Electric power cutoff device

Abstract

This electric power cutoff device comprises a main relay and a drive circuit. The main relay is a latching relay that can be switched between an ON state and an OFF state. In the ON state, the main relay connects a solar panel to a cable. In the OFF state, the main relay disconnects the solar panel from the cable. The main relay is set to the ON state in a normal power generation state in which the solar panel is generating power and a current is flowing through the cable. The main relay is kept in the ON state even in a non-power generation state in which the solar panel is not generating power. The drive circuit switches the main relay to the OFF state by a power generation voltage of the solar panel in an abnormal power generation state in which the solar panel is generating power and the cable is disconnected.

Description

Power cutoff device

[0001] The present invention relates to a power cutoff device in a solar power generation system.

[0002] Conventionally, there has been known a power cutoff device that automatically cuts off a solar panel of a solar power generation system when a cable break is detected in the solar power generation system. For example, in Patent Document 1, a power conditioner detects the voltage and current of the solar panel using a sensor. The power conditioner determines whether a break has occurred based on the detected voltage and current using an electronic circuit including a microcomputer, and if a break has occurred, the power conditioner cuts off the solar panel from the cable.

[0003] Patent No. 7117630

[0004] The power cutoff device described above requires a power source to operate the sensor and electronic circuitry in order to detect a cable break and cut off the solar panel. An object of the present invention is to cut off the solar panel when a cable break occurs in a solar power generation system without using a separate power source to detect a cable break.

[0005] One aspect of the present invention is a power interruption device for disconnecting a solar panel from a cable in a solar power generation system when the cable is broken. The power interruption device includes a main relay and a drive circuit. The main relay is a latching relay that can be switched between an ON state and an OFF state. When in the ON state, the main relay connects the solar panel to the cable. When in the OFF state, the main relay disconnects the solar panel from the cable. The main relay is set to the ON state in a normal power generation state in which the solar panel is generating power and current is flowing through the cable. The main relay is also maintained in the ON state in a non-power generation state in which the solar panel is not generating power. When in an abnormal power generation state in which the solar panel is generating power and the cable is broken, the drive circuit switches the main relay to the OFF state using the voltage generated by the solar panel.

[0006] In the power cutoff device according to this aspect, the main relay is set to the ON state during normal power generation, when the solar panel is generating power and current is flowing through the cable. During abnormal power generation, when the solar panel is generating power and the cable is broken, the main relay is switched to the OFF state by the voltage generated by the solar panel. This allows the solar panel to be shut off in the event of a cable break without using a power source. Furthermore, even during non-power generation, such as at night, when the solar panel is not generating power, the self-holding function of the latching relay keeps the main relay in the ON state. This allows the supply of power from the solar panel to be smoothly resumed when power generation by the solar panel resumes. Furthermore, reducing the number of times the main relay is opened and closed reduces the possibility of failure.

[0007] According to the present invention, it is possible to shut down the solar panel when a cable breaks in a solar power generation system without using a separate power source for detecting a cable break.

[0008] Fig. 1 is a schematic diagram showing the configuration of a solar power generation system; Fig. 2 is a schematic diagram showing the configuration of a power cut-off device in an initial state of the solar power generation system; Fig. 3 is a schematic diagram showing the configuration of a power cut-off device at startup; Fig. 4 is a schematic diagram showing the configuration of a power cut-off device in a normal power generation state; Fig. 5 is a schematic diagram showing the configuration of a power cut-off device in a non-power generation state; Fig. 6 is a schematic diagram showing the configuration of a power cut-off device in an abnormal power generation state.

[0009] Hereinafter, a power interruption device for a solar power generation system according to an embodiment will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a solar power generation system 1. As shown in Fig. 1, the solar power generation system 1 includes a solar panel 2, a power conditioner 3, a cable 4, and a power interruption device 5.

