Solar power generation system

Abstract

To provide a photovoltaic power generation system capable of achieving both reduction in an installation cost and improvement of stability of a cut-off device.SOLUTION: A photovoltaic power generation system 1 comprises a string 2, an inverter 3, a first cut-off device 4, and a second cut-off device 5. The string 2 includes a plurality of solar cell module groups. The first cut-off device 4 is connected to a first cable run. The second cut-off device 5 is connected to a second cable run. The first cut-off device 4 cuts off the connection between the plurality of solar cell module groups connected to the first cable run according to a first control signal. The second cut-off device 5 is driven by power supplied from the first cut-off device 4, and cuts off the connection between the plurality of solar cell module groups connected to the second cable run according to a second control signal. The first cut-off device 4 comprises a first semiconductor switching element 47 and a first switching unit 44a connected in series to the first semiconductor switching element 47.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a photovoltaic power generation system.

Background Art

[0002] In the United States, for the purpose of protecting firefighters from electric shock and the like during emergencies such as fires, the introduction of a so-called rapid shutdown function that immediately stops power generation by a photovoltaic power generation system during emergencies is mandated by NEC (National Electrical Code). For example, Patent Document 1 discloses a photovoltaic power generation system that stops the output of power from a solar cell module to an inverter according to the operating state of the inverter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a photovoltaic power generation system, in order to further improve the safety of firefighters during a fire or the like, for example, it is preferable to install a cutoff device having a rapid shutdown function for each solar cell module. However, when a cutoff device is installed for each solar cell module, the installation cost of the cutoff device becomes high.

[0005] Furthermore, in the circuit breaker of a solar power generation system, a switching element that opens and closes mechanical contacts, such as a relay, is used as the switching element to interrupt the circuit of the solar power generation system. The power to drive this switching element is supplied from the solar cell module of the solar power generation system. In other words, the power generated by the solar cell module is used to drive external devices (e.g., inverters) and to drive the switching element. In this case, if the amount of power generated by the solar cell module decreases for some reason, and the switching element is no longer supplied with the power necessary to drive it, a phenomenon may occur where, for example, even if the power from the solar cell module is used to try to close the contacts of the switching element (try to turn the switching element ON), the contacts immediately open (the switching element turns OFF), and this repeats. Also, if the amount of power generated from the solar cell module becomes unstable, the switching element may repeatedly switch between ON and OFF states. The occurrence of this phenomenon can destabilize the operation of the solar power generation system, for example, by preventing the system from starting up.

[0006] The object of the present invention is to provide a solar power generation system that can achieve both a reduction in the installation cost of the shutoff device and an improvement in stability. [Means for solving the problem]

[0007] A photovoltaic power generation system according to one aspect of the present invention comprises a string, an inverter, a first circuit breaker, and a second circuit breaker. The string includes a plurality of solar cell module groups connected in series with each other. Each of the plurality of solar cell module groups includes one or a plurality of solar cell modules connected in series. The inverter is connected to the string and converts the DC power output from the string into AC power. The first circuit breaker is connected to a first circuit that connects the plurality of solar cell module groups together. The second circuit breaker is connected to a second circuit that connects a plurality of solar cell module groups that are different from the plurality of solar cell module groups connected to the first circuit. The open-circuit voltage of each of the plurality of solar cell module groups in the string is less than or equal to a predetermined open-circuit voltage. The first circuit breaker is connected to a power line that is connected to the second circuit breaker and disconnects the plurality of solar cell module groups connected to the first circuit in response to a first control signal from the inverter. The second circuit breaker is driven by power supplied from the first circuit breaker via the power line and disconnects the plurality of solar cell module groups connected to the second circuit in response to a second control signal from the first circuit breaker.

[0008] Furthermore, the multiple groups of solar cell modules in the string include a first group. The first circuit breaker includes a first switch connected to the anode terminal of the first group, a first semiconductor switching element connected in series between the anode terminal of the first group and the first switch, and a first power supply unit whose anode terminal is connected between the anode terminal of the first group and the first semiconductor switching element, and whose cathode terminal is connected to the cathode terminal of the first group, and which generates power to drive the first switch. In addition, the first semiconductor switching element turns OFF when the amount of power generated by the first group falls below a predetermined threshold.

[0009] In this solar power generation system, the first and second circuit breakers are in a master-slave relationship. The second circuit breaker disconnects the connections between multiple solar cell module groups in response to a second control signal output from the first circuit breaker. Furthermore, the second circuit breaker is powered by the first circuit breaker. This simplifies the configuration of the second circuit breaker, thereby reducing its installation cost. In addition, since the open-circuit voltage of each group of solar cell module is below a predetermined open-circuit voltage, a highly safe solar power generation system can be provided.

[0010] Furthermore, in this solar power generation system, the first semiconductor switching element of the first circuit breaker turns OFF when the amount of power generated by the first group connected to the first circuit breaker falls below a predetermined threshold. As a result, when the amount of power generated by the first group is small, the circuit from the first group to the inverter is interrupted, and the first group is able to supply power only to the first power supply unit. In other words, when the amount of power generated by the first group is small, the power generated by the first group is used only to drive the switching unit. As a result, even if the amount of power generated by the first group is small or unstable, the first switching unit can maintain a closed state (ON state). As a result, the solar power generation system operates stably.

[0011] The first circuit breaker may have a first bypass element. One end of the first bypass element is connected to the cathode-side terminal of the first group. The other end of the first bypass element is connected between the first switch and the first semiconductor switching element. In this case, even if the power generation of the first group decreases, the power generated by other solar cell module groups can be propagated to the inverter via the first bypass element.

[0012] The first semiconductor switching element may be a MOSFET element or an IGBT element. In this case, the power required to turn the first semiconductor switching element ON or OFF can be reduced.

[0013] The first circuit breaker may include a second switching unit connected to the cathode-side terminal of the first group. In this case, multiple circuits can be switched on and off with a single first circuit breaker.

[0014] The second switching unit may be driven by power supplied from the first power supply unit. In this case, additional wiring for supplying power to drive the switching unit can be omitted when installing the first circuit breaker. This reduces the installation cost of the first circuit breaker. Furthermore, since the driving voltage range of the first circuit breaker can be kept small, the manufacturing cost of the first circuit breaker can be reduced.

[0015] The first circuit breaker may be capable of independently controlling the opening and closing of the first and second switching sections. In this case, for example, if a malfunction such as a contact failure occurs in the first switching section, the second switching section, which is functioning normally, can be used as is.

[0016] The string of solar cell module groups may include a second group. The second circuit breaker may have a third switch connected to the anode terminal of the second group, and a second semiconductor switching element connected in series between the anode terminal of the second group and the third switch. The second semiconductor switching element may also be turned OFF when the power generation of the second group falls below a predetermined threshold. In this case, if the power generation of the second group is small, the power generated by the second group is not transmitted to the inverter. As a result, the solar power generation system operates stably.

[0017] The second circuit breaker may have a second bypass element. One end of the second bypass element is connected to the cathode-side terminal of the second group. The other end of the second bypass element is connected between the third switch and the second semiconductor switching element. In this case, even if the power generation in the second group decreases, the power generated by other solar cell module groups can be propagated to the inverter via the second bypass element.

[0018] The second semiconductor switching element may be a MOSFET element or an IGBT element. In this case, the power required to turn the second semiconductor switching element ON or OFF can be reduced.

[0019] The second circuit breaker may include a fourth switching unit connected to the cathode-side terminal of the second group. In this case, multiple circuits can be switched on and off by a single first circuit breaker.

[0020] The second circuit breaker may be capable of independently controlling the opening and closing of the third and fourth switching sections. In this case, for example, if a malfunction such as a contact failure occurs in the third switching section, the fourth switching section, which is functioning normally, can be used as is.

