Solar power generation system
The photovoltaic power generation system stabilizes operation and reduces costs by employing semiconductor switching elements to manage circuit connections in a string of solar cell module groups with controlled open-circuit voltages, addressing the challenges of high installation costs and instability in existing systems.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- OMRON CORP
- Filing Date
- 2022-05-02
- Publication Date
- 2026-06-30
Smart Images
Figure 0007881975000001 
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Abstract
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 mandatory under 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. This switching element is driven by power from the solar cell module. If the amount of power generated by the solar cell module is less than the power required to drive the switching element, 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 may immediately open (the switching element turns OFF), and this phenomenon may repeat. Also, if the amount of power generated from the solar cell module is unstable, the switching element may repeatedly switch between the ON and OFF states. These phenomena make the operation of the solar power generation system unstable.
[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 connected to the anode-side terminal of the second group. The first switching unit includes a first switching unit and a first semiconductor switching element connected in parallel to the first switching unit. The first semiconductor switching element is ON before the switching operation of the first switching unit.
[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, the first switching unit of the first circuit breaker includes a first switch and a first semiconductor switching element that turns ON before the first switch operates. Therefore, in the first circuit breaker, the first semiconductor switching element turns ON before the first switch operates, so that when the power generation of the second group is less than the driving power of the first switch and / or the power generation of the second group is unstable, the first switch operates in accordance with the power generation of the second group, thereby avoiding the phenomenon of repeated connection and disconnection of the circuit to which the anode terminal of the second group is connected. As a result, the operation of the solar power generation system is stabilized.
[0009] The first switching unit may further include a second switching unit connected in series with the first semiconductor switching element. In this case, the first semiconductor switching element can be reliably electrically isolated from the photovoltaic power generation system.
[0010] The first circuit breaker may further include a second switching unit connected to the cathode-side terminal of the second group. The second switching unit may include a third switching unit and a second semiconductor switching element connected in parallel to the third switching unit. The second semiconductor switching element may be ON before the switching operation of the third switching unit. In this case, multiple circuits can be switched on and off with a single first circuit breaker. Furthermore, in the second switching unit, when the power generation of the second group is less than the driving power of the third switching unit, and / or when the power generation of the second group is unstable, the third switching unit switches on and off according to the power generation of the second group, thereby avoiding the phenomenon of repeated connection and disconnection of the circuit to which the cathode-side terminal of the second group is connected.
[0011] The second switching unit may further include a fourth switching unit connected in series with the second semiconductor switching element. In this case, the second semiconductor switching element can be reliably electrically isolated from the photovoltaic power generation system.
[0012] The first circuit breaker may be capable of independently controlling the switching of the first switching unit and the second switching unit. In this case, for example, if a malfunction occurs in the first switching unit, the circuit can be interrupted using the second switching unit, which is functioning normally.
[0013] The first circuit breaker may further include a first bypass element connected in parallel to the second group. 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.
[0014] 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 further include a second circuit breaker driven by the power generated by one or multiple of the solar cell modules connected in series belonging to the fourth group. The second circuit breaker may have a third switching unit connected to the anode terminal of the fourth group. The third switching unit may include a fifth switching unit and a third semiconductor switching element connected in parallel to the fifth switching unit. The third semiconductor switching element may be in the ON state before the switching operation of the fifth switching unit. In this case, when the power generation of the fourth group is less than the driving power of the fifth switching unit and / or the power generation of the fourth group is unstable, the fifth switching unit can be switched on and off according to the power generation of the fourth group, thereby avoiding the phenomenon of repeated connection and disconnection of the circuit to which the anode terminal of the fourth group is connected.
[0015] The third switching unit may further include a sixth switching unit connected in series with the third semiconductor switching element. In this case, the third semiconductor switching element can be reliably electrically isolated from the photovoltaic power generation system.
[0016] The second circuit breaker may further include a fourth switching unit connected to the cathode-side terminal of the fourth group. The fourth switching unit may further include a seventh switching unit and a fourth semiconductor switching element connected in parallel to the seventh switching unit. The fourth semiconductor switching element may be ON before the switching operation of the seventh switching unit. In this case, multiple circuits can be switched on and off with a single second circuit breaker. Furthermore, in the fourth switching unit, when the power generation of the fourth group is less than the driving power of the seventh switching unit, and / or when the power generation of the fourth group is unstable, the seventh switching unit switches on and off according to the power generation of the fourth group, thereby avoiding the phenomenon of repeated connection and disconnection of the circuit to which the cathode-side terminal of the fourth group is connected.
