first positive electrode wire L11 and the first negative electrode wire L21. However, since the current from the disconnected power generator 30 will no longer flow to the arc location, the arc condition will be resolved. On the other hand, if the generated arc is a parallel arc, the current from the disconnected power generator 30 will continue to flow through the short-circuited portion of the first positive electrode wire L11A and the first negative electrode wire L21A in the first circuit M1, so the arc condition may persist.

[0027] Therefore, in the circuit breaker A1 of this embodiment, the switch control unit 15 short-circuits the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 where an arc is detected using the third switch 3. As a result, the voltage between the first positive electrode wire L11 and the first negative electrode wire L21 is forcibly reduced, and the current from the first generator 30A flows through the third switch 3 and no longer flows to the arc generation site, thus eliminating the arc condition. Thus, according to the circuit breaker A1 of this embodiment, it is possible to reliably eliminate DC arcs.

[0028] (2)Details The circuit breaker A1 and the junction box 70 according to this embodiment will be described in detail below with reference to the drawings.

[0029] As shown in Figure 2, the DC power generation system 100 according to this embodiment includes a first power generation device 30A, a second power generation device 30B, and a third power generation device 30C. Hereinafter, the first power generation device 30A, the second power generation device 30B, and the third power generation device 30C may be collectively referred to simply as "multiple power generation devices 30." Also, any one of the first power generation device 30A, the second power generation device 30B, and the third power generation device 30C may be referred to simply as "power generation device 30."

[0030] (2-1) Connection box The junction box 70 is installed between the first power generator 30A, the second power generator 30B, and the third power generator 30C and the PCS 40 (see Figure 1). The PCS 40 is a centralized power conditioner, and the junction box 70 plays the role of supplying the DC power generated by the first power generator 30A, the second power generator 30B, and the third power generator 30C to the PCS 40.

[0031] The junction box 70 is connected to the first power generator 30A via the first circuit M1. As shown in Figure 2, the first circuit M1 connected to the first power generator 30A includes the first positive electrode wire L11A and the first negative electrode wire L21A. The junction box 70 is connected to the second power generator 30B via the first circuit M1. The first circuit M1 connected to the second power generator 30B includes the first positive electrode wire L11B and the first negative electrode wire L21B. The junction box 70 is connected to the third power generator 30C via the first circuit M1. The first circuit M1 connected to the third power generator 30C includes the first positive electrode wire L11C and the first negative electrode wire L21C.

[0032] Hereafter, the first positive pole wire L11A, the first positive pole wire L11B, and the first positive pole wire L11C may be collectively referred to simply as "first positive pole wire L11." The first negative pole wire L21A, the first negative pole wire L21B, and the first negative pole wire L21C may be collectively referred to simply as "first negative pole wire L21."

[0033] The junction box 70 is connected to the PCS40 via the second circuit M2. As shown in Figure 2, the second circuit M2 connected to the PCS40 includes the second positive electrode wire L12 and the second negative electrode wire L22.

[0034] (2-2) Enclosure As shown in Figure 2, the junction box 70 includes a housing 19. The housing 19 houses the circuit breaker A1 inside. The housing 19 includes a plurality (three in Figure 2) of first input terminals 6, a plurality (three in Figure 2) of second input terminals 7, a first output terminal 8, and a second output terminal 9.

[0035] The multiple (three in the diagram) first input terminals 6 are input terminals to which the first positive electrode wire L11 of the first circuit M1 is connected. More specifically, as shown in Figure 2, the first input terminal 6A is the input terminal to which the first positive electrode wire L11A of the first circuit M1 connected to the first power generator 30A is connected. The first input terminal 6B is the input terminal to which the first positive electrode wire L11B of the first circuit M1 connected to the second power generator 30B is connected. The first input terminal 6C is the input terminal to which the first positive electrode wire L11C of the first circuit M1 connected to the third power generator 30C is connected.

[0036] The multiple (three in the diagram) second input terminals 7 are input terminals to which the first negative pole wire L21 of the first circuit M1 is connected. More specifically, as shown in Figure 2, the second input terminal 7A is the input terminal to which the first negative pole wire L21A of the first circuit M1 connected to the first power generator 30A is connected. The second input terminal 7B is the input terminal to which the first negative pole wire L21B of the first circuit M1 connected to the second power generator 30B is connected. The second input terminal 7C is the input terminal to which the first negative pole wire L21C of the first circuit M1 connected to the third power generator 30C is connected.

[0037] The first output terminal 8 is the output terminal to which the second positive electrode wire L12 of the second circuit M2 is connected. The second output terminal 9 is the output terminal to which the second negative electrode wire L22 of the second circuit M2 is connected.

[0038] (2-3) Circuit breaker The circuit breaker A1 is housed inside the casing 19 of the junction box 70. The circuit breaker A1 comprises a first circuit breaker 10A, a second circuit breaker 10B, a third circuit breaker 10C, a plurality of sensors 11, an arc detection unit 14, and a switch control unit 15.

[0039] The first circuit breaker 10A is connected to the first circuit M1, which is connected to the first power generator 30A. The first switch 1 of the first circuit breaker 10A is a switch device that conducts or disconnects the first positive wire L11A. The second switch 2 of the first circuit breaker 10A is a switch device that conducts or disconnects the first negative wire L21A. The third switch 3 of the first circuit breaker 10A is a switch device that short-circuits or opens the first positive wire L11A and the first negative wire L21A.

[0040] The second circuit breaker 10B is connected to the first circuit M1, which is connected to the second power generator 30B. The first switch 1 of the second circuit breaker 10B is a switch device that conducts or disconnects the first positive wire L11B. The second switch 2 of the second circuit breaker 10B is a switch device that conducts or disconnects the first negative wire L21B. The third switch 3 of the second circuit breaker 10B is a switch device that short-circuits or opens the first positive wire L11B and the first negative wire L21B.

[0041] The third circuit breaker 10C is connected to the first circuit M1, which is connected to the third power generator 30C. The first switch 1 of the third circuit breaker 10C is a switch device that conducts or disconnects the first positive wire L11C. The second switch 2 of the third circuit breaker 10C is a switch device that conducts or disconnects the first negative wire L21C. The third switch 3 of the third circuit breaker 10C is a switch device that short-circuits or opens the first positive wire L11C and the first negative wire L21C.

[0042] In the following, the first circuit breaker 10A, the second circuit breaker 10B, and the third circuit breaker 10C may be collectively referred to simply as "multiple circuit breakers 10." Furthermore, any one of the first circuit breaker 10A, the second circuit breaker 10B, and the third circuit breaker 10C may be referred to simply as "circuit breaker 10."

[0043] Multiple sensors 11 are connected to each of the multiple first circuits M1. Each of the multiple sensors 11 has a current detection unit 12 and a voltage detection unit 13. The multiple current detection units 12 detect each current output through the multiple first circuits M1. The voltage detection unit 13 is a "voltage sensor" as defined in this disclosure. Therefore, the multiple voltage detection units 13 detect each voltage output through the multiple first circuits M1.