[0021] The first circuit breaker may, in response to a first control signal from the inverter, disconnect the connections between multiple solar cell module groups connected to the first circuit, and then output a second control signal to the second circuit breaker. In this case, the voltage related to the second circuit breaker can be reduced. This makes it possible to reduce the cost of the second circuit breaker.

[0022] The first circuit breaker may output a second control signal to the second circuit breaker using a communication method different from power line communication via a communication line connected to the first and second circuit breakers. In this case, stable communication from the first circuit breaker to the second circuit breaker becomes possible.

[0023] Multiple groups of solar cell modules in a string may have an open-circuit voltage of 165V or less per group. In this case, a safer solar power generation system can be provided.

[0024] The inverter may output the first control signal to the first circuit breaker via power line communication. In this case, when installing the first circuit breaker in an existing solar power generation system, additional wiring to ensure communication between the inverter and the first circuit breaker can be omitted, thus reducing the installation cost of the first circuit breaker.

[0025] The inverter may output a first control signal to the first cutoff device by wireless communication. In this case, it becomes possible to output a first control signal to the first cutoff device by remote operation.

[0026] At least one of the plurality of solar cell module groups of the string may include a plurality of solar cell modules connected in series. In this case, the plurality of solar cell modules can be cut off by the first cutoff device or the second cutoff device.

Advantages of the Invention

[0027] According to the present invention, in a photovoltaic power generation system, it is possible to provide a photovoltaic power generation system that can achieve both reduction of the installation cost of the cutoff device and improvement of stability.

Brief Description of the Drawings

[0028] [Figure 1] FIG. 1 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to one aspect of the present invention. [Figure 2] FIG. 2 is a block diagram schematically showing the configuration of the first cutoff device. [Figure 3] FIG. 3 is a circuit diagram schematically showing the configuration of the regulator. [Figure 4] FIG. 4 is a block diagram schematically showing the configuration of the second cutoff device. [Figure 5] FIG. 5 is a diagram for explaining an example of the operation modes of the first cutoff device and the second cutoff device. [Figure 6] FIG. 6 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment. [Figure 7] FIG. 7 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment. [Figure 8] FIG. 8 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment.

Modes for Carrying Out the Invention

[0029] Figure 1 is a schematic block diagram showing the configuration of a photovoltaic power generation system 1 according to one aspect of the present invention. The photovoltaic power generation system 1 comprises a string 2, an inverter 3, at least one first circuit breaker 4, and at least one second circuit breaker 5. In this embodiment, the at least one first circuit breaker 4 includes a plurality of first circuit breakers 4a, 4b, and the at least one second circuit breaker 5 includes a plurality of second circuit breakers 5a, 5b.

[0030] String 2 includes multiple solar cell module groups 6A to 6H connected in series with each other. Each of the multiple solar cell module groups 6A to 6H includes one or multiple solar cell modules 6 connected in series. That is, String 2 includes multiple (16 in this embodiment) solar cell modules 6 connected in series with each other. The photovoltaic power generation system 1 may also include a solar cell array in which multiple String 2s are connected in parallel.

[0031] Multiple solar cell module groups 6A to 6H have an open-circuit voltage below a predetermined open-circuit voltage for each group. The predetermined open-circuit voltage is, for example, 165V. That is, string 2 is divided into multiple solar cell module groups such that the open-circuit voltage for each group is 165V or less. The open-circuit voltage of solar cell module 6 is, for example, 50V. Hereafter, solar cell module groups 6A to 6H may be referred to as groups 6A to 6H.

[0032] Each of groups 6A, 6C, 6E, and 6G contains one solar cell module 6. Each of groups 6B, 6D, 6F, and 6H contains three solar cell modules 6 connected in series with each other. Therefore, the open-circuit voltage of groups 6A, 6C, 6E, and 6G is 50V, and the open-circuit voltage of groups 6B, 6D, 6F, and 6H is 150V.

[0033] Groups 6A to 6H are arranged alphabetically from 6A to 6H and connected in series with each other. Each of groups 6A to 6H includes an anode terminal and a cathode terminal. The anode terminal of each group 6A to 6H is the anode terminal of the solar cell module 6 that is closest to the anode of the inverter 3 among the solar cell modules 6 belonging to each group 6A to 6H. The cathode terminal of each group 6A to 6H is the cathode terminal of the solar cell module 6 that is furthest from the anode of the inverter 3 among the solar cell modules 6 belonging to each group 6A to 6H.

[0034] For example, the anode terminal of group 6A is formed by the anode terminal of the solar cell module 6 of group 6A. The anode terminal of group 6A is connected to the anode terminal of inverter 3. The cathode terminal of group 6A is formed by the cathode terminal of the solar cell module 6 of group 6A. The cathode terminal of group 6A is connected to the anode terminal of group 6B.

[0035] For example, the anode terminal of group 6B is connected to the anode terminal of the solar cell module 6 that is closest to group 6A among the solar cell modules 6 belonging to group 6B. The cathode terminal of group 6B is connected to the cathode terminal of the solar cell module 6 that is furthest from group 6A among the solar cell modules 6 belonging to group 6B. The cathode terminal of group 6B is connected to the anode terminal of group 6C.

[0036] The cathode terminal of group 6C is connected to the anode terminal of group 6D. The cathode terminal of group 6D is connected to the anode terminal of group 6E. The cathode terminal of group 6E is connected to the anode terminal of group 6F. The cathode terminal of group 6F is connected to the anode terminal of group 6G. The cathode terminal of group 6G is connected to the anode terminal of group 6H. The cathode terminal of group 6H is connected to the cathode terminal of inverter 3.

[0037] The solar cell module 6 generates electricity from sunlight and outputs the generated electricity to the inverter 3. The inverter 3 is connected to string 2 via power lines. The inverter 3 converts the DC power output from the solar cell modules 6 of string 2 into AC power. The inverter 3 is connected to the power grid 7 and supplies the AC power to the commercial power grid and load devices.

[0038] In detail, the inverter 3 includes a DC / DC converter 3a, a DC / AC inverter 3b, and a control unit 3c. The DC / DC converter 3a converts the voltage of the power output from the solar cell module 6 to a predetermined voltage and inputs it to the DC / AC inverter 3b. The DC / AC inverter 3b converts the DC power output from the solar cell module 6 to AC power via the DC / DC converter 3a. The control unit 3c includes a CPU and memory, and controls the DC / DC converter 3a and the DC / AC inverter 3b. The control unit 3c also outputs a first control signal to the first circuit breakers 4a and 4b via power line communication.

[0039] The first circuit breaker 4a and the second circuit breaker 5a are in a master-slave relationship. The first circuit breaker 4a functions as the master to the second circuit breaker 5a, and the second circuit breaker 5a functions as the slave to the first circuit breaker 4a. In other words, the first circuit breaker 4a controls the second circuit breaker 5a.

[0040] Similarly, the first circuit breaker 4b and the second circuit breaker 5b have a master-slave relationship. The first circuit breaker 4b functions as the master to the second circuit breaker 5b, and the second circuit breaker 5b functions as the slave to the first circuit breaker 4b. In other words, the first circuit breaker 4b controls the second circuit breaker 5b.

[0041] In this embodiment, the first circuit breaker 4 and the second circuit breaker 5 are in a one-to-one relationship, with one second circuit breaker provided for each first circuit breaker.

[0042] The first circuit breaker 4a is connected to the circuit connecting groups 6A to 6H. In this embodiment, the first circuit breaker 4a is connected to the circuit 8a connecting group 6A and group 6B, and to the circuit 8b connecting inverter 3 and group 6A. The first circuit breaker 4a is connected to the anode and cathode terminals of group 6A. The first circuit breaker 4a disconnects the connection between group 6A and group 6B, and the connection between inverter 3 and group 6A, in response to a first control signal from inverter 3.

