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 comprises a string, an inverter, and a plurality of cut-off devices. The string includes a plurality of solar cell module groups. The plurality of cut-off devices cut off the connection between the plurality of solar cell module groups according to a control signal from the inverter. The plurality of solar cell module groups include a first group, a second group connected to the first group, and a third group connected to the second group. The plurality of cut-off devices include a first switching unit connected to the second group, a semiconductor switching element connected in series to the first switching unit, and a power supply unit connected to the second group and generating power for driving the first switching unit. The semiconductor switching element is turned off when a power generation amount of the second group is smaller than a prescribed threshold value.SELECTED DRAWING: Figure 1

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, and a plurality of disconnectors. 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 plurality of disconnectors disconnect the connections between the plurality of solar cell module groups in response to control signals from the inverter. Each of the plurality of solar cell module groups has an open-circuit voltage that is less than or equal to a predetermined open-circuit voltage. The plurality of solar cell module groups includes a first group, a second group connected to the first group, and a third group connected to the second group. The plurality of disconnectors includes a first disconnector. The first disconnector includes a first switching unit, a first semiconductor switching element, and a first power supply unit. The first switching unit is connected to the anode-side terminal of the second group. The first semiconductor switching element is connected in series between the anode-side terminal of the second group and the first switching unit. The first power supply unit generates power to drive the first switching unit. The first power supply unit has its anode terminal connected between the anode terminal of the second group and the first semiconductor switching element, and its cathode terminal connected to the cathode terminal of the second group. The first semiconductor switching element turns OFF when the power generation of the second group falls below a predetermined threshold.

[0008] In this solar power generation system, each of the multiple solar cell module groups has an open-circuit voltage below a predetermined open-circuit voltage, thus providing a highly safe solar power generation system. Furthermore, when the power generation of the second group falls below a predetermined threshold, the first semiconductor switching element turns OFF. Therefore, when the power generation of the second group is low, the circuit from the second group to the inverter is interrupted, and the second group is able to supply power only to the first power supply unit. In other words, when the power generation of the second group is low, the power generated by the second group is used only to drive the first switching unit. As a result, even if the power generation of the second group is low or unstable, the first switching unit can remain closed (ON). As a result, the solar power generation system operates stably.

[0009] The first circuit breaker may include a first bypass element. The first bypass element may have one end connected to the cathode-side terminal of the second group and the other end connected between the first switch and the first 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 first bypass element.

[0010] 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.

[0011] The first circuit breaker may include a second switching unit connected to the cathode-side terminal of the second group. In this case, multiple circuits can be switched on and off by the first circuit breaker.

[0012] The second switching unit may be driven by power supplied from the first power supply unit. In this case, the second switching unit can be kept in the closed state (ON state) even if the power generation of the second group is small or unstable.

[0013] 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.

[0014] At least one of the first, second, and third groups of the multiple solar cell module groups may include multiple solar cell modules connected in series. In this case, the first disconnector can disconnect all of the multiple solar cell modules together.

[0015] The multiple solar cell module groups may further include a fourth group connected to the third group, and a fifth group connected to the fourth group. The multiple circuit breakers may include a second circuit breaker. The second circuit breaker may include a third switch, a second semiconductor switching element, and a second power supply unit. The third switch may be connected to the anode terminal of the fourth group. The second semiconductor switching element may be connected in series between the anode terminal of the fourth group and the third switch. The second power supply unit may generate power to drive the third switch. The anode terminal of the second power supply unit may be connected between the anode terminal of the fourth group and the second semiconductor switching element, and the cathode terminal may be connected to the cathode terminal of the fourth group. The second semiconductor switching element may be turned OFF when the power generation of the fourth group falls below a predetermined threshold. In this case, if the power generation of the fourth group is small, the power from the fourth group can be used only to drive the third switch. If power from the fourth group is supplied only to the third switch, the third switch can remain closed (ON) even if the power generation from the fourth group is small or unstable. As a result, the solar power generation system operates stably.