[0017] The fourth switching unit may further include an eighth switching unit connected in series with the fourth semiconductor switching element. In this case, the fourth semiconductor switching element can be reliably electrically isolated from the photovoltaic power generation system.
[0018] The second circuit breaker may be capable of independently controlling the switching of the third switching unit and the fourth switching unit. In this case, for example, if a malfunction occurs in the third switching unit, the circuit can be interrupted using the fourth switching unit, which is functioning normally.
[0019] The second circuit breaker may further include a second bypass element connected in parallel to the fourth group. In this case, even if the power generation in 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.
[0020] 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.
[0021] 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.
[0022] The inverter may output control signals to multiple circuit breakers via wireless communication. In this case, it becomes possible to output control signals to multiple circuit breakers by remote control. [Effects of the Invention]
[0023] 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. [Brief explanation of the drawing]
[0024] [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 blocking 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 blocking device. [Figure 5] FIG. 5 is a diagram showing an example of the configuration of the first and second switching units. [Figure 6] FIG. 6 is a diagram showing another example of the configuration of the first and second switching units. [Figure 7] FIG. 7 is a diagram showing still another example of the configuration of the first and second switching units. [Figure 8] FIG. 8 is a diagram for explaining an example of the operation mode of a blocking device. [Figure 9] FIG. 9 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment. [Figure 10] FIG. 10 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment. [Figure 11] FIG. 11 is a block diagram schematically showing the configuration of a photovoltaic power generation system according to another embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0025] FIG. 1 is a block diagram schematically showing the configuration of a photovoltaic power generation system ❶ according to one aspect of the present invention. The photovoltaic power generation system ❶ includes a string ❷, an inverter ❸, and a plurality of blocking devices ❹.
[0026] Note: In the translation of the text from line , the numbers "1", "2", "3", and "4" in "photovoltaic power generation system ❶", "string ❷", "inverter ❸", and "blocking devices ❹" are added for clarity in the English expression to correspond to the reference numbers in the original text. They are not part of the original text's tags and are used to better represent the relationships in the English translation.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.
[0027] 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 6E in this embodiment are examples of groups 1 to 5.
[0028] Each of groups 6A through 6F contains 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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, the multiple circuit breakers 4 are composed of three 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.
[0036] 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.
[0037] 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.
[0038] Figure 2 is a schematic block diagram showing the configuration of the circuit breaker 4a. The circuit breaker 4a includes a regulator 41, a signal receiving unit 42, a control unit 43, a relay 44, a bypass circuit 45, a bypass element 46, and a signal detection unit 47.
[0039] The regulator is connected in parallel to group 6B. The regulator 41 generates a power supply to drive the circuit breaker 4a using the power generated by the solar cell module 6, and supplies a stable power supply to the circuit breaker 4a. Here, the power supply for the circuit breaker 4a is generated using only the power generated by the solar cell module 6 of group 6B.
[0040] Figure 3 is a schematic circuit diagram showing the configuration of regulator 41. The configuration of regulator 41 is a well-known configuration and 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.
[0041] 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 47 that detects control signals from the control unit 3c of the inverter 3.
[0042] The control unit 43 includes a CPU, memory, etc. The control unit 43 controls the opening and closing of the relay 44 based on the signal output from the signal receiving unit 42.
[0043] The relay 44 includes a first switching section 44a and a second switching section 44b. The first switching section 44a is located in the circuit 8b. The first switching section 44a connects / disconnects group 6B and group 6C. The first switching section 44a is connected to the anode terminal of group 6B and the cathode terminal of group 6C.
[0044] The second switching unit 44b is located in the circuit 8a. The second switching unit 44b connects / disconnects group 6A and group 6B. The second switching unit 44b is connected to the anode terminal of group 6A and the cathode terminal of group 6B. In this embodiment, the second switching unit 44b may be omitted.
[0045] When the circuit breaker 4a is not supplied with power from the regulator 41, the first switching unit 44a and the second switching unit 44b are always in the OFF 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.
[0046] 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.
[0047] The bypass element 46 is connected in parallel to group 6B. Specifically, one end of the bypass element 46 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 46 is connected between the anode terminal of group 6B and the first switching unit 44a. The bypass element 46 is, for example, a diode having an anode connected between the cathode terminal of group 6B and the second switching unit 44b, and a cathode connected between the anode terminal of group 6B and the first switching unit 44a.