[0043] The first circuit breaker 4a outputs a second control signal to the second circuit breaker 5a via a communication line 10a connected to the first circuit breaker 4a and the second circuit breaker 5a, using a communication method different from power line communication. The first circuit breaker 4a outputs the second control signal to the second circuit breaker 5a using a serial communication method such as LIN (Local Interconnect Network) communication or SPI (Serial Peripheral Interface) communication. The first circuit breaker 4a disconnects the connection between group 6A and group 6B, and the connection between inverter 3 and group 6A, before outputting the second control signal to the second circuit breaker 5a.

[0044] The first circuit breaker 4a is connected to a power line 20a that is connected to the second circuit breaker 5a. The first circuit breaker 4a supplies power to the second circuit breaker 5a via the power line 20a to drive the second circuit breaker 5a.

[0045] Figure 2 is a schematic block diagram showing the configuration of the first circuit breaker 4. The first circuit breaker 4 includes a power supply unit 41 (an example of the first power supply unit), a signal receiving unit 42, a control unit 43, a relay 44, a bypass circuit 45, a first semiconductor switching element 47, and a first bypass element 48.

[0046] The power supply unit 41 is a regulator connected in parallel to the solar cell module group. Specifically, the anode terminal of the power supply unit 41 is connected to the anode terminal of group 6A, and the cathode terminal is connected to the cathode terminal of group 6A. The power supply unit 41 is configured with a circuit as shown in Figure 3, for example. Figure 3 is a schematic circuit diagram showing the configuration of the power supply unit 41. The power supply unit 41 includes input terminals 21a, 21b, output terminals 22a, 22b, line filter 23, capacitors 24, 25, boost circuit 26, switching element 27, control circuit 28, transformer 29, diode 30, DC / DC converter 31, feedback circuit 32, etc.

[0047] The power supply unit 41 generates drive power to operate the first circuit breaker 4 and the second circuit breaker 5, using the power generated by the solar cell module 6 as its power source. Here, the drive power for the first circuit breaker 4 is generated using only the power generated by the solar cell module 6 of group 6A. The power supply unit 41 outputs the drive power for the second circuit breaker 5 to the second circuit breaker 5 via the power line 20a.

[0048] The signal receiving unit 42 receives a first control signal from the control unit 3c of the inverter 3 and outputs the received first control signal to the control unit 43. More specifically, the signal receiving unit 42 receives the first control signal from the control unit 3c of the inverter 3 via a signal detection unit 46 that detects the first control signal from the control unit 3c of the inverter 3.

[0049] The control unit 43 includes a CPU, memory, etc. Based on the signal output from the signal receiving unit 42, the control unit 43 controls the current flowing through the coil of the relay 44 to open and close the contacts of the relay 44. The relay 44 is, for example, a mechanical relay capable of switching high-voltage DC current. The control unit 43 is supplied with power to drive the relay 44 from the power supply unit 41.

[0050] The control unit 43 outputs a second control signal to a plurality of second circuit breakers 5 via the communication line 10 using a communication method different from power line communication. The control unit 43 outputs the second control signal to the plurality of second circuit breakers 5 after disconnecting the connection between group 6A and group 6B. The control unit 43 determines whether the connection between group 6A and group 6B has been disconnected, for example, by monitoring the voltage between the contacts of the relay 44.

[0051] The relay 44 includes a first switching unit 44a and a second switching unit 44b. The first switching unit 44a is located in the circuit 8b to which the anode terminal of group 6A is connected, and switches the connection between the inverter 3 and group 6A. The second switching unit 44b is located in the circuit 8a to which the cathode terminal of group 6A is connected, and switches the connection between group 6A and group 6B. In this embodiment, the second switching unit 44b may be omitted.

[0052] When no power is supplied from the power supply unit 41, the first switching unit 44a and the second switching unit 44b are always in the open state. Therefore, when the first circuit breaker 4 is not driven, the connection between the inverter 3 and group 6A, and the connection between group 6A and group 6B are disconnected.

[0053] The bypass circuit 45 is a circuit that allows the signal receiving unit 42 to receive the first control signal from the control unit 3c when the first circuit breaker 4 is in the tripped state. When the circuits 8a and 8b are tripped by the first circuit breaker 4, the signal receiving unit 42 can receive the first control signal from the control unit 3c via the bypass circuit 45.

[0054] The first semiconductor switching element 47 is connected in series with the first switching unit 44a in the circuit 8b. Specifically, one end of the first semiconductor switching element 47 is connected to the anode terminal of group 6A. On the other hand, the other end of the first semiconductor switching element 47 is connected to the first switching unit 44a. The first semiconductor switching element 47 is, for example, a MOSFET element or an IGBT (Insulated Gate Bipolar Transistor) element.

[0055] The first semiconductor switching element 47 is connected to the control unit 43, which controls the switching between the ON state and the OFF state of the first semiconductor switching element 47. Here, the "ON state" means that one end and the other end of the first semiconductor switching element 47 are conductive. On the other hand, the "OFF state" means that the one end and the other end of the first semiconductor switching element 47 are in an insulated state.

[0056] When the first semiconductor switching element 47 is a MOSFET element or an IGBT element, the control unit 43 is connected to the gate terminal of the first semiconductor switching element 47. The control unit 43 can turn the first semiconductor switching element 47 ON or OFF by outputting a predetermined voltage signal to the gate terminal. When a voltage signal is output to the gate terminal to turn the MOSFET element or IGBT element ON or OFF, almost no current flows through the gate terminal. In this way, by using a MOSFET element, IGBT element, etc. as the first semiconductor switching element 47, the power required to turn the first semiconductor switching element 47 ON or OFF can be reduced.

[0057] In the first circuit breaker 4, when the first semiconductor switching element 47 is in the OFF state, the anode terminal of group 6A and the inverter 3 are disconnected. On the other hand, even when the first semiconductor switching element 47 is in the OFF state, the power supply unit 41 is not disconnected from group 6A. In other words, when the first semiconductor switching element 47 is in the OFF state, the power generated by group 6A is supplied to the power supply unit 41, but not to the inverter 3.

[0058] The control unit 43 turns off the first semiconductor switching element 47 when the power generation of group 6A is less than a predetermined threshold. As a result, when the power generation of group 6A is less than a predetermined threshold, the power from group 6A is supplied to the first circuit breaker 4 (power supply unit 41) and the second circuit breaker 5. As a result, when the power generation of group 6A is small, the power from group 6A can be used only to drive the first switching unit 44a and the second switching unit 44b and the second circuit breaker 5. If the power from group 6A is supplied only to the first switching unit 44a and the second switching unit 44b, the first switching unit 44a and the second switching unit 44b can maintain a closed state (ON state) even if the power generation of group 6A is small or unstable. As a result, the photovoltaic power generation system 1 operates stably. The above threshold can be set to the amount of power at which the first switching unit 44a and the second switching unit 44b operate stably, for example, even when power from group 6A is supplied to the power supply unit 41, inverter 3, and second circuit breaker 5.

[0059] Furthermore, because the first circuit breaker 4 has a first semiconductor switching element 47, even if there is an abnormality in the power generation amount of group 6A, the first switching unit 44a and the second switching unit 44b can maintain a closed state (ON state). Therefore, the possibility of these switching units opening and closing when a high voltage is applied to the first switching unit 44a and the second switching unit 44b is reduced. For this reason, the first switching unit 44a and the second switching unit 44b do not need to have large voltage withstand characteristics and can be made inexpensive.

[0060] The first bypass element 48 is connected in parallel to group 6A. Specifically, one end of the first bypass element 48 is connected between the cathode terminal of group 6A and the second switching unit 44b. On the other hand, the other end of the first bypass element 48 is connected between the first switching unit 44a and the first semiconductor switching element 47. The first bypass element 48 is, for example, a diode having an anode connected to the cathode side of group 6A and a cathode connected between the first switching unit 44a and the first semiconductor switching element 47.