[0010] The solar panel 2 generates electricity using sunlight. The power conditioner 3 controls the power generated by the solar panel 2. The power conditioner 3 converts the power generated by the solar panel 2 and supplies it to electrical devices or a battery. The cable 4 connects the solar panel 2 to the power conditioner 3. The cable 4 includes a first cable 4A and a second cable 4B. For example, the first cable 4A is connected to the positive terminal of the solar panel 2, and the second cable 4B is connected to the negative terminal of the solar panel 2.

[0011] The power cutoff device 5 disconnects the solar panel 2 from the cable 4 when the cable 4 is broken. FIG. 2 is a schematic diagram showing the configuration of the power cutoff device 5. As shown in FIG. 2, the power cutoff device 5 includes a main relay 6, a main circuit 7, and a drive circuit 8. The main relay 6 can be switched between an on state and an off state. When the main relay 6 is in the on state, it connects the solar panel 2 to the cable 4. When the main relay 6 is in the off state, it disconnects the solar panel 2 from the cable 4.

[0012] The main relay 6 includes a set coil 11, a reset coil 12, and main contacts 13 and 14. The main relay 6 has a self-holding function that maintains the states of the main contacts 13 and 14 when the set coil 11 and the reset coil 12 are not energized. The main relay 6 is a magnetically held two-winding latching relay. Components of the main relay 6, such as the iron core, yoke, and iron pieces, are made of semi-hard magnetic material. In the main relay 6, even when the current to the coils 11 and 12 is stopped, the positions of the main contacts 13 and 14 are maintained by the residual magnetic flux of the semi-hard magnetic material.

[0013] In detail, in the main relay 6, when the set coil 11 is energized, the main contacts 13 and 14 are connected. This sets the main relay 6 to an ON state. Even if the energization to the set coil 11 is cut off, the main relay 6 remains in the ON state. In the main relay 6, when the reset coil 12 is energized, the main contacts 13 and 14 are separated. This sets the main relay 6 to an OFF state. Even if the energization to the reset coil 12 is cut off, the main relay 6 remains in the OFF state.

[0014] The main circuit 7 is connected to the solar panel 2 and the cable 4. The main circuit 7 includes a first main circuit 7A and a second main circuit 7B. The first main circuit 7A is connected to the positive terminal of the solar panel 2 and the first cable 4A. The second main circuit 7B is connected to the negative terminal of the solar panel 2 and the second cable 4B. The main relay 6 is connected to the first main circuit 7A. A diode 15 is connected to the first main circuit 7A. The diode 15 is connected to the first main circuit 7A on the power conditioner 3 side of the main relay 6.

[0015] The drive circuit 8 switches the main relay 6 between an ON state and an OFF state depending on the state of the solar power generation system 1. When the solar power generation system 1 is in a normal power generation state, the drive circuit 8 sets the main relay 6 to an ON state. In the normal power generation state, in the solar power generation system 1, the solar panel 2 generates power and a current flows through the cable 4.

[0016] The drive circuit 8 keeps the main relay 6 in the ON state when the solar power generation system 1 is in a non-power generating state. In the non-power generating state, the solar panel 2 in the solar power generation system 1 is not generating power. The drive circuit 8 switches the main relay 6 to the OFF state when the solar power generation system 1 is in an abnormal power generating state. In the abnormal power generating state, the solar panel 2 in the solar power generation system 1 is generating power, but no current flows through the cable 4 because the cable 4 is broken.

[0017] In the following description, when a relay or switch is in the on state, it means that the contacts of the relay or switch are in contact and electrically connected, and when a relay or switch is in the off state, it means that the contacts of the relay or switch are open and electrically disconnected.

[0018] The drive circuit 8 includes a set coil circuit 16 and a reset coil circuit 17. The set coil circuit 16 is connected to the first main circuit 7A via a resistor R1. The set coil circuit 16 is connected to the first main circuit 7A on the solar panel 2 side of the main relay 6. The set coil circuit 16 is connected to the set coil 11. A start switch 19 is connected to the set coil circuit 16. The start switch 19 is biased to the off state by a spring 20.