[0048] The bypass element 46 forms an electrical circuit that "bypasses" group 6B and propagates power generated by other solar cell module groups when group 6B is unable to output sufficient power due to an abnormality such as a sudden power drop or abnormal heat generation in group 6B. The bypass element 46 can immediately form an electrical circuit that bypasses the abnormal group 6B based on its electrical characteristics when group 6B is unable to output sufficient power, even without a command from an external signal.
[0049] Furthermore, the connection positions of the two terminals of the bypass element 46 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 46 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 46 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.
[0050] 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.
[0051] 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.
[0052] As shown in Figure 4, the circuit breaker 4b includes a regulator 51, a signal receiving unit 52, a control unit 53, a relay 54, a bypass circuit 55, a bypass element 56, and a signal detection unit 57. The relay 54 includes a first switching unit 54a and a second switching unit 54b. Since the components of the circuit breaker 4b are the same as those of the circuit breaker 4a, they will be described briefly.
[0053] The regulator 51 generates the 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.
[0054] 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.
[0055] The control unit 53 controls the opening and closing 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.
[0056] Bypass element 56 is connected in parallel to group 6D. Bypass element 56 is, for example, a diode having an anode connected between the cathode terminal of group 6D and the second switching unit 54b, and a cathode connected between the anode terminal of group 6D and the first switching unit 54a.
[0057] 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 regulator, 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 bypass element 66, and a signal detection unit. Since the components of the circuit breaker 4c are the same as those of the circuit breaker 4a, their explanation is omitted.
[0058] 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.
[0059] The detailed configurations of the first switching unit 44a and the second switching unit 44b will now be described with reference to Figure 5. The first switching unit 44a includes a switching unit 61a and a semiconductor switching element 63a. The second switching unit 44b includes a switching unit 61b and a semiconductor switching element 63b.
[0060] The switching units 61a and 61b are, for example, switching elements that connect / disconnect the electrical circuits connected to the switching units 61a and 61b by opening and closing contacts. The switching units 61a and 61b are, for example, mechanical relays.
[0061] The opening / closing section 61a has one end connected to the anode terminal of group 6B and the other end connected to the cathode terminal of group 6C, and is driven to open and close by the control unit 43.
[0062] The opening / closing section 61b has one end connected to the anode terminal of group 6A and the other end connected to the cathode terminal of group 6B, and is driven to open and close by the control unit 43.
[0063] The semiconductor switching element 63a is connected in parallel to the switching unit 61a and causes a separate circuit from the switching unit 61a to be either conductive or insulated. The semiconductor switching element 63b is connected in parallel to the switching unit 61b and causes a separate circuit from the switching unit 61b to be either conductive or insulated. The semiconductor switching elements 63a and 63b are, for example, MOSFET elements and IGBT (Insulated Gate Bipolar Transistor) elements.
[0064] The gate electrodes of the semiconductor switching elements 63a and 63b are connected to the control unit 43. The control unit 43 can turn the semiconductor switching elements 63a and 63b ON or OFF by outputting a predetermined voltage signal to these gate terminals. Here, "ON state" means that the semiconductor switching elements 63a and 63b are in a conductive state. On the other hand, "OFF state" means that the semiconductor switching elements 63a and 63b are in an insulated state.
[0065] When a voltage signal is output to the gate terminal to turn semiconductor switching elements 63a and 63b, such as MOSFET elements and IGBT elements, ON or OFF, almost no current flows through the gate terminal. In this way, by using MOSFET elements, IGBT elements, etc., as semiconductor switching elements 63a and 63b, the power required to turn the semiconductor switching elements 63a and 63b ON or OFF can be reduced.
[0066] When the power generation of group 5B is low and / or unstable, the switching unit 61a of the first switching unit 44a and the switching unit 61b of the second switching unit 44b may repeatedly switch on and off, in which case the operation of the photovoltaic power generation system 1 becomes unstable. For this reason, when the power generation of group 5B is low and / or unstable, the semiconductor switching elements 63a and 63b are turned ON before the switching units 61a and 61b are switched on. That is, before the switching units 61a and 61b are switched on, a circuit separate from the switching units 61a and 61b is made conductive. Specifically, when switching the switching units 61a and 61b from the open state to the closed state in order to turn on the first switching unit 44a and the second switching unit 44b, the semiconductor switching elements 63a and 63b are turned ON while the switching units 61a and 61b are in the open state, and then the switching units 61a and 61b are switched from the open state to the closed state.