[0061] When the solar cell modules of group 6A are shaded at sunrise or sunset, or when a sudden power drop or abnormal heat generation occurs in group 6A, making it impossible to output sufficient power from group 6A, the first bypass element 48 forms a circuit that propagates power generated by other solar cell module groups, bypassing group 6A. Specifically, when the amount of power generated from group 6A is insufficient and the first semiconductor switching element 47 is in the OFF state, and the first switching unit 44a and the second switching unit 44b are in the closed state, the first bypass element 48 forms a path that transmits power generated by other solar cell module groups to the inverter 3 (first circuit breaker 4).

[0062] The first bypass element 48, which is a diode, can immediately form a circuit that bypasses the malfunctioning group 6A based on its electrical characteristics when it is no longer able to output sufficient power from group 6A, even without a command from an external signal.

[0063] The second circuit breaker 5a is connected to a circuit that connects different groups, such as group 6A and group 6B, which are connected to circuit 8a. In this embodiment, the second circuit breaker 5a is connected to circuit 8c that connects group 6B and group 6C, and to circuit 8d that connects group 6C and group 6D. The second circuit breaker 5a is connected to the anode and cathode terminals of group 6C. The second circuit breaker 5a disconnects the connection between group 6B and group 6C, and the connection between group 6C and group 6D, in response to a second control signal output from the first circuit breaker 4a via the communication line 10a.

[0064] The second circuit breaker 5a is driven by power supplied from the first circuit breaker 4a via the power line 20a. More specifically, the second circuit breaker 5a is driven by a drive power generated by the power supply unit 41 of the first circuit breaker 4a, which is supplied from the first circuit breaker 4a to the second circuit breaker 5a via the power line 20a.

[0065] Figure 4 is a schematic block diagram showing the configuration of the second circuit breaker 5a. The second circuit breaker 5a includes a control unit 53, a relay 54, a bypass circuit 55, a second semiconductor switching element 56, and a second bypass element 57.

[0066] The control unit 53 includes a CPU, memory, etc. The control unit 53 controls the current flowing through the coil of the relay 54 in response to a second control signal from the first circuit breaker 4, thereby controlling the opening and closing of the contacts of the relay 54. The relay 44 is, for example, a mechanical relay, capable of switching high-voltage DC current. The control unit 53 receives the second control signal from the first circuit breaker 4 via a communication interface (not shown) connected to the communication line 10, and opens the contacts of the relay 54. The power to drive the relay 54 is supplied to the control unit 53 from the first circuit breaker 4 via the power line 20a.

[0067] The relay 54 includes a third switching section 54a and a fourth switching section 54b. The third switching section 54a is located in the circuit 8c to which the anode terminal of group 6C is connected, and switches the connection between group 6B and group 6C. The third switching section 54a is connected to the cathode terminal of group 6B and the second semiconductor switching element 56. The fourth switching section 54b is located in the circuit 8d to which the cathode terminal of group 6C is connected, and switches the connection between group 6C and group 6D.

[0068] When the first circuit breaker 4 is not supplying power, the third switching section 54a and the fourth switching section 54b are always in the open state. Therefore, when the second circuit breaker 5a is not driven, the connection between group 6B and group 6C, and the connection between group 6C and group 6D are disconnected.

[0069] The bypass circuit 55 is a circuit that allows the signal receiving unit 42 of the first circuit breaker 4 to receive the first control signal from the control unit 3c via power line communication when the second circuit breaker 5 is in an interrupted state. By providing the bypass circuit 55, it becomes possible to continue power line communication.

[0070] The second semiconductor switching element 56 is connected in series with the third switching unit 54a in the circuit 8c. Specifically, one end of the second semiconductor switching element 56 is connected to the anode terminal of group 6C. On the other hand, the other end of the second semiconductor switching element 56 is connected to the third switching unit 54a. The second semiconductor switching element 56 is, for example, a MOSFET element or an IGBT (Insulated Gate Bipolar Transistor) element.

[0071] The second semiconductor switching element 56 is connected to the control unit 53. The control unit 53 controls the switching between the ON state and the OFF state of the second semiconductor switching element 56.

[0072] When the second semiconductor switching element 56 is a MOSFET element or an IGBT element, the control unit 53 is connected to the gate terminal of the second semiconductor switching element 56. The control unit 53 can turn the second semiconductor switching element 56 ON or OFF by outputting a predetermined voltage signal to the gate terminal. When a voltage signal is output to the gate terminal to turn the MOSFET element or IGBT element ON or OFF, almost no current flows through the gate terminal. In this way, by using a MOSFET element, IGBT element, etc. as the second semiconductor switching element 56, the power required to turn the second semiconductor switching element 56 ON or OFF can be reduced.

[0073] In the second circuit breaker 5, when the second semiconductor switching element 56 is in the OFF state, the anode terminal of group 6C and group 6B are disconnected. In other words, when the second semiconductor switching element 56 is in the OFF state, the power generated by group 6C is not supplied to the inverter 3.

[0074] The control unit 53 turns off the second semiconductor switching element 56 when the power generation amount of group 6C is less than a predetermined threshold. As a result, when the power generation amount of group 6C is less than the predetermined threshold, power from group 6C is not supplied to the inverter 3. This prevents the entire solar power generation system 1 from becoming unstable due to low power from group 6C. The threshold can be, for example, the amount of power that allows the solar power generation system 1 to operate stably even when power from group 6C is supplied to the inverter 3.

[0075] The second bypass element 57 is connected in parallel to group 6C. Specifically, one end of the second bypass element 57 is connected between the cathode terminal of group 6C and the fourth switching unit 54b. On the other hand, the other end of the second bypass element 57 is connected between the third switching unit 54a and the second semiconductor switching element 56. The second bypass element 57 is, for example, a diode having an anode connected to the cathode side of group 6C and a cathode connected between the third switching unit 54a and the second semiconductor switching element 56.

[0076] When a sudden power drop or abnormal heat generation occurs in group 6C, and group 6C is unable to output sufficient power, the second bypass element 57 forms a circuit that transmits power generated by other solar cell module groups, bypassing group 6C. Specifically, when the amount of power generated from group 6C is insufficient, causing the second semiconductor switching element 56 to turn OFF and the third and fourth switching units 54a and 54b to close, the second bypass element 57 forms a path that transmits power generated by other solar cell module groups to the inverter 3.

[0077] The second bypass element 57, which is a diode, can immediately form a circuit that bypasses the malfunctioning group 6C based on its electrical characteristics when it is no longer able to output sufficient power from group 6C, even without a command from an external signal.

[0078] The relay 54 of the second circuit breaker 5b opens and closes the connection between group 6D and group 6E, and between group 6E and 6F. The relay 54 of the second circuit breaker 5c opens and closes the connection between group 6F and group 6G, and between group 6G and group 6H. The second circuit breaker 5b has the same configuration as the second circuit breaker 5a, except that the circuits it connects to are different, so a detailed explanation is omitted.

[0079] The first circuit breaker 4b has the same configuration as the first circuit breaker 4a, except that the circuit to which it is connected is different. The second circuit breaker 5b has the same configuration as the second circuit breaker 5a, except that the circuit to which it is connected is different. Furthermore, the relationship between the first circuit breaker 4b and the second circuit breaker 5b is the same as the relationship between the first circuit breaker 4a and the second circuit breaker 5a described above, so it will be explained briefly.

[0080] The first circuit breaker 4b is connected to the circuit 8e connecting group 6D and group 6E, and to the circuit 8f connecting group 6E and group 6F. The first circuit breaker 4b is connected to the anode and cathode terminals of group 6E. The first circuit breaker 4b disconnects the connection between group 6D and group 6E, and the connection between group 6E and group 6F, in response to the first control signal from the inverter 3.

[0081] The first circuit breaker 4b outputs a second control signal to the second circuit breaker 5b using a communication method different from power line communication via the communication line 10b connected to the first circuit breaker 4b and the second circuit breaker 5b. The first circuit breaker 4b disconnects the connection between group 6D and group 6E, and the connection between group 6E and group 6F, before outputting the second control signal to the second circuit breaker 5b.