[0019] The reset coil circuit 17 is connected to the first main circuit 7A via a resistor R2. The reset coil circuit 17 is connected to the first main circuit 7A between the main relay 6 and the diode 15. The reset coil circuit 17 is connected to the reset coil 12. A capacitor C1 is connected to the reset coil circuit 17. The capacitor C1 is connected in parallel to the reset coil 12.

[0020] The drive circuit 8 includes a first coil circuit 21, a second coil circuit 22, and a third coil circuit 23. The first coil circuit 21 is connected to the first main circuit 7A. The first coil circuit 21 is connected in parallel with the diode 15. The second coil circuit 22 is connected to the first main circuit 7A via a resistor R3. The second coil circuit 22 is connected to the first main circuit 7A between the main relay 6 and the diode 15. The third coil circuit 23 is connected to the first main circuit 7A via a resistor R4. The third coil circuit 23 is connected to the first main circuit 7A between the main relay 6 and the diode 15.

[0021] The drive circuit 8 includes a first drive relay 24, a second drive relay 25, and a third drive relay 26. The first drive relay 24 includes first contacts 27, 28 and a first coil 29. The first contacts 27, 28 are connected to the third coil circuit 23. The first contacts 27, 28 are configured to open and close the third coil circuit 23. The first coil 29 is connected to the first coil circuit 21. The first drive relay 24 is a normally open (a-contact) type relay. That is, when no current flows through the first coil 29, the first drive relay 24 is set to an off state. When current flows through the first coil 29, the first drive relay 24 is set to an on state. The first drive relay 24 is driven by the current flowing through the first coil 29. That is, when current flows through the cable 4, the first drive relay 24 is set to an on state. When no current flows through the cable 4, the first drive relay 24 is set to an off state.

[0022] The second drive relay 25 includes second contacts 31, 32 and a second coil 33. The second contacts 31, 32 are connected to the third coil circuit 23. The second contacts 31, 32 are configured to open and close the third coil circuit 23. The second contacts 31, 32 are connected in parallel with the first contacts 27, 28. The second coil 33 is connected to the second coil circuit 22. The second drive relay 25 is a normally closed (b) contact relay. That is, when no current flows through the second coil 33, the second drive relay 25 is set to an ON state. When current flows through the second coil 33, the second drive relay 25 is set to an OFF state. The second drive relay 25 is driven by the current flowing through the second coil circuit 22. That is, when a power generation voltage is generated by the solar panel 2, the second drive relay 25 is set to an OFF state. When a power generation voltage is not generated by the solar panel 2, the second drive relay 25 is set to an ON state.

[0023] The third drive relay 26 includes third contacts 34, 35 and a third coil 36. The third contacts 34, 35 are connected to the reset coil circuit 17. The third contacts 34, 35 are provided to be able to open and close the reset coil circuit 17. The third coil 36 is connected to the third coil circuit 23. The third drive relay 26 is a normally closed (b) contact relay. That is, when no current flows through the third coil 36, the third drive relay 26 is set to an ON state. When current flows through the third coil 36, the third drive relay 26 is set to an OFF state. The third drive relay 26 is driven by a current flowing through the third coil circuit 23. That is, when current flows through the third coil circuit 23, the third drive relay 26 is set to an OFF state. When no current flows through the third coil circuit 23, the third drive relay 26 is set to an ON state.

[0024] Next, the operation of the power interruption device 5 will be described. Figure 2 shows the drive circuit 8 of the power interruption device 5 in the initial state. As shown in Figure 2, in the initial state, the main relay 6 is in the off state. Therefore, no current flows through the first coil circuit 21, and the first drive relay 24 is in the off state. No current flows through the second coil circuit 22, and the second drive relay 25 is in the on state. No current flows through the third coil circuit 23, and the third drive relay 26 is in the on state.