[0067] After the switching sections 61a and 61b are closed, the semiconductor switching elements 63a and 63b may remain in the ON state or be switched to the OFF state. This is because, if the switching sections 61a and 61b are closed, the first switching section 44a and the second switching section 44b can be turned ON regardless of the state of the semiconductor switching elements 63a and 63b. Whether to keep the semiconductor switching elements 63a and 63b in the ON state or switch them to the OFF state can be appropriately determined depending on the application.
[0068] On the other hand, when switching the switching units 61a and 61b from the closed state to the open state in order to turn off the first switching unit 44a and the second switching unit 44b, the semiconductor switching elements 63a and 63b are turned ON while the switching units 61a and 61b are in the closed state, and then the switching units 61a and 61b are switched from the closed state to the open state. After the switching units 61a and 61b are in the open state, the semiconductor switching elements 63a and 63b are switched from the ON state to the OFF state. It is preferable that this operation be performed before the power generation of group 5B becomes small and / or unstable.
[0069] The above operation prevents the phenomenon in which the switching units 61a and 61b repeatedly switch between open and closed states when the power generation of group 5B is low and / or unstable. This is because the switching units 61a and 61b do not operate when the power generation of group 5B is low and / or unstable. As a result, the photovoltaic power generation system 1 can operate stably even when the power generation of group 5B is low and / or unstable.
[0070] Furthermore, even when the power generation of group 5B is stable and sufficiently large, when opening and closing the switching units 61a and 61b, the semiconductor switching elements 63a and 63b are turned ON before opening and closing the switching units 61a and 61b.
[0071] Semiconductor switching elements 63a and 63b, such as MOSFET elements and IGBT elements, generate almost no noise components when switching between ON and OFF states due to their characteristics. Similarly, switching units 61a and 61b, such as relays, do not generate significant noise components unless a large voltage is applied across them during switching operations. Therefore, by setting the semiconductor switching elements 63a and 63b to the ON state before switching operations, a large voltage is not applied across the switching units 61a and 61b, thus reducing the generation of noise components during switching operations. As a result, the generation of noise components is suppressed in the first switching unit 44a and the second switching unit 44b, stabilizing the operation of the solar power generation system 1. Furthermore, since significant noise components are no longer generated in the switching units 61a and 61b, they do not need to have high voltage withstand characteristics. Consequently, the cost of the switching units 61a and 61b can be reduced.
[0072] The first switching section 54a of the circuit breaker 4b includes a switching unit 61c and a semiconductor switching element 63c. One end of the switching unit 61c is connected to the anode terminal of group 6D, and the other end is connected to the cathode terminal of group 6E. The semiconductor switching element 63c is connected in parallel to the switching unit 61c.
[0073] The second switching section 54b of the circuit breaker 4b includes a switching unit 61d and a semiconductor switching element 63d. One end of the switching unit 61d is connected to the anode terminal of group 6C, and the other end is connected to the cathode terminal of group 6D. The semiconductor switching element 63c is connected in parallel to the switching unit 61c.
[0074] Each of the first switching section 64a and the second switching section 64b of the circuit breaker 4c includes an opening / closing section (not shown) and a semiconductor switching element (not shown).
[0075] The first switching section 54a of the circuit breaker 4b and the first switching section 64a of the circuit breaker 4c have the same configuration as the first switching section 44a of the circuit breaker 4a, so their description is omitted. The second switching section 54b of the circuit breaker 4b and the second switching section 64b of the circuit breaker 4c have the same configuration as the second switching section 44b of the circuit breaker 4a, so their description is omitted.
[0076] As another example of the configuration of the first switching units 44a, 54a and the second switching units 44b, 54b, as shown in Figure 6, other switching units 65a to 65d may be connected in series with the semiconductor switching elements 63a to 63d. The semiconductor switching elements 63a to 63d are electrically insulated by alternating P-type semiconductor regions and N-type semiconductor regions in a semiconductor material. In other words, complete insulation is not achieved in the semiconductor switching elements 63a to 63d. On the other hand, the switching units 61a to 61d completely interrupt the circuit when the two contacts are separated during interruption. Therefore, by connecting other switching units 65a to 65d in series with the semiconductor switching elements 63a to 63d, the semiconductor switching elements 63a to 63d can be reliably electrically isolated from the photovoltaic power generation system 1. In addition, other switching units may be connected in series with the semiconductor switching elements in the first switching unit 54a and the second switching unit 54b of the interruption device 4c.