[0082] The first circuit breaker 4b is driven by the power generated by the solar cell module 6 belonging to group 6E. The first circuit breaker 4b is connected to a power line 20b which is connected to the second circuit breaker 5b. The first circuit breaker 4b supplies power to the second circuit breaker 5b via the power line 20b to drive the second circuit breaker 5b.

[0083] The second circuit breaker 5b is connected to the circuit 8g connecting group 6F and group 6G, and to the circuit 8h connecting group 6G and group 6H. The second circuit breaker 5b disconnects the connection between group 6F and group 6G, and the connection between group 6G and group 6H, in response to the second control signal output from the first circuit breaker 4b via the communication line 10b.

[0084] Next, an example of the operating modes of the first circuit breakers 4a, 4b and the second circuit breakers 5a, 5b will be described with reference to Figure 5. The operating modes of the first circuit breakers 4a, 4b and the second circuit breakers 5a, 5b include three operating modes: start mode, active mode, and safety mode. The safety mode includes a normal circuit breaker mode and an emergency safety circuit breaker mode. Therefore, the first circuit breakers 4a, 4b and the second circuit breakers 5a, 5b operate in four operating modes: start mode, active mode, normal circuit breaker mode, and emergency safety circuit breaker mode.

[0085] The start mode is the mode when sunlight first hits the solar cell module 6. At this time, the solar cell module 6 generates electricity from the sunlight. The first circuit breakers 4a and 4b are then driven by a drive power generated by the power supply unit 41 from the electricity generated by the solar cell module 6. When the first circuit breakers 4a and 4b are driven and the control unit 43 receives a first control signal from the control unit 3c of the inverter 3 via the signal receiving unit 42, the control unit 43 closes the first switching unit 44a and the second switching unit 44b of the relay 44.

[0086] Furthermore, the first circuit breakers 4a and 4b supply the drive power generated by the power supply unit 41 to the second circuit breakers 5a and 5b. This drives the second circuit breakers 5a and 5b. When the second circuit breakers 5a and 5b are driven and the control unit 53 receives a command signal from the first circuit breakers 4a and 4b that is different from the second control signal, for example, the control unit 53 closes the third switching unit 54a and the fourth switching unit 54b of the relay 54. As a result, groups 6A to 6H are connected in string 2 via the first circuit breakers 4a and 4b and the second circuit breakers 5a and 5b, and the power generated by the solar cell module 6 is output to the inverter 3.

[0087] In the start mode (especially at sunrise) when sunlight begins to hit the solar cell module 6, the amount of power generated from the solar cell module group is small. Therefore, if the power from the solar cell module group is used for both driving the switch and supplying power to the inverter 3 in the start mode, there may be insufficient power to drive the switch, and the switch may repeatedly attempt to transition from the open state (OFF state) to the closed state (ON state) but immediately return to the open state (OFF state).

[0088] Therefore, in start mode, when the amount of power generated from the solar cell module group connected to the first disconnection device 4 is less than a predetermined threshold, the control unit 43 turns the first semiconductor switching element 47 to the OFF state. As a result, the first switching unit 44a and the second switching unit 44b can maintain the closed state (ON state) even when the amount of power generated from the solar cell module group is small.

[0089] Furthermore, the control unit 43 closes the first switching unit 44a and the second switching unit 44b using power from the solar cell module group while keeping the first semiconductor switching element 47 in the OFF state. As a result, the first circuit breaker 4 can transmit power generated by other solar cell module groups to the inverter 3 via the first bypass element 48.

[0090] On the other hand, when the amount of power generated from the solar cell module group connected to the second circuit breaker 5 is less than a predetermined threshold, the control unit 53 turns off the second semiconductor switching element 56. This prevents the entire solar power generation system 1 from becoming unstable due to low power from the solar cell module group connected to the second circuit breaker 5.

[0091] Furthermore, the control unit 53 closes the third switching unit 54a and the fourth switching unit 54b using power from the solar cell module group connected to the first circuit breaker 4, while keeping the second semiconductor switching element 56 in the OFF state. As a result, the second circuit breaker 5 can transmit power generated by other solar cell module groups to the inverter 3 via the second bypass element 57.

[0092] Subsequently, when the amount of power generated from the solar cell module group becomes sufficiently large (i.e., when the amount of power generated from the solar cell module group exceeds a predetermined threshold), the control units 43 and 53 turn on the first semiconductor switching element 47 and the second semiconductor switching element 56, respectively. This allows the power generated by the solar cell module group to be used to supply power to the inverter 3 only after the amount of power generated from the solar cell module group has become sufficiently large.

[0093] The active mode is the state in which the solar cell module 6 generates electricity by receiving sunlight during the day, and is essentially the same as the start mode. Therefore, in the active mode, groups 6A to 6H are connected via the first circuit breakers 4a and 4b and the second circuit breakers 5a and 5b, and the power generated by the solar cell module 6 is output to the inverter 3.

[0094] In active mode, the amount of power generated from a solar cell module group may decrease due to reasons such as shading the solar cell module group or a malfunction in one of the solar cell modules included in the solar cell module group. To prepare for such situations, in active mode, when the amount of power generated by the solar cell module group connected to the first disconnector 4 falls below a predetermined threshold, the control unit 43 turns the first semiconductor switching element 47 to the OFF state. As a result, the power from the solar cell module group is used only to drive the first switching unit 44a and the second switching unit 44b, so that the first switching unit 44a and the second switching unit 44b can maintain the closed state (ON state) even when the amount of power generated by the solar cell module group is low.

[0095] Furthermore, the control unit 43 closes the first switching unit 44a and the second switching unit 44b using power from the solar cell module group while keeping the first semiconductor switching element 47 in the OFF state. As a result, the first circuit breaker 4 can transmit power generated by other normal solar cell module groups to the inverter 3 via the first bypass element 48.

[0096] On the other hand, when the amount of power generated by the solar cell module group connected to the second circuit breaker 5 falls below a predetermined threshold, the control unit 53 turns the second semiconductor switching element 56 OFF. This prevents the entire solar power generation system 1 from becoming unstable due to low power from the solar cell module group connected to the second circuit breaker 5.

[0097] Furthermore, the control unit 53 closes the third switching unit 54a and the fourth switching unit 54b using the power of the solar cell module group connected to the first circuit breaker 4, while keeping the second semiconductor switching element 56 in the OFF state. As a result, the second circuit breaker 5 can transmit the power generated by the other solar cell module group to the inverter 3 via the second bypass element 57.

[0098] The normal shutdown mode is the mode used when the solar cell module 6 is not receiving sunlight due to nighttime or weather conditions such as rain. Therefore, in the normal shutdown mode, the solar cell module 6 is not generating power. In the normal shutdown mode, the control unit 3c of the inverter 3 outputs a first control signal. For this reason, in the normal shutdown mode, the first switch 44a and second switch 44b of the first shutdown device 4, and the third switch 54a and fourth switch 54b of the second shutdown devices 5a to 5c are all open. In the normal shutdown mode, the solar cell module 6 is not generating power, and therefore no power supply is being supplied from the solar cell module 6 to the first shutdown devices 4a and 4b and the second shutdown devices 5a and 5b.

[0099] When transitioning from start mode or active mode to normal shut-off mode, for example at sunset, the amount of power generated from the solar cell module group decreases. Therefore, when transitioning to normal shut-off mode, if the power generated by the solar cell module group is used for both driving the switch and supplying power to the inverter 3, there may be insufficient power to drive the switch, potentially causing the switch to repeatedly return to the open state (OFF state) even after attempting to transition from the open state (OFF state) to the closed state (ON state).

[0100] Therefore, when transitioning to the normal shutoff mode, if sufficient power cannot be obtained from the solar cell module group connected to the first shutoff device 4 (i.e., when the power generated by the solar cell module group falls below a predetermined threshold), the control unit 43 turns the first semiconductor switching element 47 OFF. As a result, the power from the solar cell module group is used only to drive the first switching unit 44a and the second switching unit 44b, so that even if the power generated from the solar cell module group is small, the first switching unit 44a and the second switching unit 44b can maintain the closed state (ON state).