[0016] The second circuit breaker may include a second bypass element. The second bypass element may have one end connected to the cathode-side terminal of the fourth group and the other end connected between the third switch and the second semiconductor switching element. In this case, even if the power generation of the fourth group decreases, the power generated by the other solar cell module groups can be propagated to the inverter via the second bypass element.

[0017] 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.

[0018] The second circuit breaker may include a fourth switching unit connected to the cathode-side terminal of the fourth group. In this case, multiple circuits can be switched on and off by the second circuit breaker.

[0019] The fourth switching unit may be driven by power supplied from the second power supply unit. In this case, even if the power generation of the fourth group is small or unstable, the fourth switching unit can be kept in the closed state (ON state).

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

[0022] The inverter may output control signals to multiple circuit breakers via power line communication. In this case, when installing multiple circuit breakers in an existing solar power generation system, additional wiring to ensure communication between the inverter and the multiple circuit breakers can be omitted, thus reducing the cost of installing multiple circuit breakers.

[0023] The inverter may output a control signal to a plurality of disconnecting devices by wireless communication. In this case, it becomes possible to output a control signal to the plurality of disconnecting devices by remote operation.

Advantages of the Invention

[0024] 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 disconnecting devices and improvement of stability.

Brief Description of the Drawings

[0025] [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 a disconnecting device. [Figure 3] FIG. 3 is a circuit diagram schematically showing the configuration of a regulator. [Figure 4] FIG. 4 is a block diagram schematically showing the configuration of a disconnecting device. [Figure 5] FIG. 5 is a diagram for explaining an example of the operation mode of a disconnecting 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.

Embodiments for Carrying Out the Invention

[0026] FIG. 1 is a block diagram schematically showing the configuration of a photovoltaic power generation system 1 according to one aspect of the present invention. The photovoltaic power generation system 1 includes a string 2, an inverter 3, and a plurality of disconnecting devices 4.

[0027] String 2 includes multiple groups of solar cell modules connected in series with each other. Each of these solar cell module groups includes one or multiple solar cell modules 6 connected in series. That is, String 2 includes multiple (18 in this embodiment) solar cell modules 6 connected in series with each other. In this embodiment, the multiple groups of solar cell modules consist of six solar cell module groups 6A to 6F. The photovoltaic power generation system 1 may also include a solar cell array in which multiple strings 2 are connected in parallel.

[0028] Each of the multiple solar cell module groups 6A to 6F has an open-circuit voltage below a predetermined open-circuit voltage. The predetermined open-circuit voltage is, for example, 165V. That is, String 2 is grouped so that the open-circuit voltage of each group is 165V or less. The open-circuit voltage of each solar cell module 6 is, for example, 50V. Hereafter, solar cell module groups 6A to 6F may be referred to as groups 6A to 6F. Note that groups 6A to 6F in this embodiment are just one example of groups 1 to 6.

[0029] Each of groups 6A through 6F includes three solar cell modules 6 connected in series with each other. Therefore, the open-circuit voltage of each of groups 6A through 6F is 150V.

[0030] Groups 6A to 6F are arranged alphabetically from group 6A to group 6F and connected in series with each other. Each of groups 6A to 6F includes an anode terminal and a cathode terminal. The anode terminal of each group 6A to 6F 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 6F. The cathode terminal of each group 6A to 6F 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 6F.

[0031] The anode terminal of group 6A is formed by the anode terminal of the solar cell module 6 that is closest to group 6B among the solar cell modules 6 belonging to group 6A, and is connected to the cathode terminal of group 6B. The cathode terminal of group 6A is formed by the cathode terminal of the solar cell module 6 that is furthest from group 6B among the solar cell modules 6 belonging to group 6A, and is connected to the cathode terminal of inverter 3.

[0032] The anode terminal of group 6B is formed by the anode terminal of the solar cell module 6 closest to group 6C among the solar cell modules 6 belonging to group 6B, and is connected to the cathode terminal of group 6C. The cathode terminal of group 6B is formed by the cathode terminal of the solar cell module 6 closest to group 6A among the solar cell modules 6 belonging to group 6B, and is connected to the anode terminal of group 6A.