[0077] As yet another example of the configuration of the first switching units 44a, 54a and the second switching units 44b, 54b, two-pole switching elements may be used in the switching units 61a, 61b, as shown in Figure 7. In this case, before switching units 61a, 61b are opened or closed, semiconductor switching elements 63a, 63b connected in parallel to the switching units 61a, 61b to be opened or closed are turned ON. Similarly, two-pole switching elements may be used in the switching units 61c, 61d, or two-pole switching elements may be used in the switching unit of the circuit breaker 4c.
[0078] Next, referring to Figure 8, 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.
[0079] 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 regulator 41 from the electricity generated by the solar cell module 6 of group 6B. When 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 turns on the semiconductor switching elements 63a and 63b, and then closes the switching units 61a and 61b. As a result, the first switching unit 44a and the second switching unit 44b are turned on.
[0080] In start mode, the power generation of group 6B is low, which can cause the switching units 61a and 61b to repeatedly switch on and off, destabilizing the operation of the solar power generation system 1. Therefore, in start mode, the semiconductor switching elements 63a and 63b are initially turned ON when the power generation of group 6B is low. At this time, the switching units 61a and 61b are in the open state. Subsequently, when the power generation of group 6B becomes greater than the driving power of the switching units 61a and 61b, the switching units 61a and 61b are turned OFF. This prevents the switching units 61a and 61b from repeatedly switching on and off. In addition, the first switching unit 44a and the second switching unit 44b can be turned ON by a separate circuit (i.e., semiconductor switching elements 63a and 63b) from the switching units 61a and 61b, thus ensuring a circuit connecting the string 2 and the inverter 3 in start mode.
[0081] 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 circuit breakers 4a to 4c, and the power generated by the solar cell module 6 is output to the inverter 3.
[0082] In active mode, if the power generation of group 6B decreases (for example, if the solar cell module group is shaded), the semiconductor switching elements 63a and 63b are turned ON, and the switching units 61a and 61b are opened. Subsequently, when the power generation of group 6B becomes greater than the driving power of the switching units 61a and 61b, the switching units 61a and 61b are switched from the open state to the closed state. This prevents the phenomenon in active mode where the switching units 61a and 61b repeatedly open and close when the power generation of group 6B decreases. In addition, since the semiconductor switching elements 63a and 63b can turn ON the first switching unit 44a and the second switching unit 44b, even if the power generation of group 6B decreases in active mode, the power generated by string 2 can be supplied to inverter 3.
[0083] 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, and no power supply is being supplied from the solar cell module 6 to the shutdown devices 4a to 4c. For this reason, in the normal shutdown mode, the first switching units 44a, 54a, 64a and the second switching units 44b, 54b, 64b are all open. 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. However, since the inverter 3 is powered by an AC power source, it is possible for the control unit 3c of the inverter 3 to always output a control signal, except in the emergency safety shutdown mode.
[0084] In the normal shutoff mode, if the power generation of group 6B is unstable due to unstable weather or other reasons, the semiconductor switching elements 63a and 63b are turned ON when the power generation of group 6B is small, similar to the start mode, and the switching units 61a and 61b are closed when the power generation of group 6B becomes greater than the driving power of the switching units 61a and 61b.
[0085] 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 circuit breakers 4a to 4c are in the start mode or active mode, the operating mode of the circuit breakers 4a to 4c is switched to the emergency safety shutdown mode.
[0086] In detail, when the operation switch 35 is operated, the control unit 3c stops outputting the control signal. When the signal detection unit 47 detects that the control signal has stopped at a certain period of time, the first switching unit 44a and the second switching unit 44b of the relay 44 are turned OFF via the signal receiving unit 42 and the control unit 43. As a result, the connection between group 6A and group 6B, and the connection between group 6B and group 6C are disconnected.
[0087] Similarly, when the disconnector 4b detects a periodic cessation of the control signal, it controls the first switching unit 54a and the second switching unit 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 disconnector 4c detects a periodic cessation of the control signal, it controls the first switching unit 64a and the second switching unit 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.
[0088] Since the operation of circuit breakers 4b and 4c in each mode is the same as that of circuit breaker 4a, a detailed explanation will be omitted.