[0101] Furthermore, the control unit 43 closes the first switching unit 44a and the second switching unit 44b using power from the solar cell module group while keeping the first semiconductor switching element in the OFF state. This allows power to be transmitted to the inverter 3 via the first bypass element 48 when sufficient power is being generated by other solar cell module groups. Subsequently, at an appropriate timing in the normal shutoff mode, the control unit 43 opens the first switching unit 44a and the second switching unit 44b.

[0102] On the other hand, when transitioning to the normal shutdown mode, if sufficient power cannot be obtained from the solar cell module group connected to the second shutdown device 5, the control unit 53 turns off the second semiconductor switching element 56. This prevents the entire solar power generation system 1 from becoming unstable due to low power from the solar cell module group connected to the second shutdown device 5.

[0103] Furthermore, the control unit 53 closes the third switching unit 54a and the fourth switching unit 54b using the power of the solar cell module group connected to the first circuit breaker 4, while keeping the second semiconductor switching element 56 in the OFF state. As a result, the second circuit breaker 5 can transmit the power generated by the other solar cell module group to the inverter 3 via the second bypass element 57.

[0104] In normal shutdown mode, if the power generation of the solar cell module 6 of group 6A is unstable due to reasons such as unstable weather, the relay 44 of the first shutdown device 4a and the relay 54 of the second shutdown device 5a will switch between ON and OFF states depending on the power supplied from the solar cell module 6 of group 6A. As a result, a phenomenon may occur where the relays 44 and 54 repeatedly switch between the ON and OFF states.

[0105] Therefore, if the amount of power generated from the solar cell module group connected to the first circuit breaker 4 is unstable and may fall below a predetermined threshold, and the first switching unit 44a to the fourth switching unit 54b may repeatedly switch on and off, the control unit 43 turns the first semiconductor switching element 47 to the OFF state. As a result, even if the amount of power generated from the solar cell module group is unstable and falls below a predetermined threshold, the power from the solar cell module group can be used only to drive the first switching unit 44a to the fourth switching unit 54b, so that the first switching unit 44a to the fourth switching unit 54b can maintain a closed state (ON state).

[0106] Furthermore, the control unit 43 closes the first switching unit 44a and the second switching unit 44b using power from the solar cell module while keeping the first semiconductor switching element 47 in the OFF state. As a result, the first circuit breaker 4 can transmit power generated by other normal solar cell module groups to the inverter 3 via the first bypass element 48.

[0107] On the other hand, if the amount of power generated from the solar cell module group connected to the second circuit breaker 5 is unstable and may fall below a predetermined threshold, the control unit 53 turns off the second semiconductor switching element 56. This prevents the entire solar power generation system 1 from becoming unstable due to unstable power from the solar cell module group connected to the second circuit breaker 5.

[0108] Furthermore, the control unit 53 closes the third switching unit 54a and the fourth switching unit 54b using the power of the solar cell module group connected to the first circuit breaker 4, while keeping the second semiconductor switching element 56 in the OFF state. As a result, the second circuit breaker 5 can transmit the power generated by the other solar cell module group to the inverter 3 via the second bypass element 57.

[0109] The emergency safety shutdown mode is a mode in which the power circuits 8a to 8h are shut off during the start mode or active mode, thereby stopping the power output from the solar cell module 6 to the inverter 3. In this embodiment, as shown in Figure 1, the operation switch 35 is connected to the inverter 3, and when the operation switch 35 is operated while the first circuit breakers 4a and 4b are in the start mode or active mode, the operating mode of the first circuit breakers 4a and 4b is switched to the emergency safety shutdown mode.

[0110] In detail, when the operation switch 35 is operated, the control unit 3c stops outputting the first control signal. When the signal detection unit 46 of the first disconnection device 4a detects the periodic cessation of the first control signal, the first switching unit 44a and the second switching unit 44b of the relay 44 are opened via the signal receiving unit 42 and the control unit 43. At this time, the control unit 43 turns off the first semiconductor switching element 47 and then opens the first switching unit 44a and the second switching unit 44b of the relay 44. As a result, the connection between group 6A and group 6B, and the connection between inverter 3 and group 6A are disconnected, and the output of power from the solar cell module 6 to inverter 3 is stopped.

[0111] After opening the first switching section 44a and the second switching section 44b of the relay 44, the first disconnector 4a outputs a second control signal to the second disconnector 5a via the communication line 10a. Upon receiving the second control signal from the first disconnector 4a, the second disconnector 5a disconnects the connection between group 6B and group 6C, and the connection between group 6C and group 6D. At this time, the control unit 53 turns off the second semiconductor switching element 56, and then opens the third switching section 54a and the fourth switching section 54b of the relay 54.

[0112] Similarly, when the signal detection unit 46 of the first circuit breaker 4b detects a periodic cessation of the first control signal, the control unit 43 of the first circuit breaker 4b opens the first switching unit 44a and the second switching unit 44b of the relay 44 of the first circuit breaker 4b, thereby disconnecting the connection between group 6D and group 6E, and between group 6E and group 6F. After opening the first switching unit 44a and the second switching unit 44b, the first circuit breaker 4b outputs a second control signal to the second circuit breaker 5b. Upon receiving the second control signal from the first circuit breaker 4b, the second circuit breaker 5b opens the third switching unit 54a and the fourth switching unit 54b of the relay 54, thereby disconnecting the connection between group 6F and group 6G, and between group 6G and group 6H. As a result, all groups 6A to 6H are separated from each other, and the open-circuit voltage of string 2 is divided to 165V or less.

[0113] In the solar power generation system 1 with the above configuration, the first circuit breaker 4a and the second circuit breaker 5a are in a master-slave relationship, and the second circuit breaker 5a disconnects the connections between multiple solar cell module groups 6B to 6D in accordance with the second control signal output from the first circuit breaker 4a. Furthermore, the second circuit breaker 5a is supplied with power from the first circuit breaker 4a. This simplifies the configuration of the second circuit breaker 5a, thereby reducing the installation cost of the second circuit breaker 5a.

[0114] Furthermore, since the open-circuit voltage of each of the multiple solar cell module groups 6A to 6H is 165V or less, a highly safe solar power generation system can be provided. In addition, the second control signal output from the first circuit breaker 4a is output via the communication line 10a using a communication method different from power line communication, so it is less susceptible to noise compared to power line communication, enabling stable communication from the first circuit breaker 4a to the second circuit breaker 5a.

[0115] Furthermore, in the above-described photovoltaic power generation system 1, after the connection between group 6A and group 6B is interrupted by the first interruption device 4a, the connections between the multiple solar cell module groups 6B to 6D are interrupted by the second interruption device 5a, thereby reducing the voltage related to the second interruption device 5a. This makes it possible to reduce the cost of the second interruption device 5a.

[0116] Furthermore, in the solar power generation system 1 with the above configuration, the first semiconductor switching element 47 of the first circuit breaker 4 turns OFF when the amount of power generated by the first group connected to the first circuit breaker 4 falls below a predetermined threshold. As a result, when the amount of power generated by the first group is small, the circuit from the first group to the inverter 3 is interrupted, and the first group is able to supply power only to the power supply unit 41 and the second circuit breaker 5. In other words, when the amount of power generated by the first group is small, the power generated by the first group is used only to drive the switching units. As a result, the first switching units 44a to the fourth switching units 54b can maintain a closed state (ON state) even when the amount of power generated by the first group is small. As a result, the solar power generation system 1 operates stably.