[0044] The arc detection unit 14 detects arcs based on signals from multiple current detection units 12. Details of the processing of the arc detection unit 14 are described in "(2-4) Operation Description". The arc detection unit 14 mainly consists of a computer system having one or more processors and memory. The function of the arc detection unit 14 is realized when the processor of the computer system executes a program recorded in the memory of the computer system. The program may be recorded in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card.

[0045] The switch control unit 15 controls the opening and closing of at least one of the circuit breakers 10, including the first circuit breaker 10A, the second circuit breaker 10B, and the third circuit breaker 10C, according to the control signal from the arc detection unit 14.

[0046] (2-4) Operation Description Next, the operation of the circuit breaker A1 according to this embodiment will be explained with reference to the drawings. The operation of the circuit breaker A1 described below is a process mainly performed by the arc detection unit 14 when an arc occurs during the normal operation of the DC power generation system 100.

[0047] (2-4-1) Normal operation During normal operation, the MPPT control of PCS40 adjusts the current and voltage of the DC power supplied from the first generator 30A, the second generator 30B, and the third generator 30C to the value that maximizes the power output.

[0048] In normal operation, at the first circuit breaker 10A, the first switch 1 conducts the first positive wire L11A, and the second switch 2 conducts the first negative wire L21A. The third switch 3 opens the connection between the first positive wire L11A and the first negative wire L21A (see Figure 2).

[0049] Similarly, in the second circuit breaker 10B, the first switch 1 conducts the first positive wire L11B, and the second switch 2 conducts the first negative wire L21B. The third switch 3 opens the connection between the first positive wire L11B and the first negative wire L21B (see Figure 2).

[0050] Similarly, in the third circuit breaker 10C, the first switch 1 conducts the first positive wire L11C, and the second switch 2 conducts the first negative wire L21C. The third switch 3 opens the connection between the first positive wire L11C and the first negative wire L21C (see Figure 2).

[0051] First, the arc detection unit 14 acquires current signals from multiple current detection units 12 (see Figure 2) (step S1 in Figure 3). Then, the arc detection unit 14 acquires voltage signals from multiple voltage detection units 13 (see Figure 2) (step S2 in Figure 3). In normal operation, the acquisition of current signals from the multiple current detection units 12 and the acquisition of voltage signals from the multiple voltage detection units 13 are performed continuously at predetermined intervals.

[0052] (2-4-2) Arc generation detection Next, the arc detection unit 14 detects whether or not an arc has occurred (step S3 in Figure 3). More specifically, the arc detection unit 14 detects the occurrence of an arc based on high-frequency noise contained in the current signal of at least one of the multiple current detection units 12. When an arc occurs, arc noise is generally generated. This arc noise superimposes a small amount of noise on the entire circuit of the DC power generation system 100. There is a clear difference in the noise intensity at higher frequencies (especially in the range of 1 kHz to 100 kHz) compared to when no arc has occurred. By detecting the high-frequency noise as arc noise superimposed on the signal from the current detection unit 12, it becomes possible to detect the occurrence of an arc. The arc detection unit 14 can detect the occurrence of an arc by analyzing the frequency characteristics of the current signal of at least one of the multiple current detection units 12. If the arc detection unit 14 detects the occurrence of an arc, it proceeds to the next arc determination step (S4). On the other hand, if the arc detection unit 14 does not detect the occurrence of an arc, it returns to step S1.

[0053] (2-4-3) Arc determination Next, the arc detection unit 14 determines whether an arc has occurred (step S4 in Figure 3). More specifically, the arc detection unit 14 determines whether the generated arc is a parallel arc or a series arc based on the change in the current value of the current detection unit 12 before and after the arc is detected in at least one of the multiple first circuits M1. When a series arc occurs due to an unexpected break in at least one of the first positive wire L11 and the first negative wire L21 of the first circuit M1 being subjected to a load, the impedance of the circuit increases and the current decreases. On the other hand, when a parallel arc occurs due to a short circuit between the conductors of the first positive wire L11 and the first negative wire L21 of the first circuit M1 due to damage to the wire, current from other power generation devices 30 flows into the first circuit M1 where the arc occurred, causing an excessive current to flow in the reverse direction. Therefore, by comparing the fluctuations in the current value of the current detection unit 12 before and after the detection of an arc in at least one of the multiple first circuits M1, it is possible to determine whether the generated arc is a parallel arc or a series arc.

[0054] (2-4-4) Identifying the location of the arc Next, the arc detection unit 14 identifies the location of the arc (step S5 in Figure 3). More specifically, the arc detection unit 14 analyzes the voltage-current operating point of each power generator 30 based on signals from multiple current detection units 12 and multiple voltage detection units 13. Then, it identifies the location of the arc based on the fluctuations in the voltage-current operating point of each power generator 30 before and after the arc is detected. In the DC power generation system 100 of this embodiment, as shown in Figure 1, a junction box 70 is placed between the multiple power generators 30 and the PCS 40. Therefore, arcs can occur in multiple first circuits M1 between the multiple power generators 30 and the junction box 70 (more specifically, outside the housing 19 in Figure 2), and in second circuits M2 between the junction box 70 (more specifically, outside the housing 19 in Figure 2) and the PCS 40.

[0055] Below, the principle for identifying the location of an arc when a parallel arc occurs in the first circuit M1 or the second circuit M2 will be explained using Figures 4 to 7.

[0056] Figure 4 is a schematic diagram illustrating an example of the operation of the circuit breaker A1 when an arc occurs in the first circuit M1. In Figure 4, the junction box 70 and the housing 19 are omitted, but a parallel arc 111 is generated in the first circuit M1 between the first power generator 30A and the junction box 70.

[0057] Figure 5 is a graph showing an example of the fluctuations in the current-voltage operating points of each power generator 30 before and after the occurrence of a parallel arc 111 in the first circuit M1 connected to the first power generator 30A. The vertical axis of the graph shows the current value of the current detection unit 12, and the horizontal axis shows the voltage value of the voltage detection unit 13. The solid line of the graph shows the voltage-current characteristics of each power generator 30 during normal operation. Voc represents the open-circuit voltage, and Isc represents the short-circuit current. Vpm represents the maximum output operating voltage, and Ipm represents the maximum output operating current. Q represents the voltage-current operating point of each power generator 30 before the occurrence of the parallel arc 111 in Figure 4 (during normal operation). For convenience, it is assumed here that the first power generator 30A, the second power generator 30B, and the third power generator 30C are operating at the same operating point before the occurrence of the parallel arc 111 in the first circuit M1 in Figure 4. Q1A represents the operating point of the first power generator 30A after the occurrence of the parallel arc 111 in Figure 4. Q1B indicates the operating point of the second power generator 30B after the generation of the parallel arc 111 in Figure 4. Q1C indicates the operating point of the third power generator 30C after the generation of the parallel arc 111 in Figure 4.

