Solar power generation system
The photovoltaic power generation system addresses high costs and limited voltage reduction in emergencies by employing inexpensive relay contacts and discharge circuits to minimize electric shock risk through voltage reduction to single module output levels.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- OSAKA ELECTRO-COMMUNICATION UNIVERSITY
- Filing Date
- 2024-11-05
- Publication Date
- 2026-05-19
AI Technical Summary
Existing solar power generation systems face high costs and limited voltage reduction in emergencies due to the need for expensive relay contacts with large cutoff capacities, and maintain series connections of solar cell modules, increasing the risk of electric shock during faults.
A photovoltaic power generation system with an inverter, circuit breaker, and string configuration, using inexpensive relay contacts with smaller interrupting capacities, and additional relay contacts to disconnect module units, along with discharge circuits to reduce circuit voltage in emergencies.
The system effectively reduces circuit voltage to the output voltage of a single module unit, minimizing the risk of electric shock at a lower cost by using less expensive relay contacts and discharge circuits.
Smart Images
Figure 2026081625000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a technique for preventing electric shock accidents caused by a solar power generation system.
Background Art
[0002] A solar power generation system has a configuration in which solar cell modules that generate electricity by the photovoltaic effect are arranged. Each solar cell module constituting the solar power generation system continues to generate electricity as long as light is irradiated on the cell. Therefore, in a solar power generation system, when a ground fault or a short circuit fault occurs inside the system due to various reasons such as fire, natural disaster, and aging deterioration, an operator who performs work for inspection, fire extinguishing, and restoration is exposed to the risk of electric shock.
[0003] On the other hand, Patent Document 1 discloses a technique for preventing the occurrence of electric shock accidents in a solar power generation system. In the technique described in Patent Document 1, a cutoff device including a relay contact is provided for each group composed of a plurality of solar cell modules, and the connection between the groups is cut off by the cutoff device in an emergency.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] In the technique described in Patent Document 1, since a high-voltage direct current is cut off by one of the cutoff devices in an emergency, it is necessary to provide a relay contact with a large cutoff capacity, which is expensive, in each cutoff device. Further, in this technique, since the series connection of a plurality of solar cell modules constituting each group is maintained even in an emergency, the effect of reducing the voltage of the circuit is limited.
[0006] In view of the above circumstances, the present invention aims to provide a technology that can sufficiently reduce the voltage of the circuit in a solar power generation system at a low cost. [Means for solving the problem]
[0007] To achieve the above objective, a photovoltaic power generation system according to one embodiment of the present invention comprises an inverter, a circuit breaker, and a string, all connected in series with each other. The interruption unit has a first relay contact. The string has multiple module units connected in series with each other. Each of the aforementioned module units comprises a solar cell module and a second relay contact connected in series with the solar cell module. The photovoltaic power generation system further comprises a control unit that closes both the first and second relay contacts in the operating state and opens both the first and second relay contacts in the emergency state, and opens the first relay contact and then opens the second relay contact when switching from the operating state to the emergency state.
[0008] In this solar power generation system, when switching from the operating state to the emergency state, the first relay contact of the interruption unit interrupts the high-voltage DC current between the inverter and the string, and then the second relay contact of each module unit disconnects the connections between the module units that make up the string. Therefore, in this solar power generation system, the first relay contact of the interruption unit is required to have an interruption capacity that can interrupt the string, while the second relay contact of each module unit only opens and closes the circuit after the current has been interrupted. Thus, inexpensive relay contacts with a small interruption capacity can be used as the second relay contacts provided for each of the multiple module units. Furthermore, in this solar power generation system, a second relay contact is provided for each module unit to disconnect all connections between module units in an emergency. As a result, this solar power generation system can suppress the maximum voltage of the circuit in an emergency to the output voltage of a single module unit's solar cell module. Therefore, this solar power generation system can sufficiently reduce the voltage of the circuit at a low cost.
[0009] Preferably, each of the plurality of module units further has a bypass circuit equipped with a protection diode connected in parallel to the solar cell module. In this configuration, if the first relay contact does not open before the second relay contact for any reason when switching from the operating state to the emergency state, the generation of an arc when the second relay contact opens and closes can be suppressed, thereby protecting the contact of the second relay.
[0010] Preferably, each of the plurality of module units further has a discharge circuit equipped with a discharge resistor and a third relay contact connected in parallel to the solar cell module. In this case, the control unit opens the third relay contact in the operating state, closes the third relay contact in the emergency state, and opens the first relay contact before closing the third relay contact when switching from the operating state to the emergency state. In this configuration, the discharge circuit in each module unit forms a closed circuit including the solar cell module and discharge resistor, thereby keeping the maximum voltage of the circuit lower than the output voltage of the solar cell module in an emergency situation.