[0089] 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, the first switching unit 44a of the circuit breaker 4a includes an opening / closing unit 61a and a semiconductor switching element 63a that turns ON before the opening / closing operation of the opening / closing unit 61a. Therefore, in the circuit breaker 4a, by turning ON before the opening / closing operation of the opening / closing unit 61a, when the power generation amount of group 6B is less than the driving power of the opening / closing unit 61a, and / or when the power generation amount of group 6B is unstable, the opening / closing unit 61a opens and closes according to the power generation amount of group 6B, thereby avoiding the phenomenon of repeated connection and disconnection of the circuit to which the anode terminal of group 6B is connected. As a result, the operation of the photovoltaic power generation system 1 is stabilized.
[0090] Furthermore, since a large voltage is no longer applied to both ends of the switching unit 61a, the switching unit 61a is less likely to generate noise components and chattering during switching operations. In addition, due to its characteristics, the semiconductor switching element 63a is less likely to generate noise components and chattering during switching operations between the ON state and the OFF state. As a result, the generation of noise components and chattering is suppressed in the first switching unit 44a, and the operation of the solar power generation system 1 is stabilized.
[0091] Furthermore, the same effects and advantages as those of the first switching unit 44a of the circuit breaker 4a can be obtained by the second switching unit 44b of the circuit breaker 4a, the first switching unit 54a and the second switching unit 54b of the circuit breaker 4b, and the first switching unit 64a and the second switching unit 64b of the circuit breaker 4c.
[0092] 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.
[0093] 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.
[0094] As simplified in Figure 9, 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 module groups may include two solar cell modules 6.
[0095] As simplified in Figure 10, multiple circuit breakers 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.
[0096] 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 11, 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.
[0097] 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.
[0098] 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]
[0099] 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 44a First Switching Section 44b Second Switching Section 48 First Bypass Element 61a Opening / closing section (an example of the first opening / closing section) 61b Opening / closing section (an example of the third opening / closing section) 63a Semiconductor switching element (an example of a first semiconductor switching element) 65a Other opening / closing parts (an example of a second opening / closing part) 65b Other opening / closing parts (an example of the fourth opening / closing part)
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 include a first circuit breaker that is driven by power generated by one or a plurality of solar cell modules connected in series belonging to the second group. The first circuit breaker includes a first switching unit connected to the anode terminal of the second group and a second switching unit connected to the cathode terminal of the second group. The first switching unit includes a first switching unit and a first semiconductor switching element connected in parallel to the first switching unit. The first semiconductor switching element is turned ON before the opening and closing operation of the first switching unit. The second switching unit includes a third switching unit and a second semiconductor switching element connected in parallel to the third switching unit. The second semiconductor switching element turns ON before the opening and closing operation of the third switching unit. The first circuit breaker is capable of independently controlling the opening and closing of the first switching unit and the second switching unit. Solar power generation system.
2. The first switching unit further includes a second switching unit connected in series with the first semiconductor switching element. The photovoltaic power generation system according to claim 1.
3. The photovoltaic power generation system according to claim 1, wherein the second switching unit further includes a fourth switching unit connected in series with the second semiconductor switching element.
4. The photovoltaic power generation system according to claim 1, wherein the first circuit breaker further includes a first bypass element connected in parallel to the second group.
5. 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 further include a second circuit breaker that is driven by power generated by one or a plurality of solar cell modules connected in series belonging to the fourth group. The second circuit breaker has a third switching unit connected to the anode terminal of the fourth group, The third switching unit includes a fifth switching unit and a third semiconductor switching element connected in parallel to the fifth switching unit. The photovoltaic power generation system according to claim 1, wherein the third semiconductor switching element is turned ON before the opening and closing operation of the fifth opening and closing unit.
6. The photovoltaic power generation system according to claim 5, wherein the third switching unit further includes a sixth switching unit connected in series with the third semiconductor switching element.
7. The second circuit breaker further includes a fourth switching unit connected to the cathode-side terminal of the fourth group, The fourth switching unit further includes a seventh switching unit and a fourth semiconductor switching element connected in parallel to the seventh switching unit. The photovoltaic power generation system according to claim 5, wherein the fourth semiconductor switching element is turned ON before the opening and closing operation of the seventh opening and closing unit.
8. The photovoltaic power generation system according to claim 7, wherein the fourth switching unit further includes an eighth switching unit connected in series with the fourth semiconductor switching element.
9. The photovoltaic power generation system according to claim 7, wherein the second circuit breaker is capable of independently controlling the opening and closing of the third switching unit and the fourth switching unit.
10. The photovoltaic power generation system according to claim 5, wherein the second circuit breaker further includes a second bypass element connected in parallel to the fourth group.
11. 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 10.
12. 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 10.
13. 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 10.