[0058] When a parallel arc 111 occurs in the first circuit M1 between the first power generator 30A and the junction box 70, the operating point Q1A of the first power generator 30A deviates significantly from the voltage-current characteristics of normal operation, as shown in Figure 5. The voltage at the operating point Q1A drops significantly to about the arc voltage (tens of volts), and the current at the operating point Q1A flows backward from the first circuit M1 connected to the second power generator 30B and the third power generator 30C, resulting in an excessive current flowing in the reverse direction. The operating point Q1A deviates significantly from the voltage-current characteristics of normal operation.

[0059] On the other hand, the operating point Q1B of the second generator 30B and the operating point Q1C of the third generator 30C are on the normal operating voltage-current characteristics, as shown in Figure 5. Since no abnormality occurs in the first circuit M1 between the second generator 30B and the third generator 30C and the junction box 70, the voltage at operating points Q1B and Q1C drops significantly to about the arc voltage (tens of volts), but the current rises to about the short-circuit current Isc. The operating points Q1B and Q1C are on the normal operating voltage-current characteristics. Due to the symmetry of the circuit, the voltage and current fluctuations at operating points Q1B and Q1C are the same.

[0060] Therefore, if a parallel arc occurs, for example, the fluctuation amount from the operating point Q to the operating point Q1A of the first power generator 30A, the fluctuation amount from the operating point Q to the operating point Q1B of the second power generator 30B, and the fluctuation amount from the operating point Q to the operating point Q1C of the third power generator 30C are compared. If there is an operating point with a large fluctuation (especially a large fluctuation in current), it can be determined that a parallel arc occurred in the first circuit M1 between the power generator 30 and the junction box 70 corresponding to the operating point with the large fluctuation.

[0061] Figure 6 is a schematic diagram illustrating the operation of the circuit breaker A1 when an arc occurs in the second circuit M2. In Figure 6, the junction box 70 and housing 19 are omitted, but a parallel arc 111 is generated in the second circuit M2 between the junction box 70 and PCS40.

[0062] Figure 7 is a graph showing an example of the fluctuations in the current-voltage operating points of each power generator 30 before and after the occurrence of the parallel arc 111 in the second circuit M2 of Figure 6. Q represents the voltage-current operating point of each power generator 30 before the occurrence of the parallel arc 111 in Figure 6. For convenience, it is assumed here that the first power generator 30A, the second power generator 30B, and the third power generator 30C are operating at the same operating point before the occurrence of the parallel arc 111 in the second circuit M2 of Figure 6. Q2A represents the operating point of the first power generator 30A after the occurrence of the parallel arc 111 in Figure 6. Q2B represents the operating point of the second power generator 30B after the occurrence of the parallel arc 111 in Figure 6. Q2C represents the operating point of the third power generator 30C after the occurrence of the parallel arc 111 in Figure 6.

[0063] If a parallel arc 111 occurs in the second circuit M2 between the junction box 70 and the PCS 40, as shown in Figure 7, the operating points Q2A, Q2B, and Q2C of each power generator 30 are on the normal operating voltage-current characteristics. In the first circuit M1 between the multiple power generators 30 and the junction box 70, no abnormality occurs, so although the voltages at the operating points Q2A, Q2B, and Q2C drop significantly to about the arc voltage (tens of volts), the current rises to about the short-circuit current Isc. The operating points Q2A, Q2B, and Q2C are on the normal operating voltage-current characteristics. Due to the symmetry of the circuit, the voltage and current fluctuations at the operating points Q2A, Q2B, and Q2C are the same.

[0064] Therefore, if a parallel arc occurs, for example, the fluctuation amount from the operating point Q to the operating point Q2A of the first power generator 30A, the fluctuation amount from the operating point Q to the operating point Q2B of the second power generator 30B, and the fluctuation amount from the operating point Q to the operating point Q1C of the third power generator 30C are compared. If the fluctuation amounts of all the operating points of the multiple power generators 30 are approximately the same, it can be determined that a parallel arc occurred in the second circuit M2 between the junction box 70 and the PCS 40.

[0065] Furthermore, even if a series arc occurs in the first circuit M1 or the second circuit M2, the voltage-current operating point of each power generator 30 can be analyzed, and the location of the series arc can be identified based on the fluctuations in the voltage-current operating point of each power generator 30 before and after the arc was detected. If there is an operating point among the operating points of the multiple power generators 30 that shows a large fluctuation (especially a large fluctuation in current), the arc detection unit 14 identifies that a series arc occurred in the first circuit M1 between the power generator 30 corresponding to the operating point with the large fluctuation and the junction box 70. Also, if all of the operating points of the multiple power generators 30 fluctuate to a similar extent, the arc detection unit 14 identifies that a series arc occurred in the second circuit M2 between the junction box 70 and the PCS 40.

[0066] (2-4-5) Switch control Next, the switch control unit 15 controls the opening and closing of at least one of the circuit breakers 10, including the first circuit breaker 10A, the second circuit breaker 10B, and the third circuit breaker 10C, according to the control signal from the arc detection unit 14 (step S6 in Figure 3).

[0067] For example, in Figure 2, if a series arc is detected in the first circuit M1 between the first power generator 30A and the junction box 70, the switch control unit 15, in accordance with the control signal from the arc detection unit 14, uses the first switch 1 to interrupt the first positive electrode wire L11A of the first circuit M1 at the first circuit breaker 10A. Then, the second switch 2 interrupts the first negative electrode wire L21A of the first circuit M1. In the case of a series arc, the point of breakage in at least one of the first positive electrode wire L11A and the first negative electrode wire L21A can be the point of arc generation. However, since both the first positive electrode wire L11A and the first negative electrode wire L21A are interrupted, no current flows to the point of arc generation. As a result, the arc condition is resolved.

[0068] On the other hand, as shown in Figure 4, if a parallel arc 111 is detected in the first circuit M1 between the first power generator 30A and the junction box 70, the switch control unit 15 will, at the first circuit breaker 10A, use the first switch 1 to interrupt the first positive wire L11A of the first circuit M1. Then, use the second switch 2 to interrupt the first negative wire L21A of the first circuit M1. Finally, use the third switch 3 to short-circuit the first positive wire L11A and the first negative wire L21A of the first circuit M1.

[0069] If a parallel arc 111 occurs in the first circuit M1 between the first power generator 30A and the junction box 70, current flows through the short-circuited portion of the first positive wire L11A and the first negative wire L21A. Therefore, simply interrupting both the first positive wire L11A and the first negative wire L21A at the first circuit breaker 10A may not be enough to prevent the arc from continuing. The third switch 3 short-circuits the first positive wire L11A and the first negative wire L21A in the first circuit M1, forcibly lowering the voltage between the first positive wire L11A and the first negative wire L21A. As a result, the current supplied from the first power generator 30A flows through the third switch 3 and no longer flows to the arc generation site, thus eliminating the arc. Therefore, according to the circuit breaker A1 of this embodiment, it is possible to reliably eliminate the arc generated in the first circuit M1 between the power generator 30 and the junction box 70.