[0025] Fig. 3 shows the drive circuit 8 of the power interruption device 5 at startup. As shown in Fig. 3, when the power interruption device 5 is started, the start switch 19 is operated to the ON state. When the solar panel 2 is generating power, the voltage generated by the solar panel 2 causes current to flow through the set coil circuit 16, setting the main relay 6 to the ON state. This causes current to flow through the first main circuit 7A and the first coil circuit 21, setting the first drive relay 24 to the ON state. The voltage generated by the solar panel 2 causes current to flow through the second coil circuit 22, setting the second drive relay 25 to the OFF state. The voltage generated by the solar panel 2 causes current to flow through the third coil circuit 23, setting the third drive relay 26 to the OFF state.

[0026] The start switch 19 returns to the OFF state after operation. Figure 4 shows the drive circuit 8 of the power cutoff device 5 in a normal power generation state after startup. In a normal power generation state, the solar panel 2 generates power, the cable 4 is not broken, and current flows to the power conditioner 3 via the cable 4. As shown in Figure 4, in a normal power generation state, the start switch 19 is set to the OFF state. The first drive relay 24 is set to the ON state, the second drive relay 25 is set to the OFF state, and the third drive relay 26 is set to the OFF state. Therefore, no current flows through either the set coil circuit 16 or the reset coil circuit 17, and the main relay 6 is held in the ON state due to the self-holding function of the latching relay.

[0027] At night or when the weather is cloudy and there is insufficient sunlight, the solar power generation system 1 enters a non-power-generating state in which the solar panel 2 does not generate power. FIG. 5 shows the drive circuit 8 of the power cutoff device 5 in the non-power-generating state. As shown in FIG. 5, in the non-power-generating state, no current flows through the first main circuit 7A and the first coil circuit 21. Therefore, the first drive relay 24 is set to the OFF state. No voltage is generated by the solar panel 2, and no current flows through the second coil circuit 22. Therefore, the second drive relay 25 is set to the ON state. No current flows through the third coil circuit 23, and the third drive coil is set to the ON state. However, no voltage is generated by the solar panel 2, and no current flows through the reset coil circuit 17. Therefore, the main relay 6 is held in the ON state by the self-holding function of the latching relay.

[0028] When sunlight recovers and the solar panel 2 resumes power generation, current flows through the first main circuit 7A and the first coil circuit 21, setting the first drive relay 24 to the ON state. Current flows through the second coil circuit 22 due to the voltage generated by the solar panel 2, setting the second drive relay 25 to the OFF state. Current flows through the third coil circuit 23 due to the voltage generated by the solar panel 2, setting the third drive relay 26 to the OFF state. This returns the drive circuit 8 to the normal power generation state shown in FIG. 4.

[0029] When the solar power generation system 1 transitions from a normal power generation state to a non-power generation state, the capacitor C1 delays the response of the reset coil 12 so that the current flowing through the reset coil circuit 17 does not switch the main relay 6 to the OFF state. Furthermore, during the transition between the normal power generation state and the non-power generation state, the resistance value of the second coil circuit 22 is set so that the first drive relay 24 turns ON first and then the second drive relay 25 turns OFF, or the second drive relay 25 turns ON first and then the first drive relay 24 turns OFF.

[0030] In the solar power generation system 1, if the cable 4 breaks while the solar panel 2 is generating power, the solar power generation system 1 enters an abnormal power generation state. FIG. 6 illustrates the drive circuit 8 in an abnormal power generation state. In the abnormal power generation state, the solar panel 2 generates a power generation voltage, but due to the break in the cable 4, no current flows through the first main circuit 7A and the first coil circuit 21. Therefore, as shown in FIG. 6 , the first drive relay 24 is set to the OFF state. Because the voltage generated by the solar panel 2 causes current to flow through the second coil circuit 22, the second drive relay 25 is set to the OFF state. Therefore, no current flows through the third coil circuit 23, and the third drive coil is set to the ON state. As a result, the voltage generated by the solar panel 2 causes current to flow through the reset coil circuit 17, energizing the reset coil 12 and switching the main relay 6 to the OFF state. As a result, the power cutoff device 5 disconnects the solar panel 2 from the cable 4. After the solar panel 2 is disconnected, no current flows through the reset coil circuit 17. However, the self-holding function of the latching relay keeps the main relay 6 in the OFF state.