[0033] The anode terminal of group 6C is connected to the cathode terminal of group 6D. The cathode terminal of group 6C is connected to the anode terminal of group 6B. The anode terminal of group 6D is connected to the cathode terminal of group 6E. The cathode terminal of group 6D is connected to the anode terminal of group 6C. The anode terminal of group 6E is connected to the cathode terminal of group 6F. The cathode terminal of group 6E is connected to the anode terminal of group 6D. The anode terminal of group 6F is connected to the anode terminal of inverter 3. The cathode terminal of group 6F is connected to the anode terminal of group 6E.

[0034] 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.

[0035] 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 control signals to multiple circuit breakers 4 via power line communication.

[0036] Multiple circuit breakers 4 are connected to the circuits that connect groups 6A to 6F to each other. The multiple circuit breakers 4 interrupt the connections between groups 6A to 6F in response to control signals from the inverter 3. The multiple circuit breakers 4 include circuit breakers 4a to 4c. In this embodiment, circuit breaker 4a is an example of a first circuit breaker, and circuit breaker 4b is an example of a second circuit breaker.

[0037] The circuit breaker 4a is connected to circuit 8a, which connects group 6A and group 6B, and to circuit 8b, which connects group 6B and group 6C. The circuit breaker 4a disconnects the connection between group 6A and group 6B, and the connection between group 6B and group 6C, in response to a control signal from inverter 3. Specifically, the circuit breaker 4a disconnects circuits 8a and 8b by interrupting the voltage output from the solar cell module 6 of group 6B in response to a control signal from inverter 3. This disconnects the connection between group 6A and group 6B, and the connection between group 6B and group 6C.

[0038] The circuit breaker 4a is driven by the power generated by the solar cell module 6 of group 6B. The circuit breaker 4a is, for example, externally mounted to the solar cell module 6 of group 6B.

[0039] Figure 2 is a schematic block diagram showing the configuration of the circuit breaker 4a. The circuit breaker 4a includes a power supply unit 41, a signal receiving unit 42, a control unit 43, a relay 44, a bypass circuit 45, a semiconductor switching element 47, and a bypass element 48.

[0040] The power supply unit 41 is a regulator connected in parallel to group 6B. Specifically, the anode terminal of the power supply unit 41 is connected to the anode terminal of group 6B, and the cathode terminal is connected to the cathode terminal of group 6B.

[0041] 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.

[0042] The power supply unit 41 generates drive power to drive the circuit breaker 4a using the power generated by the solar cell module 6 as its power source. Here, the drive power for the circuit breaker 4a is generated using only the power generated by the solar cell module 6 of group 6B.

[0043] The signal receiving unit 42 receives control signals from the control unit 3c of the inverter 3 and outputs the received control signals to the control unit 43. More specifically, the signal receiving unit 42 receives control signals from the control unit 3c of the inverter 3 via a signal detection unit 46 that detects control signals from the control unit 3c of the inverter 3.

[0044] 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.

[0045] Relay 44 includes a first switching section 44a and a second switching section 44b. The first switching section 44a is connected to the anode terminal of group 6B. The first switching section 44a is located in circuit 8b and switches the connection between group 6B and group 6C. The second switching section 44b is connected to the cathode terminal of group 6B. The second switching section 44b is located in circuit 8a and switches the connection between group 6A and group 6B. Hereafter, the first switching section 44a and the second switching section 44b may be referred to as switching sections 44a and 44b.

[0046] When no power is supplied from the power supply unit 41, the switching units 44a and 44b are always in the open state. Therefore, when the circuit breaker 4a is not driven, the connection between group 6A and group 6B, and the connection between group 6B and group 6C are disconnected.

[0047] The bypass circuit 45 is a circuit that allows the signal receiving unit 42 to receive control signals from the control unit 3c when the connections between groups 6A to 6F are interrupted. When the connections between group 6A and group 6B, and between group 6B and group 6C are interrupted, the signal receiving unit 42 can receive control signals from the control unit 3c via the bypass circuit 45.