[0011] In the aforementioned emergency situation, it is preferable that the disconnecting section and the module unit are configured such that the disconnected wires are connected to ground. Preferably, at least one of the plurality of module units is configured to be connected to earth in the emergency situation. In this configuration, the potential of the interrupted circuit can be set to 0V.
[0012] The solar power generation system preferably further includes an abnormality detection unit. In this case, when an abnormality is detected by the abnormality detection unit, the control unit switches from the operating state to the emergency state. In this configuration, since the operating state is automatically switched to the emergency state in accordance with the detection of an abnormality by the abnormality detection unit, the voltage of the circuit can be rapidly decreased when an abnormality occurs.
Effects of the Invention
[0013] As described above, the present invention can provide a technique capable of sufficiently reducing the voltage of a circuit at low cost in a solar power generation system.
Brief Description of the Drawings
[0014] [Figure 1] It is a schematic configuration diagram of a solar power generation system according to an embodiment of the present invention. [Figure 2] It is a diagram showing an operation of switching from an operating state to an emergency state in the above solar power generation system. [Figure 3] It is a diagram showing an operation of switching from an operating state to an emergency state in the above solar power generation system. [Figure 4] It is a diagram showing another embodiment of the above solar power generation system. [Figure 5] It is a diagram showing another embodiment of the above solar power generation system. [Figure 6] It is a diagram showing another embodiment of the above solar power generation system. [Figure 7] It is a diagram showing another embodiment of the above solar power generation system.
Modes for Carrying Out the Invention
[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0016] [Schematic Configuration of Photovoltaic Power Generation System 100] FIG. 1 is a schematic configuration diagram of a photovoltaic power generation system 100 according to an embodiment of the present invention. The photovoltaic power generation system 100 includes a string 1, an inverter 2, a cutoff section 3, a control section 4, and an abnormality detection section 5. In the photovoltaic power generation system 100, the string 1, the inverter 2, and the cutoff section 3 are connected in series with each other to form the main circuit of the photovoltaic power generation system 100.
[0017] The string 1 has a plurality of module units 10 connected in series with each other. The number of module units 10 in the string 1 can be arbitrarily determined according to the target output voltage, installation space, etc. Further, the photovoltaic power generation system 100 may be configured to have a plurality of strings 1 connected in parallel with each other.
[0018] The inverter 2 converts the DC power output from the string 1 into AC power. The inverter 2 may have other functions as needed, and for example, it can be configured as a PCS (Power Conditioner System) equipped with various protection and control functions necessary for coordinated operation with the commercial power system and automatic operation.
[0019] The cutoff section 3 has a first relay contact C1 provided between the string 1 and the inverter 2. The cutoff section 3 connects the string 1 and the inverter 2 by setting the first relay contact C1 to the closed state, and releases the connection between the string 1 and the inverter 2 by setting the first relay contact C1 to the open state. The cutoff section 3 needs to have a cutoff capacity sufficient to cut off the string 1.
[0020] The control unit 4 controls the operation of the string 1 and the shut-off unit 3. The abnormality detection unit 5 detects abnormalities such as sudden changes in the output of the solar power generation system 100 itself or abnormalities in the environment surrounding the solar power generation system 100. In the solar power generation system 100, the control unit 4 controls the operation of the string 1 and the shut-off unit 3 based on whether or not an abnormality has been detected by the abnormality detection unit 5. The abnormality detection unit 5 can be configured to detect, for example, fires or natural disasters by using known sensors.
[0021] [Configuration of Module Unit 10] Each module unit 10 constituting String 1 includes a solar cell module 11 and a second relay contact C2. In each module unit 10, the solar cell module 11 and the second relay contact C2 are connected in series with each other, and the second relay contact C2 is located on the negative terminal side of the solar cell module 11.
[0022] The solar cell module 11 can have any configuration, for example, it can be configured as a single-crystal silicon system, polycrystalline silicon system, ribbon silicon system, spherical silicon system, thin-film silicon system, heterojunction (HIT) system, CIGS system, CdTe system, dye-sensitized system, III-V multijunction type, quantum dot type, perovskite type, etc.
[0023] In String 1, all module units 10 are connected in series by closing the second relay contact C2 of all module units 10. Conversely, in String 1, all connections of each module unit 10 that form a series connection are released by opening the second relay contact C2 of all module units 10.