[0031] The power cutoff device 5 according to the present embodiment described above can cut off the solar panel 2 in the event of a cable break in the photovoltaic power generation system 1 without using a power source to detect a break in the cable 4. Furthermore, the drive circuit 8 is configured using a simple combination of relays. This reduces the risk of failure in the power cutoff device 5 compared to when a complex electronic circuit including a microcomputer or the like is used. Furthermore, the cost of the power cutoff device 5 can be reduced.

[0032] 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 gist of the invention.

[0033] The configuration of the drive circuit 8 described above is not limited to that of the above embodiment and may be modified. For example, the arrangement of each relay or switch may be changed. A resistor may be provided instead of the diode 15. Alternatively, the generated current may be passed directly to a relay coil made of thick wire.

[0034] According to the present invention, it is possible to shut down the solar panel in the event of a cable breakage in a photovoltaic power generation system without using a power source for detecting cable breakage.

[0035] 2: Solar panel, 3: Power conditioner, 4: Cable, 5: Power cutoff device, 6: Main relay, 8: Drive circuit, 11: Set coil, 12: Reset coil, 24: First drive relay, 25: Second drive relay, 26: Third drive relay, C1: Capacitor

Claims

1. A power interruption device for disconnecting the solar panel from the cable in a photovoltaic power generation system including a solar panel, a power conditioner, and a cable connecting the solar panel and the power conditioner when the cable is broken, the power interruption device comprising: a main relay that is a latching relay that can be switched between an ON state that connects the solar panel to the cable and an OFF state that disconnects the solar panel from the cable, the main relay being set to the ON state in a normal power generation state in which the solar panel is generating power and current is flowing through the cable, and being maintained in the ON state even in a non-power generation state in which the solar panel is not generating power; and a drive circuit that switches the main relay to the OFF state by the power generation voltage of the solar panel in an abnormal power generation state in which the solar panel is generating power and the cable is broken.

2. The power interruption device according to claim 1, wherein the main relay includes a set coil and a reset coil, the main relay is set to the on state when the set coil is energized by the voltage generated by the solar panel, and the drive circuit switches the main relay to the off state when the abnormal power generation state occurs by energizing the reset coil by the voltage generated by the solar panel.

3. The power interruption device according to claim 1, wherein the drive circuit includes: a first drive relay driven by the current flowing through the cable; and a second drive relay driven by the voltage generated by the solar panel.

4. The power interruption device according to claim 3, wherein in the normal power generation state, the first drive relay is in an on state and the second drive relay is in an off state; in the non-power generation state, the first drive relay is in an off state and the second drive relay is in an on state; and in the abnormal power generation state, the first drive relay and the second drive relay are in an off state.

5. The power interruption device according to claim 4, wherein, during a transition between the normal power generation state and the non-power generation state, the first drive relay is turned on first and then the second drive relay is turned off, or the second drive relay is turned on first and then the first drive relay is turned off.

6. The power interruption device according to claim 4, wherein the main relay includes a set coil and a reset coil, the main relay is set to the on state when the set coil is energized by the voltage generated by the solar panel, the main relay is set to the off state when the reset coil is energized by the voltage generated by the solar panel, the drive circuit includes a third drive relay connected to the reset coil, and when the first drive relay and the second drive relay are in the off state in the abnormal power generation state, the third drive relay is turned on, causing the reset coil to be energized by the voltage generated by the solar panel.

7. The power interruption device according to claim 6, wherein the drive circuit includes a capacitor connected in parallel to the reset coil.

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