[0048] The semiconductor switching element 47 is connected in series with the first switching unit 44a in the circuit 8b. Specifically, one end of the semiconductor switching element 47 is connected to the anode terminal of group 6A. On the other hand, the other end of the semiconductor switching element 47 is connected to the first switching unit 44a. The semiconductor switching element 47 is, for example, a MOSFET element or an IGBT (Insulated Gate Bipolar Transistor) element.

[0049] The 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 semiconductor switching element 47. Here, the "ON state" means that one end and the other end of the semiconductor switching element 47 are conductive. On the other hand, the "OFF state" means that the one end and the other end of the semiconductor switching element 47 are insulated from each other.

[0050] When the semiconductor switching element 47 is a MOSFET element or an IGBT element, the control unit 43 is connected to the gate terminal of the semiconductor switching element 47. The control unit 43 can turn the 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 semiconductor switching element 47, the power required to turn the semiconductor switching element 47 ON or OFF can be reduced.

[0051] In the circuit breaker 4a, when the semiconductor switching element 47 is in the OFF state, the anode terminal of group 6B and group 6C are disconnected. On the other hand, even when the semiconductor switching element 47 is in the OFF state, the power supply unit 41 is not disconnected from group 6B. In other words, when the semiconductor switching element 47 is in the OFF state, the power generated by group 6B is supplied to the power supply unit 41, but not to the inverter 3.

[0052] The control unit 43 turns off the semiconductor switching element 47 when the power generation of group 6B is less than a predetermined threshold. As a result, when the power generation of group 6B is less than the predetermined threshold, the power of group 6B is supplied only to the circuit breaker 4a (power supply unit 41). This allows the power from group 6B to be used only to drive the switching units 44a and 44b when the power generation of group 6B is low. If the power from group 6B is supplied only to the switching units 44a and 44b, the switching units 44a and 44b can maintain a closed state (ON state) even if the power generation of group 6B is low or unstable. As a result, the photovoltaic power generation system 1 operates stably. The above threshold can be, for example, the amount of power at which the switching units 44a and 44b operate stably even if the power of group 6B is supplied to both the power supply unit 41 and the inverter 3.

[0053] Because the circuit breaker 4a has a semiconductor switching element 47, even if there is an abnormality in the power generation amount of group 6B, the switching units 44a and 44b can maintain the closed state (ON state). Therefore, the possibility of the switching units 44a and 44b switching when a high voltage is applied to them is reduced. For this reason, the switching units 44a and 44b do not need to have large voltage withstand characteristics and can be made inexpensive.

[0054] The bypass element 48 is connected in parallel to group 6B. Specifically, one end of the bypass element 48 is connected between the cathode terminal of group 6B and the second switching unit 44b. On the other hand, the other end of the bypass element 48 is connected between the first switching unit 44a and the semiconductor switching element 47. The bypass element 48 is, for example, a diode having an anode connected to the cathode side of group 6B and a cathode connected between the first switching unit 44a and the semiconductor switching element 47.

[0055] When the solar cell modules of group 6B are shaded at sunrise or sunset, or when a sudden power drop or abnormal heat generation occurs in group 6B, and group 6B is unable to output sufficient power, the bypass element 48 forms a circuit that propagates power generated by other solar cell module groups, bypassing group 6B. Specifically, when the amount of power generated from group 6B is insufficient and the semiconductor switching element 47 is in the OFF state, and the switching parts 44a and 44b are in the closed state, the bypass element 48 forms a path that transmits power generated by other solar cell module groups to the inverter 3.

[0056] The bypass element 48 can immediately form a circuit that bypasses the malfunctioning group 6B based on its electrical characteristics when group 6B can no longer output sufficient power, even without a command from an external signal.

[0057] Furthermore, the connection positions of the two terminals of the bypass element 48 can be arbitrarily set, provided that the group 6B to which the circuit breaker 4a is connected can be bypassed, and at least one of the terminals of the bypass element 48 is connected to group 6B without going through the first switching unit 44a or the second switching unit 44b. For example, the anode of the bypass element 48 may be connected to the circuit connecting the anode terminal of group 6A and the second switching unit 44b, and the cathode may be connected to the circuit connecting the anode terminal of group 6B and the first switching unit 44a.