[0024] Furthermore, each module unit 10 further includes a bypass circuit 12 equipped with a protection diode D connected in parallel to the solar cell module 11. The bypass circuit 12 is connected to the terminal of the second relay contact C2 opposite to the solar cell module 11, that is, it is connected to the solar cell module 11 outside of the second relay contact C2.
[0025] Furthermore, each module unit 10 further includes a discharge circuit 13 equipped with a discharge resistor R and a third relay contact C3 connected in parallel to the solar cell module 11. The discharge circuit 13 is connected between the solar cell module 11 and the second relay contact C2, that is, it is connected to the solar cell module 11 inside the second relay contact C2.
[0026] [Operation of Solar Power Generation System 100] In the solar power generation system 100, the first relay contact C1 is closed during normal power generation operation to connect the string 1 and the inverter 2, and the first relay contact C1 is opened during an emergency situation where an abnormality occurs that interferes with normal power generation operation to disconnect the connection between the string 1 and the inverter 2.
[0027] Furthermore, in the solar power generation system 100, all module units 10 constituting string 1 are connected in series by closing all second relay contacts C2 during operation, and all connections of each module unit 10 constituting string 1 are disconnected by opening all second relay contacts C2 during an emergency.
[0028] In the operating state of the solar power generation system 100, the main circuit, in which the string 1, inverter 2, and breaker unit 3 are connected in series, forms a closed circuit. As a result, the total output of the solar cell modules 11 of all module units 10 constituting the string 1 is input to the inverter 2, and AC power is output by the inverter 2.
[0029] On the other hand, in an emergency situation, the solar power generation system 100 can reduce the maximum voltage of the circuit to the output voltage of the solar cell module 11 of a single module unit 10 by disconnecting each module unit 10 that makes up string 1. Therefore, the solar power generation system 100 can reduce the risk of electric shock in an emergency situation.
[0030] Furthermore, in each module unit 10, the third relay contact C3 is opened during operation, and the discharge circuit 13 is opened. Also, in each module unit 10, the third relay contact C3 is closed during emergency, and the discharge circuit 13 is closed, thereby providing a discharge effect due to the discharge resistor R.
[0031] In other words, in each module unit 10, during an emergency, the discharge circuit 13 forms a closed circuit including the solar cell module 11 and the discharge resistor R, thereby keeping the maximum voltage of the circuit lower than the open-circuit voltage of the solar cell module 11, and allowing the generated energy to be consumed by the discharge resistor R. This further reduces the risk of electric shock accidents during emergencies in the photovoltaic power generation system 100.
[0032] Figures 2 and 3 illustrate the operation of the photovoltaic power generation system 100. In both Figures 2 and 3, components other than the disconnection unit 3 in the photovoltaic power generation system 100 and the module units 10 adjacent to the disconnection unit 3 in the string 1 are omitted. All of the module units 10 constituting the string 1 have the same configuration.
[0033] In the solar power generation system 100, when switching from the operating state to the emergency state, the first relay contact C1 is first opened, as shown in Figure 2. As a result, the solar power generation system 100 interrupts the output voltage and DC current flowing through the circuit, which are the sum of the solar cell modules 11 of all module units 10 constituting the string 1, by the first relay contact C1.
[0034] In the solar power generation system 100, after opening the first relay contact C1, the second relay contact C2 is opened for all module units 10 constituting string 1, as shown in Figure 3. As a result, all connections of each module unit 10 constituting string 1 are disconnected in the solar power generation system 100.
[0035] Thus, in the solar power generation system 100, by opening the first relay contact C1 in advance, the output voltage and current of the entire string 1 are always interrupted by the first relay contact C1. Therefore, the second relay contact C2 that constitutes each module unit 10 has only the role of opening and closing the circuit.
[0036] Conversely, in the solar power generation system 100, when returning from an emergency state to an operating state, all second relay contacts C2 are closed first, and then the first relay contact C1 is closed. As a result, in the solar power generation system 100, the DC current supplying the output voltage of the entire string 1 is always initiated at the first relay contact C1.
[0037] In other words, in the solar power generation system 100, the first relay contact C1 is required to be a relay capable of interrupting string 1, while the second relay contact C2 is responsible for opening and closing circuits where no current is flowing, and therefore there are no requirements regarding its interrupting capacity. Consequently, in the solar power generation system 100, inexpensive contact components with small interrupting capacity can be used as the second relay contact C2, which is provided for each module unit 10. However, if for some reason the first relay contact C1 fails to operate or is unable to perform a preceding operation, and it is necessary to consider the possibility of a bypass circuit malfunction occurring, then a second relay contact C2 with sufficient capacity to interrupt the output of the solar cell module 11 may be used.