[0070] Furthermore, in this embodiment, if a parallel arc is detected in the first circuit M1 between the first power generator 30A and the junction box 70, the first circuit breaker 10A uses the first switch 1 to interrupt the first positive wire L11A of the first circuit M1, and the second switch 2 interrupts the first negative wire L21A of the first circuit M1. As a result, current from the second power generator 30B and the third power generator 30C does not flow into the third switch 3 of the first circuit breaker 10A, making it possible for the DC power generation system 100 to continue generating power without stopping the second power generator 30B and the third power generator 30C.

[0071] On the other hand, if an arc is detected in the second circuit M2 between the junction box 70 and the PCS 40, the switch control unit 15, in accordance with the control signal from the arc detection unit 14, will use the first switch 1 and the second switch 2 to disconnect the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 in all of the circuit breakers 10.

[0072] For example, as shown in Figure 6, if a parallel arc 111 is detected in the second circuit M2, the switch control unit 15, in accordance with the control signal from the arc detection unit 14, will, at the first circuit breaker 10A, use the first switch 1 to interrupt the first positive wire L11A of the first circuit M1, and the second switch 2 to interrupt the first negative wire L21A of the first circuit M1. At the second circuit breaker 10B, use the first switch 1 to interrupt the first positive wire L11B of the first circuit M1, and the second switch 2 to interrupt the first negative wire L21B of the first circuit M1. At the third circuit breaker 10C, use the first switch 1 to interrupt the first positive wire L11C of the first circuit M1, and the second switch 2 to interrupt the first negative wire L21C of the first circuit M1.

[0073] As a result, all of the multiple power generators 30 are disconnected, so that current from the multiple power generators 30 does not continuously flow into the arc generation point (second circuit M2). This eliminates the arc. Therefore, according to the circuit breaker A1 of this embodiment, it is possible to reliably eliminate the arc generated in the second circuit M2 between the junction box 70 and the PCS 40.

[0074] (3) Variant The above embodiments are merely one of many embodiments of this disclosure. The above embodiments can be modified in various ways depending on the design, etc., as long as the objectives of this disclosure are achieved. The following lists some modifications of the above embodiments. The modifications described below can be combined and applied as appropriate. Components similar to those in the above embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0075] In the above embodiment of the circuit breaker A1, the arc detection unit 14 determines the presence of an arc in the first circuit M1 based on the fluctuation of the current value of the current detection unit 12 before and after the arc is detected, as shown in step S4 of Figure 3 (see "(2-4-3) Arc Determination" above). The arc detection unit 14 may also determine the presence of an arc in at least one of the multiple first circuits M1 based not only on the fluctuation of the current value before and after the arc is detected, but also on the fluctuation of the voltage value. When a series arc occurs due to an unexpected break in the first circuit M1 under load, the voltage drops. On the other hand, when a parallel arc occurs due to a short circuit between the conductors of the first positive wire L11 and the first negative wire L21 due to damage to the wire, the voltage drops to approximately the arc voltage. The voltage drop due to a parallel arc is greater than the voltage drop due to a series arc. Therefore, by comparing the fluctuation of the current value and the fluctuation of the voltage value before and after the arc is detected in the first circuit M1 where the arc is detected, it is possible to improve the accuracy of arc determination.

[0076] (3-1) First variation The DC power generation system 100 of the above embodiment (see Figure 1) includes a junction box 70, but it does not necessarily have to include a junction box 70.

[0077] Figure 8 is a schematic diagram of a DC power generation system 100A including a circuit breaker A2 according to the first modified example of this disclosure. As shown in Figure 8, in the DC power generation system 100A according to the first modified example, multiple (three in the figure) first circuits M1 connected to each of multiple (three in the figure) power generation devices 30 are connected to one power conditioner 40A. The power conditioner 40A is a so-called multi-string type (distributed type) power conditioner that performs power conversion for each input from the power generation devices 30. In Figure 8, multiple (three in the figure) circuit breakers A2 are connected to each of the multiple (three in the figure) first circuits M1. The circuit breaker A2 is a device that interrupts the first circuit M1 when a DC arc occurs in the DC power generation system 100A. Hereinafter, the circuit breaker A2 connected to the first circuit M1 between the first power generation device 30A and the PCS 40A may be referred to as the first circuit breaker A2. The circuit breaker A2 connected to the first circuit M1 between the second power generator 30B and PCS 40A is sometimes referred to as the second circuit breaker A2. The circuit breaker A2 connected to the first circuit M1 between the third power generator 30C and PCS 40A is sometimes referred to as the third circuit breaker A2. As shown in Figure 8, the configuration of each of the multiple circuit breakers A2 is disclosed in Figure 9.

[0078] Figure 9 shows the configuration of the first circuit breaker A2 connected to the first circuit M1 between the first power generator 30A and PCS 40A, but the configurations of the other second and third circuit breakers A2 are similar. As shown in Figure 9, the first circuit breaker A2 comprises a circuit breaker 10, a sensor 11, an arc detection unit 14, and a switch control unit 15. Here, the circuit breaker 10, sensor 11, arc detection unit 14, and switch control unit 15 are housed inside the housing 20 of the circuit breaker A2, but some of them may be located outside the housing 20.

[0079] The circuit breaker 10 is connected to the first circuit M1 which transmits the DC power generated by the first power generator 30A. The sensor 11 (current detection unit 12) detects the current output through the first circuit M1. The arc detection unit 14 detects an arc based on the signal from the sensor 11. The circuit breaker 10 includes a first switch 1 for conducting or interrupting the positive electrode wire L11, a second switch 2 for conducting or interrupting the negative electrode wire L21, and a third switch 3 for opening or short-circuiting the positive electrode wire L11 and the negative electrode wire L21. When an arc is detected in the first circuit M1, the switch control unit 15 uses the first switch 1 and the second switch 2 to interrupt at least one of the positive electrode wire L11 and the negative electrode wire L21 of the first circuit M1, and the third switch 3 to short-circuit the positive electrode wire L11 and the negative electrode wire L21 of the first circuit M1.

[0080] Therefore, according to the first modified example, the first circuit breaker A2, the second circuit breaker A2, and the third circuit breaker A2 make it possible to reliably extinguish the arc generated in the first circuit M1 in a DC power generation system 100A equipped with a multi-string type PCS40A.

[0081] Furthermore, the first circuit breaker A2 according to the first modified example may be connected to the first circuit M1 between the power generator 30 and the PCS 40 in a DC power generation system comprising one power generator 30 and one PCS 40. A DC power generation system with such a configuration can be applied to small-scale solar power generation systems for residential use, etc.