[0058] The circuit breaker 4b has the same configuration as the circuit breaker 4a, except that the circuits to which it is connected are different. The circuit breaker 4b is connected to the circuit 8c that connects group 6C and group 6D, and to the circuit 8d that connects group 6D and group 6E. The circuit breaker 4b disconnects the connection between group 6C and group 6D, and the connection between group 6C and group 6E, in response to a control signal from the inverter 3.

[0059] The circuit breaker 4b is powered by the electricity generated by the solar cell module 6 of group 6D. The circuit breaker 4b is, for example, externally mounted to the solar cell module 6 of group 6D.

[0060] As shown in Figure 4, the circuit breaker 4b includes a power supply unit 51, a signal receiving unit 52, a control unit 53, a relay 54, a bypass circuit 55, a signal detection unit 56, a semiconductor switching element 57, and a bypass element 58. The relay 54 includes a first switching unit 54a (an example of a third switching unit) and a second switching unit 54b (an example of a fourth switching unit). Since the configurations of the circuit breaker 4b are the same as those of the circuit breaker 4a, they will be described briefly.

[0061] The power supply unit 51 generates drive power to drive the circuit breaker 4b using the power generated by the solar cell module 6 as its power source. Here, the drive power for the circuit breaker 4b is generated using only the power generated by the solar cell module 6 of group 6D.

[0062] The signal receiving unit 52 receives the control signal from the control unit 3c of the inverter 3 and outputs the received control signal to the control unit 53.

[0063] The control unit 53 controls the opening and closing of the contacts of the relay 54. The first switching unit 54a of the relay 54 is connected to the anode terminal of group 6D. The first switching unit 54a is located in the circuit 8d and opens and closes the connection between group 6D and group 6E. The second switching unit 54b is connected to the cathode terminal of group 6D. The second switching unit 54b is located in the circuit 8c and opens and closes the connection between group 6C and group 6D.

[0064] The semiconductor switching element 57 is connected in series with the first switching unit 54a in the circuit 8d. The semiconductor switching element 57 is, for example, a MOSFET element or an IGBT element.

[0065] The control unit 53 turns off the semiconductor switching element 57 when the amount of power generated by group 6D is less than a predetermined threshold. The threshold can be, for example, the amount of power at which the first switching unit 54a and the second switching unit 54b operate stably even when the power of group 6D is supplied to both the power supply unit 51 and the inverter 3.

[0066] The bypass element 58 is connected in parallel to group 6D. One end of the bypass element 58 is connected between the cathode terminal of group 6D and the second switching unit 54b. The other end of the bypass element 58 is connected between the first switching unit 54a and the semiconductor switching element 57. The bypass element 58 is, for example, a diode having an anode connected to the cathode side of group 6D and a cathode connected between the first switching unit 54a and the semiconductor switching element 57.

[0067] The circuit breaker 4c has the same configuration as the circuit breaker 4a and the circuit breaker 4b, except that the connected circuit is different. That is, the circuit breaker 4c includes a power supply unit, a signal receiving unit, a control unit, a relay 64 including a first switching unit 64a and a second switching unit 64b, a bypass circuit, a signal detection unit, a semiconductor switching element 67, and a bypass element 68. Since the components of the circuit breaker 4c are the same as those of the circuit breaker 4a, their explanation is omitted.

[0068] The circuit breaker 4c is connected to the circuit 8e connecting group 6E and group 6F, and to the circuit 8f connecting group 6F and inverter 3. The circuit breaker 4c disconnects the connection between group 6E and group 6F, and the connection between group 6F and inverter 3, in response to a control signal from inverter 3.

[0069] Next, referring to Figure 5, the operating modes of the multiple circuit breakers 4 will be explained, mainly using the operation of circuit breaker 4a as an example. The operating modes of the multiple circuit breakers 4 include three operating modes: start mode, active mode, and safety mode. The safety mode includes normal circuit breaker mode and emergency safety circuit breaker mode. Therefore, the multiple circuit breakers 4 operate in four operating modes: start mode, active mode, normal circuit breaker mode, and emergency safety circuit breaker mode.