[0038] Furthermore, in the solar power generation system 100, after opening the first relay contact C1, the third relay contact C3 is closed for all module units 10 constituting the string 1, as shown in Figure 3. As a result, in the solar power generation system 100, the discharge circuit 13 forms a closed circuit in each module unit 10 constituting the string 1. Consequently, the solar power generation system 100 can keep the maximum voltage of the circuit in an emergency state lower than the open-circuit voltage of the solar cell module 11.
[0039] Only a DC current equal to the output voltage of at most one solar cell module 11 flows through the third relay contact C3 of the discharge circuit 13 of each module unit 10. For this reason, the third relay contact C3 of the solar cell module 11 can be a relay with a breaking capacity capable of shutting off one solar cell module 11.
[0040] Furthermore, the timing for opening the third relay contact C3 when returning from an emergency state to an operating state is before closing the first relay contact C1. Also, the timing of switching between the closed and open states of the second relay contact C2 and the open and closed states of the third relay contact C3 in each module unit 10 when switching between an operating state and an emergency state may be the same or different. Moreover, the timing of switching between the closed and open states of the second relay contact C2 among multiple module units 10 when switching between an operating state and an emergency state may be the same or different. In addition, the timing of switching between the open and closed states of the third relay contact C3 among multiple module units 10 when switching between an operating state and an emergency state may be the same or different.
[0041] Furthermore, in the solar power generation system 100, if the first relay contact C1 does not open before the second relay contact C2 for any reason when switching from the operating state to the emergency state, the second relay contact C2 of one of the module units 10 constituting the string 1 will interrupt the high-voltage DC current.
[0042] In this case, in the solar power generation system 100, in the module unit 10 which includes a second relay contact C2 that attempts to interrupt a high-voltage DC current, a portion of the DC current flows to the bypass circuit 12, thereby reducing the DC current flowing to the second relay contact C2 and preventing failure due to arc generation when the second relay contact C2 is opened.
[0043] Furthermore, in the operational state of the solar power generation system 100, the bypass circuit 12 in each module unit 10 constituting string 1 can also function to prevent a decrease in the output of string 1 and avoid hot spots that occur inside the solar cell module 11 by allowing current to pass through the solar cell module 11 when power generation by the solar cell module 11 is not occurring due to shading or other reasons. Even if the solar cell module 11 cannot output power due to an internal circuit malfunction, the current can pass through the solar cell module 11 by bypassing it, thereby preventing a decrease in the output of string 1.
[0044] Furthermore, the solar power generation system 100 can be switched from the operating state to the emergency state, for example, when performing a periodic inspection, even if no abnormality occurs that would interfere with normal power generation operation. In the emergency state of the solar power generation system 100, the connection between the solar cell module 11 and the wiring cable is disconnected in each module unit 10, making it possible to perform insulation resistance measurements separately for the solar cell module 11 and the wiring cable of each module unit 10. As a result, the solar power generation system 100 can more precisely identify the parts within the string 1 where insulation abnormalities have occurred.
[0045] [Configuration of Control Unit 4] The control unit 4 is configured to control the operation of relay contacts C1, C2, and C3 as described above. As an example, the control unit 4 can be configured to have a drive circuit with a drive coil corresponding to each relay contact C1, C2, and C3. In this configuration, each relay contact C1, C2, and C3 together with its respective drive coil constitutes a mechanical relay.
[0046] For example, in the solar power generation system 100, the first relay contact C1 and the second relay contact C2 can be set as normally open contacts (a-contacts), and the third relay contact C3 can be set as a normally closed contact (b-contact). In this case, the control unit 4 continues to supply power to each drive coil by the drive circuit during operation, and stops supplying power to each drive coil by the drive circuit during an emergency.
[0047] When switching from an operating state to an emergency state, the control unit 4 can design the drive circuit such that, for example, the supply of power to the drive coil corresponding to relay contact C2 is delayed compared to the supply of power to the drive coil corresponding to the first relay contact C1, in order to activate the first relay contact C1 before relay contact C2.
[0048] The solar power generation system 100 is configured such that when an abnormality is detected by the abnormality detection unit 5, the control unit 4 switches from the operating state to the emergency state. Alternatively, the solar power generation system 100 may be configured such that when the abnormality detection unit 5 detects that the abnormality has been resolved, the control unit 4 switches from the emergency state to the operating state. Furthermore, it is preferable that the solar power generation system 100 is configured so that the control unit 4 can switch between the operating state and the emergency state by on-site operation or remote operation, without relying on the abnormality detection unit 5.
[0049] [Other embodiments] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.