[0117] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

[0118] The number of groups of multiple solar cell module groups is not limited to the embodiment described above. String 2 only needs to be divided into multiple solar cell module groups such that the open-circuit voltage of each group is 165V or less. For example, as shown in Figure 6, the first circuit breakers 4a, 4b and the second circuit breakers 5a, 5b may be used to divide the multiple solar cell module groups 6A to 6H so that each group includes three solar cell modules 6 connected in series. In the example shown in Figure 6, the first circuit breaker 4a is driven by the power generated by the three solar cell modules 6 belonging to group 6A.

[0119] Furthermore, as shown in Figure 7, either the first circuit breaker 4a, 4b or the second circuit breaker 5a, 5b may be provided for each of the multiple solar cell module groups 6A to 6D.

[0120] In the above embodiment, each relay 44 of the first circuit breakers 4a and 4b had two contacts, a first switching section 44a and a second switching section 44b. However, as shown in Figure 8, the relay 44 may be composed of two relays, each having a single contact. That is, the control unit 43 of the first circuit breakers 4a and 4b may be configured to independently control the switching of the first switching section 44a and the second switching section 44b. Similarly, in the second circuit breakers 5a and 5b, the control unit 53 may be configured to independently control the third switching section 54a and the fourth switching section 54b of the relay 54. Although not shown in Figure 8, the first circuit breakers 4a and 4b have a first semiconductor switching element 47 and a first bypass element 48, and the second circuit breakers 5a and 5b have a second semiconductor switching element 56 and a second bypass element 57.

[0121] In the above embodiment, the first circuit breaker 4a was connected to the circuit 8a connecting group 6A and group 6B, and to the circuit 8b connecting inverter 3 and group 6A. However, the arrangement of the first circuit breaker 4a and the second circuit breaker 5b may be swapped. For example, the first circuit breaker 4a may be connected to the circuit 8c and the circuit 8d, and the second circuit breaker 5a may be connected to the circuit 8a and the circuit 8b.

[0122] In the above embodiment, the first control signal was output from the inverter 3 to the first circuit breakers 4a and 4b via power line communication. However, as shown in Figure 7, the first control signal may be output to the first circuit breakers 4a and 4b via wireless communication such as Wi-Fi (registered trademark). Alternatively, the inverter 3 and the first circuit breakers 4a and 4b may be configured to communicate with each other via wireless communication.

[0123] The number of first or second circuit breakers is not limited to the above embodiment. Furthermore, in the above embodiment, one second circuit breaker 5 was provided for one first circuit breaker 4, but multiple second circuit breakers 5 may be provided for one first circuit breaker 4. In this case, power is supplied from one first circuit breaker 4 to multiple second circuit breakers 5.

[0124] In modes other than the emergency safety shutdown mode or a portion of the normal shutdown mode (when "no power generation" is shown in Figure 5), the first control signal S1 and the second control signal S2 are always output, and the output of the first control signal S1 and the second control signal S2 may be stopped in the emergency safety shutdown mode and a portion of the normal shutdown mode. In this case, the first shutdown device and the second shutdown device close their switching parts when they receive the first control signal S1 and the second control signal S2, and open their switching parts when they do not receive the first control signal S1 and the second control signal S2.

[0125] (Note) (1) A photovoltaic power generation system (e.g., photovoltaic power generation system 1) comprises a string (e.g., string 2), an inverter (e.g., inverter 3), a first circuit breaker (e.g., first circuit breaker 4), and a second circuit breaker (e.g., second circuit breaker 5). The string includes a plurality of solar cell module groups (e.g., solar cell module groups 6A to 6H) connected in series with each other. Each of the plurality of solar cell module groups includes one or a plurality of solar cell modules (e.g., solar cell module 6) connected in series. The inverter is connected to the string and converts the DC power output from the string into AC power. The first circuit breaker is connected to a first circuit that connects the plurality of solar cell module groups together. The second circuit breaker is connected to a second circuit that connects a plurality of solar cell module groups that are different from the plurality of solar cell module groups connected to the first circuit. The plurality of solar cell module groups in the string have an open-circuit voltage of less than or equal to a predetermined open-circuit voltage for each group. The first circuit breaker is connected to a power line that is connected to the second circuit breaker and disconnects the connections between the plurality of solar cell module groups connected to the first circuit in response to a first control signal from the inverter. The second circuit breaker is powered by electricity supplied from the first circuit breaker via a power line, and in response to a second control signal from the first circuit breaker, it disconnects the connections between multiple solar cell module groups connected to the second circuit.

[0126] Furthermore, the multiple groups of solar cell modules in the string include a first group. The first disconnector includes a first switch (e.g., first switch 44a) connected to the anode terminal of the first group, a first semiconductor switching element (e.g., first semiconductor switching element 47) connected in series between the anode terminal of the first group and the first switch, and a first power supply unit (e.g., power supply unit 41) whose anode terminal is connected between the anode terminal of the first group and the first semiconductor switching element, and whose cathode terminal is connected to the cathode terminal of the first group, and which generates power to drive the first switch. Furthermore, the first semiconductor switching element turns OFF when the amount of power generated by the first group falls below a predetermined threshold.

[0127] In this solar power generation system, the first and second circuit breakers are in a master-slave relationship. The second circuit breaker disconnects the connections between multiple solar cell module groups in response to a second control signal output from the first circuit breaker. Furthermore, the second circuit breaker is powered by the first circuit breaker. This simplifies the configuration of the second circuit breaker, thereby reducing its installation cost. In addition, since the open-circuit voltage of each group of solar cell module is below a predetermined open-circuit voltage, a highly safe solar power generation system can be provided.

[0128] Furthermore, in this solar power generation system, the first semiconductor switching element of the first circuit breaker turns OFF when the amount of power generated by the first group connected to the first circuit breaker falls below a predetermined threshold. As a result, when the amount of power generated by the first group is small, the circuit from the first group to the inverter is interrupted, and the first group is able to supply power only to the first power supply unit. In other words, when the amount of power generated by the first group is small, the power generated by the first group is used only to drive the switching unit. As a result, even if the amount of power generated by the first group is small or unstable, the first switching unit can maintain a closed state (ON state). As a result, the solar power generation system operates stably.

[0129] (2) In the photovoltaic power generation system described in (1) above, the first circuit breaker may have a first bypass element (for example, a first bypass element 48). One end of the first bypass element is connected to the cathode-side terminal of the first group. The other end of the first bypass element is connected between the first switch and the first semiconductor switching element. In this case, even if the amount of power generated in the first group decreases, the power generated by other solar cell module groups can be propagated to the inverter via the first bypass element.

[0130] (3) In the photovoltaic power generation systems described in (1) and (2) above, the first semiconductor switching element may be a MOSFET element or an IGBT element. In this case, the power required to turn the first semiconductor switching element ON or OFF can be reduced.

[0131] (4) In the photovoltaic power generation systems described in (1) to (3) above, the first circuit breaker may include a second switching unit (for example, a second switching unit 44b) connected to the cathode terminal of the first group. In this case, multiple circuits can be switched on and off with a single first circuit breaker.

[0132] (5) In the solar power generation system described in (4) above, the second switch unit may be driven by power supplied from the first power supply unit. In this case, additional wiring for supplying power to drive the switch unit can be omitted when installing the first circuit breaker. This reduces the installation cost of the first circuit breaker. In addition, the driving voltage range of the first circuit breaker can be kept small, thus reducing the manufacturing cost of the first circuit breaker.

[0133] (6) In the solar power generation system described in (4) to (5) above, the first circuit breaker may be capable of independently controlling the opening and closing of the first switching unit and the second switching unit. In this case, for example, if a malfunction such as a contact failure occurs in the first switching unit, the second switching unit, which is operating normally, can be used as is.

[0134] (7) In the photovoltaic power generation system described in (1) to (5) above, the multiple groups of solar cell modules in the string may include a second group. The second circuit breaker may include a third switch (e.g., third switch 54a) connected to the anode terminal of the second group, and a second semiconductor switching element (e.g., second semiconductor switching element 56) connected in series between the anode terminal of the second group and the third switch. The second semiconductor switching element may also be turned OFF when the power generation of the second group falls below a predetermined threshold. In this case, if the power generation of the second group is small, the power generated by the second group is not transmitted to the inverter. As a result, the photovoltaic power generation system operates stably.