[0082] (3-2) Second variation In the first modified example described above, as shown in Figure 8, the multiple (three in the figure) circuit breakers A2 are located outside the multi-string type power conditioner 40A, but they may also be located inside the power conditioner 40A.

[0083] In the second modified example, the first circuit breaker A2 is connected to the DC input side (e.g., before the DC / DC converter) inside the power conditioner 40A, which is connected to the first power generator 30A via the first circuit M1. Similarly, the second circuit breaker A2 is connected to the DC input side (e.g., before the DC / DC converter) inside the power conditioner 40A, which is connected to the second power generator 30B via the first circuit M1. Furthermore, the third circuit breaker A2 is connected to the DC input side (e.g., before the DC / DC converter) inside the power conditioner 40A, which is connected to the third power generator 30C via the first circuit M1. Note that the configurations of the first circuit breaker A2, the second circuit breaker A2, and the third circuit breaker A2 are the same as the configuration of circuit breaker A2 in the first modified example (see Figure 9).

[0084] Therefore, according to the first circuit breaker A2, second circuit breaker A2, and third circuit breaker A2 of the second modified example, similar to the first modified example, it becomes possible to reliably extinguish the arc generated in the first circuit M1 in a DC power generation system 100A equipped with a multi-string type PCS40A.

[0085] (3-3) Third Variation Furthermore, the circuit breaker A2 may be installed not only inside the multi-string type power conditioner 40A as shown in Figure 8, but also inside the centralized type power conditioner 40 as shown in Figure 1.

[0086] Returning to Figure 1, in the DC power generation system 100 according to this embodiment, the DC power generated by the multiple power generation devices 30 is transmitted to the PCS 40 via the second circuit M2. The circuit breaker A2 according to the third modified example is connected to the DC input side inside the PCS 40 (for example, before the DC / DC converter) in the DC power generation system 100 as shown in Figure 1.

[0087] The configuration of the circuit breaker A2 in the third modified example is generally the same as the configuration of the first circuit breaker A2 in the first modified example (see Figure 9). The difference is that the first circuit breaker A2 in the first modified example is connected to the first circuit M1 between the first power generator 30A and PCS40A, while the circuit breaker A2 in the third modified example is connected to the second circuit M2 inside PCS40.

[0088] Therefore, according to the third modified example, the circuit breaker A2 makes it possible to reliably eliminate the arc generated in the second circuit M2 in a DC power generation system 100 equipped with a centralized PCS 40.

[0089] In a DC power generation system 100 equipped with a centralized PCS40 as shown in Figure 1, the circuit breaker A1 is housed inside the junction box 70, and the circuit breaker A2 according to the third modified example is housed inside the PCS40. As a result, the multiple circuit breakers 10 are connected to each of the multiple first circuits M1 and second circuits M2 that transmit DC power. This makes it possible to reliably extinguish arcs generated in the multiple first circuits M1 and second circuits M2.

[0090] (3-4) Fourth variation In the above embodiment of the circuit breaker A1 and the modified circuit breaker A2, as shown in Figures 2 and 9, in the first circuit M1, the third switch 3 of the circuit breaker 10 is connected to the power generation device 30 side than the first switch 1 and the second switch 2. In the first circuit M1, the first switch 1 and the second switch 2 may be connected to the power generation device 30 side than the third switch 3. In other words, in the circuit breaker 10, the positions of the third switch 3 and the first switch 1 and the second switch 2 are interchangeable.

[0091] (3-5) Fifth variation In addition, in the circuit breaker A1 of the above embodiment and the circuit breaker A2 of the above modified example, the switches constituting the circuit breaker 10 may use semiconductor switch elements as described above.

[0092] The following describes the case in which a circuit breaker 10 is constructed using semiconductor switching elements.

[0093] Figure 10 shows an example of a circuit diagram of a power conditioner 40. As shown in Figure 10, the input side of the PCS 40 is connected to the first circuit M1 via a DC breaker 50. The output side of the PCS 40 is connected to the grid 55 via a contactor 53 and an AC breaker 54. The PCS 40 converts the DC power output from the power generator 30 via the first circuit M1 into AC power and outputs it to the grid 55.

[0094] As shown in Figure 10, the PCS40 includes a boost circuit 41, an inverter circuit 42, and a noise filter 43.

[0095] The boost circuit 41 is a non-isolated boost type DC / DC converter. As shown in Figure 10, the boost circuit 41 includes an input capacitor C0, an inductor L0, a diode D0, and a switching element Q0.

[0096] The first electrode of the input capacitor C0 is connected to the high-potential input terminal of the boost circuit 41. The high-potential input terminal of the boost circuit 41 is connected to the positive electrode wire L11 of the first circuit M1. The second electrode of the input capacitor C0 is connected to the low-potential input terminal of the boost circuit 41. The low-potential input terminal of the boost circuit 41 is connected to the negative electrode wire L21 of the first circuit M1.

[0097] The first end of inductor L0 is connected to the high-potential input terminal of the boost circuit 41, and further connected to the first electrode of the input capacitor C0. The second end of inductor L0 is connected to the anode of diode D0. The cathode of diode D0 is connected to the high-potential output terminal of the boost circuit 41, and further connected to the first electrode of the first output capacitor C11.

[0098] The switching element Q0 is a semiconductor switching element such as an IGBT (Insulated Gate Bipolar Transistor). The source of the switching element Q0 is connected to the low-potential input and output terminals of the boost circuit 41, and further connected to the second electrode of the input capacitor C0. The drain of the switching element Q0 is connected to the connection point between the second terminal of the inductor L0 and the anode of the diode D0. The switching element Q0 is turned on / off by the control signal SG0 provided from the PCS control unit 45.

[0099] The boost circuit 41 can boost the voltage across the input capacitor C0 by controlling the switching element Q0 with PWM (Pulse Width Modulation) by the PCS control unit 45. Specifically, the PCS control unit 45 boosts the voltage across the input capacitor C0 by switching control of the switching element Q0, and outputs the boosted DC voltage to the output capacitor C1 and the inverter circuit 42.

[0100] As shown in Figure 10, the output capacitor C1 is connected between the boost circuit 41 and the inverter circuit 42. The output capacitor C1 is composed of a first output capacitor C11 and a second output capacitor C12 connected in series. The first electrode of the first output capacitor C11 is connected to the high-potential output terminal of the boost circuit 41 and the high-potential input terminal of the inverter circuit 42. The second electrode of the second output capacitor C12 is connected to the low-potential input terminal of the inverter circuit 42. The output capacitor C1 has the function of stabilizing the DC voltage output from the boost circuit 41.

[0101] As shown in Figure 10, the inverter circuit 42 has four switching elements Q1 to Q4 connected in a full bridge configuration. Each of the switching elements Q1 to Q4 is a semiconductor switching element, such as an IGBT (Insulated Gate Bipolar Transistor).