[0070] 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. Then, the circuit breaker 4a is driven by the drive power generated by the power supply unit 41 from the electricity generated by the solar cell module 6. When the circuit breaker 4a is driven and the control unit 43 receives a control signal from the control unit 3c of the inverter 3 via the signal receiving unit 42, the control unit 43 closes the switching units 44a and 44b of the relay 44.

[0071] Similarly, the circuit breaker 4b is driven by the drive power generated by the power supply unit 51 of the circuit breaker 4b from the power generated by the solar cell module 6. When the circuit breaker 4b is driven and the control unit 53 receives a control signal from the control unit 3c of the inverter 3 via the signal receiving unit 52, the control unit 53 closes the first switching unit 54a and the second switching unit 54b of the relay 54. The circuit breaker 4c behaves in the same way as the circuit breaker 4a. As a result, groups 6A to 6F are connected in a string 2 via multiple circuit breakers 4 (circuit breakers 4a to 4c), and the power generated by the solar cell module 6 is output to the inverter 3.

[0072] In start mode (especially at sunrise), the amount of power generated from the solar cell module group is small. Therefore, in start mode, if, for example, the power generated by the solar cell module 6 of group 6B is used for both driving the switchgear 44a and 44b and supplying power to the inverter 3, there may be insufficient power to drive the switchgear 44a and 44b. This could cause the switchgear 44a and 44b to 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).

[0073] Therefore, in start mode, when the power generation of group 6B is less than a predetermined threshold, the control unit 43 turns off the semiconductor switching element 47. As a result, the power from group 6B is used only to drive the switching units 44a and 44b, so that the switching units 44a and 44b can maintain a closed state (ON state) even if the power generation from group 6B is small. If the switching units 44a and 44b can maintain a closed state, the power generated by other solar cell module groups is propagated to the inverter 3 via the bypass element 48.

[0074] Subsequently, when the power generation of group 6B exceeds a predetermined threshold, the control unit 43 turns on the semiconductor switching element 47. This allows the power generated by group 6B to be used to drive the switching units 44a and 45b and to supply power to the inverter 3 only after the power generation of group 6B has become sufficiently large.

[0075] The active mode is the state in which the solar cell module 6 receives sunlight during the day and generates electricity, and is essentially the same as the start mode. Therefore, in the active mode, groups 6A to 6F are connected via multiple circuit breakers 4 (circuit breakers 4a to 4c), and the power generated by the solar cell module 6 is output to the inverter 3.

[0076] In active mode, for example, when the power generation of group 6B falls below a predetermined threshold due to weather conditions or a malfunction of the solar cell module, the control unit 43 turns off the semiconductor switching element 47. This allows the power from group 6B to be used only to drive the switching units 44a and 44b, so that even if the power generation of group 6B is low, the switching units 44a and 44b can maintain the closed state (ON state).

[0077] In addition, in start mode and active mode, when the power generation of group 6D falls below a predetermined threshold, the control unit 53 of the circuit breaker 4b turns off the semiconductor switching element 57. Similarly, when the power generation of group 6F falls below a predetermined threshold, the control unit of the circuit breaker 4c turns off the semiconductor switching element 67.

[0078] 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, or when the power generation of the solar cell module 6 is unstable. In the normal shutdown mode, when the solar cell module 6 is not generating power, no control signal is output from the control unit 3c of the inverter 3, and the first and second switching units of the shutdown devices 4a to 4c are all in the open state.

[0079] In normal shut-off mode, if the power generation of the solar cell module 6 is unstable due to reasons such as unstable weather, a control signal is output from the control unit 3c of the inverter 3. For example, if the power generation of group 6B is unstable and does not fall below a predetermined threshold, the switching units 44a and 44b of the relay 44 are turned ON or ON / OFF according to the power supplied from the solar cell module 6 of group 6B.