[0135] (8) In the photovoltaic power generation system described in (7) above, the second circuit breaker may have a second bypass element (for example, a second bypass element 57). One end of the second bypass element is connected to the cathode-side terminal of the second group. The other end of the second bypass element is connected between the third switch and the second semiconductor switching element. In this case, even if the amount of power generated in the second group decreases, the power generated by other solar cell module groups can be propagated to the inverter via the second bypass element.

[0136] (9) In the photovoltaic power generation system described in (7) to (8) above, the second semiconductor switching element may be a MOSFET element or an IGBT element. In this case, the power required to turn the second semiconductor switching element ON or OFF can be reduced.

[0137] (10) In the photovoltaic power generation system described in (7) to (9) above, the second circuit breaker may include a fourth switching unit (e.g., a fourth switching unit 54b) connected to the cathode terminal of the second group. In this case, multiple circuits can be switched on and off with a single first circuit breaker.

[0138] (11) In the solar power generation system described in (10) above, the second circuit breaker may be capable of independently controlling the opening and closing of the third switching unit and the fourth switching unit. In this case, for example, if a malfunction such as a contact failure occurs in the third switching unit, the fourth switching unit, which is operating normally, can be used as is.

[0139] (12) In the photovoltaic power generation system described in (1) to (11) above, the first circuit breaker may, in response to the first control signal from the inverter, disconnect the connections between the multiple solar cell module groups connected to the first circuit, and then output a second control signal to the second circuit breaker. In this case, the voltage related to the second circuit breaker can be reduced. This makes it possible to reduce the cost of the second circuit breaker.

[0140] (13) In the solar power generation system described in (1) to (12) above, the first circuit breaker may output a second control signal to the second circuit breaker using a communication method different from power line communication via a communication line connected to the first and second circuit breakers. In this case, stable communication from the first circuit breaker to the second circuit breaker becomes possible.

[0141] (14) In the photovoltaic power generation systems described in (1) to (13) above, the open-circuit voltage of each group of solar cell modules in a string may be 165V or less. In this case, a more safe photovoltaic power generation system can be provided.

[0142] (15) In the photovoltaic power generation systems described in (1) to (14) above, the inverter may output the first control signal to the first circuit breaker via power line communication. In this case, when installing the first circuit breaker in an existing photovoltaic power generation system, additional wiring to ensure communication between the inverter and the first circuit breaker can be omitted, thus reducing the installation cost of the first circuit breaker.

[0143] (16) In the solar power generation systems described in (1) to (15) above, the inverter may output a first control signal to the first circuit breaker via wireless communication. In this case, it becomes possible to output the first control signal to the first circuit breaker by remote operation.

[0144] (17) In the photovoltaic power generation systems described in (1) to (16) above, at least one of the multiple groups of solar cell modules in a string may include multiple solar cell modules connected in series. In this case, the multiple solar cell modules can be shut off by the first or second shut-off device. [Industrial applicability]

[0145] According to the present invention, it is possible to provide a solar power generation system that can achieve both a reduction in the installation cost of the shut-off device and an improvement in stability. [Explanation of symbols]

[0146] 1. Solar power generation system 2 strings 3 Inverter 4. First circuit breaker 5. Second circuit breaker 6. Solar cell modules 6A~6H Solar Panel Module Group 44a First opening / closing section 44b Second opening / closing section 47. First Semiconductor Switching Element 48 First Bypass Element 54a Third opening / closing section 54b Fourth opening / closing section 56 Second Semiconductor Switching Element 57 Second bypass element

Claims

1. A string comprising multiple groups of solar cell modules, each containing one or more solar cell modules connected in series, and each group of solar cell modules connected in series with respect to the others, An inverter connected to the string, which converts the DC power output from the string into AC power, A first circuit breaker connected to a first circuit that connects the multiple solar cell module groups, A second circuit breaker connected to a second circuit that connects multiple solar cell module groups that are different from the multiple solar cell module groups connected to the first circuit, Equipped with, The plurality of solar cell module groups in the string have an open-circuit voltage that is less than or equal to a predetermined open-circuit voltage for each group. The first circuit breaker is connected to a power line that is connected to the second circuit breaker, and in response to a first control signal from the inverter, it disconnects the connections between the plurality of solar cell module groups connected to the first circuit. The second circuit breaker is driven by power supplied from the first circuit breaker via the power line, and in response to a second control signal from the first circuit breaker, it disconnects the connections between the plurality of solar cell module groups connected to the second circuit. The plurality of solar cell module groups in the string include a first group, The first circuit breaker is, A first switching unit connected to the anode terminal of the first group, A first semiconductor switching element is connected in series between the anode terminal of the first group and the first switching unit, The anode terminal is connected between the anode terminal of the first group and the first semiconductor switching element, and the cathode terminal is connected to the cathode terminal of the first group, and the first power supply unit generates power to drive the first switching unit, It has, The first semiconductor switching element turns OFF when the power generation amount of the first group falls below a predetermined threshold. Solar power generation system.

2. The photovoltaic power generation system according to claim 1, wherein the first circuit breaker has a first bypass element, one end of which is connected to the cathode-side terminal of the first group, and the other end of which is connected between the first switching unit and the first semiconductor switching element.

3. The photovoltaic power generation system according to claim 1, wherein the first semiconductor switching element is a MOSFET element or an IGBT element.

4. The photovoltaic power generation system according to claim 1, wherein the first circuit breaker includes a second switching unit connected to the cathode-side terminal of the first group.

5. The photovoltaic power generation system according to claim 4, wherein the second opening / closing unit is driven by power supplied from the first power supply unit.

6. The photovoltaic power generation system according to claim 4, wherein the first shutoff device is capable of independently controlling the opening and closing of the first opening / closing section and the second opening / closing section.

7. The plurality of solar cell module groups in the string include a second group, The above-mentioned second circuit breaker is, A third switching unit connected to the anode terminal of the second group, A second semiconductor switching element is connected in series between the anode terminal of the second group and the third switching unit, It has, The photovoltaic power generation system according to claim 1, wherein the second semiconductor switching element is turned OFF when the amount of power generated by the second group falls below a predetermined threshold.

8. The photovoltaic power generation system according to claim 7, wherein the second circuit breaker has a second bypass element, one end of which is connected to the cathode-side terminal of the second group and the other end of which is connected between the third switching unit and the second semiconductor switching element.

9. The photovoltaic power generation system according to claim 7, wherein the second semiconductor switching element is a MOSFET element or an IGBT element.

10. The photovoltaic power generation system according to claim 7, wherein the second circuit breaker includes a fourth switching unit connected to the cathode-side terminal of the second group.

11. The photovoltaic power generation system according to claim 10, wherein the second shutoff device can independently control the opening and closing of the third opening / closing section and the fourth opening / closing section.

12. The first circuit breaker disconnects the connections between the plurality of solar cell module groups connected to the first circuit in response to the first control signal from the inverter, and then outputs the second control signal to the second circuit breaker. The photovoltaic power generation system according to claim 1.

13. The first circuit breaker outputs the second control signal to the second circuit breaker using a communication method different from power line communication via a communication line connected to the first circuit breaker and the second circuit breaker. The photovoltaic power generation system according to claim 1.

14. The plurality of solar cell module groups in the string have an open-circuit voltage of 165V or less for each group. The photovoltaic power generation system according to claim 1.

15. The inverter outputs the first control signal to the first circuit breaker via power line communication. The photovoltaic power generation system according to claim 1.

16. The inverter outputs the first control signal to the first circuit breaker via wireless communication. The photovoltaic power generation system according to claim 1.

17. At least one of the plurality of solar cell module groups of the string includes a plurality of solar cell modules connected in series, The photovoltaic power generation system according to claim 1.

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