[0102] In the inverter circuit 42, a series circuit of switching elements Q1 and Q3, and a series circuit of switching elements Q2 and Q4 are connected in parallel across the output capacitor C1. The drains of switching elements Q1 and Q2 are both connected to the high-potential output terminal of the boost circuit 41 and to the first electrode of the first output capacitor C11. The sources of switching elements Q3 and Q4 are both connected to the second electrode of the second output capacitor C12.

[0103] The inverter circuit 42 is a DC / AC converter. In the inverter circuit 42, switching elements Q1 to Q4 are PWM controlled by the PCS control unit 45 to convert DC voltage to AC voltage.

[0104] As shown in Figure 10, the noise filter 43 includes two inductors L1 and L2 and two capacitors C21 and C22. The first end of inductor L1 is connected to the connection point (first connection point) between the source of switching element Q1 and the drain of switching element Q3. The second end of inductor L1 is connected to capacitor C21. The first end of inductor L2 is connected to the connection point (second connection point) between the source of switching element Q2 and the drain of switching element Q4. The second end of inductor L2 is connected to capacitor C22. The noise filter 43 has the function of removing high-frequency components from the AC voltage output from the inverter circuit 42 and generating a sinusoidal voltage.

[0105] The PCS control unit 45 primarily consists of a computer system having, for example, one or more processors and one or more memories. That is, the functions of the PCS control unit 45 are realized when one or more processors execute a program recorded in one or more memories of the computer system. The program may be pre-recorded in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card. The PCS control unit 45 may be composed of, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0106] The PCS control unit 45 outputs control signals SG0 to SG4 for controlling the five switching elements Q0 to Q4. The control signals SG0 to SG4 are applied directly to the gates of the switching elements Q0 to Q4, either directly or via a drive circuit, to individually turn the switching elements Q0 to Q4 on or off. The PCS control unit 45 controls the switching elements Q0 to Q4 using a PWM method with an adjustable duty cycle.

[0107] With the above configuration, under normal operation, the PCS 40 converts the DC power output from the power generator 30 via the first circuit M1 into AC power and outputs it to the grid 55.

[0108] Incidentally, the DC breaker 50 connected to the input side of PCS40 and the AC breaker 54 connected to the output side of PCS40 are controlled to be closed during normal operation. Also, the contactor 53 is in a closed state during power generation and is controlled to be open when stopped.

[0109] As shown in Figure 10, the DC breaker 50 is connected to the first circuit M1. The DC breaker 50 includes a first relay circuit 51 and a second relay circuit 52. The first relay circuit 51 has the function of conducting or interrupting the first positive wire L11 of the first circuit M1. The second relay circuit 52 has the function of conducting or interrupting the first negative wire L21 of the first circuit M1. The first relay circuit 51 corresponds to the "first switch" as referred to in this disclosure. The second relay circuit 52 corresponds to the "second switch" as referred to in this disclosure.

[0110] Furthermore, if an arc is detected in the first circuit M1, the DC breaker 50 will interrupt at least one of the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1. At this time, the PCS control unit 45 controls all of the switching elements Q1 to Q4 of the inverter circuit 42 to be in the off state. This protects the switching elements Q1 to Q4.

[0111] In the boost circuit 41, the drain of the switching element Q0 is connected to the high-potential output terminal of the boost circuit 41 and is connected to the first positive electrode wire L11 of the first circuit M1 via an inductor L0. The source of the switching element Q0 is connected to the low-potential output terminal of the boost circuit 41 and is connected to the first negative electrode wire L21 of the first circuit M1. In other words, the switching element Q0 can open or short-circuit the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 by a control signal SG0 provided by the PCS control unit 45. Therefore, the switching element Q0 may correspond to the "third switch" as referred to in this disclosure.

[0112] Furthermore, in the series circuit of switching elements Q1 and Q3 of the inverter circuit 42, the drain of switching element Q1 is connected to the high-potential output terminal of the boost circuit 41, and the source of switching element Q3 is connected to the low-potential output terminal of the boost circuit 41. In other words, switching elements Q1 and Q3 can open or short-circuit the first positive wire L11 and the first negative wire L21 of the first circuit M1 by control signals SG1 and SG3 provided by the PCS control unit 45. Therefore, switching elements Q1 and Q3 can correspond to the "third switch" as referred to in this disclosure.

[0113] Furthermore, in the series circuit of switching elements Q2 and Q4 of the inverter circuit 42, the drain of switching element Q2 is connected to the high-potential output terminal of the boost circuit 41, and the source of switching element Q4 is connected to the low-potential output terminal of the boost circuit 41. In other words, switching elements Q2 and Q4 can open or short-circuit the first positive wire L11 and the first negative wire L21 of the first circuit M1 by control signals SG2 and SG4 provided from the PCS control unit 45. Therefore, switching elements Q2 and Q4 can correspond to the "third switch" as referred to in this disclosure.

[0114] Thus, according to the fifth modification, the existing DC breaker 50 can be used to configure the first switch 1 and the second switch 2 of the circuit breaker 10. Furthermore, the third switch 3 of the circuit breaker 10 can be configured using semiconductor elements that constitute part of the power conversion circuit (more specifically, the boost circuit 41 and the inverter circuit 42) that converts DC power to AC power.

[0115] Therefore, according to the fifth modification, there is no need to add new switches such as relays to configure the circuit breaker 10, making it possible to reliably extinguish arcs with a simpler configuration.

[0116] In the fifth modified example, the first switch 1 and the second switch 2 of the circuit breaker 10 are configured using an existing DC breaker 50 (first relay circuit 51 and second relay circuit 52). However, the first switch 1 and the second switch 2 may also be configured using semiconductor switching elements that constitute part of the power conversion circuit (more specifically, the boost circuit 41 and the inverter circuit 42). In other words, at least one of the switches, the first switch 1, the second switch 2, and the third switch 3, may be configured using one or more semiconductor switching elements included in the power conversion circuit.

[0117] Furthermore, as mentioned above, in the fifth modified example, parts of the circuit breakers A1 and A2 are mounted inside the PCS40. In other words, at least parts of the circuit breakers A1 and A2 may be mounted inside the PCS40.

[0118] (3-6) Sixth Variation In the above embodiment, the circuit breaker A1 detects the occurrence of an arc based on whether or not high-frequency arc noise is detected (see "(2-4-2) Arc Occurrence Detection"). After an arc is detected, the first positive wire L11 and the first negative wire L21 may be short-circuited by the third switch 3, and then the arc may be determined based on whether or not high-frequency arc noise continues.

[0119] The following describes the arc detection method according to the sixth modified example. The arc detection method according to the sixth modified example can be performed by the first circuit breaker A1 when an arc occurs in the first circuit M1 between the first power generator 30A and PCS 40A, as shown in Figures 8 and 9.