[0050] For example, in the solar power generation system 100, the position of the second relay contact C2 in each module unit 10 only needs to be such that the connection state between each module unit 10 can be changed by the second relay contact C2, and it may be on the positive terminal side of the solar cell module 11 rather than the negative terminal side.
[0051] Furthermore, as shown in Figure 4, each module unit 10 may have a second relay contact C2 on both the positive and negative sides of the solar cell module 11. In this configuration, both the positive and negative terminals of the solar cell module 11 can be opened, further reducing the risk of ground faults, short circuits, and electric shock accidents of the solar cell module 11 in emergency situations.
[0052] Furthermore, as shown in Figure 5, in each module unit 10, the second relay contact C2 is changed to a switching contact (c-contact) in which, when the terminal on the main circuit side is open, the terminal on the discharge circuit 13 side is closed. This allows the second relay contact C2 to also function as the third relay contact C3. This reduces the number of components.
[0053] Furthermore, as shown in Figure 6, the solar power generation system 100 can be configured to include ground wires E. Each ground wire E connects the wires from which the circuit breaker 3 and module units 10 are disconnected to earth, that is, it connects the circuit breaker 3 and all module units 10 constituting the string 1 to earth. In this case, each ground wire E is provided with a fourth relay contact C4.
[0054] The fourth relay contact C4 is open during operation and closed during an emergency. This allows the potential of the circuit breaker 3 and the multiple module units 10 constituting the string 1 to be set to 0V in the solar power generation system 100 during an emergency. This further reduces the risk of electric shock during an emergency.
[0055] Furthermore, as shown in Figure 7, in the solar power generation system 100, by changing the first relay contact C1 to a switching contact (c-contact) where the terminal on the main circuit side is open and the terminal on the ground wire E is closed, the first relay contact C1 can also function as the fourth relay contact C4. This reduces the number of components.
[0056] Furthermore, the solar power generation system 100 is not limited to a configuration in which the first relay contact C1 is connected in series with the inverter 2 in the main circuit, that is, where the first relay contact C1 is located on the DC side of the inverter 2. In other words, the solar power generation system 100 may also have the first relay contact C1 located on the AC side of the inverter 2, and in this case as well, the first relay contact C1 can interrupt the DC current of the main circuit on the DC side of the inverter 2, just as described above.
[0057] The solar power generation system 100 may have other configurations in addition to the above configuration. Furthermore, the solar power generation system 100 may have a configuration in which at least one of the bypass circuit 12 and the discharge circuit 13 is not provided in the plurality of module units 10 that constitute the string 1. Moreover, the solar power generation system 100 may have a configuration in which the abnormality detection unit 5 is not provided. [Explanation of Symbols]
[0058] 1... String 2…Inverter 3... Blocking section 4…Control Unit 5... Anomaly detection unit 10…Module Unit 11… Solar cell modules 12…Bypass circuit 13…Discharge circuit 100... Solar power generation system C1...First relay contact C2...Second relay contact C3...Third relay contact D...Protection diode R…discharge resistance E...Ground wire
Claims
1. It comprises an inverter, a circuit breaker, and a string, all connected in series with each other. The interruption unit has a first relay contact, The string has multiple module units connected in series with each other. Each of the aforementioned plurality of module units comprises a solar cell module and a second relay contact connected in series with the solar cell module. The system further comprises a control unit that, in the operating state, keeps both the first and second relay contacts closed, in the emergency state, keeps both the first and second relay contacts open, and opens the first relay contact and then opens the second relay contact when switching from the operating state to the emergency state. A solar power generation system equipped with the following features.
2. A solar power generation system according to claim 1, Each of the aforementioned module units further comprises a bypass circuit equipped with a protection diode connected in parallel to the solar cell module. Solar power generation system.
3. A photovoltaic power generation system according to claim 1 or 2, Each of the aforementioned module units further comprises a discharge circuit equipped with a discharge resistor and a third relay contact connected in parallel to the solar cell module. The control unit opens the third relay contact in the operating state, closes the third relay contact in the emergency state, and opens the first relay contact and then closes the third relay contact when switching from the operating state to the emergency state. Solar power generation system.
4. A photovoltaic power generation system according to claim 1 or 2, In the aforementioned emergency situation, the disconnector and the module unit are configured to connect the disconnected wires to ground. At least one of the plurality of module units is configured to be connected to earth in the emergency situation. Solar power generation system.
5. A photovoltaic power generation system according to claim 1 or 2, The aforementioned solar power generation system further comprises an abnormality detection unit, When the abnormality detection unit detects an abnormality, the control unit switches from the operating state to the emergency state. Solar power generation system.