[0080] The emergency safety shutdown mode is a mode in which the circuits 8a to 8f are shut off during the start mode or active mode, stopping the output of power 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 multiple circuit breakers 4 are in the start mode or active mode, the operating mode of the multiple circuit breakers 4 is switched to the emergency safety shutdown mode.

[0081] In detail, when the operation switch 35 is operated, the control unit 3c stops outputting the control signal. When the signal detection unit 46 detects that the control signal has stopped at a certain period of time, the switching parts 44a and 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 semiconductor switching element 47 and then opens the switching parts 44a and 44b of the relay 44. As a result, the connection between group 6A and group 6B, and the connection between group 6B and group 6C are disconnected, and the output of power from the solar cell module 6 to the inverter 3 is stopped.

[0082] Similarly, when the circuit breaker 4b detects a periodic cessation of the control signal, it controls the switching parts 54a and 54b of the relay 54 to the open state. This disconnects the connection between group 6C and group 6D, and between group 6D and group 6E. Similarly, when the circuit breaker 4c detects a periodic cessation of the control signal, it controls the switching parts 64a and 64b of the relay 64 to the open state. This disconnects the connection between group 6E and group 6F, and between group 6F and inverter 3. As a result, all groups 6A to 6F are separated from each other, and the open-circuit voltage of string 2 is divided to 165V or less.

[0083] In the above-described photovoltaic power generation system 1, each of the multiple solar cell module groups 6A to 6F has an open-circuit voltage of 165V, thus providing a highly safe photovoltaic power generation system. Furthermore, when the power generation of group 6B falls below a predetermined threshold, the semiconductor switching element 47 turns OFF. As a result, when the power generation of group 6B is low, the circuit from group 6B to inverter 3 is interrupted, and group 6B is able to supply power only to the power supply unit 41. In other words, when the power generation of group 6B is low, the power generated by group 6B is used only to drive the switching units 44a and 44b. As a result, even if the power generation of group 6B is low or unstable, the switching units 44a and 44b can maintain a closed state (ON state). As a result, the photovoltaic power generation system operates stably. The same effects as those of the switching units 44a and 44b of the circuit breaker 4a can be obtained with the switching units 54a and 54b of the circuit breaker 4b and the switching units 64a and 64b of the circuit breaker 4c.

[0084] 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.

[0085] The number of groups of multiple solar cell module groups, and the number of solar cell modules included in each group, are not limited to the above embodiment. String 2 only needs to be divided into multiple solar cell module groups such that the open-circuit voltage for each group is 165V or less. Similarly, in the above embodiment, the multiple circuit breakers 4 included three circuit breakers 4a to 4c, but the number of multiple circuit breakers 4 is not limited to the above embodiment.

[0086] As simplified in Figure 6, the multiple circuit breakers 4 should be arranged such that, when interrupted, the open-circuit voltage of the string 2 is divided to 165V or less. In Figure 6, the multiple circuit breakers 4 include four circuit breakers 4a to 4d. Also, each of groups 6A, 6C, 6E, and 6G includes three solar cell modules 6 connected in series with each other, and each of groups 6B, 6D, 6F, and 6H includes one solar cell module 6. Therefore, the open-circuit voltage of groups 6A, 6C, 6E, and 6G is 150V, and the open-circuit voltage of groups 6B, 6D, 6F, and 6H is 50V. Alternatively, at least one of the multiple solar cell module groups may include two solar cell modules 6.

[0087] As simplified in Figure 7, the multiple disconnection devices 4 may be placed in each of the multiple solar cell module groups. In this case, it is preferable that each of the multiple solar cell module groups includes multiple solar cell modules 6.

[0088] In the above embodiment, the relay 44 of the circuit breaker 4a had two contacts, a first switching section 44a and a second switching section 44b. However, as simply shown in Figure 8, the relay 44 may be composed of two relays, each having a single contact. That is, the circuit breaker 4a may be configured to allow independent switching control of the first switching section 44a and the second switching section 44b. Similarly, the circuit breaker 4b may be configured to allow independent control of the first switching section 54a and the second switching section 54b. Likewise, the circuit breaker 4c may be configured to allow independent control of the first switching section 64a and the second switching section 64b.