[0120] First, when the arc detection unit 14 detects the occurrence of an arc, the switch control unit 15, in accordance with the control signal from the arc detection unit 14, short-circuits the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 where the arc was detected using the third switch 3. If the generated arc is a parallel arc, the current from the first power generator 30A flows through the third switch 3 because the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 are short-circuited by the third switch 3, and the arc condition is resolved. As a result, no abnormal current flows at the arc generation location (short-circuit location). Note that abnormal current refers to a current signal containing high-frequency arc noise. Therefore, if the abnormal current stops after the arc detection unit 14 short-circuits the first positive electrode wire L11 and the first negative electrode wire L21 of the first circuit M1 using the third switch 3, it can determine that the generated arc is a parallel arc.

[0121] However, if the generated arc is a series arc, the arc generation site can be at least one of the open ends of the first positive wire L11 and the first negative wire L21. Therefore, simply short-circuiting the first positive wire L11 and the first negative wire L21 of the first circuit M1 with the third switch 3 does not resolve the arc condition, and the abnormal current continues to flow at the arc generation site (open end). Accordingly, the arc detection unit 14 can determine that the generated arc is a series arc if the abnormal current continues even after short-circuiting the first positive wire L11 and the first negative wire L21 of the first circuit M1 with the third switch 3.

[0122] If the arc detection unit 14 determines that the generated arc is a series arc, it shuts off at least one of the first switch 1 and the second switch 2. As a result, the current from the first generator 30A stops flowing to the arc generation site, the arc condition is resolved, and the abnormal current stops. The first circuit breaker A1 then terminates its operation.

[0123] Therefore, according to the arc detection method of the sixth modified example, after an arc is detected, the first positive electrode wire L11 and the first negative electrode wire L21 are short-circuited by the third switch 3, and then the arc is determined by whether or not an abnormal current continues. This makes it possible to determine the presence of an arc even when it is difficult to determine the presence of an arc based solely on the fluctuation in current values ​​before and after arc detection.

[0124] The power generation device 30 in the above embodiment is a solar power generation device, but any other power generation device that generates DC power may be used. For example, the power generation device 30 may be a hydroelectric power generation device.

[0125] (summary) Based on the embodiments described above, the following aspects are disclosed.

[0126] The circuit breaker (A1) of the first embodiment comprises a plurality of circuit breakers (10; 10A, 10B, 10C), a plurality of current sensors (12), an arc detection unit (14), and a control unit (15). The plurality of circuit breakers (10; 10A, 10B, 10C) are connected to each of a plurality of first circuits (M1) that transmit DC power. The plurality of current sensors (12) detect each current output through the plurality of first circuits (M1). The arc detection unit (14) detects arcs based on signals from the plurality of current sensors (12). Each of the plurality of first circuits (M1) includes a positive electrode wire (L11) and a negative electrode wire (L21). Each of the plurality of circuit breakers (10) has a first switch (1), a second switch (2), and a third switch (3). The first switch (1) causes each of the multiple circuit breakers (10) to conduct or interrupt the positive electrode wire (L11). The second switch (2) causes the negative electrode wire (L21) to conduct or interrupt. The third switch (3) opens or short-circuits the positive electrode wire (L11) and the negative electrode wire (L21). If an arc is detected in at least one of the multiple first circuits (M1), the control unit (15) uses the first switch (1) and the second switch (2) to interrupt at least one of the positive electrode wire (L11) and the negative electrode wire (L21) of the first circuit (M1) where the arc was detected. Then, the third switch (3) short-circuits the positive electrode wire (L11) and the negative electrode wire (L21) of the first circuit (M1) where the arc was detected.

[0127] In this embodiment, when an arc is detected, the first switch (1) and the second switch (2) are used to disconnect both the positive electrode wire (L11) and the negative electrode wire (L21) of the first circuit (M1) where the arc was detected. If the generated arc is a series arc, the point of breakage in at least one of the positive electrode wire (L11) and the negative electrode wire (L21) may be the point of arc generation, but since no current flows at the point of arc generation, the arc condition is resolved. On the other hand, if the generated arc is a parallel arc, current flows through the short-circuited portion of the positive electrode wire (L11) and the negative electrode wire (L21). For this reason, simply disconnecting both the positive electrode wire (L11) and the negative electrode wire (L21) of the first circuit (M1) where the arc was detected using the first switch (1) and the second switch (2) may not be sufficient to prevent the arc condition from continuing. The third switch (3) short-circuits the positive electrode wire (L11) and the negative electrode wire (L21) of the first circuit (M1) where the arc was detected, thereby forcibly lowering the voltage between the positive electrode wire (L11) and the negative electrode wire (L21). As a result, the current supplied from the power generator (30) flows through the third switch (3) and no longer flows to the arc generation site, thus eliminating the arc. This makes it possible to reliably eliminate the DC arc generated in the first circuit (M1).

[0128] In the second embodiment of the circuit breaker (A1), each of the plurality of first circuits (M1) is connected to a plurality of power generators (30; 30A, 30B, 30C) that generate DC power. When an arc is detected in the second circuit (M2), the control unit (15) uses the first switch (1) and the second switch (2) to interrupt the positive electrode wire (L11) and negative electrode wire (L21) of the first circuit (M1) at all of the plurality of circuit breakers (10A, 10B, 10C). The second circuit (M2) is a circuit connected in series with a plurality of first circuits (M1) connected in parallel.

[0129] In this configuration, all of the multiple power generation devices (30;30A, 30B,30C) are disconnected, so current from the multiple power generation devices (30;30A, 30B,30C) does not continuously flow into the arc generation site. This makes it possible to reliably eliminate the DC arc generated in the second circuit (M2).

[0130] In the third embodiment of the circuit breaker (A1), in the first or second embodiment, the arc detection unit (14) detects whether or not an arc is occurring based on high-frequency noise contained in the signal from at least one of the plurality of current sensors (12).

[0131] According to this embodiment, it becomes possible to detect the occurrence of a DC arc by detecting high-frequency noise as arc noise superimposed on the signal from the current sensor (12).

[0132] In the fourth embodiment of the circuit breaker (A1), in any one of the first to third embodiments, the arc detection unit (14) determines whether the generated arc is a parallel arc or a series arc based on the change in the current value before and after the arc is detected in at least one of the plurality of first circuits (M1) (M1).

[0133] In this embodiment, when the first circuit (M1) is subjected to a load and an unexpected break occurs, a series arc is generated, causing the circuit impedance to increase and the current to decrease. On the other hand, when a parallel arc is generated in the first circuit (M1) due to a short circuit between the positive electrode wire (L11) and the negative electrode wire (L21) caused by damage to the wire, an excessive current flows in the reverse direction because it flows back from the other power generation device (30). Therefore, by comparing the fluctuations in current values ​​before and after the arc is detected, it is possible to determine whether the generated DC arc is a parallel arc or a series arc.