[0089] In the above embodiment, control signals were output to the multiple circuit breakers 4 via power line communication, but control signals may also be output to the multiple circuit breakers 4 via wireless communication such as Wi-Fi (registered trademark). Alternatively, the inverter 3 and the multiple circuit breakers 4 may be configured to communicate with each other via wireless communication.

[0090] In modes other than the emergency safety shutdown mode and some of the normal shutdown modes (when "no power generation" is shown in Figure 5), the control signal from the inverter 3 may be stopped, and in the emergency safety shutdown mode and some of the normal shutdown modes, the control signal from the inverter 3 may be output. In this case, the multiple shutdown devices 4 may open the first and second switching units of the relay when they receive a control signal from the inverter 3, and close the first and second switching units of the relay when they do not receive a control signal. [Explanation of Symbols]

[0091] 1. Solar power generation system 2 strings 3 Inverter 4. Multiple circuit breakers 4a Circuit breaker (an example of a first circuit breaker) 6. Solar cell modules 41 Power Supply Section (An example of the First Power Supply Section) 44a First opening / closing section 44b Second opening / closing section 47. Semiconductor switching element (An example of a first semiconductor switching element) 48 Bypass element (an example of a first 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, Multiple disconnection devices that disconnect the connections between the multiple solar cell module groups in response to a control signal from the inverter, Equipped with, Each of the aforementioned plurality of solar cell module groups has an open-circuit voltage that is less than or equal to a predetermined open-circuit voltage. The plurality of solar cell module groups include a first group, a second group connected to the first group, and a third group connected to the second group. The plurality of circuit breakers, A first switching unit connected to the anode terminal of the second group, A first semiconductor switching element is connected in series between the anode terminal of the second group and the first switching unit, The anode terminal is connected between the anode terminal of the second group and the first semiconductor switching element, and the cathode terminal is connected to the cathode terminal of the second group, and the first power supply unit generates power to drive the first switching unit, Includes a first circuit breaker, The first semiconductor switching element turns OFF when the power generation amount of the second 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 includes a first 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 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 first circuit breaker includes a second switching unit connected to the cathode-side terminal of the second group, The photovoltaic power generation system according to claim 1.

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

7. At least one of the first group, second group, and third group of the plurality of solar cell module groups includes the plurality of solar cell modules connected in series. The photovoltaic power generation system according to claim 1.

8. The plurality of solar cell module groups further include a fourth group connected to the third group and a fifth group connected to the fourth group, The plurality of circuit breakers, A third switching unit connected to the anode terminal of the fourth group, A second semiconductor switching element is connected in series between the anode terminal of the fourth group and the third switching unit, The anode terminal is connected between the anode terminal of the fourth group and the second semiconductor switching element, and the cathode terminal is connected to the cathode terminal of the fourth group, and the second power supply unit generates power to drive the third switching unit, Further includes a second circuit breaker, The second semiconductor switching element turns OFF when the power generation amount of the fourth group falls below a predetermined threshold. The photovoltaic power generation system according to claim 1.

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

10. The photovoltaic power generation system according to claim 8, wherein the second semiconductor switching element is a MOSFET element or an IGBT element.

11. The second circuit breaker includes a fourth switching unit connected to the cathode-side terminal of the fourth group, The photovoltaic power generation system according to claim 8.

12. The solar power generation system according to claim 11, wherein the fourth switching unit is driven by power supplied from the second power supply unit.

13. The second shutoff device is capable of independently controlling the opening and closing of the third opening / closing section and the fourth opening / closing section. The photovoltaic power generation system according to claim 11.

14. Each of the plurality of solar cell module groups in the string has an open-circuit voltage of 165V or less. A solar power generation system according to any one of claims 1 to 13.

15. The inverter outputs the control signals to the plurality of circuit breakers via power line communication. A solar power generation system according to any one of claims 1 to 13.

16. The inverter outputs the control signal to the plurality of circuit breakers via wireless communication. A solar power generation system according to any one of claims 1 to 13.

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