[0134] The fifth embodiment of the circuit breaker (A1) further comprises a plurality of voltage sensors (13) in the fourth embodiment. The plurality of voltage sensors (13) detect the respective voltages output through a plurality of first circuits (M1). The arc detection unit (14) determines whether the generated arc is a parallel arc or a series arc based on the change in voltage value before and after the arc is detected in at least one of the plurality of first circuits (M1).

[0135] In this configuration, when the first circuit (M1) is subjected to a load and an unexpected break occurs, a series arc occurs, causing a voltage drop. On the other hand, when a parallel arc occurs in the first circuit (M1) due to a short circuit between the positive electrode wire (L11) and the negative electrode wire (L21) caused by damage to the wire, the voltage drops to approximately the arc voltage. The voltage drop due to the parallel arc is greater than the voltage drop due to the series arc. Therefore, by comparing the voltage fluctuations before and after the arc is detected, it becomes possible to improve the accuracy of determining the occurrence of a DC arc.

[0136] The sixth embodiment of the circuit breaker (A1) further comprises a plurality of voltage sensors (13) in any one of the first to fifth embodiments. The plurality of voltage sensors (13) detect the respective voltages output through a plurality of first circuits (M1). Each of the plurality of first circuits (M1) is connected to a plurality of power generators (30; 30A, 30B, 30C) that generate DC power. The arc detection unit (14) analyzes the voltage-current operating point of each of the plurality of power generators (30; 30A, 30B, 30C) based on signals from the plurality of current sensors (12) and the plurality of voltage sensors (13). The location of the arc is identified based on the fluctuations in the voltage-current operating point of each of the plurality of power generators (30; 30A, 30B, 30C) before and after the arc is detected.

[0137] According to this embodiment, the current-voltage operating point of each power generator (30) fluctuates due to the occurrence of an arc. Based on the signals from the current sensor (12) and the voltage sensor (13), the voltage-current operating point of each power generator (30) is analyzed, and the location of the arc is identified based on the fluctuations in the voltage-current operating point of each power generator (30) before and after the arc is detected. This makes it possible to reliably eliminate DC arcs.

[0138] The junction box (70) of the seventh embodiment comprises one of the first to sixth embodiments of a circuit breaker (A1) and a housing (19) that houses the circuit breaker (A1).

[0139] According to this embodiment, it becomes possible to reliably eliminate the DC arc in the junction box (70) housing the circuit breaker (A1).

[0140] The configurations relating to the second to sixth aspects are not essential to the circuit breaker (A1) and can be omitted as appropriate.

[0141] The eighth embodiment of the circuit breaker (A1, A2) comprises a current sensor (12), an arc detection unit (14), a circuit breaker (10), and a control unit (15). The current sensor (12) detects the current output through the circuits (M1, M2) that transmit DC power. The arc detection unit (14) detects an arc based on the signal from the current sensor (12). The circuit breaker (10) is connected to the circuits (M1, M2). The circuits (M1, M2) include a positive electrode wire (L11) and a negative electrode wire (L21). The circuit breaker (10) has a first switch (1), a second switch (2), and a third switch (3). The first switch (1) conducts or disconnects the positive electrode wire (L11). The second switch (2) conducts or disconnects the negative electrode wire (L21). The third switch (3) opens or short-circuits the positive terminal wire (L11) and the negative terminal wire (L21).

[0142] Furthermore, if an arc is detected in the circuit (M1, M2), the control unit (15) uses the first switch (1) and the second switch (2) to disconnect at least one of the positive electrode wire (L11) and negative electrode wire (L21) of the circuit (M1, M2). Then, the third switch (3) short-circuits the positive electrode wire (L11) and negative electrode wire (L21) of the circuit (M1, M2). [Explanation of Symbols]

[0143] 1. Switch 1 2. Second switch 3. Third switch 5. Solar panels 6, 6A~6C First Input Terminal 7, 7A~7C 2nd input terminal 8. First Output Terminal 9. Second output terminal 10 Circuit breakers 11 sensors 12 Current detection unit (current sensor) 13. Voltage detection unit (voltage sensor) 14 Arc detection unit 15 Switch control unit 19 cabinets 30 Power generation equipment 40, 40A Power Conditioner (PCS) 70 junction box 100, 100A DC power generation system 111 Arc (Parallel Arc) A1, A2 circuit breaker L11 First positive wire L21 1st negative electrode wire L12 2nd positive electrode wire L22 2nd negative electrode wire M1 1st electrical circuit M2 2nd electrical circuit

Claims

1. Multiple circuit breakers connected to each of the multiple first circuits that transmit DC power, Multiple current sensors for detecting each current output through the multiple first circuits, Based on signals from the aforementioned multiple current sensors, an arc detection unit detects an arc, It comprises a control unit and, Each of the aforementioned plurality of first circuits includes a positive electrode wire and a negative electrode wire. Each of the aforementioned plurality of circuit breakers is A first switch that connects or disconnects the positive electrode wire, A second switch for conducting or disconnecting the negative electrode wire, It includes a third switch that opens or short-circuits the positive electrode wire and the negative electrode wire, The control unit, If an arc is detected in at least one of the plurality of first circuits, the first switch and the second switch will disconnect at least one of the positive electrode wire and the negative electrode wire of the first circuit in which the arc was detected, and the third switch will short-circuit the positive electrode wire and the negative electrode wire of the first circuit in which the arc was detected. Circuit breaker.

2. Each of the aforementioned multiple first circuits is connected to a plurality of power generation devices that generate DC power. When an arc is detected in the second circuit connected in series with the plurality of first circuits connected in parallel, the control unit will, using the first and second switches, disconnect the positive and negative terminal wires of the first circuits in all of the plurality of circuit breakers. The circuit breaker according to claim 1.

3. The arc detection unit detects whether or not an arc is occurring based on high-frequency noise contained in the signal from at least one of the plurality of current sensors. The circuit breaker according to claim 1.

4. The arc detection unit determines whether the generated arc is a parallel arc or a series arc based on the change in current value before and after the detection of the arc in at least one of the plurality of first circuits. The circuit breaker according to claim 3.

5. The system further comprises a plurality of voltage sensors for detecting each voltage output through the plurality of first circuits, The arc detection unit determines whether the generated arc is a parallel arc or a series arc based on the voltage fluctuation before and after the detection of the arc in at least one of the plurality of first circuits. The circuit breaker according to claim 4.

6. The system further comprises a plurality of voltage sensors for detecting each voltage output through the plurality of first circuits, Each of the aforementioned multiple first circuits is connected to a plurality of power generation devices that generate DC power. The arc detection unit analyzes the voltage-current operating point of each of the multiple power generation devices based on the signals from the multiple current sensors and the multiple voltage sensors, and identifies the location where the arc occurred based on the fluctuations in the voltage-current operating point of each of the multiple power generation devices before and after the arc was detected. The circuit breaker according to claim 4.

7. A circuit breaker according to any one of claims 1 to 6, The system comprises a housing for the aforementioned circuit breaker, Connection box.

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